DOW CHEMICAL CO /DE/
SC 13E3, 1998-09-04
CHEMICALS & ALLIED PRODUCTS
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<PAGE>

- -------------------------------------------------------------------------------
- -------------------------------------------------------------------------------

                    SECURITIES AND EXCHANGE COMMISSION
                         Washington, D.C. 20549
        
                    ----------------------------------

                     RULE 13E-3 TRANSACTION STATEMENT
        (Pursuant to Section 13(e) of the Securities Exchange Act of 1934)

                    ----------------------------------

                          MYCOGEN CORPORATION
                          (Name of the Issuer)

                        THE DOW CHEMICAL COMPANY
                          ROFAN SERVICES INC.
                            CENTEN AG INC.
                          DOW AGROSCIENCES LLC
                                 and
                     AGROSCIENCES ACQUISITION INC.
                 (Name of Person(s) Filing Statement)

                             COMMON STOCK
                      PAR VALUE $0.001 PER SHARE
       (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                    (Title of Class of Securities)

                             628452 10 4
                (CUSIP Number of Class of Securities)

       John Scriven              Jane M. Gootee         Brian G. Taylorson
  Vice President, General        Vice President              President
   Counsel and Secretary       Rofan Services Inc.         Centen Ag Inc.
  The Dow Chemical Company       2030 Dow Center          2030 Dow Center
      2030 Dow Center        Midland, Michigan 48674  Midland, Michigan 48674
  Midland, Michigan 48674         (517) 636-1000           (517) 636-1000
       (517) 636-1000

                 Louis W. Pribila             Brian G. Taylorson
            Vice President, Secretary              President
               and General Counsel         AgroSciences Acquisition Inc.
              Dow AgroSciences LLC               2030 Dow Center
              9330 Zionsville Road           Midland, Michigan 48674
           Indianapolis, Indiana 46268           (517) 636-1000
                 (317) 337-3000

                                 with a copy to:

                                 Scott J. Davis
                                James T. Lidbury
                              Mayer, Brown & Platt
                            190 South LaSalle Street
                             Chicago, Illinois 60603
                                 (312) 782-0600
             (Name, Address and Telephone Number of Person Authorized to 
     Receive Notices and Communications on Behalf of Persons Filing Statement)

This statement is filed in connection with (check the appropriate box):
     a.   / /  The filing of solicitation materials or an information statement
               subject to Regulation 14A, Regulation 14C or Rule 13e-3(c) under
               the Securities Act of 1934.
     b.   / /  The filing of a registration statement under the Securities Act
               of 1933.
     c.   /X/  A tender offer.
     d.   / /  None of the above.
Check the following box if the soliciting materials or information statement
referred to in checking box (a) are preliminary copies:  / /
                              CALCULATION OF FILING FEE
<TABLE>
- --------------------------------------------------------------------------
- --------------------------------------------------------------------------
Transaction Valuation*                   Amount of Filing Fee
<S>                                            <C>
- --------------------------------------------------------------------------
$374,232,918                                    $74,847
- --------------------------------------------------------------------------
- --------------------------------------------------------------------------
</TABLE>
*    For purposes of calculating the filing fee only.  This amount assumes the
     purchase of 11,532,381 shares of common stock (the "Shares") of the subject
     company at $28.00 in cash per Share as well as the purchase of 3,568,635
     Shares subject to outstanding options at $28.00 per Share less the
     average exercise price per Share subject to such options of $13.6174.
     Check box if any part of the fee is offset as provided by Rule 0-11(a)(2)
     and identify the filing with which the offsetting fee was previously paid.
     Identify the previous filing by registration statement number, or the Form
     or Schedule and the date of its filing.

/X/  Amount Previously Paid:       $74,847
     Form or Registration Number:  Schedule 14D-1.
     Filing Party:                 The Dow Chemical Company, Rofan Services 
                                   Inc., Centen Ag Inc., Dow AgroSciences LLC
                                   and AgroSciences Acquisition Inc.
     Date Filed:                   September 4, 1998.
- -------------------------------------------------------------------------------
- -------------------------------------------------------------------------------
<PAGE>

                           INTRODUCTION

     This Rule 13e-3 Transaction Statement (the "Statement") is being filed 
by The Dow Chemical Company ("TDCC"), Rofan Services Inc. ("Rofan"), Centen 
Ag Inc. ("Centen"), AgroSciences Acquisition Inc. ("Purchaser") and Dow 
AgroSciences LLC ("Parent").  Rofan and Centen are wholly owned subsidiaries 
of TDCC, a public corporation whose stock is traded on the NYSE.  Rofan and 
Centen own 63% and 37%, respectively, of the interests of Parent.  Parent 
owns 69% of the common stock of Purchaser, and Centen owns the remaining 31% 
of the common stock of Purchaser.  Parent holds approximately 68.3% of the 
outstanding shares of common stock, par value $0.001 per share (the 
"Shares"), of Mycogen Corporation (the "Company").  This Statement relates to 
a proposed merger (the "Merger") in which Purchaser would merge with and into 
the Company and the Shares other than those Shares held by Parent or 
Purchaser would be converted into the right to receive $28.00 per Share in 
cash.

     The following cross reference sheet is being supplied pursuant to 
General Instruction F to the Statement and shows the location in the Offer to 
Purchase dated September 4, 1998 (the "Offer to Purchase") filed as 
Exhibit 99(d)(1) hereto by the Purchaser with the Securities and Exchange 
Commission on the date hereof, of the information required to be included 
in response to the items of this Statement. The information set forth in the 
Offer to Purchase, which is attached hereto as Exhibit 99(d)(1), is hereby 
expressly incorporated herein by reference and the responses to each item 
are qualified in their entirety by the provisions of the Offer to Purchase. 

                                     -1-

<PAGE> 

                             CROSS REFERENCE SHEET

<TABLE>
<CAPTION>

ITEM IN SCHEDULE 13E-3                          WHERE LOCATED IN SCHEDULE 14D-1
- ----------------------                          -------------------------------
<S>                                             <C>

Item 1(a)-(c) . . . . . . . . . . . . . . . .   Item 1(a)-(c)
Item 1(d)-(f) . . . . . . . . . . . . . . . .   *
Item 2. . . . . . . . . . . . . . . . . . . .   Item 2
Item 3(a)(1). . . . . . . . . . . . . . . . .   Item 3(a)(1)
Item 3(a)(2). . . . . . . . . . . . . . . . .   Item 3(b)
Item 3(b) . . . . . . . . . . . . . . . . . .   *
Item 4. . . . . . . . . . . . . . . . . . . .   *
Item 5(a)-(e) . . . . . . . . . . . . . . . .   Item 5(a)-(e)
Item 5(f) . . . . . . . . . . . . . . . . . .   Item 5(g)
Item 5(g) . . . . . . . . . . . . . . . . . .   *
Item 6(a) . . . . . . . . . . . . . . . . . .   Item 4(a)
Item 6(b) . . . . . . . . . . . . . . . . . .   *
Item 6(c)-(d) . . . . . . . . . . . . . . . .   Item 4(b)-(c)
Item 7(a) . . . . . . . . . . . . . . . . . .   Item 5
Item 7(b)-(d) . . . . . . . . . . . . . . . .   *
Item 8. . . . . . . . . . . . . . . . . . . .   *
Item 9. . . . . . . . . . . . . . . . . . . .   *
Item 10 . . . . . . . . . . . . . . . . . . .   Item 6
Item 11 . . . . . . . . . . . . . . . . . . .   Item 7
Item 12 . . . . . . . . . . . . . . . . . . .   *
Item 13 . . . . . . . . . . . . . . . . . . .   *
Item 14 . . . . . . . . . . . . . . . . . . .   *
Item 15(a). . . . . . . . . . . . . . . . . .   *
Item 15(b). . . . . . . . . . . . . . . . . .   Item 8
Item 16 . . . . . . . . . . . . . . . . . . .   Schedule 14D-1
Item 17(a). . . . . . . . . . . . . . . . . .   Item 11(b)
Item 17(b). . . . . . . . . . . . . . . . . .   *
Item 17(c). . . . . . . . . . . . . . . . . .   Item 11(c)
Item 17(d). . . . . . . . . . . . . . . . . .   *
Item 17(e). . . . . . . . . . . . . . . . . .   *
Item 17(f). . . . . . . . . . . . . . . . . .   Not Applicable
</TABLE>
- -----------------
*     This information is provided only in this Schedule 13E-3.

                               -2-

<PAGE>

ITEM 1.       ISSUER AND CLASS OF SECURITY SUBJECT TO THE TRANSACTION.

     (a)      The name of the subject company is Mycogen Corporation, a 
corporation organized under the laws of California (the "Company"), which has 
its principal executive offices at 5501 Oberlin Drive, San Diego, California 
92121. Capitalized terms used in this Schedule 13E-3 and not defined herein 
shall have the meanings set forth in the Offer to Purchase dated September 4, 
1998 (the "Offer to Purchase") attached hereto as Exhibit 99(d)(1).

     (b)      The information set forth in the "Introduction" of the Offer to 
Purchase is incorporated herein by reference.

     (c)-(d) and (f) The information set forth in "The Tender Offer - 6. 
Price Range of the Shares" of the Offer to Purchase is incorporated herein by 
reference.

     (e)      Not Applicable.


ITEM 2.       IDENTITY AND BACKGROUND.

     (a)-(d) and (g)  The information set forth in "Introduction," "The 
Tender Offer - 8. Certain Information Concerning Purchaser, Parent and 
Certain Affiliates of Parent" and Schedule I of the Offer to Purchase is 
incorporated herein by reference.

     (e)-(f)   During the last five years, neither The Dow Chemical Company, 
a Delaware corporation, nor Rofan Services Inc., a Delaware corporation, nor 
Centen Ag Inc., a Delaware corporation, nor Dow AgroSciences LLC, a Delaware 
limited liability company ("Parent"), nor AgroSciences Acquisition Inc., a 
Delaware corporation ("Purchaser") and a majority-owned subsidiary of Parent, 
nor, to the best of their  knowledge, any of the individuals listed in "The 
Tender Offer - 8. Certain Information Concerning Purchaser, Parent and 
Certain Affiliates of Parent" or in Schedule I of the Offer to Purchase has 
(i) been convicted in a criminal proceeding (excluding traffic violations or 
similar misdemeanors) or (ii) been a party to a civil proceeding of a 
judicial or administrative body of competent jurisdiction and, as a result of 
such proceeding, was or is subject to a judgment, decree or final order 
enjoining future violations of, or prohibiting activities subject to, federal 
or state securities laws or finding any violation of such laws.

ITEM 3.       PAST CONTACTS, TRANSACTIONS OR NEGOTIATIONS.

     (a)      The information set forth in "The Tender Offer - 8. Certain 
Information Concerning Purchaser, Parent and Certain Affiliates of Parent" 
and "The Tender Offer - 9. Background of the Offer" of the Offer to Purchase 
is incorporated herein by reference.

     (b)      The information set forth in "The Tender Offer -- 9. Background 
of the Offer" of the Offer to Purchase is incorporated herein by reference.

ITEM 4.       TERMS OF THE TRANSACTION.

     The information set forth in "Introduction" and "The Tender Offer -- 10. 
 Purpose of the Offer; The Merger Agreement" of the Offer to Purchase is 
incorporated herein by reference.

ITEM 5.       PLANS OR PROPOSALS OF THE ISSUER OR AFFILIATE.

     The information set forth in "The Tender Offer--9. Background of the 
Offer," "The Tender Offer--10. Purpose of the Offer; The Merger Agreement" 
and "The Tender Offer -- 12. Certain Effects of the Offer; Exchange Act 
Registration; Filing Requirements" of the Offer to Purchase is incorporated 
herein by reference.

ITEM 6.       SOURCE AND AMOUNTS OF FUNDS OR OTHER CONSIDERATION.

     (a)      The information set forth in "The Tender Offer - 11. Source and 
Amount of Funds" of the Offer to Purchase is incorporated herein by reference.

     (b)      The information set forth in "The Tender Offer -- 16. Fees and 
Expenses" of the Offer to Purchase is incorporated herein by reference.

                                  -3-

<PAGE>

     (c)-(d)  None.

ITEM 7.       PURPOSE(S), ALTERNATIVES, REASONS AND EFFECTS.

     The information set forth in "The Tender Offer -- 5. Certain Tax 
Consequences," "The Tender Offer -- 9. Background of the Offer," "The Tender 
Offer -- 10.   Purpose of the Offer; The Merger Agreement" and "The Tender 
Offer -- 12. Certain Effects of the Offer" of the Offer to Purchase is 
incorporated herein by reference.

ITEM 8.       FAIRNESS OF THE TRANSACTION.

     (a)-(b) and (d)-(e)   The information set forth in "Recommendation of the
Company's Board of Directors" and "The Tender Offer -- 9.  Background of the
Offer" of the Offer to Purchase is incorporated herein by reference.

     (c)      The Merger is structured to require the approval of at least a 
majority of the unaffiliated security holders.

     (f)      Not Applicable.

ITEM 9.       REPORTS, OPINIONS, APPRAISALS AND CERTAIN NEGOTIATIONS.

     The information set forth in "Recommendation of the Company's Board of 
Directors," "The Tender Offer  --  9. Background of the Offer" and "The 
Tender Offer -- 16.  Fees and Expenses" of the Offer to Purchase is 
incorporated herein by reference.

ITEM 10.      INTEREST IN SECURITIES OF THE ISSUER.

<TABLE>
<CAPTION>                                      SHARES
                                            BENEFICIALLY   PERCENTAGE
          NAME                                 OWNED       OF CLASS  
          -----------------------           -------------  -----------
<S>                                         <C>            <C>
(a)-(b)   The Dow Chemical Company           24,766,157      68.3%
          2030 Dow Center                   
          Midland, MI 48674                 
          (517) 636-1000                    
                                            
          Rofan Services, Inc.               24,766,157      68.3%
          2030 Dow Center                   
          Midland, MI 48674                 
          (517) 636-1000                    
                                            
          Centen Ag Inc.                              0         0%
          2030 Dow Center                                
          Midland, MI 48674                              
          (517) 636-1000                                 
                                            
          Dow AgroSciences LLC               24,766,157      68.3%
          9330 Zionsville Road              
          Indianapolis, IN 46268            
          (317) 337-3000                    
                                            
          AgroSciences Acquisition Inc.               0         0%
          2030 Dow Center
          Midland, MI 48674
          (517) 636-1000
</TABLE>

     The information set forth in "The Tender Offer--6. Price Range of the 
Shares" and "The Tender Offer--8. Certain Information Concerning Purchaser, 
Parent and Certain Affiliates of Parent" of the Offer to Purchase is 
incorporated herein by reference.

ITEM 11.      CONTRACTS, ARRANGEMENTS OR UNDERSTANDINGS WITH RESPECT TO THE
              ISSUER'S SECURITIES.

     The information set forth in "The Tender Offer - 8. Certain Information 
Concerning Purchaser, Parent and Certain Affiliates of Parent," "The Tender 
Offer--9. Background of the Offer" and "The Tender Offer - 10. Purpose of the 
Offer; Merger Agreement" of the Offer to Purchase is incorporated herein by 
reference.

ITEM 12.      PRESENT INTENTION AND RECOMMENDATION OF CERTAIN PERSONS WITH 
              REGARD TO THE TRANSACTION.

     (a)      The information set forth in "The Tender Offer--8. Certain 
Information Concerning Purchaser, Parent and Certain Affiliates of Parent" of 
the Offer to Purchase is incorporated herein by reference.

     (b)      The information set forth in "The Tender Offer--9. Background 
of the Offer" of the Offer to Purchase is incorporated herein by reference.


                                     -4-

<PAGE>

ITEM 13.      OTHER PROVISIONS OF THE TRANSACTION.

     (a)      The information set forth in "The Tender Offer -- 10. Purpose 
of the Offer; The Merger Agreement" is incorporated herein by reference.

     (b)      Not applicable.

     (c)      Not applicable.
     

                                      -5-

<PAGE>

ITEM 14.      FINANCIAL INFORMATION.

     The information set forth in "The Tender Offer -- 7.  Certain 
Information Concerning the Company"  and "The Tender Offer--8. Certain 
Information Concerning Purchaser, Parent and Certain Affiliates of Parent" of 
the Offer to Purchase and the Company's Annual Report on Form 10-K for the 
year ended August 31, 1997, and the Company's Quarterly Reports on Form 10-Q 
for the quarters ended November 30, 1997, February 28, 1998, and May 31, 
1998, is incorporated herein by reference.

ITEM 15.      PERSONS AND ASSETS EMPLOYED, RETAINED OR UTILIZED.

     (a)      The information set forth in "The Tender Offer -- 10. Purpose 
of the Offer; Merger Agreement" of the Offer to Purchase is incorporated 
herein by reference.

     (b)      The information set forth in "The Tender Offer -- 16. Fees and 
Expenses" of the Offer to Purchase is incorporated herein by reference.

ITEM 16.      ADDITIONAL INFORMATION.

     Reference is hereby made to the Offer to Purchase and the related Letter 
of Transmittal, copies of which are attached hereto as Exhibits 99(d)(1) and 
99(d)(2), respectively, and which are incorporated herein in their entirety 
by reference.

<TABLE>
<CAPTION>
ITEM 17.            MATERIAL TO BE FILED AS EXHIBITS.
<S>                 <C>
(a) and (f) . . .   Not Applicable.
(b)-(e) . . . . .   A list of exhibits filed with this Schedule 13E-3
                    is set forth on the Exhibit Index immediately 
                    following the signature page of this Schedule 13E-3 
                    and is incorporated herein by reference.
</TABLE>

                                   -6-
<PAGE>

                                SIGNATURES


     After due inquiry and to the best of my knowledge and belief, I certify 
that the information set forth in this statement is true, complete and 
correct.

Dated:  September 4, 1998.    THE DOW CHEMICAL COMPANY


                              By /s/ G. MICHAEL LYNCH
                                 --------------------------------------
                                 Name:  G. Michael Lynch
                                 Title: Vice President and Controller


                              ROFAN SERVICES INC.


                              By /s/ J. PEDRO REINHARD
                                 --------------------------------------
                                 Name: J. Pedro Reinhard
                                 Title: President


                              CENTEN AG INC.


                              By /s/ BRIAN G. TAYLORSON
                                 --------------------------------------
                                 Name: Brian G. Taylorson
                                 Title: President


                              DOW AGROSCIENCES LLC


                              By /s/ LOUIS W. PRIBILA
                                 --------------------------------------
                                 Name: Louis W. Pribila
                                 Title: Vice President, Secretary and
                                        General Counsel


                              AGROSCIENCES ACQUISITION INC.


                              By /s/ BRIAN G. TAYLORSON
                                 --------------------------------------
                                 Name: Brian G. Taylorson
                                 Title: President

                                 -7-

<PAGE>

                                 EXHIBIT INDEX
<TABLE>
<CAPTION>
                                                                                  SEQUENTIALLY
  EXHIBIT NO.                   DESCRIPTION                                       NUMBERED PAGE
 ------------                   -----------                                      ---------------
 <S>               <C>                                                           <C>
  99(b)(1)          Salomon Smith Barney Report to Dow AgroSciences LLC 
                    dated August 3, 1998.                                        
  99(b)(2)          Wasserstein Perella & Co., Inc. Report to the Special 
                    Committee of Mycogen Corporation dated August 3, 1998.       
  99(b)(3)          Wasserstein Perella & Co., Inc. Report to the Special 
                    Committee of Mycogen Corporation dated August 31, 1998.      
  99(b)(4)          Opinion of Wasserstein Perella & Co., Inc. to the Special 
                    Committee of Mycogen Corporation dated August 31, 1998 
                    (Incorporated herein by reference from Schedule III to the 
                    Offer to Purchase).                                          
  99(c)(1)          Agreement and Plan of Merger among Mycogen Corporation, 
                    Dow AgroSciences LLC and AgroSciences Acquisition Inc. 
                    dated as of August 31, 1998. (Incorporated herein by 
                    reference from Exhibit 99.1 to Amendment No. 15 to 
                    Schedule 13D filed September 1, 1998).                       
  99(c)(2)          Confidentiality Agreement among Mycogen Corporation, The 
                    Dow Chemical Company and Dow AgroSciences LLC dated July 
                    16, 1998.                                                    
  99(c)(3)          Exchange and Purchase Agreement among Mycogen 
                    Corporation, Agrigenetics, Inc., DowElanco and United 
                    AgriSeeds, Inc. dated as of January 15, 1996 
                    (Incorporated herein by reference from Exhibit 99(a)(1) 
                    to Schedule 13D filed January 25, 1996).                     
  99(c)(4)          Amendment to Exchange and Purchase Agreement between 
                    Mycogen Corporation and Dow AgroSciences LLC dated as of 
                    July 22, 1998 (Incorporated herein by reference from 
                    Exhibit 99(1) to Amendment No. 14 to Schedule 13D filed 
                    July 23, 1998).                                              
  99(c)(5)          Technology Agreement among Mycogen Corporation, 
                    Agrigenetics, Inc. and DowElanco dated as of February 
                    19, 1996 (Incorporated herein by reference from Exhibit B 
                    to Exhibit 99(a)(1) to Schedule 13D filed January 25, 
                    1996).                                                       
  99(c)(6)          Brassica License and Research Agreement between Dow 
                    Elanco Canada and Mycogen Corporation dated October 30, 
                    1997.                                                        
  99(c)(7)          Restated Loan Agreement between Dow AgroSciences LLC and 
                    Mycoyen S.A. dated May 15, 1998.                             
  99(c)(8)          Loan Agreement between Dow Elanco and Mycogen Corporation 
                    dated as of April 1, 1997 (the "Dow Loan Agreement").        
  99(c)(9)          Amendment No. 1 to Dow Loan Agreement dated as of 
                    September 29, 1997.                                          
  99(c)(10)         Amendment No. 2 to Dow Loan Agreement dated as of 
                    November 14, 1997.                                           
  99(c)(11)         Amendment No. 3 to Dow Loan Agreement dated as of 
                    November 18, 1997.                                           
  99(c)(12)         Amendment No. 4 to Dow Loan Agreement dated as of April 
                    6, 1998.                                                     
  99(c)(13)         Amendment No. 5 to Dow Loan Agreement dated as of October 
                    1, 1997.                                                     
  99(c)(14)         Loan Agreement between Mycogen Corporation and DowElanco 
                    dated as of April 1, 1997 (the "Mycogen Loan Agreement").    
  99(c)(15)         Amendment No. 1 to Mycogen Loan Agreement dated as of 
                    April 6, 1998.                                               
  99(c)(16)         Amendment No. 2 to Mycogen Loan Agreement dated as of 
                    October 1, 1997.                                             
  99(c)(17)         Memorandum of Understanding dated September 3, 1998.         
  99(d)(1)          Offer to Purchase dated September 4,
                    1998.                                                        
  99(d)(2)          Form of Letter of Transmittal.                               
  99(d)(3)          Form of Notice of Guaranteed Delivery.                       
  99(d)(4)          Form of Letter to Brokers, Dealers,
                    Commercial Banks, Trust Companies and
                    other Nominees dated September 4, 1998.                      
  99(d)(5)          Form of Letter to Clients for use by
                    Brokers, Dealers, Commercial Banks,
                    Trust Companies and other Nominees.                          
  99(d)(6)          Form of Option Election.                                     
  99(d)(7)          Form of Stock Purchase Election.                             
  99(d)(8)          Form of Restricted Stock Election.                           
  99(d)(9)          Guidelines for Certification of
                    Taxpayer Identification Number on
                    Substitute Form W-9.                                         
  99(d)(10)         Form of Summary Advertisement.                               
  99(e)(1)          Chapter 13 of the California General Corporation Law 
                    (Incorporated herein by reference from Schedule II to
                    the Offer to Purchase).                                      
  99(g)(1)          Complaint filed in Susser v. Mycogen Corporation et al. 
                    (Superior Court of the State of California, County of San 
                    Diego, filed May 1, 1998).                                   
  99(g)(2)          Complaint filed in Harbor Finance Partners v. Mycogen 
                    Corporation et al. (Superior Court of the State of 
                    California, County of San Diego, filed May 1, 1998).         
  99(g)(3)          Complaint filed in Ellis Investments, Ltd. v.  
                    Eibl et al. (Superior Court of the State of California, 
                    County of San Diego, filed May 1, 1998).                     
  99(g)(4)          Complaint filed in Kolb v. Mycogen Corporation et al. 
                    (Superior Court of the State of California, County of San 
                    Deigo, filed May 5, 1998).                                   
  99(g)(5)          Complaint filed in Anderson v. Mycogen Corporation et al.
                    (Superior Court of the State of California, County of 
                    San Diego, filed May 5, 1998).                               
  99(g)(6)          Complaint filed in Boettcher v. Mycogen Corporation et al. 
                    (Superior Court of the State of California, County of San 
                    Diego, filed May 8, 1998).                                   
  99(g)(7)          Complaint filed in Verrone v. Mycogen Corporation et al. 
                    (Superior Court of the State of California, County of San 
                    Diego, filed May 15, 1998).                                  
  99(g)(8)          Order of Consolidation entered in Susser v. Mycogen 
                    Corporation et al. (Superior Court of State of 
                    California, County of San Diego, entered June 22, 1998).     
</TABLE>



<PAGE>

PROJECT MONDAY


                                              AUGUST 3, 1998
                                              CONFIDENTIAL
<PAGE>

AGENDA


     1. OVERVIEW OF PUBLIC MARKET VALUATION AND DATA                   1
     2. OVERVIEW OF PROJECTIONS                                        5
     3. PRELIMINARY VALUATION ANALYSIS -- AS OF APRIL 28, 1998         9
     4. VALUATION UPDATE -- AS OF AUGUST 3, 1998                      27
<PAGE>

OVERVIEW OF PUBLIC MARKET
VALUATION AND DATA






                                                                       -1-
<PAGE>

MONDAY STOCK PRICE PERFORMANCE

     MONDAY'S STOCK PRICE HAS EXPERIENCED SIGNIFICANT VOLATILITY ASSOCIATED 
     LESS WITH ITS OPERATING PERFORMANCE THAN WITH OWNERSHIP CHANGES AND 
     LITIGATION OUTCOMES. MONDAY'S STOCK WHICH WAS TRADING AROUND $18 TO $20 
     FOLLOWING A PERIOD OF POOR PERFORMANCE, HAS RECENTLY TRADED AS HIGH AS 
     $23.75 FOLLOWING DOW'S ANNOUNCEMENT.

          DAILY DATA -- 7/1/97 THROUGH 7/31/98

          [graph plot points to follow]

          Monday: Price (left axis)
          Monday: Volume (right axis)

     (a)  1/6/98    Monday announces joint-venture with J.G. Boswell that 
                    will be called Phylogen Seed Company.
     (b)  1/16/98   Dow Chemical raises Monday stake to 62.9%.
     (c)  2/3/98    Monday loses $70.2mm patent suit against Monsanto.
     (d)  3/17/98   Pioneer Hi-Bred sells its remaining 2mm shares of Monday 
                    to Dow AgroSciences for $20.06 per share.
     (e)  3/20/98   Monday is awarded $174.9mm in damages in a breach of 
                    contract suit against the Monsanto Company.
     (f)  4/20/98   Monday acquires Dinamilho Carol Productos Agricolas, a 
                    Brazilian seed corn producer.
     (g)  5/1/98    Dow Chemical makes announcement.
     (h)  6/30/98   Monday wins lawsuit against Monsanto. Monsanto 
                    immediately appeals the decision.


                                                                        -2-
<PAGE>

STOCK PERFORMANCE

     MONDAY HAS UNDERPERFORMED BOTH ITS PEERS AND THE S&P 400.

          DAILY DATA -- 7/1/97 THROUGH 7/31/98

          [graph plot points to follow]

          Monday
          Custom Index: (ABTX, DKB, DLP, ELM, MTC, PHB)
          S&P Composite Average (400 Stocks)


                                                                        -3-

<PAGE>
<TABLE>
MONDAY CORP. - WALL STREET COMMENTARY
                                                                                 PRICE     PRICE TARGET
WALL STREET COMMENTARY                                     RATING                TARGET         DATE         1998E EPS    1999E EPS

ING Baring Furman Selz (7/08/98)

<S>                                                               <C>         <C>        <C>              <C>          <C>

"While we believe it is possible that Dow could raise its offer    Hold         NA            NA           ($0.95)      ($0.04)
above $20.50/share, we do not believe Monday shares at $23 3/8
present an attractive investment opportunity. We retrieve our
HOLD rating."
- --------------------------------------------------------------------------------------------------------------------------------
Deutsche Morgan Grenfell. (4/15/98)

"By 2002 Monday could have a meaningful seed business with sales   Bay         $35            NA           ($0.75)       $0.10
of $500 million (more than double the level we are anticipating
for FY98). By then, Monday should also have a meaningful cotton
seed business, an area in which the company had no presence just
last year. We think that Dow Agri-Sciences shares our view on
Monday, and that is why it continues to buy more shares, now 
owning 69% of Monday."
- --------------------------------------------------------------------------------------------------------------------------------
Salomon Smith Barney (3/20/98)

"We continue to rate Monday a hold because it has not yet been     Hold        $24           4/99           ($0.40)       $0.01
able to secure high enough quality germ plasm and a sizeable
enough market share to suggest that price will be driven by
fundamentals and has not yet convinced us that its technology
position is increasing in value."
- --------------------------------------------------------------------------------------------------------------------------------
IBEST Estimates (as of 7/16/98) # of Estimates: 1998: 8, 1999:6                                             ($0.51)       $0.06
- --------------------------------------------------------------------------------------------------------------------------------
First Call Estimates (as of 7/9/98) # of Estimates: 
1998: 8, 1999:6                                                                                             ($0.61)      ($0.04)
- --------------------------------------------------------------------------------------------------------------------------------
Monday Estimates (a)                                                                                        ($0.39)       $0.02
- --------------------------------------------------------------------------------------------------------------------------------
Base Case Estimates (a)                                                                                     ($0.46)(b)   ($0.19)
- --------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(a)  Calculated based on 37.9mm fully diluted shares.
(b)  Includes projected loss from write down of $12.0mm in 1998.

                                                                         -4-
<PAGE>

OVERVIEW OF PROJECTIONS

                                                                         - 5-


<PAGE>

OVERVIEW OF PROJECTIONS

     TWO SETS OF PROJECTIONS HAVE BEEN UTILIZED IN THIS ANALYSIS, THE MONDAY 
     AND THE BASE CASE PROJECTIONS:

     * The Monday Projections:
       ----------------------
       * Compiled by Monday management
       * Per Monday presentation to Dow AgroSciences ("DAS") Operating
         Committee (December 1997)
       * Revised from Monday Board approved 1998 5-year plan (Sept. 1997)
       * Detailed projections provided for both seed and intellectual
         property segments

     * Base Case:
       ---------
       * Based on Monday Projections
       * Reflects DAS Management's latest update to Monday projections
       * Monday's projections adjusted to reflect DAS assumptions regarding:
          * Monday's under performance for the year to date 1998
          * Weak competitive position
          * Lower corn market share gains
          * Product mix by corn product line
          * SARD expense levels
       * Detailed projections provided for both seed and intellectual
         property segments

                                                                          -6-
<PAGE>

PROJECTIONS COMPARISON

(Dollars in millions)
<TABLE>
<CAPTION>

                             Budget                                     Projections
                              1998     1999     2000     2001     2002     2003     2004     2005     2006     2007     CAGR
<S>                          <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>
REVENUES
Monday Projection            $220.5   $248.6   $278.0   $319.3   $372.5   $393.3   $447.6   $538.7   $601.9   $687.0   13.5%
  GROWTH                         --     12.8%    11.8%    14.9%    16.7%     5.6%    13.8%    20.3%    11.7%    14.1%  
Base Case                     213.8    245.1    273.9    312.5    361.6    390.0    427.1    464.2    493.4    550.3   11.1%
  GROWTH                         --     14.7%    11.7%    14.1%    15.7%     7.8%     9.5%     8.7%     6.3%    11.5%

Difference                     (6.7)    (3.5)    (4.1)    (6.8)   (10.9)    (3.3)   (20.5)   (74.5)  (108.5)  (136.8)
  AS A % OF MONDAY              3.0%     1.4%     1.5%     2.1%     2.9%     0.8%     4.6%    13.8%    18.0%    19.9%

GROSS PROFIT
Monday Projection             $99.3   $115.7   $128.4   $141.8   $169.2   $190.4   $223.2   $279.5   $315.8   $373.1   15.8%
  MARGIN                       45.1%    46.5%    46.2%    44.4%    45.4%    48.4%    49.9%    51.9%    52.5%    54.3%
  GROWTH                         --     16.5%    11.0%    10.4%    19.3%    12.6%    17.2%    25.2%    13.0%    18.2%

Base Case                      94.5    104.7    114.6    128.3    154.1    173.7    197.8    224.5    241.7    282.1   12.9%
  MARGIN                       44.2%    42.7%    41.8%    42.6%    42.6%    44.5%    46.3%    48.4%    49.0%    51.3%
  GROWTH                         --     10.9%     9.4%    12.0%    20.2%    12.7%    13.9%    13.5%     7.7%    16.7%

Difference                     (4.9)   (11.0)   (13.8)   (13.5)   (19.0)   (16.7)   (25.4)   (55.1)   (74.1)   (91.0)
  AS A % OF MONDAY              4.9%     9.5%    10.8%     9.5%     8.9%     8.8%    11.4%    19.7%    23.5%    24.4%

</TABLE>

  (CONTINUED ON NEXT PAGE)


                                                                          -7-

<PAGE>

PROJECTIONS COMPARISON (CONTINUED)

(Dollars in millions except per share) 
<TABLE>
<CAPTION>

                             Budget                                     Projections
                              1998     1999     2000     2001     2002     2003     2004     2005     2006     2007
<S>                          <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>
EBITDA
Monday Projection             $10.0    $17.7    $20.4    $20.6    $25.2    $25.2    $40.4    $75.4    $96.6   $128.7
  MARGIN                        4.5%     7.1%     7.4%     6.4%     6.8%     6.4%     9.0%    14.0%    16.0%    18.7%
  GROWTH                         --     77.3%    14.8%     1.0%    22.7%    (0.3%)   60.3%    86.8%    28.1%    33.2%

Base Case                      (1.9)     3.9     14.0     12.8     17.2     31.0     42.6     59.8     64.9     82.2
  MARGIN                       (0.9%)    1.6%     5.1%     4.1%     4.8%     8.0%    10.0%    12.0%    13.2%    14.9%
  GROWTH                         --       NM    260.1%    (8.1%)   34.3%    80.0%    37.2%    31.1%    16.4%    26.6%

Difference                    (11.9)   (13.9)    (6.4)    (7.8)    (8.0)     5.8      2.2    (19.6)   (31.6)   (46.5)
  AS A % OF MONDAY            119.3%    78.2%    31.5%    37.7%    31.8%    23.2%     5.5%    26.0%    32.8%    36.1%

EBIT
Monday Projection             ($2.2)    $3.8     $4.7     $3.9     $7.7     $9.3    $23.8    $58.3    $79.1   $112.1
  MARGIN                       (1.0%)    1.5%     1.7%     1.2%     2.1%     2.4%     5.3%    10.8%    13.1%    16.3%

Base Case                     (14.1)    (9.0)    (0.0)    (2.1)     1.5     16.9     27.7     40.3     49.1     67.2
  MARGIN                       (6.6%)   (3.7%)   (0.0%)   (0.7%)    0.4%     4.3%     6.5%     8.7%     9.9%    12.2%

Difference                    (11.9)   (12.8)    (4.7)    (6.0)    (6.3)     7.6      3.9    (18.0)   (30.0)   (44.8)
  BASE CASE AS A % OF MONDAY  645.9%  (235.5%)   (0.4%)  (53.0%)   19.0%   181.4%   116.4%    69.2%    62.1%    60.0%

NET INCOME
Monday Projection            ($14.8)    $0.6    ($0.4)   ($2.4)   ($1.4)   ($1.1)    $7.5    $29.2    $43.2    $65.1
  MARGIN                       (6.7%)    0.2%    (0.1%)   (0.8%)   (0.4%)   (0.3%)    1.7%     5.4%     7.2%     9.5%
  GROWTH                         --    104.1%   168.5%  (485.1%)   40.2%    19.9%   752.6%   290.3%    47.9%    50.6%
EPS                           ($0.39)   $0.02   ($0.01)  ($0.06)  ($0.04)  ($0.03)   $0.20    $0.74    $1.09    $1.61

Base Case                     (17.6)    (7.2)    (2.8)    (5.2)    (4.1)     4.9     11.6     20.4     27.2     39.3
  MARGIN                       (8.2%)   (3.0%)   (1.0%)   (1.6%)   (1.1%)    1.3%     2.7%     4.4%     5.5%     7.1%
  GROWTH                         --     58.9%    61.5%    (84.9%)  21.1%   220.9%   136.4%    75.9%    33.0%    44.7%
EPS                           ($0.46)  ($0.19)  ($0.07)   ($0.14) ($0.11)   $0.13    $0.31    $0.51    $0.68    $0.97

Difference                     (2.8)    (7.8)    (2.4)    (2.8)    (2.6)     6.1      4.1     (8.8)   (16.1)   (25.8)
  BASE CASE AS A % OF MONDAY  119.3%      NM    681.0%   215.2%   283.7%  (428.0%)  155.0%    69.9%    62.8%    60.4%
</TABLE>

                                                                            -8-
<PAGE>

PRELIMINARY VALUATION ANALYSIS
- - AS OF APRIL 28, 1998







                                                                            -9-

<PAGE>

OVERVIEW OF PRELIMINARY VALUATION ANALYSIS
(AS OF APRIL 28, 1998)

     SEVERAL FACTORS AFFECTED MONDAY'S VALUATION PROCESS, INCLUDING THE 
     FOLLOWING ISSUES:

     *  Monday's historical and projected lack of profitability

     *  Monday's significant near-term negative cash flows

     *  Differing views on when and if Monday will become profitable

     *  Monday's public market value may be overstated due to research 
        analysts' projections which seem optimistic when compared to the 
        Monday and Base Case projections

     *  The Company's small size and weak market position relative to its 
        competitors must be considered; this leaves it at a significant 
        competitive disadvantage

     *  Limited comparable company universe and Monday's unique nature 
        reduces comparability

     *  Intellectual property and litigation components are difficult to 
        isolate for valuation purposes

                                                                          -10-

<PAGE>

SUMMARY OF PRELIMINARY VALUATION ANALYSIS
(AS OF APRIL 28, 1998)

[graphic]

(CONTINUED ON NEXT PAGE)


                                                                           -11-

<PAGE>



SUMMARY OF PRELIMINARY VALUATION ANALYSIS
(AS OF APRIL 28, 1998) (CONTINUED)

     <TABLE>
     <CAPTION>
     COMPARABLE PUBLIC COMPANY ANALYSIS                             VALUE RANGE
                                                                  ---------------
     <S>                                                          <C>
     Revenue Multiple ($6.34-$13.68 with 20-30%                   $ 7.60 - $17.79
     minority interests acquisition premium)

     Discounted 2002 EBITDA Multiple

       Monday Projections ($4.99 - $10.09 with 20-30%               5.98 -  13.12
       minority interests acquisition premium)

       Base Case Projections ($2.71 - $6.06 with 20-30%             3.25 -   7.88
       minority interests acquisition premium)

     DISCOUNTED CASH FLOW ANALYSIS

       Monday - 4 Year Projections                                  6.65 -   8.92

       Monday - 9 Year Projections                                  8.62 -  15.51

       Base Case - 4 Year Projections                               5.21 -   6.95

       Base Case - 9 Year Projections                               5.07 -   9.59

     PRECEDENT ACQUISITION TRANSACTIONS                            15.23 -  19.89

</TABLE>
                                                                           -12-

<PAGE>

COMPARABLE COMPANIES ANALYSIS (AS OF APRIL 28, 1998)

     WE HAVE ANALYZED COMPARABLE COMPANIES IN ORDER TO DETERMINE MONDAY'S 
     PUBLIC MARKET VALUATION. HOWEVER, THE FOLLOWING FACTORS IMPACT THE 
     EFFECTIVENESS OF THE METHODOLOGY:

     *    Comparable universe is limited
           * Few comparables with similar size and focus / nature

     *    Wide range of comparable valuation multiples

     *    Intellectual property component

     *    Valuation also driven by earnings growth rate

     *    Limited investment research on a number of companies in the sector

     *    Monday's lack of profitability and differing internal and external 
          growth and profitability projections

     *    Merger activity in sector may be imputed in stock prices


                                                                        -13-
<PAGE>

COMPARABLE COMPANIES ANALYSIS (AS OF APRIL 28, 1998)

     IN ORDER TO VALUE MONDAY, WE CONSIDERED THE FOLLOWING ISSUES, AMONGST 
     OTHERS, WHEN ANALYZING THE COMPARABLE COMPANIES:

     *    Historical and projected lack of profitability

           * Least profitable of the comparables
           * Near-term earnings outlook not comparable

     *    Market and competitive positions less established than the 
          comparable universe

           * Pioneer and DEKALB are market leaders in the corn seed market
           * Seed quality, brand recognition
           * Reduced economies of scale to offset development costs

     *    Intellectual property component

           * More technology than seed plays, such as AgriBioTech
           * Partially offset by limited access to quality germplasm
           * Pioneer Hi-Bred's access to key Monday technology

     *    Earnings growth rate

           * Monday's 5-year earnings growth rate is above the low growth 
          fruit and vegetable seed producers, but less than the market leaders'


                                                                           -14-
<PAGE>

COMPARABLE COMPANIES ANALYSIS (AS OF APRIL 28, 1998)

     SALOMON SMITH BARNEY ESTIMATES A PUBLIC MARKET VALUATION RANGE OF 1.2X 
     to 2.5X REVENUE, BASED UPON AN ANALYSIS OF COMPARABLE COMPANIES. OTHER 
     TRADITIONAL VALUATION MEASURES SUCH AS MULTIPLES OF PROJECTED 1998/1999 
     EPS AND HISTORIC EBITDA MULTIPLES ARE NOT MEANINGFUL DUE TO NEGATIVE 
     FINANCIAL PERFORMANCE.

     COMPARABLE COMPANY ANALYSIS

     <TABLE>
     <CAPTION>
                                                  IMPLIED EQUITY VALUE     20% - 30% MINORITY
                               SELECTED RANGE         PER SHARE (a)           ACQ. PREMIUM
                              ----------------   ----------------------   --------------------
                    MONDAY     LOW     HIGH        LOW         HIGH          LOW        HIGH
     -----------------------------------------------------------------------------------------
     <S>            <C>       <C>      <C>        <C>          <C>         <C>          <C>

     LTM Revenues   $214.0    1.2x     2.5x       $6.34        $13.68      $7.60        $17.79
     -----------------------------------------------------------------------------------------
     </TABLE>

     (a)  Fully Diluted Shares Outstanding = 37.9 million. 
          Net debt = $16.7 million


                                                                           -15-
<PAGE>

COMPARABLE COMPANIES VALUATION (AS OF APRIL 28, 1998)

     MONDAY'S LACK OF PROFITABILITY SIGNIFICANTLY REDUCES THE RELEVANCE OF 
     VALUATIONS DRIVEN BY HISTORIC FINANCIAL RESULTS. BY PERFORMING AN 
     ANALYSIS* ON MONDAY'S 2002 FINANCIALS AND DISCOUNTING THIS VALUATION 
     BACK, WE ATTEMPT TO CAPTURE THE IMPACT OF FUTURE PROFITABILITY.

     4-YEAR DISCOUNTED SHARE VALUE

     <TABLE>
     <CAPTION>
                                                                     FIRM 2002 VALUE         VALUE PER SHARE 2002 (a)
                                                                ------------------------     ------------------------
                                                                    LOW          HIGH            LOW          HIGH
                                                                ------------------------     ------------------------

                                                                     EBITDA MULTIPLE
                                                                ------------------------
     PROJECTION                                                       20.0x  -   30.0x
     ------------------------------------------------------
     <S>                             <C>      <C>                   <C>        <C>               <C>          <C>

     2002 EBITDA Monday Case (mm)    $25.2    (6.8% margin)         $505.0  -  $757.4            $ 9.50   -   $16.17

     2002 EBITDA Base Case (mm)       17.2    (4.8% margin)          344.5  -   516.8              5.16   -     9.71
     </TABLE>



     <TABLE>
     <CAPTION>
                         1998 - IMPLIED VALUE PER SHARE
                        WITHOUT MINORITY INTEREST PREMIUM
                      -------------------------------------
                        MONDAY CASE           BASE CASE
                      ----------------     ----------------
     COST OF EQUITY    LOW       HIGH       LOW       HIGH
     ---------------------------------     ----------------
     <S>              <C>       <C>        <C>       <C>

          12.5%       $5.93  -  $10.09     $3.22  -  $6.06
          15.0%        5.43  -    9.24      2.95  -   5.55
          17.5%        4.99  -    8.48      2.71  -   5.09
     ---------------------------------     ----------------
     </TABLE>


     <TABLE>
     <CAPTION>
                         1998 - IMPLIED VALUE PER SHARE
                        WITH MINORITY INTEREST PREMIUM (b)
                      -------------------------------------
                        MONDAY CASE           BASE CASE
                      ----------------     ----------------
     COST OF EQUITY    LOW       HIGH       LOW       HIGH
     ---------------------------------     ----------------
     <S>              <C>       <C>        <C>       <C>

          12.5%       $7.12  -  $13.12     $3.87  -  $7.88
          15.0%        6.52  -   12.02      3.54  -   7.22
          17.5%        5.98  -   11.03      3.25  -   6.62
     ---------------------------------     ----------------
     </TABLE>

     * Lower EBITDA caused by intellectual property losses and expenses 
       results in the company's EBITDA multiple being above that of seed 
       operations.
     Note: Number of fully-diluted shares outstanding: 37.9mm
     (a)  Based on 2002 Net Debt of $145.0mm (Monday case) and $149.1 (Base 
          case)
     (b)  Implied share price including minority interest acquisition premium 
          of 20% at low end of range and 30% at high end of range.


                                                                           -16-
<PAGE>

ANALYSIS OF COMPARABLE PUBLIC AGRICULTURAL
BIOTECHNOLOGY COMPANIES (AS OF APRIL 28, 1998)

<TABLE>
<CAPTION>
    VALUATION MULTIPLES                        STOCK     PRICE VS.    MARKET               PRICE (B)/             FIRM    
                                                                               ----------------------------------
    (DELIVER IN MILLIONS, EXCEPT STOCK PRICE)  PRICE(S)  LTM HIGH      CAP.      1998 EPS  1999 EPS  2000 EPS(A)  VALUE (C) 
    ------------------------------------------------------------------------------------------------------------------------
    <S>                                        <C>       <C>          <C>        <C>       <C>       <C>          <C>
(d) AgriBioTech Inc. (ABTX)                    $14.38    (26.5%)      93.76       56.3x     22.8x      14.8x        85.40
(e) DEKALB (DKB)                                33.38    (54.4%)      1,155       42.2      29.3       23.4         1,265
    Delta and Pine Land (DLP)                   43.31    (19.8%)      1,648       65.6      42.1       32.1         1,774
(f) Empresas Ca. Modema (ELM)                   20.06     (2.3%)      2,308       20.5      20.1       13.2         1,681
    Monsando (MTC)                              54.31     (6.7%)     32,346       46.0      38.5       28.9        36,905
    Pioneer Hi-Bred (PHB)                       35.81     (7.2%)      8,747       31.5      25.5       21.3         8,266
(g) Vilmorin (RIN)                             100.15      9.4%         296       20.9      17.6       15.0           385
    ------------------------------------------------------------------------------------------------------------------------
    Median                                                                        42.3x     25.5x      21.3x
    Mean                                                                          40.4      28.8       21.2
    ------------------------------------------------------------------------------------------------------------------------
(h) Monday                                     $20.06    (21.6%)       $722        NM        NM         NM           $769

</TABLE>




<TABLE>
<CAPTION>
       FIRM VALUE/LTM     PROJECTED EPS GROWTH (B)     1999 PYE     2000 P/H
- ------------------------  ----------------------------------------------------
REVENUES   EBITDA    EBIT   2-YEAR        5-YEAR      5-YEAR CO.    5-YEAR CO.
- ------------------------------------------------------------------------------
<S>        <C>      <C>      <C>          <C>            <C>           <C> 
  1.2x     34.1x    38.7x     NM          30.0%          6.3x          0.5x
  2.7      20.0     26.0     44.3%        25.0%          1.2           0.9x
  9.2      46.3     54.9     56.1%        30.0%          1.4           1.1x
  1.8      20.7     39.6      2.0%        15.2%          1.3           0.9x
  4.9      22.1     31.2     20.5%        20.0%          1.9           1.4x
  4.6      18.4     23.1      NM          20.0%          1.3           1.1x
  1.1       8.9     11.6     18.6%        10.0%          1.8           1.5x
- ------------------------------------------------------------------------------
  2.7x     28.7x    31.3x                                1.3x          1.3x
  3.6      26.9     32.1                                 2.0           1.1
- ------------------------------------------------------------------------------
  3.6x      NM       NM       NM          22.5%          NM             NM

</TABLE>


Note: EBITDA, EBIT, Net Income to Common, and EPS adjusted for unusual and 
non-recurring items.
LTM: Latest Twelve Months as of 12/31/97.
NM: Not Meaningful
(a) Stock price as of April 24, 1998
(b) 2-Year EPS; IBES Estimated.
    5-Year growth: Salomon Smith Barney Estimates for ABTX, DKB, DLP, MTC, 
    and PHB (Wilbur). Long term growth for ELM, Monday, and RJN from IBES.
(c) Firms Value equals equity value (all fully diluted shares at the stock
    price less any option proceeds) plus straight debt, minority interest,
    straight preferred stock, all out-of-the-money convertibles, less 
    investments in unconsolidated affiliates and cash.
(d) Pro formas for announced acquisitions.
(e) Stock price as of January 17, 1998, 30 days prior to sale announcement.
(f) Sold major components of business. Pro formas financials (1997A) taken 
    from Merrill Lynch report (Andrews).
(g) Estimated for U.S. CAAP.
(h) Company estimates for EPS calculations.
(i) IBES Estimates, as if not available, calculated by growing 1999 EPS by 
    estimated 5 year growth.

                                                                        -17-
<PAGE>

ANALYSIS OF COMPARABLE PUBLIC AGRICULTURAL
BIOTECHNOLOGY COMPANIES (AS OF APRIL 28, 1998)

<TABLE>
<CAPTION>
                                                 LTM MARGINS                             LTM RETURN ON AVERAGE ASSETS  RETURN ON
                              ------------------------------------------------------    ------------------------------
    OPERATING MARGINS         GROSS PROFIT   SG&A    R&D    EBITDA    EBIT   NET INCOME    SALES    EBITDA    EBIT     LTM EQUITY
    ------------------------------------------------------------------------------------------------------------------------------
    <S>                       <C>            <C>    <C>     <C>      <C>        <C>         <C>     <C>      <C>          <C>
(a) AgriBioTech Inc. (ABTX)      19.8%        NA     NA      3.5%     3.1%        NA         NM      7.2%     6.3%         NM
    DEKALB (DKB)                 49.0%       25.2%  13.5%   13.5%    10.4%       6.9%       89.2%   12.1%     9.3%        15.8%
    Deka and Pinc Land (DLP)     36.1%       11.5%   7.9%   19.9%    16.7%      10.0%       84.6%   16.8%    14.2%        25.6%
(b) Empresas La Moderna (ELM)      NA         NA      NA     8.8%     4.6%      (3.1%)      39.0%    3.4%     1.0%         NM  
(c) Moneamo (MTC)                58.9%       29.2%  13.9%   22.2%    15.7%      11.2%       68.3%   15.2%    10.7%        21.6%
    Pioneer Hi-Bred (PHB)        56.8%       20.5%   8.6%   24.8%    19.8%      12.9%       78.6%   19.5%    15.5%        22.6%
(d) Vilmorin (RIN)               64.8%       30.4%    NA    12.5%     9.6%       4.2%       85.3%   10.7%     8.2%         9.9%
    ------------------------------------------------------------------------------------------------------------------------------
    Median                      52.9%       28.5%  11.9%   13.5%    10.4%       8.5%       81.6%   12.1%     9.3%        21.4%
    Mean                         47.6%       24.9%  10.9%   15.0%    11.4%       7.0%       74.2%   12.1%     9.4%        19.1%
    ------------------------------------------------------------------------------------------------------------------------------
    Monday                       40.3%       31.3%  12.4%   (6.8%)  (12.2%)    (13.3%)      77.0%    NM       NM           NM

</TABLE>


Note: EBITDA, EBIT, Net Income to Common, and EPS adjusted for unusual and 
non-recurring items.
LTM: Last Twelve Months.
(a)  Pro forma for announced acquisitions.
(b)  Sold major components of business. Pro forma financials 
     (1997A) taken from Merrill Lynch report (Andrews).
(c)  R&D reported as technological expense.
(d)  Estimated for U.S. GAAP.

                                                                        -18-

<PAGE>

DISCOUNTED CASH FLOW ANALYSIS (AS OF APRIL 28, 1998)

     THE QUALITY OF THE VALUATIONS DERIVED FROM DISCOUNTED CASH FLOW ANALYSES 
     ARE DEPENDENT ON THE QUALITY OF THE PROJECTIONS, THE DISCOUNT RATE, AND 
     TERMINAL VALUATION MULTIPLES UTILIZED.

          Two sets of projections have been discounted: (i) the Monday 
          projecitons (ii) the Base Case projections

          The seed and intellectual property operations have significantly 
          different risk profiles. As such, the results of these operations 
          should be discounted at different discount rates

          An important factor in DCF is the terminal, or exit valuation 
          multiple. Seed and intellectual property valuations are primarily 
          driven by EBITDA and revenue multiples

          Terminal value multiples have been adjusted to reverse variances 
          created from recent M&A transactions

                                                                          -19-
<PAGE>

DCF VALUATION SUMMARY (AS OF APRIL 28, 1998)

<TABLE>
<CAPTION>
                                                  $ PER SHARE
                                    4-YEAR PROJECTIONS      9-YEAR PROJECTIONS
                                       LOW       HIGH         LOW       HIGH
<S>                                    <C>       <C>          <C>       <C>

     MONDAY CASE
          Seed                         $6.07  -  $8.17        $6.86  -  $12.26
          Intell. Property              0.00  -   0.17         1.18  -    2.67
          NOL                           0.58  -   0.58         0.58  -    0.58
                                       _______________        ________________
          Equity Value                  6.65      8.92         8.62      15.51

     BASE CASE
          Seed                         $4.64  -  $6.38         $3.68  -  $6.96
          Intell. Property              0.00  -   0.00          0.82  -   2.06
          NOL                           0.57  -   0.57          0.57  -   0.57
                                       _______________         _______________
          Equity Value                  5.21      6.95          5.07      9.59
</TABLE>

                                                                           -20-
<PAGE>
DISCOUNT CASH FLOW ANALYSIS - SEED OPERATIONS
(AS OF APRIL 28, 1998)

DISCOUNTED CASH FLOW ANALYSIS OF THE SEED OPERATIONS BASED ON MONDAY(a) 
AND BASE CASE(b) PROJECTIONS GENERATED THE FOLLOWING VALUATION RANGES:

<TABLE>
<CAPTION>
MONDAY PROJECTIONS                                               BASE CASE PROJECTIONS
                          Terminal EBITDA Multiple Range                          Terminal EBITDA Multiple Range
                     12.0x    13.5x    15.0x    16.5x   18.0x                 12.0x    13.5x    15.0x    16.5x   18.0x
         WACC         Equity Value per share as of 9/1/98         WACC          Equity Value per share as of 9/1/98
<S>         <C>      <C>      <C>      <C>      <C>      <C>         <C>      <C>      <C>      <C>      <C>      <C>
4 Year      12.0%    $5.54    $6.47    $7.40    $8.34    $9.27       12.0%    $4.20    $4.97    $5.75    $6.52    $7.30
DCF         12.5%     5.42     6.33     7.25     8.17     9.08       12.5%     4.10     4.86     5.62     6.30     7.14
            13.0%     5.30     6.20     7.10     8.00     8.90       13.0%     4.00     4.79     5.50     6.25     6.99
            13.5%     5.18     6.07     6.95     7.83     8.72       13.5%     3.91     4.54     5.38     6.11     6.85
            14.0%     5.07     5.94     6.81     7.68     8.54       14.0%     3.82     4.54     5.26     5.98     6.70
</TABLE>


<TABLE>
<CAPTION>
                          EBITDA Perpetuity Growth Rate                            EBITDA Perpetuity Growth Rate
                     3.00%    4.00%    5.00%    6.00%    7.00%                3.00%    4.00%    5.00%    6.00%    7.00%
         WACC   Implied Equity Value per share as of 9/1/98         WACC   Implied  Equity Value per share as of 9/1/98
<S>         <C>      <C>      <C>      <C>      <C>      <C>         <C>      <C>      <C>      <C>      <C>      <C>
9 Year      12.0%    $8.40    $9.81   $11.64   $14.07   $17.48       12.0%    $4.62    $5.48    $6.59    $8.06   $10.12
DCF         12.5%     7.47     8.69    10.24    12.26    15.02       12.5%     4.06     4.80     5.73     6.96     8.63
            13.0%     6.66     7.72     9.04    10.74    13.00       13.0%     3.56     4.20     5.08     6.03     7.40
            13.5%     5.94     6.86     8.00     9.44    11.32       13.5%     3.12     3.68     4.37     9.24     6.36
            14.0%     5.32     6.10     7.09     8.32     9.90       14.0%     2.73     3.22     3.81     4.56     5.52
</TABLE>

Note: Number of Fully-Diluted Shares: 37.9mm. Net Debt as of 9/1/98
(a) Per Monday presentation to DAS Operating Committee - 12/97.
(b) Monday 12/97 presentation adjusted by DAS working group.


                                                                            -21-
<PAGE>

DISCOUNT CASH FLOW ANALYSIS - INTELLECTUAL PROPERTY OPERATIONS 
(AS OF APRIL 28, 1998)

DISCOUNTED CASH FLOWS ANALYSIS OF THE INTELLECTUAL PROPERTY OPERATIONS 
BASED ON MONDAY(a) AND BASE-CASE PROJECTIONS(b) GENERATED THE FOLLOWING 
VALUATION RANGES:


<TABLE>
<CAPTION>
MONDAY PROJECTIONS                                               BASE CASE PROJECTIONS
                          Terminal Revenue Multiple Range                          Terminal Revenue Multiple Range
                      6.0x      7.0x      8.0x     9.0x     10.0x                6.0x       7.0x       8.0x       9.0x   10.0x
         WACC         Equity Value per share as of 9/1/98         WACC          Equity Value per share as of 9/1/98
<S>         <C>       <C>       <C>       <C>      <C>      <C>         <C>      <C>        <C>        <C>        <C>       <C>
4 YEAR      15.0%    ($0.14)   ($0.02)    $0.11    $0.23    $0.35       15.0%    ($0.29)    ($0.18)    ($0.07)    $0.04     $0.15
DCF         17.5%     (0.17)    (0.05)     0.06     0.17     0.29       17.5%     (0.31)     (0.21)     (0.10)    (0.00)     0.10
            20.0%     (0.19)    (0.09)     0.02     0.12     0.23       20.0%     (0.32)     (0.23)     (0.13)    (0.04)     0.05
            22.5%     (0.21)    (0.11)    (0.02)    0.08     0.18       22.5%     (0.33)     (0.24)     (0.16)    (0.08)     0.01
            25.0%     (0.23)    (0.14)    (0.05)    0.04     0.13       25.0%     (0.34)     (0.26)     (0.18)    (0.10)    (0.03)
</TABLE>


<TABLE>
<CAPTION>
                          Terminal Revenue Multiple Range                          Terminal Revenue Multiple Range
                     6.0x     7.0x     8.0x    9.0x     10.0x                 6.0x    7.0x    8.0x    9.0x    10.0x
         WACC           Equity Value per share as of 9/1/98         WACC       Equity Value per share as of 9/1/98
<S>         <C>      <C>      <C>      <C>      <C>      <C>         <C>      <C>      <C>      <C>      <C>      <C>
9 Year      15.0%    $2.15    $2.56    $2.96    $3.37    $3.78       15.0%    $1.60    $1.95    $2.30    $2.65    $3.00
DCF         17.5%     1.66     2.00     2.33     2.67     3.01       17.5%     1.20     1.49     1.78     2.06     2.35
            20.0%     1.27     1.55     1.82     2.10     2.38       20.0%     0.88     1.11     1.35     1.59     1.83
            22.5%     0.95     1.18     1.41     1.65     1.88       22.5%     0.62     0.82     1.01     1.21     1.41
            25.0%     0.70     0.89     1.08     1.28     1.47       25.0%     0.41     0.57     0.74     0.90     1.07
</TABLE>

Note: Number of Fully-Diluted Shares: 37.9mm. Net Debt as of 9/1/98.
(a) Per Monday presentation to DAS Operating Committee - 12/97
(b) Monday 12/97 presentation adjusted by DAS working group.



                                                                          -22-




<PAGE>

PRECEDENT M&A TRANSACTIONS (AS OF APRIL 28, 1998)

THIS ANALYSIS UTILIZES THE VALUATION OF PRECEDENT TRANSACTIONS IN ORDER TO 
DETERMINE MONDAY'S PRIVATE MARKET VALUATION. HOWEVER, MANY OF THE 
TRANSACTIONS INVOLVE A CHANGE OF CONTROL, THEREFORE THE RELEVANCE TO THE 
MONDAY SITUATION SHOULD BE QUESTIONED. THE FOLLOWING FACTORS IMPACT THE 
EFFECTIVENESS OF THE EVALUATION:

- - Monday's lack of profitability

- - Few publicly disclosed transactions

- - Market position of target

- - Combination of seed and technology valuation

- - Control and non-control transactions

- - Wide range of valuation multiples

- - Differential between intellectual property and seed sector transaction 
  multiples

- - Recent transactions reflect increasing valuations for seed companies

(CONTINUED ON NEXT PAGE)


SALOMON SMITH BARNEY                                                       -23-
- --------------------
A MEMBER OF TRAVELERS GROUP

<PAGE>

PRECEDENT M&A TRANSACTIONS (AS OF APRIL 28, 1998)

WHEN VALUING MONDAY, WE CONSIDER BOTH SEED AND INTELLECTUAL PROPERTY DRIVEN 
AGRICULTURAL BIOTECHNOLOGY TRANSACTION MULTIPLES, ARRIVING AT DIFFERENT 
RESULTS. MONDAY'S INTELLECTUAL PROPERTY PORTFOLIO REPRESENTS A MORE 
SIGNIFICANT PORTION OF THE COMPANY'S VALUE THAN THE PERCENT OF TRAIT REVENUES.

PRECEDENT TRANSACTIONS ANALYSIS

<TABLE>
<CAPTION>
                                       Selected Range
                                       --------------
                                        Low      High
                                       ----     -----
- -----------------------------------------------------
<S>                                    <C>      <C>
LTM Revenues
  Seeds                                2.0x      3.0x
  Intellectual Property                6.0      10.0
- -----------------------------------------------------
</TABLE>

By examining the intellectual property component of Monday, and based on 
discussions with DAS management, we arrived at an intellectual property 
revenue weighting of between 5% and 20%.

BLENDED MULTIPLE ANALYSIS

<TABLE>
<CAPTION>
                                    Weight                Multiple                                       % of Value
                              ------------------     ------------------        Implied Equity        -------------------
                    Monday    Int. Prop.    Seed     Int. Prop.    Seed      Value Per Share (a)     Int. Prop.    Seed 
- ------------------------------------------------------------------------------------------------------------------------
<S>                 <C>       <C>           <C>      <C>           <C>       <C>                     <C>           <C>
LTM Revenues        $214.0       20%         80%        8.0x       2.5x            $19.89              45.0%       55.0%
                                 15%         85%        8.0        2.5              18.34              36.6%       63.4%
                                 10%         90%        8.0        2.5              16.79              26.7%       73.3%
                                  5%         95%        8.0        2.5              15.23              14.7%       85.3%
- ------------------------------------------------------------------------------------------------------------------------
</TABLE>
(a) Fully Diluted Shares Outstanding = 37.9 million. Net debt = $16.7 million.


SALOMON SMITH BARNEY                                                       -24-
- --------------------
A MEMBER OF TRAVELERS GROUP
<PAGE>

COMPARABLE M&A TRANSACTIONS (AS OF APRIL 28, 1998)

10 PRECEDENT TRANSACTIONS DRIVEN BY SEED VALUATIONS WERE IDENTIFIED:

<TABLE>
<CAPTION>
($ IN MILLIONS, EXCEPT PER SHARE AMOUNT)
                                                                    Transaction Details                   Acquisition Multiples
                                                       ---------------------------------------------   ---------------------------
                                                       Implied Enterprise
Date Ann.           Target               Acquiror             Value          Consideration             Sales    EBITDA       EBIT
- ----------  ---------------------  ------------------  -------------------   -----------------------   -----    ------      ------
<S>         <C>                    <C>                 <C>                   <C>                       <C>      <C>         <C>
* 04/20/98  Dinamilho Carol        Monday                      $28           N.A.                       2.3x      N.A.       N.M.
            Productos Agricolas

* 11/24/97  Agroceres (Brazil)     Monsanto                    230           N.A.                       2.1x      N.A.       N.A.

  09/16/97  Sunseed                AgrEvo                      N.A.          N.A.                       N.A.      N.A.       N.A.

  08/07/97  Pioneer Hi-Bred        DuPont                     8,570          $1,710 for 20%             4.8x     19.0x      23.6x

  12/12/96  Verneuil Holding       Monday                      N.A.          Purchased 18.75% of        N.A.      N.A.       N.A.
                                                                             Verneuil in exchange
                                                                             for Monday's European
                                                                             seed business

  10/01/96  Morgan Seeds           Monday                       27           Cash                       1.1x      N.A.       N.A.

  09/24/96  Asgrow                 Monsanto                    240           Cash                       N.A.      N.A.       N.A.
            Agronomics (Seminis)     

  05/21/96  Sure Grow Group        Delta & Pine Land            70           Stock                      N.A.      N.A.       N.A.
            
            
            
  03/11/96  Dekalb Genetics        Monsanto                    462           $1.52 for 10% of voting    1.3x     11.9x      16.8x
                                                                             stock, and 39% of non-
                                                                             voting stock
            
            
            
  02/21/95  Delta & Pine Land      Monday Plant                N.A.          N.A.                       N.A.      N.A.       N.A.
                                   Science
            
                                                                             ----------------------------------------------------
                                                                             Mean                      2.3x      15.5x      20.2x
                                                                             Median                    2.1x      15.5x      20.2x
                                                                             ----------------------------------------------------
</TABLE>

Source: Securities Data Company, Bloomberg News Services, and SEC filings.
Note: For private firms with undisclosed financial statements, Implied 
      Equity Value is assumed to be Implied Enterprise Value.
* Dow AgroSciences estimates.

(CONTINUED ON NEXT PAGE)


SALOMON SMITH BARNEY                                                       -25-
- --------------------
A MEMBER OF TRAVELERS GROUP
<PAGE>

COMPARABLE M&A TRANSACTIONS (AS OF APRIL 28, 1998) (CONTINUED)

12 PRECEDENT TRANSACTIONS DRIVEN BY INTELLECTUAL PROPERTY VALUATIONS WERE 
IDENTIFIED:

<TABLE>
<CAPTION>
($ IN MILLIONS, EXCEPT PER SHARE AMOUNT)
                                                                    Transaction Details                   Acquisition Multiples
                                                       ---------------------------------------------   ---------------------------
                                                       Implied Enterprise
Date Ann.          Target                Acquiror             Value          Consideration             Sales    EBITDA       EBIT
- ---------  ---------------------   ------------------  -------------------   -----------------------   -----    ------      ------
<S>        <C>                     <C>                 <C>                   <C>                       <C>      <C>         <C>
04/06/98   Seed breeding program   Phytogen Seed               N.A.          N.A.                       N.A.      N.A.       N.A.
                                   (Monday & J.G.
                                   Boswell)

01/06/98   Phytogen Cotton         Monday                      N.A.          $12 in cash, breeding      N.A.      N.A.       N.A.
                                                                             materials, licenses, 
                                                                             and patents

11/24/97   Mendel Biotechnology    Monsanto/ELM                $150          $30 in cash for 20%        N.A.      N.A.       N.A.
                                                                             

05/13/97   Mogen                   Zeneca                        75          N.A.                       11.7x     N.A.       N.A.

04/01/97   Calgene                 Monsanto                     594          $240 in cash for            3.0x     N.M.       N.M.
                                                                             remaining 45%

01/06/97   Holden                  Monsanto                   1,020          Purchase of Holden and     N.A.      N.A.       N.A.
                                                                             2 seed distributors

08/17/96   Plant Genetic Systems   Hoechst Schering             739          Purchase 75% of PGS        96.2x     N.A.       N.A.
           (PGS)                   AgrEvo                     
                                   
07/31/96   Calgene                 Monsanto                   1,077          $50 in cash for 5.7%       10.3x     N.M.       N.M.
                                                                             (and control)

04/08/96   Agraceius-Transgenic    Monsanto                     150          Cash                       N.A.      N.A.       N.A.
           Plant Business

01/29/96   DNA Plant Technology    Bionova (Empresas           N.A.          Contributes Bionova for    N.A.      N.A.       N.A.
                                   La Moderna)                               70% in new entity

06/28/95   Calgene                 Monsanto                    N.A.          Acq. of 49.9% stake for    N.A.      N.A.       N.A.
                                                                             $30 + contribution of
                                                                             patents and equity
                                                                             interest in Gargaulo

01/06/94   Monday Plant Science    Monday                      N.A.          $7 in cash + shares for    N.A.      N.A.       N.A.
                                                                             29.5% interest


                                                                             ----------------------------------------------------
                                                                             Mean(1)                    8.3x      N.A.       N.A.
                                                                             Median(1)                 10.3x      N.A.       N.A.
                                                                             ----------------------------------------------------
</TABLE>

Source: Securities Data Company, Bloomberg News Services, and SEC filings.
Note: For private firms with undisclosed financial statements, Implied 
      Equity Value is assumed to be Implied Enterprise Value
(1) Does not include outlier (PGS)


SALOMON SMITH BARNEY                                                       -26-
- --------------------
A MEMBER OF TRAVELERS GROUP


<PAGE>

VALUATION UPDATE
- - AS OF AUGUST 3, 1998









SALOMON SMITH BARNEY                                                     -27-
- --------------------
A MEMBER OF THE TRAVELERS GROUP

<PAGE>

OVERVIEW OF UPDATED VALUATION ANALYSIS
(AS OF AUGUST 3, 1998)


          THE RECENT MERGER ACTIVITY AND CONSOLIDATION OF THE SECTOR HAS PUT 
          UPWARD PRESSURE ON INDUSTRY VALUATION MULTIPLES.

          -  Comparable companies market prices reflect BOTH future financial 
             performance as well as anticipated acquisition premiums

          -  Recent precedent transactions are not readily comparable

               -  Targets achieved higher levels of profitability than Monday

               -  Targets had operational strengths beyond those of Monday 
                  (market share, distribution, international presence, and 
                  proven commercialization of technology)



SALOMON SMITH BARNEY                                                      -28-
- --------------------
A MEMBER OF THE TRAVELERS GROUP
<PAGE>

UPDATED SUMMARY OF PRELIMINARY VALUATION ANALYSIS
(AS OF AUGUST 3, 1998)


<TABLE>
                                                                          VALUE PER SHARE (IN DOLLARS)

  COMPARABLE PUBLIC COMPANIES ANALYSIS          $0.00      $5.00      $10.00      $15.00      $20.00      $25.00      $30.00 
                                                ----------------------------------------------------------------------------- 
  <S>                                           <C>        <C>        <C>         <C>         <C>         <C>         <C>
    Rev. Multiple with Minority Interests Acq.                    $9.64                             $19.25
      Premium
                                                ----------------------------------------------------------------------------- 
                                                                 ----------------
                                                                                                    Proposed Offer
    Discounted 2002 - Monday with Minority                 $5.98                  $13.12                 Price
      Interests Acq. Premium                                                                             $20.50
                                                                 ----------------

                                                           -------------
    Discounted 2003 - Base Case with Minority   $3.25                     $7.88
      Interests Acq. Premium
                                                           -------------
                                                ----------------------------------------------------------------------------- 
  DISCOUNTED CASH FLOW ANALYSIS
                                                                 -------
                       Monday 4 Yr.                        $6.65          $8.92
                                                                 ------- 

                                                                        ------------
                       Monday 9 Yr.                                $8.62             $15.51
                                                                        ------------ 
                                                ----------------------------------------------------------------------------- 
                                                             -----
                   Base Case  4 Yr.                     $5.21      $6.95
                                                             ----- 

                                                             --------------
                   Base Case  9 Yr.                     $5.07               $9.59
                                                             -------------- 
                                                ----------------------------------------------------------------------------- 
                                                                                              ---------------
Precedent Acquisition Transactions                                                      $18.76                $25.54
                                                                                              --------------- 
                                                ----------------------------------------------------------------------------- 
</TABLE>
(CONTINUED ON NEXT PAGE)

SALOMON SMITH BARNEY                                                      -29-
- --------------------
A MEMBER OF THE TRAVELERS GROUP
<PAGE>

UPDATED SUMMARY OF PRELIMINARY VALUATION ANALYSIS
(AS OF AUGUST 3, 1998) (CONTINUED)

<TABLE>

COMPARABLE PUBLIC COMPANY ANALYSIS                        VALUE RANGE
                                                        -------------- 
  <S>                                                   <C>
  Revenue Multiple ($8.03 - $14.81 with 20-30%          $9.64 - $19.25
  minority interests acquisition premium)

  Discounted 2002 EBITDA Multiple

    Monday Projections ($4.99 - $10.09 with 20-30%       5.98 -  13.12
    minority interests acquisition premium)

    Base Case Projections ($2.71 - $6.06 with 20-30%     3.25 -   7.88
    minority interests acquisition premium)

DISCOUNTED CASH FLOW ANALYSIS
  Monday - 4 Year Projections                            6.65 -   8.92
  Monday - 9 Year Projections                            8.62 -  15.51

  Base Case - 4 Year Projections                         5.21 -   6.95
  Base Case - 9 Year Projections                         5.07 -   9.59

PRECEDENT ACQUISITION TRANSACTIONS                      18.76 -  25.54
</TABLE>


SALOMON SMITH BARNEY                                                     -30-
- --------------------
A MEMBER OF THE TRAVELERS GROUP
<PAGE>

UPDATED COMPARABLE COMPANIES ANALYSIS
(AS OF AUGUST 3, 1998)



          SALOMON SMITH BARNEY ESTIMATES A PUBLIC MARKET VALUATION OF 1.5x TO 
          2.7x REVENUE, BASED UPON THE UPDATED ANALYSIS OF COMPARABLE 
          COMPANIES.  OTHER TRADITIONAL VALUATION MEASURES SUCH AS MULTIPLES 
          OF PROJECTED 1998/1999 EPS AND HISTORIC EBITDA MULTIPLES ARE NOT 
          MEANINGFUL DUE TO NEGATIVE FINANCIAL PERFORMANCE.


COMPARABLE COMPANY ANALYSIS

<TABLE>
                           SELECTED RANGE    IMPLIED EQUITY VALUE PER SHARE (a)   20% - 30% MINORITY ACQ. PREMIUM  
                           --------------    ----------------------------------   -------------------------------  
                 MONDAY    LOW       HIGH            LOW       HIGH                      LOW           HIGH
- -----------------------------------------------------------------------------------------------------------------  
<S>              <C>       <C>       <C>            <C>       <C>                       <C>           <C>
LTM Revenues     $214.0    1.5x      2.7x           $8.03     $14.81                    $9.64         $19.25
- -----------------------------------------------------------------------------------------------------------------  
</TABLE>

(a) Fully diluted Shares Outstanding = 37.9 million.  Net debt = $16.7 million.





SALOMON SMITH BARNEY                                                      -31-
- --------------------
A MEMBER OF THE TRAVELERS GROUP
<PAGE>

ANALYSIS OF COMPARABLE PUBLIC AGRICULTURAL
BIOTECHNOLOGY COMPANIES (AS OF AUGUST 3, 1998)

<TABLE>
VALUATION MULTIPLES                                                                        PRICE (a)/                   
(DOLLARS IN MILLIONS, EXCEPT STOCK PRICE)   FISCAL       STOCK     PRICE VS.  MARKET   ------------------     FIRM 
                                          YEAR ENDED   PRICE (a)   LTM HIGH     CAP.   1998 EPS  1999 EPS   VALUE (c)  
- ----------------------------------------------------------------------------------------------------------------------- 
<S>                                       <C>          <C>         <C>        <C>      <C>       <C>        <C>         
(d)  AgriBioTech and (ABTX)                  6/30       $18.00      (39.0%)   $  471      NM       58.4x     $   645    
     DEKALB (DKB)                            8/31        92.19       (5.9%)    3,219      NM       78.1        3,482    
     Delta and Pine Land (DLP)               8/31        44.94      (16.8%)    1,897      NM       43.6        1,978    
(e)  Empresas La Moderna (ELM)              12/31        26.00       (0.5%)    2,991     86.7x     65.0        2,399    
     Monsanto (MTC)                         12/31        56.43       (6.2%)   33,914     59.0      47.2       39,192    
     Monday                                  8/31        23.38       (8.3%)      847      NM        NM           988    
     Pioneer Hi-Bred (PHB)                   8/31        31.63      (25.9%)    7,640     30.1      24.1        7,442    
- ----------------------------------------------------------------------------------------------------------------------- 
     MEDIAN                                                                              55.0x     49.3x                
     MEAN                                                                                57.3      31.6                 
- ----------------------------------------------------------------------------------------------------------------------- 


                                      FIRM VALUE/LTM       PROJECTED EPS GROWTH (b)      1999 P/E    
- -----------------------------------------------------------------------------------------------------
                                 REVENUE   EBITDA    EBIT        1996-1997    3-YEAR    5-YEAR GT.
- -----------------------------------------------------------------------------------------------------
<S>                              <C>       <C>      <C>          <C>          <C>       <C>
(d)  AgriBio Tech and (ABTX)       1.4x     40.8x   46.2m            NM        30.0%       1.7m
     DEKALB (DKB)                  6.8      71.2     NM              NM        20.0%       3.9
     Delta and Pine Land (DLP)     9.8      60.2    74.7             NM        30.0%       1.5
(e)  Empresas La Moderna (ELM)     2.7      29.4    59.4            33.3%      15.2%       2.2
     Monsanto (MTC)                5.1      22.3    31.7            16.5%      20.0%       2.4
     Monday                        4.2       NM      NM              NM        22.5%        NM
     Pioneer Hi-Bred (PHB)         4.0      16.1    20.0            24.8%      26.0%       1.2
- -----------------------------------------------------------------------------------------------------
     MEDIAN                        4.3x     35.1x   46.8x                                  1.9x
     MEAN                          4.9      40.8    46.4                                   2.1
- -----------------------------------------------------------------------------------------------------


     OTHER DATA  
     ----------  
(f)  DEKALB (DKB)                            8/31     $ 33.38       (65.9%)  $ 1,165    49.8x      26.3x       1,407    
(g)  Delta and Pine Land )DLP)               8/31       47.00       (13.0%)    1,942      NM       45.6        2,067    
(h)  Monsanto (MTC)                         12/31       54.38        (9.9%)   32,567    52.8       43.3       37,742    
(i)  Monday                                  8/31       18.25       (28.4%)      662      NM        NM           705    
(j)  Vilmorin (RIN)                          7/30      108.84        (0.6%)      322    22.5       18.9          411    

(f)  DEKALB (DKB)                  2.8x     28.8x   42.2x            NM        20.0%       1.3x
(g)  Delta and Pine Land (DLP)    10.2      62.9    78.1             NM        30.0%       1.5
(h)  Monsanto (MTC)                4.9      21.5    30.5            16.5       20.0%       2.3
(i)  Monday                        3.2       NM      NM              NM        22.5%        NM
(j)  Vilmorin (RIN)                1.2       9.4    12.3            19.1%      12.0%       1.4
</TABLE>

Note:  EBITDA, EMT, Net income to Common, and EPS adjusted for unusual and 
       nonrecurring items.
LTM:   Latest Twelve Months.
NM:    Not Meaningful.
(a)  Stock price as of July 31, 1998.
(b)  1998-1999 EPS: IBES Estimates.
     5 Yr. growth: Salomon Smith Barney Estimates for ABTX (6/98), DKB (7/98), 
     MTC (4/98), and PHB (7/98). Long term growth for ELM, MYCO and RIN from  
     IBES
(c)  Firm Value equals equity value (all fully diluted shares at the stock 
     price less any option proceeds) plus straight debt monetary interest, 
     straight preferred stock, all out-of-the-money convertibles, less 
     investments in unconsolidated affiliates and cash.
(d)  Pro forma for amortized acquisitions.
(e)  Sold major components of business. Pro forma financials (1997 A) taken 
     from Merrill Lynch report (3/98)  1998E EPS taken from Merrill Lynch 
     report (3/98).
(f)  Stock price as of January 12, 1998, 30 days prior to sale announcement.  
     Excluded from mean and median calculations.
(g)  Stock price as of April 13, 1998, 30 days prior to purchase announcement.
     Excluded from mean and median calculations.
(h)  Stock price as of May 1, 1998, 30 days prior to merger announcement.  
     Excluded from mean and median calculations.
(i)  Stock price as of March 30, 30 days prior to Dow's announcement.  Excluded
     from mean and median calculations.
(j)  French GAAP.  Excluded from mean and median calculations as a non U.S. 
     traded company.


SALOMONSMITHBARNEY                                                       -32-
- --------------------
A MEMBER OF TRAVELERS GROUP

<PAGE>

ANALYSIS OF COMPARABLE PUBLIC AGRICULTURAL
BIOTECHNOLOGY COMPANIES (AS OF AUGUST 3, 1998)

<TABLE>
                                                        LTM MARGINS                          LTM RETURN ON AVERAGE ASSETS 
                               -----------------------------------------------------------   --------------------------- 
     OPERATING MARGINS         GROSS PROFIT   SC&A     R&D    EBITDA    EBIT    NET INCOME     SALES    EBITDA    EBIT
- ------------------------------------------------------------------------------------------------------------------------ 
<S>                            <C>            <C>     <C>     <C>     <C>       <C>           <C>       <C>       <C>
(d)  AgriBioTech and (ABTX)        19.8%       N/A      NA     3.5%     3.1%       NA           NM        7.2%     6.3%
     DEKALB (DKB)                  46.3%      74.8%   14.9%    9.6%     6.5%       4.3%        95.6%      9.2%     6.2%
     Delta and Pine Land (DLP)     33.0%      12.1%    7.9%   16.2%    13.1        6.8%        73.1%     11.9%     9.5%
(b)  Empresas La Moderna (ELM)     30.2%       9.4%    5.9%    9.3%     4.6%      (3.1%)       39.0%      3.6%     1.8%
(c)  Monsanto (MTC)                59.1%      29.7%   13.3%   22.9%    16.1%      10.8%        67.2%     15.4%    10.8%
     Monday                        39.3%      30.9%   12.6%   (9.9%)  (15.3%)    (16.8%)       72.1%       NM       NM
     Pioneer Hi-Bred (PHB)         57.2%      28.4%    8.6%   25.1%    20.2%      14.2%        89.4%     22.4%    18.1%
(d)  Vilmorin (RIN)                64.8%      30.4%     NA    12.5%     9.6%       4.2%        85.3%     10.7%     8.2%
- ------------------------------------------------------------------------------------------------------------------------ 
     MEDIAN                        42.8%      28.4%   10.6%   11.0%     8.1%       4.3%        73.1%     10.7%     8.2%
     MEAN                          43.7%      23.7%   10.5%   11.2%     7.3%       2.9%        74.5%     11.5%     8.7%
- ------------------------------------------------------------------------------------------------------------------------ 
</TABLE>

Note:  EBITDA, EBIT.  Net income to Common, and EPS adjusted for unusual and 
       nonrecurring items.
LTM:   Latest Twelve Months.
(a)  Pro forma for announced acquisitions.
(b)  Sold major components of business.  Pro forma financials (1997 A) taken 
     from Merrill Lynch report (Andrews).
(c)  R&D reported as technological expense.
(d)  French GAAP.



SALOMONSMITHBARNEY                                                       -33-
- --------------------
A MEMBER OF TRAVELERS GROUP

<PAGE>

PRECEDENT M&A TRANSACTIONS (AS OF AUGUST 3, 1998)

THERE HAVE BEEN 5 ANNOUNCED TRANSACTIONS SINCE OUR INITIAL VALUATION

PRECEDENT TRANSACTIONS ANALYSIS

<TABLE>
<CAPTION>
                                       Selected Range
                                       --------------
                            Monday     Low      High
- -----------------------------------------------------
<S>                         <C>        <C>      <C>
LTM Revenues                
  Seeds                     $214.0     2.5x      3.5x
  Intellectual Property      214.0     8.0      14.0
- -----------------------------------------------------
</TABLE>

By examining the intellectual property component of Monday, and based on 
discussions with DAS management, we arrived at an intellectual property 
revenue weighting of between 5% and 20%.

BLENDED MULTIPLE ANALYSIS

<TABLE>
<CAPTION>
                                   Weight            Multiple                                  % of Value
                             -----------------   -----------------                         ------------------
                                                                       Implied Equity
                    Monday   Int. Prop.   Seed   Int. Prop.   Seed   Value Per Share (a)   Int. Prop.   Seed
- -------------------------------------------------------------------------------------------------------------
<S>                 <C>      <C>          <C>    <C>          <C>    <C>                   <C>          <C>
LTM Revenues        $214.0      20%        80%     11.0x      3.0x         $25.54            48.3%      51.7%
                                15%        85%     11.0       3.0           23.28            39.7%      60.3%
                                10%        90%     11.0       3.0           21.02            29.3%      70.7%
                                 5%        95%     11.0       3.0           18.76            16.4%      83.6%
- -------------------------------------------------------------------------------------------------------------
</TABLE>
(a) Fully Diluted Shares Outstanding = 37.9 million. Net debt = $16.7 million.


SALOMONSMITHBARNEY                                                       -34-
- --------------------
A MEMBER OF TRAVELERS GROUP

<PAGE>

RECENT COMPARABLE M&A TRANSACTIONS (AS OF AUGUST 3, 1998)

5 PRECEDENT TRANSACTIONS TOOK PLACE AFTER DOW'S PROPOSAL

<TABLE>
<CAPTION>
($ IN MILLIONS, EXCEPT PER SHARE AMOUNT)
                                                                                 Transaction Details        Acquisition Multiples
                                                                               -----------------------   ---------------------------
                                                                                 Implied Enterprise
Date Ann.           Target         Business Description      Acquiror                   Value            Sales    EBITDA       EBIT
- ----------  ---------------------  --------------------  -------------------   -----------------------   -----    ------      ------
<S>         <C>                    <C>                   <C>                   <C>                       <C>      <C>         <C>
07/15/98    Plant Breeding Intl    Winter wheat seed     Monsanto                       $522             19.6x        NA          NA
            Cambridge              producer and plant
                                   breeding development

06/29/98    Cargill International  Corn, sunflower and   Monsanto                      1,400              4.7x        NA          NA
            seed businesses        grape seed producer

06/29/98    Hungnong and Choong    Vegetable seed        Seminis                          NA                NA        NA          NA
            Ang Seed               producers

06/29/98    LSL Biotechnologies    Enhanced shelf life   Seminis                          27                NA        NA          NA
                                   seed producer

05/11/98    Dekalb Genetics        Corn seed producer    Monsanto                      3,918              8.4x     61.8x       80.5x

05/11/98    Delta and Pine Land    Cotton seed producer  Monsanto                      1,944             10.1x     73.6x       95.2x
</TABLE>



SALOMONSMITHBARNEY                                                       -35-
- --------------------
A MEMBER OF TRAVELERS GROUP
<PAGE>

COMPARABLE M&A TRANSACTIONS (AS OF AUGUST 3, 1998)

10 PRECEDENT TRANSACTIONS DRIVEN BY SEED VALUATIONS WERE IDENTIFIED:

<TABLE>
<CAPTION>
($ IN MILLIONS, EXCEPT PER SHARE AMOUNT)
                                                                    Transaction Details                   Acquisition Multiples
                                                       ---------------------------------------------   ---------------------------
                                                       Implied Enterprise
Date Acq.           Target               Acquiror             Value          Consideration             Sales    EBITDA       EBIT
- ----------  ---------------------  ------------------  -------------------   -----------------------   -----    ------      ------
<S>         <C>                    <C>                 <C>                   <C>                       <C>      <C>         <C>
* 04/20/98  Dinamilho Carol        Monday                      $28           N.A.                       2.3x      N.A.       N.M.
            Productos Agricolas

* 11/24/97  Agroceres (Brazil)     Monsanto                    230           N.A.                       2.1x      N.A.       N.A.

  09/16/97  Sunseed                AgrEvo                      N.A.          N.A.                       N.A.      N.A.       N.A.

  08/07/97  Pioneer Hi-Bred        DuPont                     8,570          $1,710 for 20%             4.8x     19.0x      23.6x

  12/12/96  Verncuil Holding       Monday                      N.A.          Purchased 18.75% of        N.A.      N.A.       N.A.
                                                                             Verncuil in exchange
                                                                             for Monday's European
                                                                             seed business

  10/01/96  Morgan Seeds           Monday                       27           Cash                       1.1x      N.A.       N.A.

  09/24/96  Asgrow                 Monsanto                    240           Cash                       N.A.      N.A.       N.A.
            Agronomics (Seminis)     

  05/21/96  Sure Grow Group        Delta & Pine Land            70           Stock                      N.A.      N.A.       N.A.
            
            
            
  03/11/96  Dekalb Genetics        Monsanto                    462           $152 for 10% of voting     1.3x     11.9x      16.8x
                                                                             stock, and 39% of non-
                                                                             voting stock
            
            
            
  02/21/95  Delta & Pine Land      Monday Plant                N.A.          N.A.                       N.A.      N.A.       N.A.
                                   Science
            
                                                                             ----------------------------------------------------
                                                                             Mean                      2.3x      15.5x      20.2x
                                                                             Median                    2.1x      15.5x      20.2x
                                                                             ----------------------------------------------------
</TABLE>

Source: Securities Data Company, Bloomberg News Services, and SEC filings.
Note: For private firms with undisclosed financial statements, Implied 
      Equity Value is assumed to be Implied Enterprise Value.
* Dow AgroSciences estimates.

(CONTINUED ON NEXT PAGE)


SALOMON SMITH BARNEY                                                       -36-
- --------------------
A MEMBER OF TRAVELERS GROUP
<PAGE>

COMPARABLE M&A TRANSACTIONS (AS OF AUGUST 3, 1998) (CONTINUED)

12 PRECEDENT TRANSACTIONS DRIVEN BY INTELLECTUAL PROPERTY VALUATIONS WERE 
IDENTIFIED:

<TABLE>
<CAPTION>
($ IN MILLIONS, EXCEPT PER SHARE AMOUNT)
                                                                    Transaction Details                   Acquisition Multiples
                                                       ---------------------------------------------   ---------------------------
                                                       Implied Enterprise
Date Acq.          Target                Acquiror             Value          Consideration             Sales    EBITDA       EBIT
- ---------  ---------------------   ------------------  -------------------   -----------------------   -----    ------      ------
<S>        <C>                     <C>                 <C>                   <C>                       <C>      <C>         <C>
04/06/98   Seed breeding program   Phytogen Seed               N.A.          N.A.                       N.A.      N.A.       N.A.
                                   (Monday & J.G.
                                   Boswell)

01/06/98   Phytogen Cotton         Monday                      N.A.          $12 in cash, breeding      N.A.      N.A.       N.A.
                                                                             materials, licenses, 
                                                                             and patents

11/24/97   Mendel Biotechnology    Monsanto/ELM                $150          $30 in cash for 20%        N.A.      N.A.       N.A.
                                                                             

05/13/97   Mogen                   Zeneca                        75          N.A.                       11.7x     N.A.       N.A.

04/01/97   Calgene                 Monsanto                     594          $240 in cash for            3.0x     N.M.       N.M.
                                                                             remaining 45%

01/06/97   Holden                  Monsanto                   1,020          Purchase of Holden and     N.A.      N.A.       N.A.
                                                                             2 seed distributors

08/17/96   Plant Genetic Systems   Hoechst Schering             739          Purchase 75% of PGS        96.2x     N.A.       N.A.
           (PGS)                   AgrEvo
                                   
07/31/96   Calgene                 Monsanto                   1,077          $50 in cash for 5.7%       10.3x     N.M.       N.M.
                                                                             (and control)

04/08/96   Agraceius-Transgenic    Monsanto                     150          Cash                       N.A.      N.A.       N.A.
           Plant Business

01/29/96   DNA Plant Technology    Bionova (Empresas           N.A.          Contributes Bionova for    N.A.      N.A.       N.A.
                                   La Moderna)                               70% in new entity

06/28/95   Calgene                 Monsanto                    N.A.          Acq. of 49.9% stake for    N.A.      N.A.       N.A.
                                                                             $30 + contribution of
                                                                             patents and equity
                                                                             interest in Gargiulo

01/06/94   Monday Plant Science    Monday                      N.A.          $7 in cash + shares for    N.A.      N.A.       N.A.
                                                                             29.5% interest


                                                                             ----------------------------------------------------
                                                                             Mean(1)                    8.3x      N.A.       N.A.
                                                                             Median(1)                 10.3x      N.A.       N.A.
                                                                             ----------------------------------------------------
</TABLE>

Source: Securities Data Company, Bloomberg News Services, and SEC filings.
Note: For private firms with undisclosed financial statements, Implied 
      Equity Value is assumed to be Implied Enterprise Value.
(1) Does not include outlier (PGS)


SALOMON SMITH BARNEY                                                       -37-
- --------------------
A MEMBER OF TRAVELERS GROUP

<PAGE>

                                                                   CONFIDENTIAL
- -------------------------------------------------------------------------------










- -------------------------------------------------------------------------------
                                                        PRESENTATION TO DOW/DAS
                                                                 August 3, 1998








                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------
TABLE OF CONTENTS

          1.  Mycogen Business Unit - Key Drivers of Growth

          2.  Discounted Cash Flow Analysis - Process and Methodology

          3.  Results of DCF Valuation

          4.  Comparable Analysis

          5.  Conclusions

          6.  Appendix:

               A.  Summary of Financial Projections

               B.  Comparable Analysis





                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                      -2-
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                                       
                   ----------------------------------------


                           Mycogen Business Units - 
                             Key Drivers of Growth


                   ----------------------------------------




                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                      -3-
<PAGE>

MYCOGEN CORPORATION                                      MYCOGEN BUSINESS UNITS
- -------------------------------------------------------------------------------

OVERVIEW

BUSINESS DESCRIPTION

- -  A DIVERSIFIED AGRIBUSINESS AND BIOTECHNOLOGY COMPANY THAT DEVELOPS AND 
   MARKETS SEED FOR IMPROVED CROP VARIETIES AND PROVIDES CROP PROTECTION 
   SERVICES

BUSINESS SEGMENTS

- -  SEED SEGMENT -- PRODUCES AND MARKETS SEED FOR MAJOR AGRICULTURAL CROPS AND 
   USES BIOTECHNOLOGY AND TRADITIONAL AND MARKER-ASSISTED BREEDING TO DEVELOP 
   CROP VARIETIES WITH GENETICALLY ENHANCED PEST AND DISEASE RESISTANCE, 
   IMPROVED VEGETABLE OIL PROFILES AND OTHER VALUE-ADDED CHARACTERISTICS

   -  Mycogen Seeds ranks fourth in the U.S. in sales of seed corn, second in 
      hybrid sunflower seed sales and is among the top five in soybean, 
      sorghum and alfalfa sales

   -  Morgan Seeds ranks second in Argentina in seed corn sales and third in 
      hybrid sunflower seed sales

   -  Dinamilho holds a 10.2% share of Brazil's high-tech corn seed market 
      and 4% of Brazil's overall corn seed market. Three additional 
      acquisitions to close in 1998 will enhance Mycogen's position in this 
      attractive and growing market

- -  CROP PROTECTION SEGMENT -- MANUFACTURES AND MARKETS ENVIRONMENTALLY 
   COMPATIBLE SPRAY-ON BIOPESTICIDES. ALSO OPERATES SOILSERV, INC., A CROP 
   PROTECTION SERVICE FOR HIGH-VALUE CROPS

   -  Biopesticide Products -- based on natural agents, such as proteins and 
      fatty acid compounds, that have specific toxic activity on target 
      pests. The Company's Bt-based biopesticides use the Company's 
      proprietary Cellcap technology

   -  Soilserv -- monitors fields and uses customized equipment to apply pest 
      control products primarily in the Salinas Valley, CA and Yuma, AZ 
      regions

ALLIANCES

- -  VERNEUIL HOLDING, S.A. -- MYCOGEN HOLDS A 35% EQUITY STAKE IN VERNEUIL AND 
   ENTERED INTO AN AGREEMENT WITH VERNEUIL TO DEVELOP OILSEED PRODUCTS AND 
   INSECT RESISTANT CORN

- -  PIONEER HYBRID INTERNATIONAL -- 10-YEAR TECHNOLOGY COLLABORATION TO 
   DEVELOP INSECT RESISTANT TRAITS FOR CORN, SOYBEAN, CANOLA, SUNFLOWER, 
   SORGHUM AND WHEAT

- -  J.G. BOSWELL -- JOINT VENTURE TO DEVELOP PEST AND HERBICIDE RESISTANT 
   COTTON

HEADQUARTERS

- -  SAN DIEGO, CA


                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                      -4-
<PAGE>

MYCOGEN CORPORATION                                      MYCOGEN BUSINESS UNITS
- -------------------------------------------------------------------------------

KEY DRIVERS OF GROWTH

TECHNOLOGY AND COMPETITIVE POSITION

- -  BT TECHNOLOGY, A CORNERSTONE OF MYCOGEN'S COMMERCIAL FUTURE, IS THE BEST 
   PROVED METHOD FOR GENETICALLY IMPROVING SEED TRAITS

   -  Bt is the best characterized transgenic technology that has been 
      applied to genetically modify seed. Despite continuing environmental 
      concerns, Bt genes are expected to be present in nearly 50% of all 
      corn and 30% of all soybean seed by 2000

   -  Bt is a proven technology. Bt seeds have been shown to prevent insect 
      damage and lower insecticide costs in a manner that does not destroy the 
      natural ecological balance as chemical insecticides do

- -  MYCOGEN IS THE MARKET LEADER IN DEVELOPING NEW INSECTICIDAL AND HERBICIDAL 
   RESISTANCE TRAITS

   -  Mycogen is the undisputed leader in the identification and 
      characterization of new Bt and related insecticidal proteins

   -  Mycogen holds patents to over 100 Bt genes with specificities toward 
      over 40 groups of insects. Many of these genes are likely to have 
      commercial applications against chewing insects, piercing and sucking 
      insects, and even nematodes

   -  Mycogen has a strong IP position in a number of technologies capable of 
      improving the disease resistance and output characteristics of a variety 
      of crops. Additionally, use of the proven Ahlquist technology promises to 
      extend the use of Bt to include the attractive market for high-value 
      perennial crops such as vines, and orchards

- -  MYCOGEN'S INTELLECTUAL PROPERTY POSITION AND INTELLECTUAL CAPITAL IS AMONG 
   THE BEST IN THE AGROBIOTECH INDUSTRY

   -  Mycogen has one of the best molecular biology IP positions amongst 
      plant biotechnology companies. Mycogen's array of promoters, expression 
      cassettes, markers, and reporter gene libraries provides critical mass 
      to any third party in the arena

   -  Newer applications, such oral immunity, are promising and provide a 
      strong platform to pursue sizable commercial opportunities. These 
      technologies are likely to command a premium price from many interested 
      parties

   -  Mycogen's scientific and operating personnel represent a significant 
      asset to any interested party. However, increased spending by 
      competitors (such as Novartis as part of it's Plant Genome Initiative), 
      could hamper the retention of quality personnel at Mycogen

                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                      -5-
<PAGE>

MYCOGEN CORPORATION                                     MYCOGEN BUSINESS UNITS
- ------------------------------------------------------------------------------

KEY DRIVERS OF GROWTH

- -------------------
PRICING AND MARGINS
- -------------------

        -  TRAITS INTRODUCED INTO EXISTING SEED SALES ADD REVENUES AND 
           REQUIRE R&D EXPENSES BUT DO NOT REQUIRE A COMMENSURATE INCREASE 
           IN SG&A

           -  Seed traits are sold as a part of existing conventional seeds. 
              There is no additional SG&A expense and these traits essentially 
              add revenues that, net of R&D expenses, directly impact the 
              bottom line

           -  Bt Cotton seed hybrids, capable of conferring resistance to 
              common cotton pests, command a price 230% that of conventional 
              cotton seed despite having the same manufacturing cost

        -  PRICING FOR NEW TRAITS IS BASED ON CAPTURING A PORTION OF THE 
           INCREASED VALUE OF THE IMPROVED SEED TO END-USERS SUCH AS FARMERS 
           AND FOOD PROCESSORS

           -  Mycogen has developed pricing assumptions for traits in 
              development that are based on their ability to decrease growing 
              costs or increase value for end-users. Conservative estimates of 
              the portion of value captured by Mycogen, based on Mycogen's 
              business plan, have been applied in the accompanying projections

           -  Similar pricing assumptions can be found in reports of analysts 
              who follow the agrobiotech sector

- --------------
ADOPTION RATES
- --------------

        -  BIOTECH TRAITS ARE ASSUMED TO BE SOLD THROUGH EXISTING MYCOGEN 
           SEED DISTRIBUTION CAPABILITIES

           -  Consistent with the operating model assumptions, traits are 
              assumed to be primarily sold in Mycogen seed through Mycogen's 
              existing seed distribution network. The impact of additional 
              sales created as a result of add-on acquisitions, other than 
              those expected to close in 1998, have not been included

           -  In certain cases, where business judgment suggests opportunity, 
              additional sales have been shown through third-party channels. 
              However, these sales are recorded only after including a 
              substantial discount (11%-50%), and represent only a small 
              fraction of both Mycogen's sales and total third-party sales 
              (typically less than 5%)

        -  ADOPTION RATES FOR NEWLY INTRODUCED TRAITS ARE CONSERVATIVELY 
           MODELED BASED ON OBSERVED ADOPTION RATES FOR EXISTING BIOTECH 
           TRAITS

           -  Adoption rates for traits into existing Mycogen seed sales base 
              are modeled using the observed rate for adoption of existing Bt 
              seed strains. Current data suggest that adoption has been rapid 
              and there is reason to believe that the adoption rate is likely 
              to speed up rather than slow down

                                                     WASSERSTEIN PERELLA & CO.
- ------------------------------------------------------------------------------

                                    - 6 -
<PAGE>

MYCOGEN CORPORATION                                     MYCOGEN BUSINESS UNITS
- ------------------------------------------------------------------------------

KEY DRIVERS OF GROWTH

- ------------
MARKET SHARE
- ------------

        -  MYCOGEN SEEDS HAVE A STRONG PRESENCE IN THE U.S. MARKET FOR MAJOR 
           ROW CROPS

           -  Mycogen currently commands about 5.2% of the U.S. corn market

           -  Mycogen seeds are planted on nearly 10% of all U.S. farms, a 
              high trial rate which suggests an expansion of Mycogen's market 
              share

           -  Mycogen's existing network of breeding stations throughout the 
              U.S., Puerto Rico, Brazil and Argentina provides the necessary 
              diversity of seed germplasm to provide a year-round supply of 
              seed with desired maturity, standability, water requirements, 
              storage properties and other characteristics

        -  MYCOGEN'S MARKET SHARE IS EXPECTED TO RISE DRIVEN BY ITS LEADING 
           HIGH-YIELDING HYBRIDS

           -  Yield is a primary determinant of adoption. In a little over 
              three years, Mycogen's corn hybrids have become amongst the 
              highest yielding hybrids currently available (see graph overleaf)

           -  Recent market indicators show Mycogen gaining in market share 
              relative to competitors. With the planned continuation of 
              current efforts, this trend is highly likely to remain in place

                                                     WASSERSTEIN PERELLA & CO.
- ------------------------------------------------------------------------------

                                    - 7 -
<PAGE>

MYCOGEN CORPORATION                                     MYCOGEN BUSINESS UNITS
- ------------------------------------------------------------------------------

COMPETITIVE CHARACTERISTICS OF RECENT MYCOGEN CORN HYBRIDS (YIELD IN BUSHELS 
PER ACRE)

TRIAL 100-106 RM

<TABLE>
<CAPTION>

         <S>                        <C>
         Novartis MAX747            169
         NK4242CBR                  176
         Mycogen x27500             172
         P3730                      166
         Mycogen 2545               167
         Mycogen x28560             191
         Mycogen x28580             183
         DK493Bt                    180
         NK4640CBR                  187
         DK512                      177
         Novartis MAX88             166
         Mycogen 2598               190
         P35N05                     197
</TABLE>

TRIAL 108-114 RM

<TABLE>
<CAPTION>

         <S>                        <C>
         DK566Bt                    178
         P3489                      175
         Novartis MAX21             170
         DK580Bt                    178
         Mycogen 2717               203
         Mycogen G28730             198
         Mycogen 2722               182
         Mycogen 7059               179
         Novartis MAX454            161
         P34R06                     184
         Mycogen 2787               188
         P3335                      192
         Mycogen 2801               187
         Mycogen 7250               185
         NK6800CBR                  174
         P33A14                     212
         Golden H. H2530Bt          170
</TABLE>

- ----------
Data:  Bt Corn yield based on multiple independent Mycogen trials.

                                                     WASSERSTEIN PERELLA & CO.
- ------------------------------------------------------------------------------

                                    - 8 -
<PAGE>

MYCOGEN CORPORATION                                     MYCOGEN BUSINESS UNITS
- ------------------------------------------------------------------------------

KEY BUSINESS SEGMENTS

- -------------------
CONVENTIONAL SEED -
CORN AND SOYBEAN
- -------------------

        -  THE CONVENTIONAL SEED BUSINESS FORMS THE BASIS FOR DISTRIBUTION OF 
           MYCOGEN TRAITS AND PROVIDES IMMEDIATE CASH FLOW TO OFFSET R&D 
           EXPENDITURES

        -  CONVENTIONAL SEED BUSINESS VALUE IS CONCENTRATED WITHIN NORTH 
           AMERICA AND BRAZIL. THIS IS BECAUSE SEED BUSINESSES NEED A 
           CRITICAL MARKET SHARE (TYPICALLY AROUND 5%) BEFORE THEY CAN SHOW 
           POSITIVE NET INCOME. BOTH NORTH AMERICA AND BRAZIL HAVE REACHED 
           THIS CRITICAL MARKET SHARE

        -  CORN AND SOYBEAN ARE THE MAJOR CROPS PLANTED IN NORTH AMERICA AND 
           BRAZIL. THEY REPRESENT MOST OF THE REVENUE AND MOST OF THE FIXED 
           AND VARIABLE COSTS

- -----------------
CORN EARLY TRAITS
- -----------------


        -  MYCOGEN'S MARKET SHARE IN THE NORTH AMERICAN CORN MARKET AND THE 
           ATTRACTIVE GROWTH PROSPECTS FOR MYCOGEN'S NEW CORN HYBRIDS PROVIDE 
           A STRONG BASE TO PROPEL SALES OF EARLY TRAITS

        -  MYCOGEN'S EXPERIENCE WITH TRANSFORMING CORN AND GAINING SUITABLE 
           EXPRESSION OF TRANSGENIC BT PROVIDES A COMPETITIVE ADVANTAGE IN 
           THE INTRODUCTION OF NEW BT-BASED EARLY TRAITS

- ---------------------
SOYBEAN OUTPUT TRAITS
- ---------------------

        -  IMPROVED SOYBEAN NUTRITIVE CONTENT WILL RESULT IN SOYBEAN FARMERS 
           AND PROCESSORS PAYING SIGNIFICANT PREMIUMS FOR SEED

           -  Soybean processing for food additives and protein 
              supplements/substitutes is a large and growing industry. Feed 
              is the primary driver of soybean value. There is significant 
              potential to increase soybean nutritive content (e.g. protein, 
              amino acid composition and processing characteristics) that 
              will significantly increase value for end-users

           -  Mycogen has access to various technologies, including 
              proprietary technologies from Demeter, that are capable of 
              improving soybean nutritive content. The potential for higher 
              prices from sales into Mycogen and third-party channels is a 
              significant source of value


                                                     WASSERSTEIN PERELLA & CO.
- ------------------------------------------------------------------------------

                                    - 9 -

<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------


                            
                       ---------------------------------
                                 DCF ANALYSIS-
                            PROCESS AND METHODOLOGY
                       ---------------------------------



                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                    -10-
<PAGE>

MYCOGEN CORPORATION                          VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
FINANCIAL PROJECTION METHODOLOGY

- -  THE SPECIAL COMMITTEE OF THE BOARD OF DIRECTORS OF MYCOGEN HAS AUTHORIZED 
   WP&CO. TO UNDERTAKE A COMPREHENSIVE REVIEW OF MYCOGEN'S PRODUCTS AND 
   DEVELOPMENT PORTFOLIO

- -  WP&CO. HAS CONDUCTED LENGTHY DUE DILIGENCE VISITS AND REVIEWED THE 
   FOLLOWING INDUSTRY AND COMPANY DOCUMENTS

   -  Company financial projections and business unit plans - current 
      projections, primarily based on existing Bt traits and the conventional 
      seed business. Also, strategic plans for all major business units, 
      including startup plans for businesses based on early stage technologies 
      and promising IP platforms

   -  Company and Competitor Financial Publications - Company/analyst 
      estimates for comparable operating ratios and projections 

   -  R&D Gap Analysis and Independent Committee Documents - Internal 
      management and scientific expert review of company strategy, R&D 
      portfolio, including early stage pipeline, IP portfolio, and required 
      funding levels to support various programs 

   -  Mycogen Partners Presentations: presentations by Mycogen partners 
      specifically relating to joint ventures. These include AC Humko, 
      Verneuil Mycogen, Morgan Seeds and Dinamilho

   -  Dow Presentations and Valuations: Analysis and valuation models built 
      by Dow in collaboration with Mycogen with respect to potential Mycogen 
      opportunities. Includes Dow Argentina opportunity analysis, Phytogen JV 
      analysis and the Dow/RCW Consultores Brazil market analysis

   -  Industry Research Reports: Proprietary industry reviews containing 
      information on competitor offerings, growth and market share. These 
      include Doane Marketing Research "Report on U.S. Farm Seed Study", 
      National Corn Growers Association reports, Context Consulting "Report 
      on Biotech Traits" and Negocios e Mercados "Report on Brazilian Seed 
      Market" 

   -  Presentations by and interviews with senior management, Special 
      Committee members, key research personnel, operating management 
      including business unit managers and sales staff and outside academic 
      specialists

- -  BASED ON INFORMATION COLLECTED FROM THESE SOURCES, WP&CO. AND MYCOGEN 
   MANAGEMENT MODIFIED COMPANY PROJECTIONS AS NECESSARY TO DEVELOP A SINGLE 
   SET OF FINANCIAL PROJECTIONS FOR THE 1998-2007 PERIOD BY BUSINESS SEGMENT. 
   THESE PROJECTIONS ARE THE BASIS FOR THE VALUATIONS DESCRIBED IN THE 
   SECTION "RESULTS OF DCF VALUATION"

- -  THESE PROJECTIONS INCLUDE THE IMPACT OF THREE PENDING ACQUISITIONS IN 
   BRAZIL. ALTHOUGH THE COMPANY'S CURRENT BALANCE SHEET DOES NOT REFLECT THE 
   COST OF THESE ACQUISITIONS, OUR BALANCE SHEET HAS INCLUDED THE INCREASE IN 
   NET DEBT AS A RESULT OF THESE ACQUISITIONS. THERE ARE NO OTHER 
   ACQUISITIONS CONTRIBUTING TO THESE PROJECTIONS

- -  SYNERGIES THAT WOULD RESULT FROM COMBINATION OF MYCOGEN WITH A THIRD 
   PARTY, THAT WOULD USUALLY BE REALIZED THROUGH AN AUCTION PROCESS, HAVE NOT 
   BEEN INCLUDED IN THE CURRENT PROJECTIONS. SYNERGIES THAT WOULD BE EXPECTED 
   IN A COMBINATION WITH DOW HAVE ALSO NOT BEEN INCLUDED IN THE CURRENT 
   VALUATION OTHER THAN THE EFFICIENT USE OF NET OPERATING LOSSES (NOL'S)

                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                    -11-
<PAGE>

MYCOGEN                                      VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
FINANCIAL PROJECTION METHODOLOGY

<TABLE>
<CAPTION>
<S>                                       <C>
  ------------------------------                         -----------------------------
        10-YEAR PROJECTIONS                                     DETAILED BASIS
  ------------------------------                         -----------------------------
                                          ------------------------------------------------------
                                            - Includes demographic factors and regional 
        Target Crop Acreage                   analysis by crop
               X                            - Shifting planting patterns
                                          ------------------------------------------------------
                                          ------------------------------------------------------
 Market Penetration of Genetically          - Adoption value of Bt and output modified seed 
          Modified Seeds                    - Presence on farmer's fields     
               X                          ------------------------------------------------------
                                          ------------------------------------------------------
  Market Share of Mycogen Product           - Preferred penetration in existing base
               X                            - Access to partners with large share of new
                                              markets
                                          ------------------------------------------------------
  Mycogen Product Selling Price     
               =                          ------------------------------------------------------
                                            - Value capture based on improved              
                                              productivity and competitive advantage       
 Mycogen product Sales Projections        ------------------------------------------------------
               -                          ------------------------------------------------------
                                            - Costs reflect minimal additional COGS and          
                                              SGA for traits above those for conventional seed   
 Fixed and Variable Costs and Taxes         - R&D investment accelerated to ensure successful      
               +                              timing of products                                 
                                          ------------------------------------------------------
                                          ------------------------------------------------------
                                            - Based on current inventory and accounts payable/
Cash Flow Impact (-W.I. -CapEx + Dep.)        receivable trends
               =                      
                                            - Additional plant expenditure is dependent 
   Mycogen Product Free Cash Flow             on sales levels and existing capacity     
                                          ------------------------------------------------------

 ---------------------------------
      VALUATION METHODOLOGY
 ---------------------------------
</TABLE>

                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                    -12-
<PAGE>

MYCOGEN                                      VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
VALUATION METHODOLOGY


[GRAPH]


                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                    -13-
<PAGE>

MYCOGEN                                      VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
IMPLICATION OF PROJECTED GROWTH RATE - NORTH AMERICA EXAMPLE

<TABLE>
<CAPTION>
        -------------     --------------     ---------------                    ------------------
                              GROWTH             IMPLIED                              MARKET
            CROP               RATE               EBIT                                SHARE*
                                                MULTIPLE 
        -------------     --------------     ---------------                    ------------------
<S>                       <C>                <C>                          <C>
                                                                                                   13.6%
                                                                                                  -------
                                                                                3.4%
                                                                               ------

          Corn Input          5.0 - 6.5%          3.3 - 4.7x                ---------------------------------
                                                                                1997                2007



                                                                                                    3.9%
                                                                                                   -----
                                                                                  0%
          Soybean Output      5.0 - 6.5%          2.5 - 3.4x                ---------------------------------
                                                                                1997                2007



                                                                                                    10%
                                                                                                  -------

                                                                                  0%
          Disease Resistance  8.0 - 10.0%         1.5 - 3.1x                ---------------------------------
          (Share of Mycogen                                                     1997                2007
            Market)

</TABLE>

- --------------------
* Assumes that total market remains constant and revenues / customer are fixed.
                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                    -14-

<PAGE>

MYCOGEN CORPORATION                          VALUATION: PROCESS AND METHODOLOGY
- --------------------------------------------------------------------------------
ILLUSTRATIVE FINANCIAL PROJECTIONS - NORTH AMERICA SOYBEAN TRAIT EXAMPLE


- - MYCOGEN'S FINANCE GROUP IN COLLABORATION WITH INDIVIDUAL BUSINESS UNITS 
  PREPARED DETAILED FINANCIAL PROJECTIONS INCLUDING PRICING, PENETRATION AND 
  MARGIN ASSUMPTIONS. A SAMPLE OF THESE PROJECTIONS (FOR THE NORTH AMERICAN 
  SOYBEAN TRAIT BUSINESS) ARE INCLUDED ON PAGE 17-19

- - WP&CO. EXAMINED THESE PROJECTIONS AND IN CONSULTATION WITH MYCOGEN 
  MANAGEMENT MODIFIED THEM AS NECESSARY TO ENSURE CONSISTENCY WITH OVERALL 
  MARKET TRENDS AND AVAILABILITY OF REQUIRED DEVELOPMENT FUNDS. A SAMPLE OF 
  THE RESULTING PROJECTIONS ARE SHOWN ON PAGE 20.

  - Ensure pricing by geographies is comparable and market share of traits 
    is consistent with planned introduction of stacked traits 

  - Allow for pricing discounts where third party sales channels or 
    technology licenses are required

  - Relate necessary R&D spending to gap analysis conducted by scientific and 
    technical planning committee. R&D spending allocated to individual 
    product lines and independent business units where possible

  - Apply consistent operating assumptions to generate cash flows for 
    individual business units and corporate center

- - THE RESULTING 10-YEAR FINANCIAL PROJECTIONS (INCLUDING 1998) WERE USED TO 
  ESTIMATE THE VALUE OF EACH LINE OF BUSINESS. ASSUMPTIONS FOR EACH BUSINESS 
  UNIT WERE APPLIED SO AS TO BE CONSISTENT IN TERMS OF GROWTH RATES, EXPECTED 
  TERMINAL MULTIPLES AND RISK ADJUSTED DISCOUNT RATES. SAMPLE VALUATION 
  SUMMARIES FOR THE NORTH AMERICAN SOYBEAN TRAIT BUSINESS UNIT ARE SHOWN ON 
  PAGE 21


                                      -15-
<PAGE>

MYCOGEN CORPORATION                          VALUATION: PROCESS AND METHODOLOGY
- --------------------------------------------------------------------------------
RECONCILIATION OF PROJECTIONS - CURRENT ESTIMATES VERSUS PRIOR BUSINESS PLANS

- - TIMING: THE PREVIOUS VERSION OF THE MYCOGEN BOARD PLAN WAS PREPARED IN 
  AUGUST 1997, NEARLY ONE YEAR AGO

- - COMMERCIALIZATION EXPERIENCE AND SUCCESS: IN THE PAST YEAR, MYCOGEN HAS MET 
  SOLID SUCCESS IN THE COMMERCIALIZATION OF NEW HYBRIDS. THESE GAINS, 
  PRIMARILY IN DEVELOPING BREEDING PROGRAMS THAT GENERATE QUALITY GERMPLASM 
  AND ESTABLISHING DEALER AND PARTNER NETWORKS, ARE EXPECTED TO ACCELERATE 
  THE GAIN OF MARKET SHARE

  - Totally Managed Feedstuff (TMF) high-silage corn has been rapidly 
    accepted by farmers. As a result Mycogen has been able to sign agreements 
    with over 20 new distributors over the past ten months. This additional 
    market share will also translate into additional revenues for early, 
    output and disease resistance traits

  - Mycogen's new corn hybrids show yields comparable to the leading Pioneer 
    hybrids. As a result, Mycogen's prior estimates for corn seed sales in 
    the 2000-2007 period have been revised slightly upward

- - STRATEGY: MYCOGEN'S STRATEGY FOR THE SOUTH AMERICA MARKET HAS FORGED AHEAD

  - Mycogen has made three significant acquisitions in the Brazilian market 
    that strengthen its presence in this large market. These acquisitions 
    were not included in the prior business plans

  - Considerable improvement has been made in rationalizing customer accounts 
    in Argentina and Brazil. This is resulting in an improvement in margins 
    that has not been included in prior business plans

- - NON-CORE CROPS: SIGNIFICANT OPPORTUNITIES EXIST FOR BT TECHNOLOGY IN RICE, 
  TURF, ALFALFA AND OTHER CROPS. THESE OPPORTUNITIES WHILE NOT INCLUDED IN 
  PREVIOUS PROJECTIONS, ARE IN CURRENT PROJECTIONS

- - NEW TECHNOLOGIES: MYCOGEN HAS DEVELOPED NEW TECHNOLOGY PLATFORMS THAT ALLOW 
  IT TO AGGRESSIVELY PURSUE NEW OPPORTUNITIES IN OUTPUT TRAIT ENHANCEMENT AND
  PLANT DISEASE RESISTANCE

  - Demeter, Ahlquist and other transgenic technologies are powerful recent 
    additions to Mycogen's IP portfolio

  - New business opportunities presented by these technologies are sizable 
    but have not been included in previous business plans

  - With Mycogen's increasing experience in plant gene characterization and 
    expression as well as in breeding elite germplasm, Mycogen is highly 
    confident that these programs, if adequately funded, will generate 
    significant value

- - R&D SPENDING: THE PROJECTIONS USED HERE HAVE BEEN DEVELOPED WITH A 
  BOTTOM-UP APPROACH TO ESTIMATING R&D FUNDING REQUIREMENTS. BASED ON 
  SCIENTIFIC PERSONNEL ASSESSMENT OF BASIC RESEARCH (GENE CHARACTERIZATION, 
  PLANT TRANSFORMATION, OPTIMIZATION AND BREEDING) TRAIT-BASED SPENDING 
  REQUIREMENTS WERE ADDED TO THE TRADITIONAL "PERCENTAGE OF SALES" APPROACH. 
  OUR MORE CONSERVATIVE APPROACH PLACES THE R&D SPENDING IN 2007 AT $215 
  MILLION AS OPPOSED TO THE CURRENT BUSINESS PLAN ESTIMATE OF $68 MILLION


- --------------------------------------------------------------------------------

                                      -16-
<PAGE>

<TABLE>
<CAPTION>
                                       -------------------------------------------------------------------------------------------
                                                                  NORTH AMERICAN SEEDS
                                                                     SOYBEAN TRAITS
                                          1998     1999     2000      2001     2002     2003      2004     2005     2006     2007 
                                       -------------------------------------------------------------------------------------------
<S>                                    <C>       <C>      <C>       <C>       <C>      <C>       <C>      <C>      <C>      <C>
SOYBEAN TRAITS MARKETED MYCOGEN RETAIL
MYCOGEN UNITS IN THOUSANDS               1,635    1,700    1,921     2,229     2,674    3,209     3,851    4,621    5,776    7,221

LIBERTY HERBICIDE (THIRD PARTY)
Seed premium value capture per bag                       $  1.00   $  1.15   $  3.25  $  3.60  $  4.00   $  4.40  $  4.75  $  5.15
% of Market Share Penetrated                                  10%       15%       20%      20%      20%       20%      20%      20%
Liberty Revenue per year (000)                              $192      $384    $1,738   $2,311   $3,081    $4,067   $5,488   $7,437

ROUNDUP READY (THRU NOVARTIS)
Seed premium value capture per bag                       $  4.00   $  5.00   $  6.00  $  7.00  $  7.00   $  6.00  $  5.00  $  5.00
% of Market Share Penetrated                                  60%       80%       80%      80%      80%       70%      70%      60%
Bt cyst Revenue per year (000)                            $4,611    $8,914   $12,837  $17,971  $21,565   $19,409  $20,218  $21,662

BT CYST
Seed premium value capture per bag                                                             $  8.00  $  8.00   $  9.50  $  9.50
% of Market Share Penetrated                                                                         2%      10%       30%      50%
Bt Cyst Revenue per year (000)                                                                    $616   $3,697   $16,463  $34,298
                                       -------------------------------------------------------------------------------------------
   TOTAL REVENUE (000)                                   $4,803    9,299    $14,575  $20,282   $25,262  $27,173   $42,168  $63,397
                                       -------------------------------------------------------------------------------------------
                                       -------------------------------------------------------------------------------------------

</TABLE>

ASSUMPTIONS

BT CYST
Market opportunity = 46,000,000 bags
Soybean yields improve 15%
Mycogen retains 25% of increased yield value

LIBERTY HERBICIDE (THIRD PARTY)
Market opportunity = 9,200,000 bags
Liberty seed premium is 50% of RR tech + genetics
Mycogen retains 50% of Liberty seed premium
RR tech fee will increase $1/bag per year, RR genetic increase $.50/bag per 
year. Current tech fee $5/bag. RR genetics @ $2/bag

                                      -17-
<PAGE>


<TABLE>
<CAPTION>
                                       ------------------------------------------------------------------------------------------
                                                                           NORTH AMERICAN SEEDS
                                                                               SOYBEAN TRAITS

                                          1998     1999     2000     2001     2002     2003     2004     2005     2006     2007
                                       ------------------------------------------------------------------------------------------
<S>                                    <C>        <C>      <C>      <C>      <C>      <C>      <C>      <C>      
SOYBEAN TRAITS TO THIRD PARTIES    

LIBERTY HERBICIDE (THIRD PARTY)      
Seed premium value capture per bag                          $ -      $ -     $ 2.00   $ 2.00   $ 2.00   $ 2.00   $ 2.00   $ 2.00
 nites (000)                                                                   300      400      500      600      700      800
% of market Share Penetrated                                                     0%       0%       1%       1%       1%       1%
Liberty Revenue per year (000)                                                   $2      $3       $5       $8       $11      $14

BT CYST
Seed premium value capture per bag                                                             $ 5.00   $ 5.00   $ 5.00   $ 5.00
 Unites (000)                                                                                     200      400    1,000    1,500
% of Market Share Penetrated                                                                       0%       0%       1%       2%
Bt cyst Revenue per year (000)                                                                 $1,000   $2,000   $5,000   $7,500
                                       ------------------------------------------------------------------------------------------
  TOTAL REVENUE (000)                                         $0       $0        $2      $3    $1,005   $2,008   $5,011   $7,514
                                       ------------------------------------------------------------------------------------------
                                       ------------------------------------------------------------------------------------------
GENERTIC ROYALTIES
 Trait Related Genetic Royalties                                                900     1,200   2,100   3,000     5,100    6,900
 Non Trait Related Genetic Royalties        85      100       125      150      200       300     300     300       300      300
                                       ------------------------------------------------------------------------------------------
  TOTAL SUNFLOWER GENETIC ROYALTIES        $85     $100      $125     $150   $1,100    $1,500  $2,400  $3,300    $5,400   $7,200
                                       ------------------------------------------------------------------------------------------
                                       ------------------------------------------------------------------------------------------
</TABLE>




ASSUMPTIONS

BT CYST
Market opportunity = 46,000,000 bags
Soybean yields improve 15%
Royalts $5.00/bax

LIBERTY HERBICIDE (THIRD PARTY)
Market opportunity = 9,200,000 bags
Liberty seed premium is 50% of RR tech + genetics
Mycogen LibertyLink genetic royalty $2.00/bag
RR tech fee will increase $1/bag per year, RR genetic increase $.50/bag per 
year. Current tech fee $5/bag. RR genetics @ $2/bag

                                     -18-

<PAGE>

<TABLE>
<CAPTION>
                        -----------------------------------------------------------------------------------------------------------
                                                             NORTH AMERICAN SEEDS                                              

                         1998       1999       2000       2001       2002      2003       2004       2005        2006       2007
                        -----------------------------------------------------------------------------------------------------------
<S>                     <C>        <C>        <C>        <C>        <C>       <C>        <C>        <C>        <C>         <C>
Note: Sales refers to total soybean sales)
SOYBEAN RESEARCH
Sales Dollars           23,457    26,557      31,473     38,207     47,886    61,130     77,758     98,591     129,841     170,554
SOYBEAN % OF SALES
Hybrid Development
Line Development          3.7%      3.7%        5.1%       5.4%       8.9%      8.3%       7.8%       7.6%        6.9%        6.2%
Trait introgression       0.2%      0.2%        0.4%       0.6%       1.0%      0.9%       0.9%       0.8%        0.8%        0.7%
                        -----------------------------------------------------------------------------------------------------------
  Total %                 3.9%      3.9%        5.5%       6.0%       9.9%      9.2%       8.6%       8.4%        7.6%        6.9%
                        -----------------------------------------------------------------------------------------------------------
SOYBEAN DOLLARS
Hybrid Development           0         0           0          0          0         0          0          0           0           0
Line Development           865       978       1,591      2,075      4,255     5,066      6,031      7,479       8,910      10,617
Trait introgression         46        62         138        231        473       563        670        831         990       1,180
                        -----------------------------------------------------------------------------------------------------------
  Total Dollars            911     1,040       1,729      2,306      4,728     5,629      6,701      8,310       9,900      11,797
                        -----------------------------------------------------------------------------------------------------------
                        -----------------------------------------------------------------------------------------------------------
TOTAL R&D DOLLARS BY ACTIVITY
Hybrid Development       7,235     8,257      10,796     13,339     17,166    20,425     23,556     30,004      36,700      44,297
Line Development         3,353     4,003       5,198      7,261     10,916    12,988     14,336     17,811      21,197      25,241
Trait introgression        533       648       1,203      2,259      3,169     3,859      6,478      7,178       7,547       8,391
Other                      125       120         126        213        295       287        347        427         576         740
                        -----------------------------------------------------------------------------------------------------------
  Total                 11,246    13,028      17,323     23,072     31,546    37,559     44,717     55,419      66,021      78,669
                        -----------------------------------------------------------------------------------------------------------
                        -----------------------------------------------------------------------------------------------------------
TOTAL R&D DOLLARS BY CROP
Crn                      9,077    10,532      13,662     18,212     23,324    27,768     33,059     40,995      48,840      58,199
Soybeans                   911     1,040       1,729      2,306      4,728     5,629      6,701      8,310       9,900      11,797
Sunflowers               1,024     1,171       1,557      2,075      2,837     3,377      4,021      4,986       5,940       7,078
Sorghum                    109       165         249        266        362       498        589        701         765         855
Other                      125       120         126        213        295       287        347        427         576         740
  Total                 11,246    13,028      17,323     23,072     31,546    37,559     44,717     55,419      66,021      78,669
                        -----------------------------------------------------------------------------------------------------------
% of Sales Dollars         11%       11%         12%        13%        14%       14%        14%        14%         14%         13%
                        -----------------------------------------------------------------------------------------------------------
                        -----------------------------------------------------------------------------------------------------------
</TABLE>


                                     -19-
<PAGE>


MYCOGEN CORPORATION
- -------------------------------------------------------------------------------
N. AMERICA SOYBEAN/SORGHUM INPUT TRAITS REVENUES AND EXPENSES ($MM, EXCEPT PER 
UNIT PRICE AND UNITS IN 000S)

<TABLE>
<CAPTION>
                               1998     1999     2000     2001     2002     2003     2004     2005     2006     2007
                             -------- -------- -------- -------- -------- -------- -------- -------- -------- --------
<S>                          <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>
Soybean Market (MM Acres)         71       71       71       71       71       71       71       71       71       71
Mycogen Market (Acres)         1,257    1,308    1,478    1,714    2,057    2,469    2,962    3,555    4,443    5,554

LIBERTY HERBICIDE
Gross Price per acre                             $1.00    $1.15    $3.25    $3.60    $4.00    $4.40    $4,75    $5.15
% Mycogen Penetration                            10.0%    15.0%    20.0%    20.0%    20.0%    20.0%    20.0%    20.0%
   Net Revenues                 $0.0     $0.0     $0.2     $0.4     $1.7     $2.3     $3.1     $4.1     $5.5     $7.4
% Third Party Penetration-      0.0%     0.0%     0.0%     0.0%     0.5%     0.7%     0.9%     1.1%     1.3%     1.5%
   Revenues (@ 55% Disc.)       $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0
ROUNDUP READY (NOVARTIS)
Gross Price per acre           $0.00    $0.00    $4.00    $5.00    $6.00    $7.00    $7.00    $6.00    $5.00    $5.00
% Mycogen Penetration           0.0%     0.0%    60.0%    80.0%    80.0%    80.0%    80.0%    70.0%    70.0%    60.0%
   Net Revenue                  $0.0     $0.0     $4.6     $8.9    $12.8    $18.0    $21.6    $19.4    $20.2    $21.7
BT CYST
Gross Price per acre           $0.00    $0.00    $0.00    $0.00    $0.00    $0.00    $8.00    $8.00    $9.50    $9.50
% Mycogen Penetration           0.0%     0.0%     0.0%     0.0%     0.0%     0.0%     2.0%    10.0%    30.0%    50.0%
    Net Revenue                 $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.6     $3.7    $16.5    $34.3
% Third Party Penetration       0.0%     0.0%     0.0%     0.0%     0.0%     0.0%     3.7%     7.3%    18.3%    27.5%
    Revenues (@ 50% Disc.)      $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.1

Sorghum Market (Acres)         9,500   10,000   10,000   10,000   10,000   10,000   10,000   10,000   10,000   10,000
Mycogen Market (Acres)           855      969    1,024    1,096    1,160    1,304    1,416    1,555    1,696    1,896
HERBICIDE
Gross Price per acre           $0.00    $0.00    $0.00    $0.00    $0.00    $0.00    $0.00    $0.00   $35.00   $35.00
% Mycogen Penetration           0.0%     0.0%     0.0%     0.0%     0.0%     0.0%     0.0%     0.0%     2.0%    10.0%
    Net Revenues                $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.1     $0.8

TOTAL MYCOGEN REV.              $0.0     $0.0     $4.7     $9.1    $13.0    $18.2    $22.4    $23.3    $37.0    $57.0
TOTAL THIRD PARTY REV.          $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.1
                             -------- -------- -------- -------- -------- -------- -------- -------- -------- --------
    TOTAL TRAIT REVENUES        $0.0     $0.0     $4.7     $9.1    $13.0    $18.2    $22.4    $23.3    $37.1    $57.1
    R&D Expenses                 0.2      0.2      0.4      0.7      1.4      1.8      2.1      2.1      3.0      4.1
        % Sales                 --       --     8.9%     7.8%    11.1%    10.1%     9.3%     9.1%     8.1%     7.2%
     INCOME BEFORE TAX         ($0.2)   ($0.2)    $4.3     $8.4    $11.6    $16.3    $20.3    $21.2    $34.1    $53.0
     Tax @ 41.0%              0.0      0.0     (1.8)    (3.4)    (4.8)    (6.7)    (8.3)    (8.7)    (14.0)   (21.7)
                             -------- -------- -------- -------- -------- -------- -------- -------- -------- --------
     CASH FLOW                 ($0.2)   ($0.2)    $2.5     $4.9     $6.8     $9.6    $12.0    $12.5    $20.1    $31.2
</TABLE>

                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -20-

<PAGE>

MYCOGEN CORPORATION
- --------------------------------------------------------------------------------
N. AMERICA SOYBEAN/SORGHUM INPUT TRAITS DISCOUNTED CASH FLOW ANALYSIS

<TABLE>
<CAPTION>
- -------------                                       -----------------------------------
DISCOUNT RATE                                         YEAR 2007 CASH FLOW GROWTH RATE
- -------------                                       -----------------------------------
                                                     5.0%      5.5%      6.0%      6.5%
                                                    -----     -----     -----     -----
<S>                                                 <C>       <C>       <C>       <C>
        20.0%     PV of Free Cash Flow              $24.8     $24.8     $24.8     $24.8
                  PV of Terminal Multiple            35.3      36.7      38.2      39.8
                                                    -----     -----     -----     -----
                  Enterprise Value                  $60.1     $61.5     $63.0     $64.6
                  Less: Net Debt                      0.0       0.0       0.0       0.0
                                                    -----     -----     -----     -----
                  EQUITY VALUE                      $60.1     $61.5     $63.0     $64.6
                  IMPLIED PERPETUITY GROWTH           5.0%      5.5%      6.0%      6.5%
                    % VALUE FROM TERMINAL MULT.      58.8%     59.7%     60.7%     61.6%

        22.0%     PV of Free Cash Flow              $22.0     $22.0     $22.0     $22.0
                  PV of Terminal Multiple            26.4      27.3      28.3      29.4
                                                    -----     -----     -----     -----
                  Enterprise Value                  $48.4     $49.3     $50.3     $51.4
                  Less: Net Debt                      0.0       0.0       0.0       0.0
                                                    -----     -----     -----     -----
                  EQUITY VALUE                      $48.4     $49.3     $50.3     $51.4
                  IMPLIED PERPETUITY GROWTH           5.0%      5.5%      6.0%      6.5%
                    % VALUE FROM TERMINAL MULT.      54.6%     55.4%     56.3%     57.2%

        24.0%     PV of Free Cash Flow              $19.6     $19.6     $19.6     $19.6
                  PV of Terminal Multiple            20.1      20.7      21.4      22.1
                                                    -----     -----     -----     -----
                  Enterprise Value                  $39.7     $40.3     $41.0     $41.7
                  Less: Net Debt                      0.0       0.0       0.0       0.0
                                                    -----     -----     -----     -----
                  EQUITY VALUE                      $39.7     $40.3     $41.0     $41.7
                  IMPLIED PERPETUITY GROWTH           5.0%      5.5%      6.0%      6.5%
                    % VALUE FROM TERMINAL MULT.      50.6%     51.4%     52.2%     53.0%
                                      --------------------------------------------------
                                      SELECTED EQUITY VALUE RANGE    $40      -      $65
                                      --------------------------------------------------
</TABLE>


- -------------------------------------------------------------------------------
                                                      WASSERSTEIN PERELLA & CO.

                                       -21-
<PAGE>

MYCOGEN CORPORATION                         VALUATION: SUMMARY OF BUSINESS UNITS
- --------------------------------------------------------------------------------
ELEMENTS OF PROJECTED BUSINESS VALUATION

<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------
BUSINESS                CROP           TRAIT                          GEOGRAPHICAL REGION
- --------                ----           -----                          -------------------
                                                        N. AMERICA    ARGENTINA      BRAZIL     OTHER
- ---------------------------------------------------------------------------------------------------------
<S>                     <C>            <C>              <C>           <C>            <C>        <C>
Biopesticides             --             --                   X                                    

SoilServ                 --             --                   X                                    

Conventional Seed
                        Corn             --                   X             X           X          
                        Soybeans         --                   X                                    
                        Sunflower        --                   X                                    
                        Sorghum          --                   X                                    
                        Alfalfa          --                   X                                    

Early Traits (Herbicide Resistance)
                        Corn           RR/LL                  X             X           X          
                        Sunflower      RR/LL                                X                      
                        Soybean        LL                     X                                    
                        Sorghum        RR/LL                  X                                    

Early Traits (Insect Resistance)
                        Corn           Bt176                  X                         
                        Corn           Spodoptera                                       X          
                        Corn           Elasmopalpost                                    X          
                        Corn           Diabrotica                                       X          
                        Corn           Helicoverpa                                      X          
                        Corn           Armyworm                                                    
                        Corn           ECB/Glufosinate        X             X                      
                        Corn           CRW/Glufosinate        X             X                      
                        Sunflower      Looper                               X                      
                        Sunflower      Head Moth              X                                    
                        Sunflower      Seed Weevil            X                                    
                        Soybean        Cyst                   X                         X          
- ---------------------------------------------------------------------------------------------------------
</TABLE>

                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------

                                       -22-
<PAGE>

MYCOGEN CORPORATION                         VALUATION: SUMMARY OF BUSINESS UNITS
- --------------------------------------------------------------------------------
ELEMENTS OF PROJECTED BUSINESS VALUATION (CONT'D)

<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------
BUSINESS                CROP           TRAIT                          GEOGRAPHICAL REGION
- --------                ----           -----                          -------------------
                                                        N. AMERICA    ARGENTINA      BRAZIL     OTHER
- ---------------------------------------------------------------------------------------------------------
<S>                     <C>            <C>              <C>           <C>            <C>        <C>
                        Sorghum        Midge
                                       Greenbug Aphid
                        Alfalfa        Weevil
                                       Lepidoptera

Output                  Corn           High Oil               X             X           X
                                       High Oil/Evt. 176      X                         
                                       Hi Oleic               X             X           X
                                       Low Phytate            X             X           X
                                       Forage Protein         X             X           X
                                       Green Gene             X             X           X
                        Soybean        High Nutrition         X                         X
                        Sunflower      High Oleic             X
                                       High Palmitic          X
                                       Quality Protein        X             X
                        Sorghum        Nutritional            X

Disease Resistance
                        Corn           Mold/Mycototoxin                     X           X
                        Sunflower      Sclerotinia            X             X
                                       Verticilian                          X
- ---------------------------------------------------------------------------------------------------------
</TABLE>

                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------

                                       -23-
<PAGE>

MYCOGEN CORPORATION                         VALUATION: SUMMARY OF BUSINESS UNITS
- --------------------------------------------------------------------------------
ELEMENTS OF PROJECTED BUSINESS VALUATION (CONT'D)

<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------
BUSINESS                CROP           TRAIT                          GEOGRAPHICAL REGION
- --------                ----           -----                          -------------------
                                                        N. AMERICA    ARGENTINA      BRAZIL     OTHER
- ---------------------------------------------------------------------------------------------------------
<S>                     <C>            <C>              <C>           <C>            <C>        <C>
JV/Partner Royalties
                        VMO            Conventional                                             Europe
                                       Early Traits                                             Europe
                                       Output Traits                                            Europe
                        Cotton         Conventional           X             X
                                       Bud/Bollworm           X             X                   Australia
                                       Boll Weevil            X             X                     and
                                       Lygus                  X                                 Greece
                        Oilseed/Humko      --                 X             X
                        Oilseed/DAS        --                 X                                  
                        Rice           Stem Borer                                               Japan
                                       Plant Hopper                                             Japan
                        Turf           White Grub             X
                                       Army/Cutworm           X
                                       Webworm                X
- ---------------------------------------------------------------------------------------------------------

                  -------------------------------------------------------------------------------------
                         Products Valued (By Region)           38            19         14          7

                         Total Product Lines Valued            78
                  -------------------------------------------------------------------------------------

                  --------------------------------------------------
                         Conventional and Other                14

                         Early Traits                          33

                         Output Traits                         25

                         Disease Resistance                     5
                  --------------------------------------------------

</TABLE>

                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------

                                       -24-
<PAGE>

MYCOGEN CORPORATION







                    RESULTS OF DISCOUNTED CASH
                         FLOW VALUATION







                                                      WASSERSTEIN PERALLA & CO.
- -------------------------------------------------------------------------------

                                       -25-

<PAGE>

MYCOGEN CORPORATION              VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- -------------------------------------------------------------------------------
SUMMARY OF VALUATION

<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------------------------
                                            Discount     Growth Rate     Valuations                Geographic Sub-     Volume
Business            Crop       Region         Rate     /EBIT Multiple   Lo         Hi     Average     Total   Totals   Share
- ------------------------------------------------------------------------------------------------------------------------------------
<S>                <C>         <C>         <C>            <C>           <C>       <C>      <C>       <C>      <C>       <C>        
BIO-PESTICIDES       -           -         11.0%-14.0%       6 -  10    $    3    $    4   $    4    $    4   $    4    $0.09-$0.12
SOILSERV             -           -         11.0%-14.0%       6 -  10    $   28    $   40   $   34    $   34   $   34    $0.72-$1.02
CONVEN. SEED       Corn        N. America  12.0%-14.0%       8 -  12    $   94    $  210   $  152  
                               Agentina    12.0%-14.0%       8 -  12    $   37    $   34   $   47  
                               Brazil      12.0%-14.0%       8 -  12    $  101    $  175   $  138  
                   Soybeans    N. America  12.0%-14.0%       8 -  12    $  (10)   $   18   $    4  
                               Brazil      12.0%-14.0%       8 -  12    $    0    $    0   $    0  
                   Sorghum     N. America  12.0%-14.0%       8 -  12    $    9    $   15   $   12  
                   Alfalfa     N. America  12.0%-14.0%       8 -  12    $    3    $    9   $    6  
                   Sunflower   N. America  12.0%-14.0%       8 -  12       $(4)      $(4)     $(4) 
                               Argentina   12.0%-14.0%       8 -  12    $   14    $   22   $   18  
                   All         N. America  12.0%-14.0%       8 -  12    $   97    $  254             $  176             $2.51-$6.54
                               Argentina   12.0%-14.0%       8 -  12    $   49    $   79             $   64             $1.28-$2.02
                               Brazil      12.0%-14.0%       8 -  12    $  101    $  175             $  138             $2.62-$4.30
                                                                                  TOTAL CONVENTIONAL SEED     $  378
                                                                                 
EARLY/INPUT TRAITS                                                               
                   Corn        N. America  20.0%-24.0%    5.0% - 6.5%   $   72 -  $  126   $   99
                               Argentina   20.0%-24.0%    5.0% - 6.5%   $    1 -  $    5   $    3
                               Brazil      20.0%-24.0%    5.0% - 6.5%   $   29 -  $   53   $   41
                   Soybeans    N. America  20.0%-24.0%    5.0% - 6.5%   $   40 -  $   65   $   52
                               Brazil      20.0%-24.0%    5.0% - 6.5%      $(0)-  $    1   $    0
                   Sunflower   N. America  20.0%-24.0%    5.0% - 6.5%      $(1)-     $(1)     $(1)
                               Argentina   20.0%-24.0%    5.0% - 6.5%      $(0)-  $    2   $    1
                   All         N. America  20.0%-24.0%    5.0% - 6.5%   $  110 -  $  190             $  150             $2.85-$4.82
                               Argentina   20.0%-24.0%    5.0% - 6.5%   $    1 -  $    7             $    4             $0.02-$0.18
                               Brazil      20.0%-24.0%    5.0% - 6.5%   $   29 -  $   54             $   41             $0.74-$1.39
                                                                                       TOTAL EARLY TRAITS     $  195
                                                                               
OUTPUT TRAITS                                                                  
                   Corn        N. America  25.0%-30.0%    5.0% - 6.5%   $    7 -  $   17   $   12
                               Argentina   25.0%-30.0%    5.0% - 6.5%      $(2)-     $(2)     $(2)
                               Brazil      25.0%-30.0%    5.0% - 6.5%   $    5 -  $   11   $    8
                   Soybean     N. America  25.0%-30.0%    5.0% - 6.5%   $  144 -  $  266   $  205
                               Brazil      25.0%-30.0%    5.0% - 6.5%   $    7 -  $   14   $   11
                   Sunflower   N. America  25.0%-30.0%    5.0% - 6.5%   $    4 -  $    8   $    6
                               Argentina   25.0%-30.0%    5.0% - 6.5%   $   13 -  $   23   $   18
                   All         N. America  25.0%-30.0%    5.0% - 6.5%   $  156 -  $  291             $  223             $4.03-$7.47
                               Argentina   25.0%-30.0%    5.0% - 6.5%   $   11 -  $   21             $   16             $0.28-$0.55
                               Brazil      25.0%-30.0%    5.0% - 6.5%   $   14 -  $   27             $   20             $0.35-$0.70
                                                                                      TOTAL OUTPUT TRAITS     $  260
                                                                                 
DISEASE RESISTANCE                                                               
                               N. America  31.0%-50.0%    8.0% - 10.0%     $(2)-  $    0      $(1)      $(1)            $0.05-$0.00
                               Argentina   31.0%-50.0%    8.0% - 10.0%     $(0)-  $    2   $    1    $    1             $0.00-$0.04
                               Brazil      31.0%-50.0%    8.0% - 10.0%     $(0)-     $(0)     $(0)      $(0)            $0.01-$0.01
                                                                       TOTAL DISEASE RESISTANCE (CURRENT)     $(1)

                   All Other Crops         45.0%-50.0%    8.0% - 10.0%  $  119 -  $  154   $  136    $  136             $3.07-$3.96
                   Rice (Japan Tobacoo)    31.0%-50.0%    5.0% - 10.0%     $(2)-  $    2      $(0)      $(0)            $0.06-$0.04
                                                                         TOTAL DISEASE RESISTANCE (OTHER)     $  136

JV/ROYALTIES
    VMO            Conventional Seed       12.0%-14.0%       % - 10     $    7 -  $   10   $    9                       $0.18-$0.27
                   Early/Input Traits      20.0%-24.0%    5.0% - 6.5 %     $(1)-     $(2)     $(2)                      $0.04-$0.04
                   Output Traits           25.0%-30.0%    5.0% - 6.5 %  $    2 -  $    4   $    3                       $0.06-$0.11
                   Disease Res.            31.0%-30.0%    5.0% - 10.0%     $(0)-  $    0   $    0                       $0.00-$0.01
                                                             TOTAL VMO  $    8    $   14             $   11   $   11  
                                                                                                    
    JG BOSWELL     Cotton                  12.0%-14.0%       % -   12   $   59 -  $   86   $   73    $   73   $   73    $1.53-$2.22
                                                                                                    
    HUMKO          Oilseed     N. America  12.0%-14.0%       % -   10   $    0 -  $    0   $    0    $    0             $0.00-$0.00
                               Argentina   12.0%-14.0%       % -   10   $    2 -  $    3   $    2    $    2             $0.06-$0.07
                                                         TOTAL OTHER    $    0 -  $    0                      $    3    
                                                                                                    
    DAS CANADA     Canola                  20.0%-24.0%       % -   12   $   13 -  $   21   $   17    $   17   $   17    $0.33-$0.54
    PHB BT ROYALTIES                       20.0%-24.0%                  $   35 -  $   38   $   36    $   36   $   36    $0.89-$0.97
    OTHER PARTNER ROYALTIES                20.0%-24.0%    1.0% - 2.5%   $   14 -  $   21   $   17    $   17   $   17    $0.35-$0.54
    Other Pests/Crops                      31.0%-50.0%    5.0% - 6.5%   $   20 -  $  104   $   62    $   62   $   62    $0.53-$2.67
                                                                                 
MISCELLANEOUS(1)                                                                 
                                                                                 
      NOL-Current (est)                                                 $   80 -  $   80   $   80    $   80             $2.07-$2.06
      NOL-Projects (est)                                                $   31 -  $   31   $   31    $   31             $0.79-$0.78
      Monsanto Settlement (80%-100% Probability)                        $   82 -  $  103   $   92    $   92             $2.12-$2.64
      35% in Vermont (at cost)                                          $    9 -  $    9   $    9    $    9             $0.24-$0.24
      Bt Blocking (50% probability)        20.0%-14.0%                  $  111 -  $  131   $  121    $  121             $2.83-$3.36
      Litigation Expense (Net of Interest) 12.0%-14.0%                    $(37)-    $(36)    $(36)     $(36)            
      Net Debt                                                            $(75)-    $(75)    $(75)     $(75)            $1.94-$1.93
                                                                                                              $  222
                                                                        ------    ------   ------    ------   ------
TOTAL                                                                   $1,068    $1,823   $1,440    $1,448   $1,448
                                                                                                     

    Shares Outstand (MM)       36.26
    Options Outstand (MM)       3.59
Final Outstanding (Treasury Method, MM)                                  38.73     38.93    38.69     38.69

                                                          Value Share   $27.57    $46.84   $37.22    $37.42


- ------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Additional opportunities remaining to be quantified include biotech 
reagent and protocol licensed royalties and oral immunity.

Note:  Initial value excludes contribution from revenue synergies, cost 
savings, and other economies of scale from consolidation with DAS.  Value per 
share calculted based on outstanding common shares, includes 3.593 million 
outstanding options with an average exercise price of $12.03

                                                       Wasserstein Peralla & Co.
- --------------------------------------------------------------------------------




                                       -26-
<PAGE>
MYCOGEN                          VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- -------------------------------------------------------------------------------
VALUATION OF BUSINESSES (AVERAGE OF PROJECTED RANGE)


                                     [GRAPH]


                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -27-
<PAGE>

MYCOGEN CORPORATION                      VALUATION: PROBABILITY-WEIGHTED METHOD
- -------------------------------------------------------------------------------
PROBABILITY-WEIGHTED VALUATION METHODOLOGY

- -  AN ALTERNATIVE METHOD OF VALUATION, RATHER THAN VARYING THE DISCOUNT RATES 
   FOR VARIOUS PROJECTS, USES PROBABILISTIC WEIGHTING OF EVENTS WITH A 
   CONSTANT RISK-ADJUSTED COST OF CAPITAL

- -  INSTEAD OF USING VARIABLE DISCOUNT RATES FOR BUSINESSES TO REFLECT THE 
   VARYING ASSOCIATED RISK, THE RISK OF A GIVEN BUSINESS IS MADE EXPLICIT 
   THROUGH DEFINED GO/NO GO DECISION STAGES

   -  The development pipeline for new products is defined in terms of 
      discrete stages with associated cost requirements. Each stage is also 
      examined in terms of success rate of various categories of projects 
      through the relevant go/no go decision pointS

   -  Scientific expert opinion is collectively applied to estimate the 
      projected probability for successfully developing new projects. Early 
      stages receive a low probability due to scientific risks, and later 
      stages receive a higher probability due to commercialization risks

- -  THE RESULTING PRODUCT ATTRITION AND SPENDING PROFILES ARE APPLIED TO 
   ESTIMATE THE PROBABILITY THAT A GIVEN PROJECT WILL PASS THROUGH SUCCESSIVE 
   STAGES OF THE DEVELOPMENT PIPELINE UNTIL COMMERCIALIZATION. THESE 
   PROBABILITY-WEIGHTED EXPENSE AND REVENUE STREAMS ARE THEN USED TO ESTIMATE 
   THE FREE CASH FLOW AND ASSOCIATED VALUATION

- -  WP&CO. HAS LOWERED MANAGEMENT PROBABILITY ESTIMATES TO REFLECT EXECUTION 
   AND COMMERCIALIZATION RISK IN LIGHT OF SIZE AND FINANCIAL RESOURCES OF 
   COMPETITORS

<TABLE>
<CAPTION>
                                                MANAGEMENT          WP&CO. MODIFIED
                                                ----------          ---------------
                                                ESTIMATES              ESTIMATES
                                                ---------              ---------
<S>                                             <C>                 <C>

Early Traits                                      100%                    90%

Output Traits                                     100%                    81%

Disease Resistance                                100%                    72%
</TABLE>

                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -28-
<PAGE>

MYCOGEN CORPORATION                      VALUATION: PROBABILITY-WEIGHTED METHOD
- -------------------------------------------------------------------------------
PRODUCT ATTRITION PROFILE FOR PROBABILITY-WEIGHTED VALUATION METHOD

<TABLE>
<CAPTION>
    ------------          -------------             ------------------
    EARLY TRAITS          OUTPUT TRAITS             DISEASE RESISTANCE
    ------------          -------------             ------------------
<S>                       <C>                       <C>

       [GRAPH]               [GRAPH]                   [GRAPH]


</TABLE>


<TABLE>
<CAPTION>

   COST  ($/MM)              T-5       T-4       T-3       T-2       T-1        T=0
                           -------   -------   -------   -------  --------   (LAUNCH)
<S>                        <C>       <C>       <C>       <C>      <C>        <C>

ACTIVITIES
Gene characterization       $2.00     $0.5      $0.0
Expression/Screening                  $1.0      $0.5
Optimization                                    $0.5      $0.1
Event Breeding                                            $0.6      $0.6

</TABLE>

                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -29-
<PAGE>

MYCOGEN CORPORATION          VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- --------------------------------------------------------------------------------
SUMMARY OF VALUATION

<TABLE>
<CAPTION>
- ----------------------------------------------------------------------------------------------------------------------------
BUSINESS                CROP         REGION       DISCOUNT      GROWTH RATE       VALUATION               GEOGRAPHIC   SUB-
                                                    RATE      /EBIT MULTIPLE     LO       HI     AVERAGE     TOTAL    TOTALS
- ----------------------------------------------------------------------------------------------------------------------------
<S>                    <C>         <C>          <C>           <C>               <C>       <C>    <C>      <C>         <C>
BIOPESTICIDES             -             -       10.0% - 14.0%      6 -    10       $3 -     $5       $4         $4        $4
SOILSERV                  -             -       10.0% - 14.0%      6 -    10      $27 -    $41      $34        $34       $34
CONVEN. SEED  
                       Corn        N. America   11.0% - 14.0%      8 -    10      $95 -   $185     $140
                                   Argentina    11.0% - 14.0%      8 -    10      $37 -    $55      $46
                                   Brazil       11.0% - 14.0%      8 -    10     $112 -   $178     $145
                       Soybeans    N. America   11.0% - 14.0%      8 -    10     ($11)-     $9      ($1)
                                   Brazil       11.0% - 14.0%      8 -    10       $0 -     $0       $0
                       Sorghum     N. America   11.0% - 14.0%      8 -    10       $9 -    $14      $12
                       Alfalfa     N. America   11.0% - 14.0%      8 -    10       $3 -     $8       $5
                       Sunflower   N. America   11.0% - 14.0%      8 -    10      ($4)-    ($4)     ($4)
                                   Argentina    11.0% - 14.0%      8 -    10      $15 -    $22      $18
                       All         N. America   11.0% - 14.0%      8 -    10     $101 -   $221                $161
                                   Argentina    11.0% - 14.0%      8 -    10      $54 -    $81                 $68
                                   Brazil       11.0% - 14.0%      8 -    10     $112 -   $178                $145
                                                                                Total Conventional Seed                 $374
EARLY/INPUT TRAITS
                       Corn        N. America   11.0% - 14.0%   5.0% -  6.5%      $63 -   $150     $106
                                   Argentina    11.0% - 14.0%   5.0% -  6.5%       $1 -     $6       $4
                                   Brazil       11.0% - 14.0%   5.0% -  6.5%      $22 -    $56      $39
                       Soybeans    N. America   11.0% - 14.0%   5.0% -  6.5%      $72 -   $154     $113
                                   Brazil       11.0% - 14.0%   5.0% -  6.5%      ($0)-     $1       $0
                       Sunflower   N. America   11.0% - 14.0%   5.0% -  6.5%      ($2)-     $0      ($1)
                                   Argentina    11.0% - 14.0%   5.0% -  6.5%      ($0)-     $4       $2
                       All         N. America   11.0% - 14.0%   5.0% -  6.5%     $134 -   $305                $219
                                   Argentina    11.0% - 14.0%   5.0% -  6.5%       $1 -    $10                  $6
                                   Brazil       11.0% - 14.0%   5.0% -  6.5%      $22 -    $57                 $40
                                                                                     Total Early Traits                 $264
OUTPUT TRAITS
                       Corn        N. America   11.0% - 14.0%   5.0% -  6.5%       $6 -    $23      $14
                                   Argentina    11.0% - 14.0%   5.0% -  6.5%      ($1)-    ($0)     ($1)
                                   Brazil       11.0% - 14.0%   5.0% -  6.5%       $2 -     $9       $5
                       Soybeans    N. America   11.0% - 14.0%   5.0% -  6.5%     $110 -   $276     $193
                                   Brazil       11.0% - 14.0%   5.0% -  6.5%       $6 -    $16      $11
                       Sunflower   N. America   11.0% - 14.0%   5.0% -  6.5%       $3 -     $7       $5
                                   Argentina    11.0% - 14.0%   5.0% -  6.5%       $8 -    $18      $13
                       All         N. America   11.0% - 14.0%   5.0% -  6.5%     $120 -   $306                $213
                                   Argentina    11.0% - 14.0%   5.0% -  6.5%       $6 -    $18                 $12
                                   Brazil       11.0% - 14.0%   5.0% -  6.5%      $10 -    $27                 $18
                                                                                    Total Output Traits                 $243
DISEASE RESISTANCE
                                   N. America   11.0% - 14.0%   8.0% - 10.0%      ($2)-    $11       $4         $4
                                   Argentina    11.0% - 14.0%   8.0% - 10.0%       $1 -    $10       $6         $6
                                   Brazil       11.0% - 14.0%   8.0% - 10.0%      ($1)-    ($1)     ($1)       $(1)
                                                                      Total Disease Resistance (Current)                  $9

    Disease Resistance - All Other Crops        11.0% - 14.0%   5.0% -  6.5%      $86 -   $176     $131       $131
                       - Rice (Japan Tobacco)   11.0% - 14.0%   5.0% -  6.5%       $3 -    $14       $8         $8
                                                                        Total Disease Resistance (Other)                $139
JV/ROYALTIES
    VMO                Conventional Seed        11.0% - 14.0%      6 -    12       $7 -    $13      $10
                       Early/Input Traits       11.0% - 14.0%   5.0% -  6.5%      ($1) -   ($1)     ($1)
                       Output Traits            11.0% - 14.0%   5.0% -  6.5%       $2 -     $4       $3
                       Disease-Res.             11.0% - 14.0%   8.0% - 10.0%       $0 -     $4       $2
                                                                     TOTAL VMO     $8      $21                 $14       $14
    JG Boswell         Cotton                   11.0% - 14.0%      6 -    12      $51 -    $93      $72        $72       $72

    Humko              Oilseed     N. America   11.0% - 14.0%      8 -    10       $0 -     $0       $0         $0
                                   Argentina    11.0% - 14.0%      8 -    10       $2 -     $3       $2         $2
                                                                 TOTAL OILSEED     $0 -     $0                            $3
    DAS Canada         Canola                   10.0% - 14.0%      4 -    10      $19 -    $40      $29        $29       $29
    PHB B1 Royalties                            10.0% - 14.0%                     $43 -    $48      $46        $46       $46
    Other Partner Royalties                     11.0% - 14.0%   5.0% -  6.5%      $10 -    $22      $16        $16       $16
    Other Pests / Crops                         11.0% - 14.0%   5.0% -  6.5%     $137 -   $334     $236       $236      $236

MISCELLANEOUS(1)
        NOL-Current (est)                                                         $80 -    $80      $80        $80
        NOL-Projected (est)                                                       $28 -    $28      $28        $28
        Monsanto Settlement (80-100% Probability)                                 $82 -   $103      $92        $92
        35% in Verneuil (at cost)                                                 $9 -     $9       $9         $9
        Bt Blocking (50% probability)           11.0% - 14.0%                    $175 -   $203     $189       $189
        Litigation Expense (Net of Interest)    11.0% - 14.0%                    ($37)    ($35)    ($36)      ($36)
        Net Debt                                                                 ($75)    ($75)    ($75)      ($75)     ($75)
                                                                                                                        $363
                                                                              -------   -------  -------    -------   -------
TOTAL                                                                          $1,110   $2,125   $1,748     $1,763    $1,763
    Shares Outstand. (MM)   36.26
    Options Outstand. (MM)   3.59
FINAL OUTSTANDING (TREASURY METHOD, MM)                                        38.35    39.05    38.89      38.90

                                                            Value/Share      $28.93   $54.41   $44.96     $45.33
- ----------------------------------------------------------------------------------------------------------------------------
</TABLE>

(1)   Additional opportunities remaining to be quantified include biotech 
      reagent and protocol licensed royalties and oral immunity.
Note: Initial value excludes contribution from revenue synergies, cost savings,
      and other economies of scale from consolidation with DAS.
      Value per share calculated based on outstanding common shares, includes 
      3.593 million outstanding options with an average exercise price of $12.03

                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------

                                       -30-


<PAGE>

MYCOGEN CORPORATION
- ------------------------------------------------------------------------------


                  ------------------------------------------

                             COMPARABLE ANALYSIS

                  ------------------------------------------


                                                     WASSERSTEIN PERELLA & CO.
- ------------------------------------------------------------------------------

                                    - 31 -
<PAGE>

MYCOGEN CORPORATION                                        COMPARABLE ANALYSIS
- ------------------------------------------------------------------------------

COMPARABLE SEED COMPANIES

  DIAMOND  MYCOGEN'S VALUE IS A COMBINATION OF ITS CONVENTIONAL SEED BUSINESS 
           AND THE VALUE DERIVED FROM ACTIVITIES IN THE AGROBIOTECH AREA

  DIAMOND  MYCOGEN'S CONVENTIONAL SEED BUSINESS IS A VALUABLE ASSET BUT HAS NO 
           CLEAR SIMILARLY SIZED AND SCOPED COMPARABLES

           -  Within the past twelve months nearly every public U.S. seed 
              company has either been acquired or received a strategic 
              minority investment. As a result, these stocks trade based on 
              their pending acquisition or in the case of Pioneer and 
              AgriBiotech on speculation of some future transaction

           -  Publicly traded seed companies are a scarce asset. Private seed 
              companies appear to be an alternative to Mycogen, but most are 
              too small, with the larger companies operating as cooperatives 
              and limited in their ability to offer control to a third party

           -  Market share remains a key determinant of value, both because 
              of the critical effect of size in determining profitability and 
              the ability to drive adoption of new hybrids in the market. 
              However, a share of the larger market for major row crops, e.g. 
              corn and soybean, is more highly valued than similar shares in 
              other small crop segments

           -  While Mycogen's seed business is smaller than both Pioneer and 
              DeKalb Genetics, these are the most comparable businesses in 
              their leadership roles in seed distribution, germplasm quality 
              and commitment to R&D

  DIAMOND  OFFSETTING MYCOGEN'S SIZE RELATIVE TO SEED COMPETITORS IS ITS 
           CLEARLY SUPERIOR POSITION RELATIVE TO MOST COMPARABLE AGROBIOTECH 
           COMPANIES

           -  Mycogen has a technology and product development portfolio that 
              is comparable to larger competitors. Mycogen dominates the 
              attractive Bt market. Mycogen holds more than four times the 
              number of Bt patents held by its closest competitor

           -  Mycogen's network of alliances and licensing rights provide 
              ready access to a critical mass of biotech tools and 
              intellectual property. In addition, Mycogen has gained 
              exclusive access to certain highly attractive new growth 
              platforms such as Ahlquist technology for insect and disease 
              resistance and oral immunity through transgenic plants

  DIAMOND  MYCOGEN'S BIOTECH CAPABILITIES ARE UNIQUE. THERE IS NO COMPARABLE 
           PUBLIC COMPANY OF ANY SIZE. HOWEVER, A GOOD HISTORICAL COMPARABLE 
           IS PROVIDED BY PGS. THIS BUSINESS, WITH NO SALES, LARGE LOSSES AND 
           AN IP POSITION CONSIDERABLY WEAKER THAN MYCOGEN'S, WAS ACQUIRED BY 
           AGREVO FOR $733 MILLION


                                                     WASSERSTEIN PERELLA & CO.
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                                    - 32 -
<PAGE>

MYCOGEN CORPORATION                                        COMPARABLE ANALYSIS
- ------------------------------------------------------------------------------

COMPARABLE COMPANY ACQUISITIONS

  DIAMOND  THE RECENT ACQUISITION OF CARGILL'S INTERNATIONAL SEED BUSINESS 
           CONTRADICTS THE NOTION THAT LOSS-MAKING MYCOGEN DIFFERS FROM OTHER 
           COMPARABLE ACQUISITIONS SINCE OTHER COMPANIES ARE ALL PROFITABLE. 
           CARGILL'S LOSS-MAKING SEED BUSINESS (-$-20 MILLION IN 1997) WAS 
           RECENTLY ACQUIRED BY MONSANTO FOR $1.4 BILLION

  DIAMOND  THERE ARE NO COMPARABLE ACQUISITIONS OF SEED COMPANIES WITH A 
           SIMILAR MARKET SHARE AND PRESENCE IN CROP SEGMENTS TO MYCOGEN. 
           HOWEVER, THE ACQUISITION OF MINORITY STAKES IN PIONEER AND THE 
           ACQUISITION OF DELTA AND PINE LAND PROVIDE SOME SIMILARITY IN 
           TERMS OF CROP PRESENCE AND MARKET SHARE, RESPECTIVELY

  DIAMOND  DOW'S 68.8% OWNERSHIP OF MYCOGEN WAS BOUGHT AT AN AGGREGATE 
           ACQUISITION PRICE OF $16.78 PER SHARE. ALTHOUGH THE INITIAL 
           PURCHASE OF 4.45 MILLION SHARES FROM LUBRIZOL TOOK PLACE AT A 25% 
           PREMIUM TO THE MARKET, THE SUBSEQUENT SHARES PURCHASED BY DOW HAVE 
           BEEN ACQUIRED AT A MINIMAL PREMIUM (LESS THAN 5% IN AGGREGATE)

  DIAMOND  COMPARABLE "SQUEEZE-OUT" TRANSACTIONS IN THE BIOTECH INDUSTRY HAVE 
           REQUIRED PREMIUM TO THE CURRENT SHAREHOLDERS OF OVER 50%. 
           ACQUIRING THE REMAINING SHARES OF MYCOGEN IN THE RANGE OF THE 
           CURRENT VALUATION OR AT A SIMILAR PREMIUM TO THE MARKET WILL STILL 
           PROVIDE DOW WITH THE COMPLETE ACQUISITION OF MYCOGEN AT AN 
           AGGREGATE PURCHASE PRICE AT OR BELOW CURRENT TRADING VALUES


                                                     WASSERSTEIN PERELLA & CO.
- ------------------------------------------------------------------------------

                                    - 33 -
<PAGE>

MYCOGEN CORPORATION                                        COMPARABLE ANALYSIS
- ------------------------------------------------------------------------------


PREMIUM ANALYSIS - MONSANTO/DEKALB GENETICS

<TABLE>
<CAPTION>
                                                                                  Premium to Prior Price
                                                        ----------------------------------------------------------------------
                                         Price/
Annc. Date  Shares(3)  % Total  Cumm %   Share(3)        1-Day              1-Week             4-Weeks           8-Weeks
- ----------  --------   -------  ------   --------       ------              ------             -------           -------

<S>         <C>        <C>      <C>      <C>            <C>        <C>      <C>        <C>     <C>        <C>    <C>       <C>
 2/11/96      0.49      1.4%      1.4%   $ 10.83        $11.42     (5%)     $10.96     (1%)    $ 7.83     38%    $ 7.58    43%
 2/11/96      2.27      6.6%      8.0%   $ 10.83        $11.42     (5%)     $10.96     (1%)    $ 7.83     38%    $ 7.58    43%
 2/11/96     10.34     29.9%     37.8%   $ 11.83        $11.42      4%      $10.96      8%     $ 7.83     51%    $ 7.58    56%
   NA         0.71      2.1%     39.9%   $ 38.26 (4)
 5/9/98      20.81     60.1%    100.0%   $100.00        $74.13     35%      $69.50     44%     $70.81     41%    $70.19    42%
            ------
 TOTAL       34.61
</TABLE>


<TABLE>
<CAPTION>

                                               Weighted Avg.      Latest Acq.
                                               -------------      -----------
   <S>                                         <C>                <C>
   PURCHASE PRICE PER SHARE                         $  65.29         $ 100.00
   Shares Outstanding (2)                               36.3             36.3
                                                    --------         --------
   Aggregate Purchase Value                         $2,371.9         $3,632.7
   Net Debt (2/98)                                     110.0            110.0
                                                    --------         --------
   ADJUSTED AGGREGATE PURCHASE VALUE                $2,481.9         $3,742.7

   LTM Sales (2/98)                                 $  468.6         $  468.6
   ADJUSTED AGGREGATE PURCHASE VALUE/SALES             5.30x            7.99x
</TABLE>


- -------------------
(1)  Estimated based on analyst estimates and news articles
(2)  Represents common equivalent shares based on respective prices
(3)  Split adjusted
(4)  Estimated average share price. Specific dates were not available


                                                     WASSERSTEIN PERELLA & CO.
- ------------------------------------------------------------------------------

                                    - 34 -
<PAGE>
                                       
MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
PREMIUM ANALYSIS - DOW/MYCOGEN
<TABLE>
<CAPTION>
                          TOTAL % 
                       ---------------                                   PREMIUM TO PRIOR PRICE
                        PRE     POST                   ----------------------------------------------------------------
ANNC. DATE    SHARES   TRANS.   TRANS.   PRICE/SHARE      1-DAY          1-WEEK           4-WEEKS            8-WEEKS
- ----------    ------   ------   ------   -----------      ------         ------           -------            -------   
<S>           <C>      <C>      <C>      <C>           <C>            <C>              <C>               <C>

  1/15/96      4.45    18.1%     12.3%      $16.27     $16.00    2%   $14.25    14%    $13.88    17%     $13.00    25%
  1/15/96      9.50    38.6%     26.3%      $13.28     $16.00  (17%)  $14.25    (7%)   $13.88    (4%)    $13.00     2%
    1996       0.85     3.4%      2.3%      $17.21(1)
  12/3/96      1.00     4.1%      2.8%      $16.75     $16.75    0%   $16.75     0%    $15.75     6%     $14.38    17%
    1997       2.29     9.3%      6.3%      $23.20(2)
   1/9/98      0.48     2.0%      1.3%      $19.46     $19.25    1%   $19.13     2%    $19.75    (1%)    $19.94    (2%)
  1/16/98      3.76    15.3%     10.4%      $19.94     $18.75    6%   $19.13     4%    $19.13     4%     $19.88     0%
    1998       0.30     1.2%      0.8%      $19.48
  3/13/98      2.00     8.1%      5.5%      $20.06     $18.31   10%   $18.75     7%    $20.63    (3%)    $21.75    (8%)
              ------  ------    ------      ------
 Subtotal     24.63   100.0%     68.2%      $16.78
   Final      11.48              31.8%
              ------            ------
   Total      36.11             100.0%
</TABLE>
<TABLE>
<S>                                        <C>         <C>            <C>              <C>               <C>
ASSUMED FINAL PURCHASE PRICE/SHARE         $20.50      $25.00         $30.00           $35.00            $40.00

Cum. Wtd. Avg. Price                       $17.96      $19.39         $20.98           $22.57            $24.16
Shares Outstanding(3)                        37.9        38.4           38.8             39.0              39.2
                                           ------      ------         ------           ------            ------
Aggregate Purchase Value                   $681.6      $744.9         $813.5           $880.8            $947.4
Net Debt (2/98)                              13.7        13.7           13.7             13.7              13.7
                                           ------      ------         ------           ------            ------
ADJUSTED AGGREGATE PURCHASE VALUE          $695.2      $758.6         $827.1           $894.5            $961.1

LTM Sales (2/98)                           $214.0      $214.0         $214.0           $214.0            $214.0
ADJUSTED AGGREGATE PURCHASE VALUE/SALES     3.25x       3.55x          3.87x            4.18x             4.49x
</TABLE>

- ----------------------------
(1) Weighted average price of various open market purchases made during 1996
(2) Weighted average price of various open market purchases made during 1997
(3) Represents common equivalent shares based on respective purchase prices 
    for final share blocks


                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------


                                      -35-
<PAGE>
                                       
MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
PREMIUM ANALYSIS FOR BIOTECH ACQUISITIONS BY MAJOR SHAREHOLDERS(1)
<TABLE>
<CAPTION>
                                                                                             SELLER CLOSING PRICE/
                                                                                         PRE-ANN. ACQUISITION PREMIUM
                                                        ANN. DEAL   PER SHARE            ----------------------------
                                                ANN.      VALUE       ACQ.     % BEING     1-DAY    30-DAY    60-DAY
ACQUIROR            SELLER                      DATE      ($MM)       PRICE    ACQUIRED    PREM.     PREM.     PREM.
- --------            ------                      ----    -------     -------    --------   ------    ------    ------
<S>                 <C>                        <C>      <C>         <C>        <C>        <C>       <C>       <C>
Monsanto Co.        Calgene Inc. (Biotech)     1/28/97    242.6       $8.00      43.7%     45.5%     60.0%     45.5%

Novartis AG         SyStemix Inc. (Biotech)    5/27/96    119.4      $19.50      26.8%     77.3%     59.2%     48.6%

Monsanto Co.        DeKalb Genetics             5/9/98  3,426.2     $100.00     60.11%    34.91%    41.22%    42.47%
</TABLE>
- -------------------------------------------------------------------------------
<TABLE>
<S>                                                                              <C>      <C>       <C>       <C>
Mean                                                                             43.5%     52.5%     53.5%     45.5%

Median                                                                           43.7%     45.5%     59.2%     45.5%

Maximum                                                                          60.1%     77.3%     60.0%     48.6%

Minimum                                                                          26.8%     34.9%     41.2%     42.5%

Mycogen Corp. Data                                                                        $23.75    $23.25    $23.00

Implied Share Price Based on Median for Biotech Transactions                              $34.55    $37.01    $33.45

Implied Share Price Based on Median for Biotech Transactions                              $36.23    $35.68    $33.47
</TABLE>
- -------------------------------------------------------------------------------


- ----------------------------
(1) Source: Securities Data Company
Note: Unless noted, days referred to are calendar days.


                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------


                                      -36-
<PAGE>

MYCOGEN CORPORATION
- --------------------------------------------------------------------------------





                    -------------------------------------



                                 CONCLUSIONS



                    -------------------------------------





                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -37-
<PAGE>

MYCOGEN CORPORATION                                                  CONCLUSIONS
- --------------------------------------------------------------------------------
SUMMARY OF VALUATION RESULTS





<TABLE>
<CAPTION>
                                                          LOW     MEAN      HIGH
                                                          ---     ----      ----
<S>                                                     <C>      <C>        <C>

      DISCOUNTED CASH FLOW
              Variable Discount Rate                    $27.57              $46.84
              Probability-Weighted Method               $28.93              $54.41

      COMPARABLE TRADING COMPANIES(1)
              Premium of 10%, Implied Multiple: 5.5x             $31.06
              Premium of 30%, Implied Multiple: 5.8x             $32.92
              Premium of 50%, Implied Multiple: 6.2x             $34.78

      COMPARABLE ACQUISITIONS(2)
              Range with and without DKB(3)             $33.24              $38.85

     BIOTECH SQUEEZE OUT
     (Comparable Range of Premiums)
              Based on Current Price                    $32.04              $42.43
              Based on Price 60 Days Prior              $32.77              $34.17
</TABLE>





(1) Comparable Companies: Pioneer, DeKalb, Delta and Pine Land, and Agribiotech.
    Acquisition premiums only applied to sales multiples for Pioneer and
    Agribiotech.

(2) Comparable acquisitions included: DeKalb(60%)/Monsanto; Calgene
    (49.9%/Monsanto); Pioneer Hi-Bred(20%)/DuPont and Delta and Pine Land/
    Monsanto.

(3) Delta and Pine Land acquisition not directly comparable due to dominant DPL
    position in cotton market.

                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -38-
<PAGE>

MYCOGEN                                                              CONCLUSIONS
- --------------------------------------------------------------------------------
GRAPHICAL SUMMARY OF VALUATION RESULTS

METHOD
- ------

- - DISCOUNTED CASH FLOW
  - Variable Discount Rate                               [LINE GRAPH]
  - Probability-Weighted   


- - COMPARABLE TRADING COMPANIES
  (Premiums only apply to PHB and AgroBiotech)
  - Premium 10%                                          [LINE GRAPH]
  - Premium 30%
  - Premium 50%


- - COMPARABLE ACQUISITIONS
  - DKB, PHB, Calgen (49,9%)                             [LINE GRAPH]
    (with and without DPL)


- - BIOTECH SQUEEZE OUT
  (Range of Biotech Premiums)                            [LINE GRAPH]
  - Based on Current Price
  - Based on Price 60 Days Prior

                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -39-
<PAGE>

MYCOGEN                                                              CONCLUSIONS
- --------------------------------------------------------------------------------
IMPLIED AGGREGATE DOW PURCHASE PRICE FOR MYCOGEN

VALUATION APPROACH
- ------------------
- - VARIABLE DISCOUNT RATE          

- - PROBABILITY-WEIGHTED            

- - COMPARABLE TRADING/ACQUISITIONS 

- - BIOTECH SQUEEZE OUT             



IMPLIED AGGREGATE PURCHASE
- --------------------------
(REMAINING BLOCK PURCHASED AT ABOVE VALUATION)

- - VARIABLE DISCOUNT RATE         

- - PROBABILITY-WEIGHTED           

- - COMPARABLE TRADING/ACQUISITIONS

- - BIOTECH SQUEEZE OUT            


                                MYCO [$23.75]


                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -40-
<PAGE>

MYCOGEN CORPORATION
- --------------------------------------------------------------------------------





                        ------------------------------



                                   APPENDIX


                            A. SUMMARY FINANCIALS
                            B. COMPARABLE ANALYSES



                        ------------------------------






                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -41-
<PAGE>

MYCOGEN CORPORATION
- --------------------------------------------------------------------------------





                        ------------------------------



                              SUMMARY FINANCIALS



                        ------------------------------






                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -42-
<PAGE>

MYCOGEN CORPORATION               VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE INCOME STATEMENT PROJECTIONS ($MM)

<TABLE>
<CAPTION>

                             1998      1999      2000      2001      2002      2003      2004       2005        2006        2007
                            ------    ------    ------    ------    ------    ------    ------    --------    --------    --------
<S>                         <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>         <C>         <C>
Revenues                    $256.5    $298.5    $355.8    $418.5    $491.3    $575.7    $702.1    $1,057.6    $1,498.5    $2,026.7
  SoilServ                  $ 34.2    $ 33.4    $ 33.4    $ 33.4    $ 33.4    $ 33.4    $ 33.4    $   33.4    $   33.4    $   33.4
  Biopesticides             $  8.3    $  7.8    $  7.8    $  7.8    $  7.8    $  7.8    $  7.8    $    7.8    $    7.8    $    7.8
  Seeds                     $186.4    $221.0    $273.3    $330.1    $400.6    $483.9    $605.0    $  957.2    $1,393.6    $1,916.3
  VMO                       $  5.9    $  7.4    $  8.1    $  9.1    $ 10.2    $ 11.5    $ 17.0    $   20.5    $   25.2    $   30.7
  Oilseed                   $ 21.7    $ 28.8    $ 33.2    $ 38.1    $ 39.3    $ 39.1    $ 38.9    $   38.7    $   38.5    $   38.5
COGS                        $147.6    $175.3    $200.1    $226.8    $252.6    $278.7    $312.7    $  361.5    $  408.9    $  464.1
  SoilServ                  $ 22.0    $ 22.3    $ 22.3    $ 22.3    $ 22.3    $ 22.3    $ 22.3    $   22.3    $   22.3    $   22.3
  Biopesticides             $  4.5    $  4.9    $  4.9    $  4.9    $  4.9    $  4.9    $  4.9    $    4.9    $    4.9    $    4.9
  Seeds                     $ 96.3    $115.8    $135.9    $157.3    $180.9    $206.1    $239.3    $  287.1    $  333.3    $  387.2
  VMO                       $  3.9    $  4.9    $  5.4    $  6.1    $  6.8    $  7.6    $  8.5    $    9.6    $   10.7    $   12.0
  Oilseed                   $ 20.9    $ 27.5    $ 31.7    $ 36.3    $ 37.8    $ 37.8    $ 37.8    $   37.8    $   37.8    $   37.8
GROSS PROFIT                $109.0    $123.2    $155.7    $191.8    $238.7    $297.0    $389.4    $  696.1    $1,089.6    $1,562.6
SG&A                        $ 68.6    $ 81.6    $ 88.9    $ 95.7    $105.0    $114.1    $127.9    $  147.0    $  173.4    $  204.9
R&D                         $ 32.5    $ 45.5    $ 56.4    $ 64.5    $ 71.3    $ 77.1    $ 86.7    $  119.5    $  164.2    $  215.0
  SoilServ                  $  0.0    $  0.0    $  0.0    $  0.0    $  0.0    $  0.0    $  0.0    $    0.0    $    0.0    $    0.0
  Biopesticides             $  1.1    $  0.8    $  0.8    $  0.8    $  0.8    $  0.8    $  0.8    $    0.8    $    0.8    $    0.8
  Seeds                     $ 30.8    $ 44.0    $ 53.9    $ 60.8    $ 66.8    $ 72.7    $ 83.0    $  116.6    $  160.8    $  211.1
  VMO                       $  0.6    $  0.7    $  1.7    $  2.8    $  3.6    $  3.6    $  2.9    $    2.1    $    2.5    $    3.1
  Oilseed                   $  0.0    $  0.0    $  0.0    $  0.0    $  0.0    $  0.0    $  0.0    $    0.0    $    0.0    $    0.0
EBITDA                      $  7.9    $ (4.0)   $ 10.4    $ 31.5    $ 62.5    $105.8    $174.8    $  429.6    $  752.0    $1,142.7
Depreciation                $  4.5    $  5.1    $  6.0    $  7.0    $  8.1    $  9.3    $ 10.8    $   13.1    $   15.3    $   17.9
Amortization                $  1.3    $  1.3    $  1.3    $  1.3    $  1.3    $  1.3    $  1.3    $    1.3    $    1.2    $    1.2
                            ------    ------    ------    ------    ------    ------    ------    --------    --------    --------
EBIT                        $  2.0    $(10.5)   $  3.1    $ 23.2    $ 53.0    $ 95.2    $162.6    $  415.2    $  735.5    $1,123.6
Royalty and Venture Income  $ (4.1)   $ (5.0)   $ (4.8)   $ (2.7)   $  2.4    $ 12.0    $ 20.6    $   29.9    $   37.0    $   48.2
TOTAL OPERATING INCOME      $ (2.1)   $(15.5)   $ (1.7)   $ 20.5    $ 55.4    $107.1    $183.2    $  445.2    $  772.6    $1,171.9
LITIGATION EXPENSES         $(20.0)   $(15.0)   $(10.0)   $ (5.0)   $ (2.0)     (2.0)     (2.0)
INTEREST EXP./REV.          $ (2.8)   $ (7.6)   $(11.7)   $(15.4)   $(17.1)   $(15.5)   $(12.7)   $   (4.7)   $   12.2    $   38.4
PRE-TAX INCOME (TOTAL)      $(24.9)   $(38.0)   $(23.4)   $  0.0    $ 36.2    $ 89.6    $168.4    $  440.5    $  784.8    $1,210.3
Taxes (@ 41%)                  0.0       0.0       0.0      (0.0)    (14.9)    (36.7)    (69.1)     (180.6)     (321.7)     (496.2)
NOL Utilization                0.0       0.0       0.0       0.0      14.9      20.6       0.0         0.0         0.0         0.0
NET INCOME                   (24.9)    (38.0)    (23.4)      0.0      36.2      73.4      99.4       259.9       463.0       714.1
E.P.S. (38.73MM SHARES)     $(0.64)   $(0.98)   $(0.61)   $ 0.00    $ 0.94    $ 1.90    $ 2.57    $   6.71    $  11.95    $  18.44

</TABLE>

                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------


                                       -43-

<PAGE>

MYCOGEN CORPORATION              VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- -------------------------------------------------------------------------------
CORPORATE BALANCE SHEET PROJECTIONS ($MM)

<TABLE>
<CAPTION>
                               1998      1999       2000       2001       2002       2003      2004      2005      2006      2007
                              -------   -------    -------    -------    -------    -------   -------   -------  --------  --------
<S>                           <C>       <C>        <C>        <C>        <C>        <C>       <C>       <C>      <C>       <C>
Cash and Equivalents             $2.2      $2.2       $2.2       $2.2       $2.2       $2.2      $2.2     $41.6    $446.5  $1,091.2
Accounts Receivable             $59.7     $70.2      $82.9      $97.4     $112.9     $128.9    $149.7    $179.4    $209.0    $244.3
Inventories                     $65.9     $79.3      $92.2     $106.1     $121.2     $137.4    $158.2    $187.5    $216.6    $250.7
PP&E                           $105.0    $107.8     $115.1     $138.3     $147.0     $155.0    $186.4    $204.8    $214.8    $227.2
Intangibles                     $31.6     $30.3      $29.0      $27.6      $26.3      $24.9     $23.6     $22.3     $21.1     $19.9
Prepaid Expenses                $18.1     $18.1      $18.1      $18.1      $18.1      $18.1     $18.1     $18.1     $18.1     $18.1
                              -------   -------    -------    -------    -------    -------   -------   -------  --------  --------
TOTAL ASSETS                   $282.5    $307.8     $339.4     $389.7     $427.6     $466.4    $538.1    $653.6  $1,126.1  $1,851.4
                              -------   -------    -------    -------    -------    -------   -------   -------  --------  --------
                              -------   -------    -------    -------    -------    -------   -------   -------  --------  --------
Advances from DAS               $13.5     $13.5      $13.5      $13.5      $13.5      $13.5     $13.5     $13.5     $13.5     $13.5
Short-term Borrowings           $73.1    $131.5     $183.6     $230.9     $228.4     $188.5    $154.0      $0.0      $0.0      $0.0
A/P & Accruals                  $19.3     $24.2      $27.1      $30.1      $34.3      $39.6     $46.4     $65.5     $65.5     $76.7
Accrued Compensation             $6.1      $6.1       $6.1       $6.1       $6.1       $6.1      $6.1      $6.1      $6.1      $6.1
Deferred Revenues                $8.2      $8.2       $8.2       $8.2       $8.2       $8.2      $8.2      $8.2      $8.2      $8.2
Other Current Liabilities       $12.9     $12.9      $12.9      $12.9      $12.9      $12.9     $12.9     $12.9     $12.9     $12.9
TOTAL CURRENT LIABILITIES      $133.1    $196.5     $251.5     $301.7     $303.4     $268.8    $241.1     $96.7    $106.2    $117.4

Long-term Liabilities           $17.1     $17.1      $17.1      $17.1      $17.1      $17.1     $17.1     $17.1     $17.1     $17.1

Paid-In Capital                 0.031     0.031      0.031      0.031      0.031      0.031     0.031     0.031     0.031     0.031
Additional PIC                 $344.7    $344.7     $344.7     $344.7     $344.7     $344.7    $344.7    $344.7    $344.7    $344.7
Retained Earning (Deficit)    ($212.4)  ($250.5)   ($273.9)   ($273.9)   ($237.6)   ($164.2)   ($64.8)   $195.1    $658.1  $1,372.2
STOCKHOLDERS EQUITY            $132.3     $94.2      $70.8      $70.8     $107.1     $180.5    $279.9    $539.8  $1,002.8  $1,716.9
                              -------   -------    -------    -------    -------    -------   -------   -------  --------  --------
TOTAL S.H. EQUITY AND LIAB.    $282.5    $307.8     $339.4     $389.7     $427.6     $466.4    $538.1    $653.6  $1,126.1  $1,851.4
                              -------   -------    -------    -------    -------    -------   -------   -------  --------  --------
                              -------   -------    -------    -------    -------    -------   -------   -------  --------  --------
NET WORKING CAPITAL             $93.4    $112.4     $135.1     $160.5     $186.9     $213.8    $248.6    $298.0    $347.2    $405.5

NET ASSETS                     $198.5    $220.2     $250.1     $298.8     $333.9     $368.8    $435.0    $502.8    $562.1    $632.7

Net Operating Income           ($24.9)   ($38.0)    ($23.4)      $0.0      $36.2      $89.6    $168.4    $440.5    $784.8  $1,210.3
Less: Taxes Paid                 $0.0      $0.0       $0.0      ($0.0)      $0.0     ($16.2)   ($69.1)  ($180.6)  ($321.7)  ($496.2)
Plus: D&A                        $5.9      $6.5       $7.4       $8.3       $9.5      $10.6     $12.2     $14.3     $16.5     $19.1
Less: Capital Expenditure      ($22.4)    ($7.9)    ($13.3)    ($30.2)    ($16.8)    ($17.2)   ($42.3)   ($31.5)   ($25.3)    $30.3)
Less: Increase in NWC          ($28.1)   ($19.0)    ($22.6)    ($25.5)    ($26.3)    ($26.9)   ($34.8)   ($49.4)   ($49.2)   ($58.3)

FREE CASH FLOW                 ($69.6)   ($58.4)    ($52.1)    ($47.3)      $2.5      $39.9     $34.5    $193.4    $404.9    $644.6

</TABLE>
- -------------------------------------------------------------------------------
                                                      WASSERSTEIN PERELLA & CO.


                                      -44-

<PAGE>

MYCOGEN CORPORATION              VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- -------------------------------------------------------------------------------
CORPORATE CASH FLOW STATEMENT ($MM)

<TABLE>
<CAPTION>
                                       1998     1999     2000     2001     2002     2003     2004     2005      2006      2007
                                      -------  -------  -------  -------  -------  -------  -------  -------  --------  --------
<S>                                   <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>       <C>
Net Income                             ($24.9)  ($38.0)  ($23.4)    $0.0    $36.2    $73.4    $99.4   $259.9    $463.0    $714.1
Depreciation                              4.5      5.1      6.0      7.0      8.1      9.3     10.8     13.1      15.3      17.9
Amortization                              1.3      1.3      1.3      1.3      1.3      1.3      1.3      1.3       1.2       1.2
Change in Working Capital:
(INC.) DEC. IN ACCTS. REC.              (17.6)   (10.5)   (12.7)   (14.5)   (15.4)   (16.0)   (20.8)   (29.7)    (29.6)    (35.4)
(INC.) DEC. IN INVENTORY                 (8.8)   (13.4)   (12.9)   (13.9)   (15.1)   (16.2)   (20.8)   (29.3)    (29.1)    (34.1)
(INC.) DEC. IN PPD. EXPENSES              --       --       --       --       --       --       --       --        --        --
INC. (DEC.) IN ACC. PAY/ACC.             (1.8)     4.9      2.9      2.9      4.2      5.3      6.8      9.6       9.5      11.2
INC. (DEC.) IN ACCRUED COMPENSA           --       --       --       --       --       --       --       --        --        --
INC. (DEC) IN DEFERRED REVENUES           --       --       --       --       --       --       --       --        --        --
INC. (DEC.) IN OTHER CURR. LIAB.          --       --       --       --       --       --       --       --        --        --
INC. (DEC.) IN LT LIABILITIES             1.6      --       --       --       --       --       --       --        --        --
CASH FLOW FROM OPERATIONS               (45.6)   (50.6)   (38.7)   (17.1)    19.4     57.1     76.7    224.9     430.2     674.9

Capital Expenditures                    (22.4)    (7.9)   (13.3)   (30.2)   (16.8)   (17.2)   (42.3)  (31.5)     (25.3)    (30.3)
CASH FLOW FROM INVESTMENTS              (22.4)    (7.9)   (13.3)   (30.2)   (16.8)   (17.2)   (42.3)  (31.5)     (25.3)    (30.3)
NET CASH FLOW                           (68.0)   (58.4)   (52.1)   (47.3)     2.5     39.9     34.5   193.4      404.9     644.6

Debt Issuance (Paydown)
ADVANCES FROM DAS                         --       --       --       --       --       --       --      --         --        --
SHORT-TERM BORROWINGS                    68.0     58.4     52.1     47.3     (2.5)   (39.9)   (34.5) (154.0)       --        --
Equity Issuance                           --       --       --       --       --       --       --      --         --        --
CASH FLOW (FINANCING)                    68.0     58.4     52.1     47.3     (2.5)   (39.9)   (34.5) (154.0)       --        --

NET INC./DEC. IN CASH                   ($0.0)    $0.0    ($0.0)    $0.0    ($0.0)    $0.0    ($0.0)  $39.4     $404.9    $644.6

Cash & Equivalents BOY                   $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2    $2.2      $41.6    $446.5
Cash & Equivalents EOY                   $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2   $41.6     $446.5  $1,091.2

</TABLE>
- -------------------------------------------------------------------------------
                                                      WASSERSTEIN PERELLA & CO.


                                      -45-

<PAGE>

MYCOGEN CORPORATION               VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE NET OPERATING LOSS CARRYFORWARDS/DEBT SCHEDULE ($MM)

<TABLE>
<CAPTION>
                              1998      1999      2000      2001      2002      2003      2004      2005      2006      2007
NOL Schedule                --------  --------  --------  --------  --------  --------  --------  --------  --------   -------
- ------------
<S>                         <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>
Start New NOL Carry(1)       $10.2      $25.8     $35.4     $35.4     $35.4     $20.6      $0.0      $0.0      $0.0      $0.0
Taxes Due                     $0.0       $0.0      $0.0     ($0.0)   ($14.9)   ($36.7)   ($69.1)  ($180.6)  ($321.7)  ($496.2)
Total New NOL Utilized        $0.0       $0.0      $0.0      $0.0     $14.9     $20.6      $0.0      $0.0      $0.0      $0.0

Balance Current NOL Carry    $10.2      $25.8     $35.4     $35.4     $20.6      $0.0      $0.0      $0.0      $0.0      $0.0
New NOL YTD                  $10.2      $15.6      $9.6      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0

Debt Schedule
- -------------

Advances from DAS            $13.5      $13.5     $13.5     $13.5     $13.5     $13.5     $13.5     $13.5     $13.5     $13.5

BOY Short Term Borrowings      5.1       73.1     131.5     183.6     230.9     228.4     188.5     154.0       -         -

Addn. Short-Term Borrow.      68.0       58.4      52.1      47.3       -         -         -         -         -         -

Debt Paid Down                 -          -         -         -        (2.5)    (39.9)    (34.5)   (154.0)      -         -
                            --------  --------  --------  --------  --------  --------  --------  --------  --------   -------
EOY Short-term Borrowings    $73.1     $131.5    $183.6    $230.9    $228.4    $188.5    $154.0      $0.0      $0.0      $0.0

</TABLE>

(1) Excludes existing NOL's existing prior to 1998.  Prior NOL's valued 
    separately subject to existing utilization limitations.

(2) NOL's generated in 1998-2007 period valued assuming accelerated utilization
    due to consolidation with larger entity.

                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------


                                                           -46-
<PAGE>

<TABLE>
<CAPTION>

Current as of:                                               Estimated Present Value of NOLs
                 7/21/98                                                              Option 1
                                    Option 1    FY 1999     FY 2000     FY 2001     FY 2002    FY 2003     FY 2004     Present Value
                                 ---------------------------------------------------------------------------------------------------
<S>                              <C>           <C>         <C>         <C>         <C>         <C>          <C>       <C>
Estimated NOL at 8/31/98 
  (federal)                       228,001,545  18,732,548  18,732,548  18,732,548  18,732,548  4,870,348         -       $68,446,166
Estimated Annual Limitation(1)     53,521,566
Estimated R&D Credit                2,071,000                                                             2,071,000    $1,543,017.32
Estimated State NOLs                            2,052,014   2,052,014   2,052,014   2,052,014  2,052,014  2,052,014   $10,070,633.87
                                                                                                                     ---------------
                                                                                                    PV =                         $80
Discount rate used for
  PV Calculation                        6.06%                                                 WHEN ITALICIZED AMOUNT FOR FY2003
                                                                                              TURNS NEGATIVE, THE FORMULAS
April 1998 federal tax exempt                                                                 NEED TO BE MODIFIED.
  rate:                                 5.05%               St. Price = $   30.00
Estimated Value - # of shares
  plus options                     39,850,340
  times buyout price =          1,195,510,200
Est. Contributions During
  Past 2 Years                    135,677,204
                                -------------           Est. Contributions Prior 2 Years
Sec. 382 Valuation              1,059,832,996           DAS                               75,000,000
                                                        Exercised                         11,899,244
W-2/1099 option income -                                To be Exercised                   48,777,960
  exercises thru above date        12,109,587                                            -----------
W-2/1099 option income -                                  Estimated Contributions        135,677,204
  est. exercises at buyout         58,737,120
Restricted Stock taxble inc -
  vested thru above date            2,074,838
Restricted Stock inc. est -
  not vested thru above date        1,080,000
Estimated 8/31/98 Other Oper.
  Loss                             30,000,000
Esimated NOL from 8/31/97         124,000,000
                                -------------
  Estimated NOL                   228,001,545

</TABLE>

Comments:

The available R&D Credit was adjusted down to an estimate of what
will actually be available for use.

The value of the state NOL is a rough estimate.

The capital Loss Carryforward of 2,618,115 was ignored
because of the uncertainty of its use.

Foreign tax credits have been ignored because of the relatively small value.

(1) Limitation may be higher for acquiror other than Dow. Also, some portion of 
carryover is not subject to current limitation.


                                                           -47-
<PAGE>

MYCOGEN CORPORATION         VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- -------------------------------------------------------------------------------
CORPORATE INCOME STATEMENT PROJECTIONS ($MM)

<TABLE>
<CAPTION>
                                       1998     1999     2000     2001     2002     2003     2004     2005     2006      2007
                                      ------   ------   ------   ------   ------   ------   ------   ------   ------   --------
<S>                                   <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>
Revenues                              $256.5   $298.5   $355.4   $416.4   $483.2   $552.5   $638.8   $776.6   $925.1   $1,105.0
    SoilServ                           $34.2    $33.4    $33.4    $33.4    $33.4    $33.4    $33.4    $33.4    $33.4      $33.4
    Biopesticides                       $8.3     $7.8     $7.8     $7.8     $7.8     $7.8     $7.8     $7.8     $7.8       $7.8
    Seeds                             $186.4   $221.0   $272.9   $328.0   $392.4   $460.7   $545.5   $681.8   $828.6   $1,006.2
    VMO                                 $5.9     $7.4     $8.1     $9.1    $10.2    $11.4    $13.2    $14.9    $16.9      $19.1
    Oilseed                            $21.7    $28.8    $33.2    $38.1    $39.3    $39.1    $38.9    $38.7    $38.5      $38.5
COGS                                  $147.6   $175.3   $200.1   $226.8   $252.6   $278.7   $312.7   $361.5   $408.9     $464.1
    Soilserv                           $22.0    $22.3    $22.3    $22.3    $22.3    $22.3    $22.3    $22.3    $22.3      $22.3
    Biopesticides                       $4.5     $4.9     $4.9     $4.9     $4.9     $4.9     $4.9     $4.9     $4.9       $4.9
    Seeds                              $96.3   $115.8   $135.9   $157.3   $180.9   $206.1   $239.3   $287.1   $333.3     $387.2
    VMO                                 $3.9     $4.9     $5.4     $6.1     $6.8     $7.6     $8.5     $9.6    $10.7      $12.0
    Oilseed                            $20.9    $27.5    $31.7    $36.3    $37.8    $37.8    $37.8    $37.8    $37.8      $37.8
GROSS PROFIT                          $109.0   $123.2   $155.3   $189.6   $230.6   $273.8   $326.1   $415.1   $516.2     $640.9
SG&A                                   $68.6    $81.6    $88.9    $95.7   $105.0   $114.1   $127.9   $147.0   $173.4     $204.9
R&D                                    $36.5    $40.8    $47.9    $50.8    $56.8    $62.7    $71.5    $87.9   $103.6     $123.0
    SoilServ                            $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0       $0.0
    Biopesticides                       $1.1     $0.8     $0.8     $0.8     $0.8     $0.8     $0.8     $0.8     $0.8       $0.8
    Seeds                              $34.7    $39.3    $46.1    $48.9    $54.6    $60.5    $69.1    $85.4   $101.0     $120.3
    VMO                                 $0.7     $0.6     $1.1     $1.1     $1.4     $1.4     $1.5     $1.6     $1.7       $1.9
    Oilseed                             $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0     $0.0       $0.0 
EBITDA                                  $3.9     $0.7    $18.4    $43.1    $68.8    $97.0   $126.7   $180.2   $239.2     $313.0
Depreciation                            $3.6     $4.0     $4.6     $5.2     $6.1     $7.1     $8.3    $10.0    $11.8      $14.0
Amortization                            $2.6     $2.6     $2.6     $2.6     $2.6     $2.6     $1.8     $1.3     $1.2       $1.2
                                     -------  --------  ------   ------   ------   ------   ------   ------   ------     ------
EBIT                                   ($2.4)   ($5.9)   $11.2    $35.2    $60.0    $87.3   $116.5   $168.9   $226.3     $297.8
Royalty and Venture Income             ($4.1)   ($5.0)   ($4.8)   ($1.5)    $3.4    $11.8    $16.4    $22.7    $24.9      $30.3
TOTAL OPERATING INCOME                 ($6.5)  ($10.9)    $6.4    $33.7    $63.4    $99.0   $133.0   $191.6   $251.1     $328.1
LITIGATION EXPENSES                   ($20.0)  ($15.0)  ($10.0)   ($5.0)   ($2.0)    (2.0)
INTEREST EXP./REV.                     ($3.0)   ($7.7)  ($11.4)  ($14.2)  ($14.7)  ($13.5)  ($12.3)  ($10.4)   ($5.7)      $1.1
PRE-TAX INCOME (TOTAL)                ($29.5)  ($33.6)  ($15.0)   $14.5    $46.7    $83.6   $120.6   $181.2   $245.5     $329.2

Taxes (@41%)                             0.0      0.0      0.0    (6.0)    (19.1)   (34.3)   (49.5)   (74.3)  (100.6)    (135.0)
NOL Utilization                          0.0      0.0      0.0     6.0      19.1      6.9      0.0      0.0      0.0        0.0
NET INCOME                             (29.5)   (33.6)   (15.0)   14.5      46.7     56.2     71.2    106.9    144.8      194.2
E.P.S. (38.35 MM SHARES)              ($0.77)  ($0.88)  ($0.39)  $0.38     $1.22    $1.47    $1.86    $2.79    $3.78      $5.06
</TABLE>

                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -48-
<PAGE>

MYCOGEN CORPORATION         VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- -------------------------------------------------------------------------------
CORPORATE BALANCE SHEET PROJECTIONS ($MM)

<TABLE>
<CAPTION>
                                       1998     1999     2000     2001     2002     2003     2004     2005     2006      2007
                                      ------   ------   ------   ------   ------   ------   ------   ------   ------   --------
<S>                                   <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>
Cash and Equivalents                   $2.2     $2.2     $2.2     $2.2     $2.2    $2.2     $2.2     $2.2     $2.2      $92.7
Accounts Receivable                   $60.1    $70.7    $83.3    $97.9   $113.3  $129.4   $150.2   $179.9   $209.5     $244.9
Inventories                           $66.5    $79.9    $92.8   $106.7   $121.9  $138.4   $158.9   $188.2   $217.4     $251.6
PP&E                                 $105.1   $108.1   $119.4   $139.2   $148.3  $160.4   $188.1   $206.8   $217.1     $299.7
Intangibles                           $30.3    $27.7    $25.1    $22.4    $19.8   $17.7    $15.3    $14.0    $12.8      $11.6
Prepaid Expenses                      $18.1    $18.1    $18.1    $18.1    $18.1   $18.1    $18.1    $18.1    $18.1      $18.1
                                     ------   ------   ------   ------   ------  ------   ------   ------   ------    -------
TOTAL ASSETS                         $282.3   $306.6   $340.9   $386.5   $423.5  $465.2   $532.8   $609.2   $677.1     $848.5 
                                     ------   ------   ------   ------   ------  ------   ------   ------   ------    -------
                                     ------   ------   ------   ------   ------  ------   ------   ------   ------    -------
Advances form DAS                     $13.5    $13.5    $13.5    $13.5    $13.5   $13.5    $13.5    $13.5    $13.5      $13.5
Short-term Borrowings                 $77.3   $130.2   $176.5   $204.6   $190.8  $171.0   $160.5   $120.4    $34.0       $0.0
A/P & Accruals                        $19.5    $24.4    $27.4    $30.3    $34.5   $39.8    $46.6    $56.2    $65.7      $76.9
Accrued Compensation                   $6.1     $6.1     $6.1     $6.1     $6.1    $6.1     $6.1     $6.1     $6.1       $6.1
Deferred Revenues                      $8.2     $8.2     $8.2     $8.2     $8.2    $8.2     $8.2     $8.2     $8.2       $8.2
Other Current Liabilities             $12.9    $12.9    $12.9    $12.9    $12.9   $12.9    $12.9    $12.9    $12.9      $12.9
TOTAL CURRENT LIABILITIES            $137.5   $195.4   $244.6   $275.7   $266.0  $251.5   $247.9   $217.4   $140.5     $117.7

Long-term Liabilities                 $17.1    $17.1    $17.1    $17.1    $17.1   $17.1    $17.1    $17.1    $17.1      $17.1

Paid In Capital                       0.031    0.031    0.031    0.031    0.031   0.031    0.031    0.031    0.031      0.031
Additional PIC                       $344.7   $344.7   $344.7   $344.7   $344.7  $344.7   $344.7   $344.7   $344.7     $344.7
Retained Earning (Deficit)          ($217.0) ($250.6) ($265.6) ($251.1) ($204.4)($148.1)  ($77.0)   $29.9   $174.8     $369.0
STOCKHOLDERS EQUITY                  $127.7    $94.1    $79.1    $93.6   $140.3  $196.6   $267.7   $374.6   $519.5     $713.7
                                     ------   ------   ------   ------   ------  ------   ------   ------   ------    -------
TOTAL S.H. EQUITY AND LIAB.          $282.3   $306.6   $340.9   $386.5   $423.5  $465.2   $532.8   $609.2   $677.1     $848.5
                                     ------   ------   ------   ------   ------  ------   ------   ------   ------    -------
                                     ------   ------   ------   ------   ------  ------   ------   ------   ------    -------
NET WORKING CAPITAL                   $94.3   $113.3   $136.0   $161.4   $187.8  $214.8   $249.6   $299.0   $348.3     $406.6
NET ASSETS                           $199.3   $221.4   $255.3   $300.6   $336.1  $375.1   $437.7   $505.8   $565.4     $636.3
Net Operating Income                 ($29.5)  ($33.6)  ($15.0)   $14.5    $46.7   $83.6   $120.6   $181.2   $245.5     $329.2
Less: Taxes paid                       $0.0     $0.0     $0.0     $0.0     $0.0  ($27.4)  ($49.5)  ($74.3) ($100.6)   ($135.0)
Plus: D&A                              $6.3     $6.6     $7.2     $7.9     $8.8    $9.7    $10.1    $11.2    $13.0      $15.2
Less: Capital Expenditure            ($21.5)   ($7.0)  ($15.9)  ($25.0)  ($15.2) ($19.2)  ($36.0)  ($28.7)  ($22.1)    ($26.6)
Less: Increase In NWC                ($29.0)  ($19.0)  ($22.7)  ($25.5)  ($26.4) ($27.0)  ($34.9)  ($49.4)  ($49.3)    ($58.4)
FREE CASH FLOW                       ($73.7)  ($53.0)  ($46.3)  ($28.1)   $13.9   $19.8    $10.5    $40.1    $86.4     $124.5

</TABLE>
                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -49-
<PAGE>

MYCOGEN CORPORATION          VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE CASH FLOW STATEMENT ($MM)


<TABLE>
<CAPTION>
                                   1998      1999      2000      2001      2002      2003      2004      2005      2006     2007
                                 --------  --------  --------  --------  --------  --------  --------  --------  --------  ------
<S>                              <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>
Net Income                        ($29.5)   ($33.6)   ($15.0)    $14.5     $46.7     $56.2     $71.2    $106.9    $144.8   $194.2
Depreciation                         3.6       4.0       4.6       5.2       6.1       7.1       8.3      10.0      11.8     14.0
Amortization                         2.6       2.6       2.6       2.6       2.6       2.6       1.8       1.3       1.2      1.2
Change in Working Capital:
(INC.) DEC. IN ACCTS. REC.         (18.0)    (10.5)    (12.7)    (14.5)    (15.5)    (16.0)    (20.8)    (29.7)    (29.6)   (35.4)
(INC.) DEC. IN INVENTORY            (9.4)    (13.4)    (12.9)    (13.9)    (15.1)    (16.2)    (20.8)    (29.3)    (29.2)   (34.2)
(INC.) DEC. IN PPD. EXPENSES         --       --        --        --        --        --        --        --        --       --   
INC. (DEC.) IN ACC. PAY/ACC.        (1.6)      4.9       2.9       3.0       4.2       5.3       6.8       9.6       9.5     11.2
INC. (DEC.) IN ACCRUED COMPENSA      --       --        --        --        --        --        --        --        --       --   
INC. (DEC.) IN DEFERRED REVENUES     --       --        --        --        --        --        --        --        --       --   
INC. (DEC.) IN OTHER CURR. LIAB.     --       --        --        --        --        --        --        --        --       --   
INC. (DEC.) IN LT LIABILITIES        1.6      --        --        --        --        --        --        --        --       --   
CASH FLOW FROM OPERATIONS          (50.6)    (46.0)    (30.4)     (3.1)     29.1      39.0      46.4      68.7     108.5    151.1

Capital Expenditures               (21.5)     (7.0)    (15.9)    (25.0)    (15.2)    (19.2)    (36.0)    (28.7)    (22.1)   (26.6)
CASH FLOW FROM INVESTMENTS         (21.5)     (7.0)    (15.9)    (25.0)    (15.2)    (19.2)    (36.0)    (28.7)    (22.1)   (26.6)
Net Cash Flow                      (72.2)    (53.0)    (46.3)    (28.1)     13.9      19.8      10.5      40.1      86.4    124.5
                                                                         
Debt Issuance (Paydown)                                                  
ADVANCES FROM DAS                    --       --        --       --         --        --        --        --        --       --   
SHORT-TERM BORROWINGS               72.2      53.0      46.3      28.1     (13.9)    (19.8)    (10.5)    (40.1)    (86.4)   (34.0)
Equity Issuance                      --       --        --       --         --        --        --        --        --       --
CASH FLOW (FINANCING)               72.2      53.0      46.3      28.1     (13.9)    (19.8)    (10.5)    (40.1)    (86.4)   (34.0)
                                                                         
NET INC./DEC. IN CASH               $0.0     ($0.0)     $0.0      $0.0     ($0.0)     $0.0      $0.0     ($0.0)     $0.0    $90.5
                                                                         
Cash & Equivalents BOY              $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2     $2.2
Cash & Equivalents EOY              $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2    $92.7
</TABLE>


                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -50-
<PAGE>
MYCOGEN CORPORATION          VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE NET OPERATING LOSS CARRYFORWARDS / DEBT SCHEDULE ($MM)


<TABLE>
<CAPTION>
                                   1998      1999      2000      2001      2002      2003      2004      2005      2006      2007
                                 --------  --------  --------  --------  --------  --------  --------  --------  --------  -------
<S>                              <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>
NOL SCHEDULE

Start New NOL Carry(1)             $12.1      $25.9    $32.0     $32.0     $26.1      $6.9      $0.0      $0.0       $0.0     $0.0
Taxes Due                           $0.0       $0.0     $0.0     ($6.0)   ($19.1)   ($34.3)   ($49.5)   ($74.3)   ($100.6) ($135.0)
Total New NOL Utilized              $0.0       $0.0     $0.0      $6.0     $19.1      $6.9      $0.0      $0.0       $0.0     $0.0

Balance Current NOL Carry          $12.1      $25.9    $32.0     $26.1      $6.9      $0.0      $0.0      $0.0       $0.0     $0.0
New NOL YTD                        $12.1      $13.8     $6.2      $0.0      $0.0      $0.0      $0.0      $0.0       $0.0     $0.0 

DEBT SCHEDULE

Advances from DAS                  $13.5      $13.5    $13.5     $13.5     $13.5     $13.5     $13.5     $13.5      $13.5    $13.5

BOY Short Term Borrowings            5.1       77.3    130.2     176.5     204.6     190.8     171.0     160.5      120.4     34.0
Addn. Short-Term Borrow.            72.2       53.0     46.3      28.1      --        --        --        --         --       --
Debt Paid Down                       --         --       --        --      (13.9)    (19.8)    (10.5)    (40.1)     (86.4)   (34.0)
                                 --------  --------  --------  --------  --------  --------  --------  --------  --------  -------
EOY Short-term Borrowings          $77.3     $130.2   $176.5    $204.6    $190.8    $171.0    $160.5    $120.4      $34.0     $0.0
</TABLE>


(1)  Excludes existing NOL's existing prior to 1998. Prior NOL's valued 
     seperately subject to existing utilization limitations
(2)  NOL's generated in 1998-2007 period valued assuming accelerated 
     utilization due to consolidation with larger entity


                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -51-
<PAGE>
MYCOGEN CORPORATION          VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE FINANCIAL RATIO PROJECTIONS ($MM)


<TABLE>
<CAPTION>
                                   1998      1999      2000      2001      2002      2003      2004      2005      2006     2007
                                 --------  --------  --------  --------  --------  --------  --------  --------  --------  ------
<S>                              <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>
COGS/Sales                         58.5%      59.7%    57.1%     54.7%      51.9%     49.4%     47.7%     45.2%     43.0%     40.9%
SG&A/Sales                         27.2%      27.8%    25.4%     23.1%      21.6%     20.2%     19.5%     18.4%     18.3%     18.0%
R&D/Sales                          14.5%      13.9%    13.7%     12.3%      11.7%     11.1%     10.9%     11.0%     10.9%     10.8%
Royalty/Sales                      -1.6%      -1.7%    -1.4%     -0.4%       0.7%      2.1%      2.6%      2.9%      2.7%      2.7%
Operating Margin                    1.3%      -0.1%     5.2%     11.3%      16.1%     20.5%     23.1%     26.6%     29.0%     31.5%

EBITDA/Sales                        1.5%       0.2%     5.3%     10.4%      14.1%     17.2%     19.3%     22.5%     25.2%     27.6%
EBIT/Sales                         -0.9%      -2.0%     3.2%      8.5%      12.3%     15.5%     17.8%     21.1%     23.8%     26.2%
Net Inc./Sales                    -11.7%     -11.4%    -4.3%      3.5%       9.6%     10.0%     10.9%     13.4%     15.2%     17.1%

Working Cap/Sales                  37.4%      38.6%    38.8%     38.9%      38.6%     38.1%     38.1%     37.4%     36.7%     35.8%
Depreciation/PP&E                   3.5%       3.7%     3.8%      3.8%       4.1%      4.4%      4.4%      4.8%      5.4%      6.1%
Depreciation/Sales                  1.4%       1.4%     1.3%      1.3%       1.3%      1.3%      1.3%      1.2%      1.2%      1.2%
PPE/Sales                          41.6%      36.8%    34.0%     33.5%      30.5%     28.4%     28.7%     25.9%     22.8%     20.2%

Debt/Assets                        38.8%      58.8%    69.1%     68.1%      56.8%     45.6%     36.7%     23.8%      6.0%      0.0%

Coverage (EBIT/Interest)           -0.8x      -0.8x     1.0x      2.5x       4.1x      6.5x      9.5x     16.2x     39.8x   -271.4x
Debt/Total Cap.                    38.8%      58.8%    69.1%     68.1%      56.8%     45.6%     36.7%     23.8%      6.0%      0.0%
</TABLE>


                                                       WASSERSTEIN PERELLA & CO.
- --------------------------------------------------------------------------------
                                     -52-
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------


                             -------------------
                             COMPARABLE ANALYSIS
                             -------------------





                                                     WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------



                                     -53-
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
SELECTED SEED COMPARABLE COMPANIES ANALYSIS

<TABLE>
<CAPTION>

TRADING STATISTICS
- ------------------ 

                                                                                                          
                       CURRENT     EQUITY      ADJUSTED     PRICE/EARNINGS   EST. 3-5    98E P/E/         
                        PRICE      MARKET       MARKET      --------------   YR. EPS     3-5 YEAR   PRICE/
COMPANY                7/28/98     VALUE        VALUE       1997     1998E    GTH.      EPS GLB(1)   BOOK 
- ----------------------------------------------------------------------------------------------------------
                       (IN $)    (IN $ MM)    (IN $ MM)      (x)      (x)      (%)         (x)        (x) 
<S>                    <C>       <C>           <C>         <C>       <C>     <C>        <C>          <C>  
Mycogen                 23.50      839.3          974.7      NM       NM       22.5       NM         4.4  
Pioneer Hi-Bred         33.00    7,972.2        7,774.2     33.5     28.8      15.0      1.92        5.7  
Dekalb Genetics(2)      70.07    2,525.0        2,765.0     87.0     89.8      25.0      3.59       11.2  
Delta & Pine Land       46.11    1,823.0        1,890.3     93.4     72.1      30.0      2.40       18.3  
Agribiotech(3)          19.69      663.0          661.6      NM      82.0      40.0      2.05        8.2  


                                                 ---------------------------------------------------------
                                                 Mean       71.3     68.2      27.5      2.49       10.9  
                                                 Median     87.0     77.0      27.5      2.23        9.7  
                                                 High       93.4     89.8      40.0      3.59       18.3  
                                                 Low        33.5     28.8      15.0      1.92        5.7  
                                                 ---------------------------------------------------------



                                                             ADJUSTED MARKET VALUE
                       ------------------------------------------------------------------------------------------------   Net Debt/
                        1997    LTM   1998E    1999E    1997    LTM      1998E    1999E    1997   LTM    1998E    1999E    MARKET  
COMPANY                SALES   SALES  SALES    SALES   EBITDA  EBITDA    EBITDA   EBITDA   EBIT   EBIT    EBIT     EBIT      CAP.  
- -----------------------------------------------------------------------------------------------------------------------------------
                        (x)      (x)    (x)     (x)     (x)     (x)       (x)       (x)      (x)   (x)     (x)     (x)        (%)  
<S>                    <C>     <C>    <C>     <C>     <C>      <C>      <C>       <C>      <C>    <C>    <C>      <C>       <C>    
Mycogen                 4.62    4.47   3.80    3.27    NM       NM       NM        NM       NM     NM     NM       NM         9.1  
Pioneer Hi-Bred         4.36    4.23   4.01    3.75   17.2     16.9      15.0     12.8     21.4   20.9   17.9     15.0       (2.6) 
Dekalb Genetics(3)      6.13    5.42   5.80    5.22   45.3     56.5      44.6     35.4     58.5   83.0   58.8     46.1        9.5  
Delta & Pine Land      10.32    9.33   7.13    5.33   50.8     57.5      33.3     22.4     58.9   71.4   37.2     24.1        3.6  
Agribiotech(3)          2.38    2.38   2.59    1.29   57.7     57.7      57.9     22.4      NM     NM    76.7     25.4       (0.2) 

          -------------------------------------------------------------------------------------------------------------------------
            Mean        5.00    5.34   4.88    3.90   42.7     47.2      37.7     23.3     46.2   58.5   47.7     27.6        2.6  
            Medium      5.24    4.82   4.90    4.48   48.0     57.0      38.9     22.4     58.5   71.4   48.0     24.8        1.7  
            High       10.32    9.33   7.13    5.33   57.7     57.7      57.9     35.4     58.9   83.0   76.7     46.1        9.5  
            Low         2.38    2.38   2.59    1.29   17.2     16.9      15.0     12.8     21.4   20.9   17.9     15.0       (2.6) 
          -------------------------------------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<CAPTION>

OPERATING STATISTICS
- --------------------

                                   TOTAL REVENUES
                           ------------------------------             EBITDA MARGIN                           EBIT MARGIN          
                            LTM       97/96%      98E/97%     --------------------------------       ------------------------------
COMPANY                    AMOUNT     GROWTH      GROWTH      1997     LTM     1998E     1999E       1997    LTM     1998E    1999E
- -------                    ------     ------      -------     ----     ---     -----     -----       ----    ---     -----    -----
                          (IN $ MM)     (%)         (%)       (%)      (%)      (%)       (%)         (%)    (%)      (%)      (%)
<S>                       <C>          <C>        <C>        <C>      <C>     <C>       <C>         <C>     <C>     <C>      <C>
Mycogen                     218        35.6       21.6        3.4      1.2     3.1        NM          NM      NM      0.8      NM
Pioneer Hi-Bred           1,840         3.7        8.7       25.3     25.1    26.8      29.4        20.3    20.2     22.4    25.1
Dekalb Genetics(2)          510        16.5        5.7       13.5      9.6    13.0      14.7        10.5     6.5      9.9    11.3
Delta & Pine Land(2)        203        19.6       44.8       20.3     16.2    21.4      23.8        17.5    13.1     19.1    22.1
Agribiotech(3)              277          NA       (8.1)       4.1      4.1     4.5       5.8         2.1     2.1      3.4     5.1

        ---------------------------------------------------------------------------------------------------------------------------
            Mean                       13.2       12.8       15.8     13.7    16.4      18.4        12.6    10.5     13.7     15.9
            Median                     16.5        7.2       16.9     12.9    17.2      19.2        14.0     9.8     14.5     16.7
            High                       19.6       44.8       25.3     25.1    26.8      29.4        20.3    20.2     22.4     25.1
            Low                         3.7       (8.1)       4.1      4.1     4.5       5.8         2.1     2.1      3.4      5.1
        ---------------------------------------------------------------------------------------------------------------------------

<CAPTION>

                                  NET INCOME MARGIN             R&D/TOTAL REVENUES
                            -----------------------------     ----------------------
                            1997    LTM    1998E    1999E     1997    1998E    1999E
                            ----    ---    -----    -----     ----    -----    -----
                             (%)    (%)     (%)      (%)       (%)     (%)      (%)
<S>                        <C>     <C>     <C>     <C>        <C>     <C>      <C>
Mycogen                      NM      NM     NM       NM       11.4    12.7     15.3
Pioneer Hi-Bred            13.6    14.6    15.0    16.9        8.2     7.7      7.8
Dekalb Genetics(2)          6.4     4.3     6.1     7.1       12.7    12.6     15.1
Delta & Pine Land(2)       10.7     6.9    10.1    11.8        7.4     6.1      4.7
Agribiotech(3)               NM      NM     1.9     2.3         NA      NA       NA
                         
        -----------------------------------------------------------------------------
            Mean           10.2     8.6     8.3     9.5        9.4     8.8      9.2
            Median         10.7     6.9     8.1     9.4        8.2     7.7      7.8
            High           13.6    14.6    15.0    16.9       12.7    12.6     15.1
            Low             6.4     4.3     1.9     2.3        7.4     6.1      4.7
        -----------------------------------------------------------------------------

</TABLE>
- ----------------------
1997 data refers to FYE 8/31/97, etc. All means and medians exclude Mycogen.
Currency are converted at current exchange rates.
EPS projections are based on 1/8/E/S consensus; other projections are based 
on selected brokers' research except Mycogen projections are provided by the 
management.
When not available, depreciation and amortization are estimated as a 
percentage of sales based on the latest released data.
When not available, LTM data is based on selected brokers' research.
(1) Represents ratio of the 1998E P/E ratio to the estimated 3-5 year 
earnings growth rate.
(2) Stock price is calculated as the average of 30-day stock prices before 
the announcement of Monsanto transactions.
(3) Agribiotech fiscal year end 6/30. LTM data represents financials for 1997 
fiscal year end pro forma for acquisitions, EBITDA estimaged per analyst 
projections of D&A margins.

- -------------------------------------------------------------------------------

                                     -54-
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
SELECTED COMPARABLE COMPANIES QUARTERLY ANALYSIS FOR FISCAL YEAR 1997

<TABLE>
<CAPTION>

                                       EBITDA MARGIN                                   EBIT MARGIN
                             -----------------------------------        --------------------------------------
                             1-QTR     2-QTR     3-QTR     4-QTR          1-QTR     2-QTR     3-QTR     4-QTR
                             -----     -----     -----     -----          -----     -----     -----     -----
<S>                          <C>       <C>       <C>       <C>            <C>       <C>       <C>       <C>
Mycogen                     (44.7%)     8.3%      13.5%    (6.2%)         (55.4%)    5.5%      10.6%    (16.4%)
Pioneer Hi-Bred             (57.8%)     6.1%      41.8%   (35.2%)         (78.9%)   (2.3%)     40.0%    (52.8%)
Dekalb Genetics              11.0%     16.1%      14.2%   (19.4%)           6.4%    14.5%      12.5%    (53.0%)
Delta & Pine Land           (82.8%)    25.2%      29.5%      NM          (101.6%)   23.3%      28.4%       NM
Agribiotech(1)              (14.0%)    (4.1%)      8.6%    (2.3%)         (16.4%)   (6.1%)      7.0%     (3.8%)

               ------------------------------------------------------------------------------------------------
                Mean        (35.9%)    10.8%      23.5%   (19.0%)         (47.6%)    7.4%      22.0%    (36.5%)
                Median      (35.9%)    11.1%      21.8%   (19.4%)         (47.7%)    6.1%      20.4%    (52.8%)
               ------------------------------------------------------------------------------------------------

<CAPTION>

                                   NET INCOME MARGIN                               R&D/TOTAL REVENUES
                            -----------------------------------        --------------------------------------
                            1-QTR     2-QTR     3-QTR     4-QTR          1-QTR     2-QTR     3-QTR     4-QTR
                            -----     -----     -----     -----          -----     -----     -----     -----
<S>                        <C>       <C>       <C>       <C>             <C>       <C>       <C>      <C>

Mycogen                    (54.7%)    3.7%      6.8%    (48.4%)          26.3%      7.8%      6.9%    22.3%
Pioneer Hi-Bred            (50.0%)   (0.8%)    25.8%    (29.6%)          33.3%     12.5%      3.1%    30.3%
Dekalb Genetics              3.1%     8.5%      7.3%    (20.1%)           8.9%     13.2%     12.8%    23.1%
Delta & Pine Land          (65.5%)   14.1%     17.9%       NM            41.0%      5.2%      3.3%      NM
Agribiotech(1)             (16.9%)   (8.9%)     6.4%     (6.2%)           1.2%      2.1%      1.4%     2.0%
                  
               --------------------------------------------------------------------------------------------
                Mean       (32.3%)    3.2%    14.3%     (18.6%)          21.1%      8.3%      5.2%    18.5%
                Median     (33.5%)    3.9%    12.6%     (20.1%)          21.1%      8.8%      3.2%    23.1%
               --------------------------------------------------------------------------------------------
</TABLE>

<TABLE>
<CAPTION>
                                      DAYS RECEIVABLE                                   DAYS OF INVENTORY
                            -----------------------------------          -----------------------------------
                            1-QTR     2-QTR     3-QTR     4-QTR          1-QTR     2-QTR     3-QTR     4-QTR
                            -----     -----     -----     -----          -----     -----     -----     -----
<S>                         <C>       <C>       <C>       <C>           <C>        <C>       <C>       <C>
Mycogen(2)(3)                129       61       85        109             761       145        89      257
Pioneer Hi-Bred(2)           178       79       34        162           1,490       515        68      558
Dekalb Genetics(2)(4)         69       33       79        357             526       147        97    1,361
Delta & Pine Land             92       99       99         NM           1,067       144        50       NM
Agribiotech(1)                97       61       81         64             289       189       122      113

        ----------------------------------------------------------------------------------------------------
          Mean               109       68       73        194             843       249        84      677
          Median              94       70       80        162             796       168        83      558
        ----------------------------------------------------------------------------------------------------

<CAPTION>

                                     DAYS PAYABLE                                 NET DEBT/BOOK EQUITY
                            -----------------------------------          -----------------------------------
                            1-QTR     2-QTR     3-QTR     4-QTR          1-QTR     2-QTR     3-QTR     4-QTR
                            -----     -----     -----     -----          -----     -----     -----     -----
<S>                         <C>       <C>       <C>       <C>            <C>       <C>       <C>       <C>
Mycogen(2)(3)               216        40        25        95            (3.4%)    8.4%      24.5%     19.5%
Pioneer Hi-Bred(2)          718       147        29       108            19.3%   (30.8%)     (9.7%)     1.7%
Dekalb Genetics(2)(4)       249        44        11       153            71.8%    35.7%      72.4%     60.8%
Delta & Pine Land           314        38        12        NM            66.1%   103.1%      34.7%     39.9%
Agribiotech(1)              104        92        64        52           (16.8%)   60.4%      64.3%     56.4%


        ----------------------------------------------------------------------------------------------------
          Mean              346        80        29       104            35.1%    42.1%      40.4%     39.7%
          Median            281        68        21       108            42.7%    48.0%      49.5%     48.2%
        ----------------------------------------------------------------------------------------------------
</TABLE>

- ------------------
Note: Days calculation assumes 360-day a year and all means and medians 
exclude Mycogen data
(1) Agribiotech data are not pro forma of acquisition
(2) Data not available to separate notes receivable from acounts receivable 
for quarterly data
(3) 2nd and 3rd quarter net debts include $14.25 million unsecured note 
payable to bank that was specified in the 10-K
(4) Accounts Payable includes only trade accounts payable

- -------------------------------------------------------------------------------

                                      -55-
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
SELECTED SEED COMPARABLE COMPANIES ANALYSIS FOR FISCAL YEAR 1994-1997



<TABLE>
<CAPTION>
                                               EBITDA MARGIN                                   EBIT MARGIN
                                    ----------------------------------             -----------------------------------
                                     1994      1995     1996     1997                1994     1995      1996     1997 
                                     ----      ----     ----     ----                ----     ----      ----     ---- 
<S>                                 <C>      <C>       <C>      <C>                <C>      <C>       <C>       <C>
Mycogen                              (5.3%)    (5.8%)   (8.7%)    3.4%              (11.0%)  (13.7%)   (14.5%)   (1.3%)
Pioneer  Hi-Bred                     25.4%     23.1%    24.6%    25.3%               20.4%    18.3%     20.2%    20.3%
Dekalb  Genetics                     10.2%     11.1%    11.4%    13.5%                6.6%     7.6%      8.5%    10.5%
Delta  &  Pine  Land                 19.3%     22.5%    20.4%    20.3%               16.1%    19.4%     17.7%    17.5%
Agribiotech  (1)                        NM    (27.0%)   (9.0%)   (0.7%)                 NM   (29.9%)   (11.2%)   (2.4%)
- -----------------------------------------------------------------------------------------------------------------------
                MEAN                 18.3%      7.4%    11.8%    14.6%               14.4%     3.8%      8.8%    11.5%
              MEDIAN                 19.3%     16.8%    15.9%    16.9%               16.1%    12.9%     13.1%    14.0%
- -----------------------------------------------------------------------------------------------------------------------




<CAPTION>
                                              NET INCOME MARGIN                             R&D/TOTAL REVENUES
                                    ----------------------------------             -----------------------------------
                                     1994      1995     1996     1997                1994     1995      1996     1997 
                                     ----      ----     ----     ----                ----     ----      ----     ---- 
<S>                                 <C>      <C>       <C>      <C>                <C>      <C>       <C>       <C>
Mycogen                              (8.8%)   (14.1%)  (19.6%)   (8.5%)              16.1%    18.7%     15.2%    11.4%
Pioneer  Hi-Bred                     12.4%     11.9%    13.0%    13.6%                7.7%     8.5%      7.9%     8.2%
Dekalb  Genetics                      3.5%      3.0%     4.4%     6.4%               13.8%    13.3%     12.3%    12.7%
Delta  &  Pine  Land                  9.7%     11.1%    10.5%    10.7%                6.8%     6.7%      6.4%     7.4%
Agribiotech  (1)                        NM    (29.6%)  (12.8%)   (4.1%)                 NM     1.2%      0.2%     1.8%
- -----------------------------------------------------------------------------------------------------------------------
                MEAN                  8.6%    (0.9%)     3.8%     6.7%                9.4%     7.4%      6.7%     7.5%
              MEDIAN                  9.7%     7.0%      7.4%     8.6%                7.7%     7.6%      7.1%     7.8%
- -----------------------------------------------------------------------------------------------------------------------




<CAPTION>
                                         SELLING/TOTAL REVENUES                                 G&A MARGIN
                                    ----------------------------------             -----------------------------------
                                     1994      1995     1996     1997                1994     1995      1996     1997 
                                     ----      ----     ----     ----                ----     ----      ----     ---- 
<S>                                 <C>      <C>       <C>      <C>                <C>      <C>       <C>       <C>
Mycogen                              22.4%     20.8%    24.3%    19.8%               14.9%    11.7%     12.7%     8.5%
Pioneer  Hi-Bred                     22.7%     23.1%    22.2%    21.0%                8.3%     8.2%      7.5%     7.3%
Dekalb  Genetics                     19.3%     20.2%    18.8%    18.2%                5.7%     8.1%      8.3%     7.6%
Delta  &  Pine  Land                  7.2%      7.7%     6.2%     6.0%               10.1%     9.7%      6.1%     5.5%
Agribiotech  (1)                        NA        NA       NA       NA                  NA       NA        NA       NA
- -----------------------------------------------------------------------------------------------------------------------
                MEAN                 16.4%     17.0%    15.7%    15.1%                8.0%     8.7%      7.3%     6.8%
              MEDIAN                 19.3%     20.2%    18.8%    18.2%                8.3%     8.2%      7.5%     7.3%
- -----------------------------------------------------------------------------------------------------------------------




<CAPTION>
                                              DAYS RECEIVABLE                              DAYS OF INVENTORY
                                    ----------------------------------             -----------------------------------
                                     1994      1995     1996     1997                1994     1995      1996     1997 
                                     ----      ----     ----     ----                ----     ----      ----     ---- 
<S>                                 <C>      <C>       <C>      <C>                <C>      <C>       <C>       <C>
Mycogen                                 86       89       70        70                 182      181       143      162
Pioneer  Hi-Bred                        39       38       44        52                 213      239       189      205
Dekalb  Genetics (2)(3)                 53       65       48        42                 218      235       177      217
Delta  &  Pine  Land                    11       19      157       187                 144      130       153      133
Agribiotech  (1)                        NM       54      104        95                  NM      145       136      170
- -----------------------------------------------------------------------------------------------------------------------
                MEAN                    34       44       88        94                 192      187       164      181
              MEDIAN                    39       46       76        74                 213      190       165      188
- -----------------------------------------------------------------------------------------------------------------------



<CAPTION>
                                               DAYS PAYABLE                                NET DEBT/BOOK EQUITY
                                    ----------------------------------             -----------------------------------
                                     1994      1995     1996     1997                1994     1995      1996     1997 
                                     ----      ----     ----     ----                ----     ----      ----     ---- 
<S>                                 <C>      <C>       <C>      <C>                <C>      <C>       <C>       <C>
Mycogen                                 22       36       33        60              (30.2%)  (13.5%)   (36.7%)   19.5%
Pioneer  Hi-Bred                        48       33       44        40               (6.1%)   (4.9%)    (4.8%)    1.7%
Dekalb  Genetics (2)(3)                 14       15       24        24              102.1%    98.8%     36.6%    60.8%
Delta  &  Pine  Land                    28       40       55        59               31.8%    11.0%     48.3%    39.9%
Agribiotech  (1)                        NM       56       82        77              (45.4%)   (9.3%)    29.9%    56.4%
- -----------------------------------------------------------------------------------------------------------------------
                MEAN                    30       36       51        50               20.6%    26.4%     27.5%    39.7%
              MEDIAN                    28       36       50        49               12.8%     8.0%     33.2%    48.2%
- -----------------------------------------------------------------------------------------------------------------------
</TABLE>



- ---------------------------
NOTE: DAYS CALCULATION ASSUMES 360-DAY A YEAR AND ALL MEANS AND MEDIANS 
EXCLUDE MYCOGEN DATA

(1) Agribiotech changed its fiscal year end in 1995. 1995 data are based on 
    nine-month period ended 6/30/95. 1997 data are not pro forma of acquisition 
    because no pro forma balance sheet number available for ratio calculation
(2) Data not available to separate trade receivables from note receivables
(3) Accounts Payable includes only trade accounts payable

                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -56-
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
SELECTED COMPARABLE ACQUISITION / VALUATION MULTIPLES

<TABLE>
<CAPTION>
                                                                                                                                   
                                                                                                                    Implied Value  
                                                                                      Adjusted Purchase Price /      of Equity /   
                                                         Implied        Adjusted     --------------------------   ---------------- 
                                              Close       Value         Purchase       LTM      LTM       LTM       Net      Book
Target                  Acquirer               Date     of Equity         Price       Sales    EBITDA     EBIT     Income    Value
- --------------          --------             --------   ----------    ------------   -------   -------   ------   --------  -------
<S>                     <C>                  <C>        <C>           <C>            <C>       <C>       <C>      <C>       <C>
SEED COMPANIES
- --------------
DELTA & PINE LAND        MONSANTO             PENDING    $1,832.5      $1,906.7       9.87 x    69.8 x   89.6 x       NM x   25.1 x

Sunseeds                 AgrEvo               10/6/97          NA            NA       2.20 x    13.1 x   18.0 x       NA x     NA x

PIONEER HI-BRED
 (16.6% STAKE)           DUPONT               9/18/97    $1,700.0      $1,700.0       4.60 x    18.4 x   22.6 x     33.9 x    8.9 x

Holden's Foundation 
 Seeds                   Monsanto              9/4/97          NA        $975.0(1)   21.67 x      NA x     NA x       NA x     NA x

Asgrow Corn & Seed       Monsanto              2/4/97          NA        $240.0       1.41 x      NA       NA         NA       NA

Morgan Seeds             Mycogen Corp.        10/1/96       $40.9         $40.9       1.10 x      NA       NA         NA       NA

Agracetus 
 (W.R. Grace)            Monsanto             5/21/96      $150.0        $150.0         NA        NA       NA         NA       NA

Sure Grow                Delta & Pine Land    5/21/96       $70.0         $78.9       3.47      17.5     19.1       29.9      3.2

Jacobs Hertz Seed
 (Monsanto)              Delta & Pine Land     2/5/96          NA            NA         NA        NA       NA         NA       NA

Cargill - Cotton & 
 Seed                    Delta & Pine Land     5/3/94          NA            NA         NA        NA       NA         NA       NA
</TABLE>

- ---------------------------
(1)  Final terms not disclosed; purchase price assumes maximum expected price.


                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -57-
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
SELECTED COMPARABLE ACQUISITION / VALUATION MULTIPLES (CONT'D)

<TABLE>
<CAPTION>
                                                                                                                                   
                                                                                                                    Implied Value  
                                                                                      Adjusted Purchase Price /      of Equity /   
                                                         Implied        Adjusted     --------------------------   ---------------- 
                                              Close       Value         Purchase       LTM      LTM       LTM       Net      Book
Target                  Acquirer               Date     of Equity         Price       Sales    EBITDA     EBIT     Income    Value
- --------------          --------             --------   ----------    ------------   -------   -------   ------   --------  -------
<S>                     <C>                  <C>        <C>           <C>            <C>       <C>       <C>      <C>       <C>
BIOTECH COMPANIES (MAJORITY STAKES)
- -----------------------------------
Monsanto                 American Home       Pending(1)   $35,563.7     $39,134.7      5.09 x    36.4 x   70.8 x      NM x     8.1 x
                         Products

Plant Breeding Int'l
 (Unilever)              Monsanto            Pending         $523.0        $523.0     19.96(2)     NA       NA        NA        NA

DEKALB GENETICS          MONSANTO            PENDING       $3,771.2(3)   $3,881.2(3)   8.28 x    61.2 x   79.7 x      NM x    16.9 x

Zeneca                   Mogen               5/13/97          $73.6         $73.6     12.80 x      NM x     NM x      NM x      NA

Bionova (ELM)            DNA Plant Tech.     9/27/96          $63.4         $67.9        NM x      NM x     NM x      NM x      NA

Plant Genetic Systems    AgrEvo              8/30/96         $733.0        $733.0        NM x      NM x     NM x      NM x      NA

CALGENE INC.             MONSANTO             4/1/96         $299.8(3)     $268.0(3)   4.80 x      NM x     NM x      NM x     3.1 x
 (49.9% SHARES)

Mycogen                  DowElanco            3/8/96         $444.7(3)     $358.1(3)   2.90 x      NM x     NM x      NM x     2.3 x
 (9.5mm shares)

United AgriSeeds Inc.    Mycogen             2/28/96          $72.4         $72.4        NA        NA       NA        NA        NA

Lubrizol                 Mycogen             1/15/96             NA            NA        NA        NA       NA        NA        NA
</TABLE>

- ---------------------------
(1)  Monsanto operating data are not pro forma of all announced acquisitions 
     and acquisitions Monsanto is currently bidding
(2)  Sales multiple calculated based on PBIC's royalty revenue
(3)  Calculated by translating the price that acquiror paid for part of the 
     target into price for the entire company


                                                      WASSERSTEIN PERELLA & CO.
- -------------------------------------------------------------------------------
                                     -58-

<PAGE>

                                                                   CONFIDENTIAL
- -------------------------------------------------------------------------------





- -------------------------------------------------------------------------------
                                       PRESENTATION TO THE SPECIAL COMMITTEE OF
                                  THE BOARD OF DIRECTORS OF MYCOGEN CORPORATION

                                                                AUGUST 31, 1998
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------
TABLE OF CONTENTS




             1.   MYCOGEN BUSINESS UNIT -- KEY DRIVERS OF GROWTH

             2.   DISCOUNTED CASH FLOW ANALYSIS -- PROCESS AND METHODOLOGY

             3.   RESULTS OF DCF VALUATION

             4.   COMPARABLE ANALYSIS

             5.   CONCLUSIONS

             6.   APPENDIX: 

                  A.   SUMMARY OF FINANCIAL PROJECTIONS

                  B.   COMPARABLE ANALYSIS


                                       2
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                         -----------------------------------


                              MYCOGEN BUSINESS UNITS --
                                KEY DRIVERS OF GROWTH


                         -----------------------------------


                                       3
<PAGE>

MYCOGEN CORPORATION                                      MYCOGEN BUSINESS UNITS
- -------------------------------------------------------------------------------
OVERVIEW

- ---------------
 BUSINESS       -    A DIVERSIFIED AGRIBUSINESS AND BIOTECHNOLOGY COMPANY THAT
 DESCRIPTION         DEVELOPS AND MARKETS SEED FOR IMPROVED CROP VARIETIES AND
- ---------------      PROVIDES CROP PROTECTION SERVICES

- ---------------
 BUSINESS       -    SEED SEGMENT -- PRODUCES AND MARKETS SEED FOR MAJOR
 SEGMENTS            AGRICULTURAL CROPS AND USES BIOTECHNOLOGY AND TRADITIONAL
- ---------------      AND MARKER-ASSISTED BREEDING TO DEVELOP CROP VARIETIES
                     WITH GENETICALLY ENHANCED PEST AND DISEASE RESISTANCE,
                     IMPROVED VEGETABLE OIL PROFILES AND OTHER VALUE-ADDED
                     CHARACTERISTICS

                          
                     -    Mycogen Seeds ranks fourth in the U.S. in sales of
                          seed corn, second in hybrid sunflower seed sales and
                          is among the top five in soybean, sorghum and alfalfa
                          sales

                     -    Morgan Seeds ranks second in Argentina in seed corn 
                          sales and third in hybrid sunflower seed sales
                          
                     -    Dinamilho holds a 10.2% share of Brazil's high-tech
                          corn seed market and 4% of Brazil's overall corn seed
                          market.  Three additional acquisitions to close in
                          1998 will enhance Mycogen's position in this
                          attractive and growing market

                -    CROP PROTECTION SEGMENT -- MANUFACTURES AND MARKETS
                     ENVIRONMENTALLY COMPATIBLE SPRAY-ON BIOPESTICIDES.  ALSO
                     OPERATES SOILSERV, INC., A CROP PROTECTION SERVICE FOR
                     HIGH-VALUE CROPS

                     -    Biopesticide Products -- based on natural agents,
                          such as proteins and fatty acid compounds, that have
                          specific toxic activity on target pests.  The
                          Company's Bt-based biopesticides use the Company's
                          proprietary Cellcap technology

                     -    Soilserv -- monitors fields and uses customized
                          equipment to apply pest control products primarily in
                          the Salinas Valley, CA and Yuma, AZ regions
- ---------------
 ALLIANCES      -    VERNEUIL HOLDING, S.A. -- MYCOGEN HOLDS A 35% EQUITY STAKE
- ---------------      IN VERNEUIL AND ENTERED INTO AN AGREEMENT WITH VERNEUIL TO
                     DEVELOP OILSEED PRODUCTS AND INSECT RESISTANT CORN

                -    PIONEER HYBRID INTERNATIONAL -- 10-YEAR TECHNOLOGY
                     COLLABORATION TO DEVELOP INSECT RESISTANT TRAITS FOR CORN,
                     SOYBEAN, CANOLA, SUNFLOWER, SORGHUM AND WHEAT

                -    J.G. BOSWELL -- JOINT VENTURE TO DEVELOP PEST AND
                     HERBICIDE RESISTANT COTTON

- ---------------
 HEADQUARTERS   -    SAN DIEGO, CA
- ---------------


                                       4
<PAGE>

MYCOGEN CORPORATION                                      MYCOGEN BUSINESS UNITS
- -------------------------------------------------------------------------------
KEY DRIVERS OF GROWTH
- ---------------
 TECHNOLOGY     -    BT TECHNOLOGY, A CORNERSTONE OF MYCOGEN'S
 AND COMPETITIVE     COMMERCIAL FUTURE, IS THE BEST PROVEN METHOD FOR
 POSITION            GENETICALLY IMPROVING SEED TRAITS
- ---------------             

                     -    Bt is the best characterized transgenic
                          technology that has been applied to
                          genetically modify seed.  Despite continuing
                          environmental concerns, Bt genes are expected
                          to be present in nearly 50% of all corn and
                          30% of all soybean seed by 2000
                          
                     -    Bt is a proven technology.  Bt seeds have been
                          shown to prevent insect damage and lower
                          insecticide costs in a manner that does not
                          destroy the natural ecological balance as
                          chemical insecticides do

                -    MYCOGEN IS THE MARKET LEADER IN DEVELOPING NEW
                     INSECTICIDAL AND HERBICIDAL RESISTANCE TRAITS

                     -    Mycogen is the undisputed leader in the
                          identification and characterization of new Bt
                          and related insecticidal proteins

                     -    Mycogen holds patents to over 100 Bt genes
                          with specificities toward over 40 groups of
                          insects.  Many of these genes are likely to
                          have commercial applications against chewing
                          insects, piercing and sucking insects, and
                          even nematodes

                     -    Mycogen has a strong IP position in a number
                          of technologies capable of improving the
                          disease resistance and output characteristics
                          of a variety of crops. Additionally, use of
                          the proven Ahlquist technology promises to
                          extend the use of Bt to include the attractive
                          market for high-value perennial crops such as
                          vines, and orchards

                -    MYCOGEN'S INTELLECTUAL PROPERTY POSITION AND
                     INTELLECTUAL CAPITAL IS AMONG THE BEST IN THE
                     AGROBIOTECH INDUSTRY

                     -    Mycogen has one of the best molecular biology
                          IP positions amongst plant biotechnology
                          companies.  Mycogen's array of promoters,
                          expression cassettes, markers, and reporter
                          gene libraries provides critical mass to any
                          third party in the arena
                          
                     -    Newer applications, such oral immunity, are
                          promising and provide a strong platform to
                          pursue sizable commercial opportunities. These
                          technologies are likely to command a premium
                          price from many interested parties

                          
                     -    Mycogen's scientific and operating personnel
                          represent a significant asset to any
                          interested party.   However, increased
                          spending by competitors (such as Novartis as
                          part of it's Plant Genome Initiative), could
                          hamper the retention of quality personnel at
                          Mycogen


                                       5
<PAGE>

MYCOGEN CORPORATION                                      MYCOGEN BUSINESS UNITS
- -------------------------------------------------------------------------------
KEY DRIVERS OF GROWTH

- ---------------             
 PRICING AND    -    TRAITS INTRODUCED INTO EXISTING SEED SALES ADD
 MARGINS             REVENUES AND REQUIRE R&D EXPENSES BUT DO NOT
- ---------------      REQUIRE A COMMENSURATE INCREASE IN SG&A

                     -    Seed traits are sold as a part of existing
                          conventional seeds.  There is no additional
                          SG&A expense and these traits essentially add
                          revenues that, net of R&D expenses, directly
                          impact the bottom line
                          
                     -    Bt Cotton seed hybrids, capable of conferring
                          resistance to common cotton pests, command a
                          price 230% that of conventional cotton seed
                          despite having the same manufacturing cost

                -    PRICING FOR NEW TRAITS IS BASED ON CAPTURING A
                     PORTION OF THE INCREASED VALUE OF THE IMPROVED SEED
                     TO END-USERS SUCH AS FARMERS AND FOOD PROCESSORS

                     -    Mycogen has developed pricing assumptions for
                          traits in development that are based on their
                          ability to decrease growing costs or increase
                          value for end-users.  Conservative estimates
                          of the portion of value captured by Mycogen,
                          based on Mycogen's business plan, have been
                          applied in the accompanying projections
                          
                     -    Similar pricing assumptions can be found in
                          reports of analysts who follow the agrobiotech
                          sector

- ---------------             
 ADOPTION RATES -    BIOTECH TRAITS ARE ASSUMED TO BE SOLD THROUGH
- ---------------      EXISTING MYCOGEN SEED DISTRIBUTION CAPABILITIES

                     -    Consistent with the operating model
                          assumptions, traits are assumed to be
                          primarily sold in Mycogen seed through
                          Mycogen's existing seed distribution network. 
                          The impact of additional sales created as a
                          result of add-on acquisitions, other than
                          those expected to close in 1998, have not been
                          included
                          
                     -    In certain cases, where business judgment
                          suggests opportunity, additional sales have
                          been shown through third-party channels. 
                          However, these sales are recorded only after
                          including a substantial discount (11%-50%),
                          and represent only a small fraction of both
                          Mycogen's sales and total third-party sales
                          (typically less than 5%)

                -    ADOPTION RATES FOR NEWLY INTRODUCED TRAITS ARE
                     CONSERVATIVELY MODELED BASED ON OBSERVED ADOPTION
                     RATES FOR EXISTING BIOTECH TRAITS

                     -    Adoption rates for traits into existing
                          Mycogen seed sales base are modeled using the
                          observed rate for adoption of existing Bt seed
                          strains.  Current data suggest that adoption
                          has been rapid and there is reason to believe
                          that the adoption rate is likely to speed up
                          rather than slow down


                                       6
<PAGE>

MYCOGEN CORPORATION                                      MYCOGEN BUSINESS UNITS
- -------------------------------------------------------------------------------
KEY DRIVERS OF GROWTH

- ---------------             
 MARKET SHARE   -    MYCOGEN SEEDS HAVE A STRONG PRESENCE IN THE U.S MARKET FOR
- ---------------      MAJOR ROW CROPS


                          
                     -    Mycogen currently commands about 5.2% of the U.S.
                          corn market
                          
                     -    Mycogen seeds are planted on nearly 10% of all U.S.
                          farms, a high trial rate which suggests an expansion
                          of Mycogen's market share
                          
                     -    Mycogen's existing network of breeding stations
                          throughout the U.S., Puerto Rico, Brazil and
                          Argentina provides the necessary diversity of seed
                          germplasm to provide a year-round supply of seed with
                          desired maturity, standability, water requirements,
                          storage properties and other characteristics

                -    MYCOGEN'S MARKET SHARE IS EXPECTED TO RISE DRIVEN BY ITS
                     LEADING HIGH-YIELDING HYBRIDS

                     -    Yield is a primary determinant of adoption.  In a
                          little over three years, Mycogen's corn hybrids have
                          become amongst the highest yielding hybrids currently
                          available (see graph overleaf)
                          
                     -    Recent market indicators show Mycogen gaining in
                          market share relative to competitors.  With the
                          planned continuation of current efforts, this trend
                          is highly likely to remain in place


                                       7
<PAGE>

MYCOGEN CORPORATION                                    MYCOGEN BUSINESS UNITS
- -----------------------------------------------------------------------------
COMPETITIVE CHARACTERISTICS OF RECENT MYCOGEN CORN HYBRIDS (YIELD IN BUSHELS 
PER ACRE)





             [GRAPH]                                   [GRAPH]






- ----------------------------
Data: Bt Corn Yield based on multiple independent Mycogen trials.


                                       8
<PAGE>


MYCOGEN CORPORATION                                      MYCOGEN BUSINESS UNITS
- -------------------------------------------------------------------------------
KEY BUSINESS SEGMENTS

- ---------------             
 CONVENTIONAL   -    THE CONVENTIONAL SEED BUSINESS FORMS THE BASIS FOR
 SEED CORN AND       DISTRIBUTION OF MYCOGEN TRAITS AND PROVIDES
 SOYBEAN             IMMEDIATE CASH FLOW TO OFFSET R&D EXPENDITURES
- ---------------
                -    CONVENTIONAL SEED BUSINESS VALUE IS CONCENTRATED
                     WITHIN NORTH AMERICA AND BRAZIL.  THIS IS BECAUSE
                     SEED BUSINESSES NEED A CRITICAL MARKET SHARE
                     (TYPICALLY AROUND 5%) BEFORE THEY CAN SHOW POSITIVE
                     NET INCOME.  BOTH NORTH AMERICA AND BRAZIL HAVE
                     REACHED THIS CRITICAL MARKET SHARE

                -    CORN AND SOYBEAN ARE THE MAJOR CROPS PLANTED IN
                     NORTH AMERICA AND BRAZIL.  THEY REPRESENT MOST OF
                     THE REVENUE AND MOST OF THE FIXED AND VARIABLE COSTS
- ---------------
 CORN EARLY     -    MYCOGEN'S MARKET SHARE IN THE NORTH AMERICAN CORN
 TRAITS              MARKET AND THE ATTRACTIVE GROWTH PROSPECTS FOR
- ---------------      MYCOGEN'S NEW CORN HYBRIDS PROVIDE A STRONG BASE TO
                     PROPEL SALES OF EARLY TRAITS

                -    MYCOGEN'S EXPERIENCE WITH TRANSFORMING CORN AND
                     GAINING SUITABLE EXPRESSION OF TRANSGENIC BT
                     PROVIDES A COMPETITIVE ADVANTAGE IN THE INTRODUCTION
                     OF NEW BT-BASED EARLY TRAITS

- ---------------
 SOYBEAN OUTPUT -    IMPROVED SOYBEAN NUTRITIVE CONTENT WILL RESULT IN
 TRAITS              SOYBEAN FARMERS AND PROCESSORS PAYING SIGNIFICANT
- ---------------      PREMIUMS FOR SEED

                     -    Soybean processing for food additives and
                          protein supplements/substitutes is a large and
                          growing industry.  Feed is the primary driver
                          of soybean value.  There is significant
                          potential to increase soybean nutritive content
                          (e.g. protein, amino acid composition and
                          processing characteristics) that will
                          significantly increase value for end-users
                          
                     -    Mycogen has access to various technologies,
                          including proprietary technologies from
                          Demeter, that are capable of improving soybean
                          nutritive content.  The potential for higher
                          prices from sales into Mycogen and third-party
                          channels is a significant source of value


                                       9
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                      -----------------------------------


                               DCF ANALYSIS --
                           PROCESS AND METHODOLOGY


                      -----------------------------------


                                      10
<PAGE>

MYCOGEN CORPORATION                          VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
FINANCIAL PROJECTION METHODOLOGY

- -    THE SPECIAL COMMITTEE OF THE BOARD OF DIRECTORS OF MYCOGEN HAS AUTHORIZED
     WP&CO. TO UNDERTAKE A COMPREHENSIVE REVIEW OF MYCOGEN'S PRODUCTS AND
     DEVELOPMENT PORTFOLIO

- -    WP&CO. HAS CONDUCTED LENGTHY DUE DILIGENCE VISITS AND REVIEWED THE
     FOLLOWING INDUSTRY AND COMPANY DOCUMENTS

     -    Company financial projections and business unit plans - current
          projections, primarily based on existing Bt traits and the
          conventional seed business.  Also, strategic plans for all major
          business units, including startup plans for businesses based on early
          stage technologies and promising IP platforms
     
     -    Company and Competitor Financial Publications - Company/analyst 
          estimates for comparable operating ratios and projections

     -    R&D Gap Analysis and Independent Committee Documents - Internal
          management and scientific expert review of company strategy, R&D
          portfolio, including early stage pipeline, IP portfolio, and required
          funding levels to support various programs

     -    Mycogen Partner Presentations:  presentations by Mycogen partners
          specifically relating to joint ventures.  These include AC Humko,
          Verneuil Mycogen, Morgan Seeds and Dinamilho

     -    Dow Presentations and Valuations:  Analysis and valuation models built
          by Dow in collaboration with Mycogen with respect to potential Mycogen
          opportunities.  Includes Dow Argentina opportunity analysis, Phytogen
          JV analysis and the Dow/ RCW Consultores Brazil market analysis

     -    Industry Research Reports:  Proprietary industry reviews containing
          information on competitor offerings, growth and  market share.  These
          include Doane Marketing Research "Report on U.S. Farm Seed Study",
          National Corn Growers Association reports, Context Consulting "Report
          on Biotech Traits" and Negocios e Mercados "Report on Brazilian Seed
          Market"

     -    Presentations by and interviews with senior management, Special
          Committee members, key research personnel, operating management
          including business unit managers and sales staff and outside academic
          specialists

- -    BASED ON INFORMATION COLLECTED FROM THESE SOURCES, WP&CO. AND MYCOGEN
     MANAGEMENT MODIFIED COMPANY PROJECTIONS AS NECESSARY TO DEVELOP A SINGLE
     SET OF FINANCIAL PROJECTIONS FOR THE 1998-2007 PERIOD BY BUSINESS SEGMENT. 
     THESE PROJECTIONS ARE THE BASIS FOR THE VALUATIONS DESCRIBED IN THE SECTION
     "RESULTS OF DCF VALUATION"

- -    THESE PROJECTIONS INCLUDE THE IMPACT OF THREE PENDING ACQUISITIONS IN
     BRAZIL.  ALTHOUGH THE COMPANY'S CURRENT BALANCE SHEET DOES NOT REFLECT THE
     COST OF THESE ACQUISITIONS, OUR BALANCE SHEET HAS INCLUDED THE INCREASE IN
     NET DEBT AS A RESULT OF THESE ACQUISITIONS.  THERE ARE NO OTHER
     ACQUISITIONS CONTRIBUTING TO THESE PROJECTIONS

- -    SYNERGIES THAT WOULD RESULT FROM COMBINATION OF MYCOGEN WITH A THIRD
     PARTY, THAT WOULD USUALLY BE REALIZED THROUGH AN AUCTION PROCESS, HAVE NOT
     BEEN INCLUDED IN THE CURRENT PROJECTIONS.  CERTAIN SYNERGIES THAT WOULD BE
     EXPECTED IN A COMBINATION WITH DOW, SUCH AS HEADCOUNT REDUCTIONS AND THE
     EFFICIENT USE OF NET OPERATING LOSSES (NOL's) HAVE BEEN INCLUDED


                                      11
<PAGE>

MYCOGEN                                VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
FINANCIAL PROJECTION METHODOLOGY

- -----------------------------------    -----------------------------------------
       10-YEAR PROJECTIONS                     DETAILED BASIS
- -----------------------------------    -----------------------------------------
                                       -----------------------------------------
      Target Crop Acreage              - Includes demographic factors and
              X                          regional analysis by crop
                                       - Shifting planting patterns
                                       -----------------------------------------
                                       -----------------------------------------
Market Penetration of Genetically      - Adoption value of Bt and output 
        Modified Seeds                   modified seed
              X                        - Presence on farmer's fields
                                       -----------------------------------------
                                       -----------------------------------------
 Market Share of Mycogen Product       - Preferred penetration in existing base
              X                        - Access to partners with large share of
                                         new markets
                                       -----------------------------------------
                                       -----------------------------------------
  Mycogen Product Selling Price        
              =                        - Value capture based on improved
 Mycogen Product Sales Projections       productivity and competitive
              -                          advantage
                                       -----------------------------------------
                                       -----------------------------------------

                                       - Costs reflect minimal additional COGS
                                         and SGA for traits above those for 
 Fixed and Variable Costs and Taxes      conventional seed
              +                        - R&D investment accelerated to ensure
                                         successful timing of products
                                       -----------------------------------------
                                       -----------------------------------------
Cash Flow Impact (-W.I. - CapEx + Dep.)- Based on current inventory and accounts
              =                          payable/receivable trends
  Mycogen Product Free Cash Flow       - Additional plant expenditure is
                                         dependent on sales levels and existing 
                                         capacity
                                       -----------------------------------------
- -----------------------------------
       VALUATION METHODOLOGY
- -----------------------------------

                                       12
<PAGE>

MYCOGEN                                VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
VALUATION METHODOLOGY

- -----------------              ---------------              -------------------
 TERMINAL VALUE:                DISCOUNT RATE                PERPETUITY VALUE:
 EBIT MULTIPLES                                                  FREE CASH
                                                                  GROWTH
- -----------------              ---------------              -------------------


                                  [GRAPH]




                                      13
<PAGE>

MYCOGEN                                     VALUATION: PROCESS AND METHODOLOGY
- ------------------------------------------------------------------------------
IMPLICATION OF PROJECTED GROWTH RATE - NORTH AMERICA EXAMPLE

<TABLE>
<CAPTION>
                                  --------
- ----                 ------       IMPLIED                ------
CROP                 GROWTH        EBIT                  MARKET
- ----                  RATE        MULTIPLE               SHARE*
                     ------       --------               ------
<S>                  <C>          <C>          <C>

                                                               13.6%
                                                   3.4%
Corn Input           5.0 - 6.5%   3.3 - 4.7x   [BAR GRAPH]  [BAR GRAPH]
                                               ------------------------
                                                   1997         2007


                                                                3.9%
                                                     
Soybean Output       5.0 - 6.5%   2.5 - 3.4x         0%     [BAR GRAPH]
                                               ------------------------
                                                   1997         2007


                                                                 10%
                                                     
Disease Resistance   8.0 - 10.0%  1.5 - 3.1x         0%     [BAR GRAPH]
(Share of Mycogen                              ------------------------
 Market)                                           1997         2007

</TABLE>


- --------------------------
*Assumes that total market remains constant and revenues / customer are fixed.


                                       14
<PAGE>

MYCOGEN CORPORATION                          VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
ILLUSTRATIVE FINANCIAL PROJECTIONS -- NORTH AMERICA SOYBEAN TRAIT EXAMPLE


- -    MYCOGEN'S FINANCE GROUP IN COLLABORATION WITH INDIVIDUAL BUSINESS UNITS
     PREPARED DETAILED FINANCIAL PROJECTIONS INCLUDING PRICING, PENETRATION AND
     MARGIN ASSUMPTIONS.  A SAMPLE OF THESE PROJECTIONS (FOR THE NORTH AMERICAN
     SOYBEAN TRAIT BUSINESS) ARE INCLUDED ON PAGE 17-19.

- -    WP&CO. EXAMINED THESE PROJECTIONS AND IN CONSULTATION WITH MYCOGEN
     MANAGEMENT MODIFIED THEM AS NECESSARY TO ENSURE CONSISTENCY WITH OVERALL
     MARKET TRENDS AND AVAILABILITY OF REQUIRED DEVELOPMENT FUNDS.

     -    Ensure pricing by geographies is comparable and market share of traits
          is consistent with planned introduction of stacked traits

     -    Allow for pricing discounts where third party sales channels or 
          technology licenses are required

     -    Relate necessary R&D spending to gap analysis conducted by scientific
          and technical planning committee.  R&D spending allocated to
          individual product lines and independent business units where possible

     -    Apply consistent operating assumptions to generate cash flows for
          individual business units and corporate center

- -    THE RESULTING 10-YEAR FINANCIAL PROJECTIONS (INCLUDING 1998) WERE USED TO
     ESTIMATE THE VALUE OF EACH LINE OF BUSINESS.  ASSUMPTIONS FOR EACH BUSINESS
     UNIT WERE APPLIED SO AS TO BE CONSISTENT IN TERMS OF GROWTH RATES, EXPECTED
     TERMINAL MULTIPLES AND RISK ADJUSTED DISCOUNT RATES.  SAMPLE VALUATION
     SUMMARIES FOR THE NORTH AMERICAN SOYBEAN TRAIT BUSINESS UNIT ARE SHOWN ON
     PAGE 20.


                                      15
<PAGE>

MYCOGEN CORPORATION                          VALUATION: PROCESS AND METHODOLOGY
- -------------------------------------------------------------------------------
RECONCILIATION OF PROJECTIONS - CURRENT ESTIMATES VERSUS PRIOR BUSINESS PLANS

- -    TIMING:  THE PREVIOUS VERSION OF THE MYCOGEN BOARD PLAN WAS PREPARED IN
     AUGUST 1997, NEARLY ONE YEAR AGO

- -    COMMERCIALIZATION EXPERIENCE AND SUCCESS:  IN THE PAST YEAR, MYCOGEN HAS
     MET SOLID SUCCESS IN THE COMMERCIALIZATION OF NEW HYBRIDS.  THESE GAINS,
     PRIMARILY IN DEVELOPING BREEDING PROGRAMS THAT GENERATE QUALITY GERMPLASM
     AND ESTABLISHING DEALER AND PARTNER NETWORKS, ARE EXPECTED TO ACCELERATE
     THE GAIN OF MARKET SHARE

     -    Totally Managed Feedstuff (TMF) high-silage corn has been rapidly
          accepted by farmers.  As a result Mycogen has been able to sign
          agreements with over 20 new distributors over the past ten months. 
          This additional market share will also translate into additional
          revenues for early, output and disease resistance traits
     
     -    Mycogen's new corn hybrids show yields comparable to the leading 
          Pioneer hybrids.  As a result, Mycogen's prior estimates for corn 
          seed sales in the 2000-2007 period  have been revised slightly upward

- -    STRATEGY:  MYCOGEN'S STRATEGY FOR THE SOUTH AMERICA MARKET HAS FORGED AHEAD

     -    Mycogen has made three significant acquisitions in the Brazilian
          market that strengthen its presence in this large market.  These
          acquisitions were not included in the prior business plans

     -    Considerable improvement has been made in rationalizing customer
          accounts in Argentina and Brazil.  This is resulting in an improvement
          in margins that has not been included in prior business plans

- -    NON-CORE CROPS:  SIGNIFICANT OPPORTUNITIES EXIST FOR BT TECHNOLOGY IN RICE,
     TURF, ALFALFA AND OTHER CROPS.  THESE OPPORTUNITIES WHILE NOT INCLUDED IN
     PREVIOUS PROJECTIONS, ARE INCLUDED IN CURRENT PROJECTIONS

- -    NEW TECHNOLOGIES:  MYCOGEN HAS DEVELOPED NEW TECHNOLOGY PLATFORMS THAT
     ALLOW IT TO AGGRESSIVELY PURSUE NEW OPPORTUNITIES IN OUTPUT TRAIT
     ENHANCEMENT AND PLANT DISEASE RESISTANCE

     -    Demeter, Ahlquist and other transgenic technologies are powerful
          recent additions to Mycogen's IP  portfolio

     -    New business opportunities presented by these technologies are sizable
          but have not been included in previous business plans

     -    With Mycogen's increasing experience in plant gene characterization
          and expression as well as in breeding elite germplasm, Mycogen is
          highly confident that these programs, if adequately funded, will
          generate significant value

- -    R&D SPENDING:  THE PROJECTIONS USED HERE HAVE BEEN DEVELOPED WITH A 
     BOTTOM-UP APPROACH TO ESTIMATING R&D FUNDING REQUIREMENTS.  BASED ON 
     SCIENTIFIC PERSONNEL ASSESSMENT OF BASIC RESEARCH (GENE 
     CHARACTERIZATION, PLANT TRANSFORMATION, OPTIMIZATION AND BREEDING) 
     TRAIT-BASED SPENDING REQUIREMENTS WERE ADDED TO THE TRADITIONAL 
     "PERCENTAGE OF SALES" APPROACH. OUR MORE CONSERVATIVE APPROACH PLACES 
     THE R&D SPENDING IN 2007 AT $215 MILLION AS OPPOSED TO THE CURRENT 
     BUSINESS PLAN ESTIMATE OF $68 MILLION


                                      16
<PAGE>

<TABLE>
<CAPTION>

                                                                       NORTH AMERICAN SEEDS
                                                                          SOYBEAN TRAITS

                                        1998    1999    2000     2001      2002      2003      2004      2005      2006      2007
                                        ------------------------------------------------------------------------------------------
<S>                                     <C>     <C>     <C>      <C>       <C>       <C>       <C>       <C>       <C>       <C>
SOYBEAN TRAITS MARKETED MYCOGEN RETAIL
MYCOGEN UNITS IN THOUSANDS              1,635   1,700   1,921    2,229     2,674     3,209     3,851     4,621     5,776     7,221

LIBERTY HERBICIDE (THIRD PARTY)
Seed premium value capture per bag                     $ 1.00   $ 1.15   $  3.25   $  3.60   $  4.00   $  4.40   $  4.75   $  5.15
% of Market Share Penetrated                               10%      15%       20%       20%       20%       20%       20%       20%
Liberty Revenue per year (000)                         $  192   $  384   $ 1,738   $ 2,311   $ 3,081   $ 4,067   $ 5,488   $ 7,437

ROUNDUP READY (THRU NOVARTIS)
Seed premium value capture per bag                     $ 4.00   $ 5.00   $  6.00   $  7.00   $  7.00   $  6.00   $  5.00   $  5.00
% of Market Share Penetrated                               60%      80%       80%       80%       80%       70%       70%       60%
Bt cyst Revenue per year (000)                         $4,611   $8,914   $12,837   $17,971   $21,565   $19,409   $20,218   $21,662

Bt CYST
Seed premium value capture per bag                                                           $  8.00   $  8.00   $  9.50   $  9.50
% of Market Share Penetrated                                                                       2%       10%       30%       50%
Bt cyst Revenue per year (000)                                                               $   616   $ 3,697   $16,463   $34,298

                                        ------------------------------------------------------------------------------------------
   TOTAL REVENUE (000)                                 $4,803   $9,299   $14,575   $20,282   $25,262   $27,173   $42,168   $63,397
                                        ------------------------------------------------------------------------------------------
                                        ------------------------------------------------------------------------------------------

</TABLE>

ASSUMPTIONS

Bt CYST
Market opportunity = 46,000,000 bags
Soybean yields improve 15%
Mycogen retains 25% of increased yield value

LIBERTY HERBICIDE (THIRD PARTY)
Market opportunity = 9,200,000 bags
Liberty seed premium is 50% of RR tech + genetics
Mycogen retains 50% of Liberty seed premium
RR tech fee will increase $1/bag per year, RR genetic increase $.50/bag per
 year. Current tech fee $5/bag, RR genetics @ $2/bag

                                      17
<PAGE>

<TABLE>
<CAPTION>


                                                                NORTH AMERICAN SEEDS
                                                                   SOYBEAN TRAITS

                                       1998  1999   2000   2001   2002     2003     2004     2005     2006     2007
                                       ------------------------------------------------------------------------------
<S>                                    <C>   <C>    <C>    <C>    <C>      <C>      <C>      <C>      <C>      <C>
SOYBEAN TRAITS TO THIRD PARTIES

LIBERTY HERBICIDE (THIRD PARTY)
Seed premium value capture per bag                  $  -   $  -   $ 2.00   $ 2.00   $ 2.00   $ 2.00   $ 2.00   $ 2.00
 Units (000)                                                         300      400      500      600      700      800
% of Market Share Penetrated                                           0%       0%       1%       1%       1%       1%
Liberty Revenue per year (000)                                    $    2   $    3   $    5   $    8   $   11   $   14

Bt CYST
Seed premium value capture per bag                                                  $ 5.00   $ 5.00   $ 5.00   $ 5.00
 Units (000)                                                                           200      400    1,000    1,500
% of Market Share Penetrated                                                             0%       0%       1%       2%
Bt cyst Revenue per year (000)                                                      $1,000   $2,000   $5,000   $7,500

                                       ------------------------------------------------------------------------------
   Total Revenue (000)                              $  0   $  0   $    2   $    3   $1,005   $2,008   $5,011   $7,514
                                       ------------------------------------------------------------------------------
                                       ------------------------------------------------------------------------------

GENETIC ROYALTIES
Trait Related Genetic Royalties                                      900    1,200    2,100    3,000    5,100    6,900
Non Trait Related Genetic Royalties     85    100    125    150      200      300      300      300      300      300
                                       ------------------------------------------------------------------------------
   Total Sunflower Genetic Royalties   $85   $100   $125   $150   $1,100   $1,500   $2,400   $3,300   $5,400   $7,200
                                       ------------------------------------------------------------------------------
                                       ------------------------------------------------------------------------------

</TABLE>

ASSUMPTIONS

Bt CYST
Market opportunity = 46,000,000 bags
Soybean yields improve 15%
Royalty $5.00/bag

LIBERTY HERBICIDE (THIRD PARTY)
Market opportunity = 9,200,000 bags
Liberty seed premium is 50% of RR tech + genetics
Mycogen LibertyLink genetic royalty $2.00/bag
RR tech fee will increase $1/bag per year, RR genetic increase $.50/bag per
 year. Current tech fee $5/bag, RR genetics @ $2/bag

                                      18
<PAGE>

<TABLE>
<CAPTION>

                                                                  NORTH AMERICAN SEEDS

                                  1998     1999     2000     2001     2002     2003     2004     2005     2006     2007
                                -----------------------------------------------------------------------------------------
<S>                             <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>     <C>      <C>
SOYBEAN RESEARCH
Sales Dollars                    23,457   26,557   31,473   38,207   47,886   61,130   77,758   98,591 129,841   170,554
SOYBEAN % OF SALES
Hybrid Development
Line Development                    3.7%     3.7%     5.1%     5.4%     8.9%     8.3%     7.8%     7.6%    6.9%      6.2%
Trait introgression                 0.2%     0.2%     0.4%     0.6%     1.0%     0.9%     0.9%     0.8%    0.8%      0.7%
                                -----------------------------------------------------------------------------------------
  Total %                           3.9%     3.9%     5.5%     6.0%     9.9%     9.2%     8.6%     8.4%    7.6%      6.9%
                                -----------------------------------------------------------------------------------------

SOYBEAN DOLLARS
Hybrid Development                    0        0        0        0        0        0        0        0       0         0
Line Development                    865      978    1,591    2,075    4,255    5,066    6,031    7,479   8,910    10,617
Trait introgression                  46       62      138      231      473      563      670      831     990     1,180
                                -----------------------------------------------------------------------------------------
  Total Dollars                     911    1,040    1,729    2,306    4,728    5,629    6,701    8,310   9,900    11,797
                                -----------------------------------------------------------------------------------------
                                -----------------------------------------------------------------------------------------

TOTAL R&D DOLLARS BY ACTIVITY
Hybrid Development                7,235    8,257   10,796   13,339   17,166   20,425   23,556   30,004  36,700    44,297
Line Development                  3,353    4,003    5,198    7,261   10,916   12,988   14,336   17,811  21,197    25,241
Trait introgression                 533      648    1,203    2,259    3,169    3,859    6,478    7,178   7,547     8,391
Other                               125      120      126      213      295      287      347      427     576       740
                                -----------------------------------------------------------------------------------------
  Total                          11,246   13,028   17,323   23,072   31,546   37,559   44,717   55,419  66,021    78,669
                                -----------------------------------------------------------------------------------------
                                -----------------------------------------------------------------------------------------

TOTAL R&D DOLLARS BY CROP
Corn                              9,077   10,532   13,662   18,212   23,324   27,768   33,059   40,995  48,840    58,199
Soybeans                            911    1,040    1,729    2,306    4,728    5,629    6,701    8,310   9,900    11,797
Sunflowers                        1,024    1,171    1,557    2,075    2,837    3,377    4,021    4,986   5,940     7,078
Sorghum                             109      165      249      266      362      498      589      701     765       855
Other                               125      120      126      213      295      287      347      427     576       740
                                -----------------------------------------------------------------------------------------
  Total                          11,246   13,028   17,323   23,072   31,546   37,559   44,717   55,419   66,021   78,669
                                -----------------------------------------------------------------------------------------
                                -----------------------------------------------------------------------------------------

% of Sales Dollars                   11%      11%      12%      13%      14%      14%      14%      14%      14%      13%

</TABLE>


                                       19
<PAGE>

MYCOGEN CORPORATION                           VALUATION: PROCESS AND METHODOLOGY
- --------------------------------------------------------------------------------
N. AMERICA SOYBEAN/SORGHUM INPUT TRAITS DISCOUNTED CASH FLOW ANALYSIS

<TABLE>
<CAPTION>

- -------------                                   -------------------------------
DISCOUNT RATE                                   YEAR 2007 CASH FLOW GROWTH RATE
- -------------                                   -------------------------------
                                                  5.0%    5.5%    6.0%    6.5%
                                                 ------  ------  ------  ------
<S>                                              <C>     <C>     <C>     <C>

     20.0%    PV of Free Cash Flow               $27.7   $27.7   $27.7   $27.7
              PV of Terminal Multiple             39.8    41.4    43.1    44.9
                                                 ------  ------  ------  ------
              Enterprise Value                   $67.5   $69.1   $70.8   $72.6
              Less: Net Debt                       0.0     0.0     0.0     0.0
                                                 ------  ------  ------  ------
              EQUITY VALUE                       $67.5   $69.1   $70.8   $72.6
              IMPLIED PERPETUITY GROWTH            5.0%    5.5%    6.0%    6.5%
                % VALUE FROM TERMINAL MULT.       59.0%   59.9%   60.9%   61.8%


     22.0%    PV of Free Cash Flow               $24.6   $24.6   $24.6   $24.6
              PV of Terminal Multiple             29.8    30.8    31.9    33.1
                                                 ------  ------  ------  ------
              Enterprise Value                   $54.3   $55.4   $56.5   $57.7
              Less: Net Debt                       0.0     0.0     0.0     0.0
                                                 ------  ------  ------  ------
              EQUITY VALUE                       $54.3   $55.4   $56.5   $57.7
              IMPLIED PERPETUITY GROWTH            5.0%    5.5%    6.0%    6.5%
                % VALUE FROM TERMINAL MULT.       54.8%   55.7%   56.5%   57.4%


     24.0%    PV of Free Cash Flow               $21.9   $21.9   $21.9   $21.9
              PV of Terminal Multiple             22.6    23.4    24.1    24.9
                                                 ------  ------  ------  ------
              Enterprise Value                   $44.5   $45.2   $46.0   $46.8
              Less: Net Debt                       0.0     0.0     0.0     0.0
                                                 ------  ------  ------  ------
              EQUITY VALUE                       $44.5   $45.2   $46.0   $46.8
              IMPLIED PERPETUITY GROWTH            5.0%    5.5%    6.0%    6.5%
                % VALUE FROM TERMINAL MULT.       50.9%   51.7%   52.5%   53.3%


           --------------------------------------------------------------------

           SELECTED EQUITY VALUE RANGE       $45             --            $73

           --------------------------------------------------------------------
</TABLE>


                                       20
<PAGE>

<TABLE>
<CAPTION> 
MYCOGEN CORPORATION                                                                            VALUATION: SUMMARY OF BUSINESS UNITS
- ------------------------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------------------------
ELEMENTS OF PROJECTED BUSINESS VALUATION

- -------------------------------------------------------------------------------------------------------------------------------
       BUSINESS                CROP                       TRAIT                          GEOGRAPHICAL REGION
       --------                ----                       -----                          -------------------
                                                                           N. AMERICA    ARGENTINA    BRAZIL           OTHER
- -------------------------------------------------------------------------------------------------------------------------------
       <S>                  <C>                        <C>                  <C>          <C>          <C>            <C>
       Biopesticides           --                          --                   X

       SoilServ                --                          --                   X

       Conventional Seed
                           Corn                            --                   X           X            X
                           Soybeans                        --                   X
                           Sunflower                       --                   X
                           Sorghum                         --                   X
                           Alfalfa                         --                   X

       Early Traits (Herbicide Resistance)
                           Corn                        RR/LL                    X           X            X
                           Sunflower                   RR/LL                                X
                           Soybean                     LL                       X
                           Sorghum                     RR/LL                    X

       Early Traits (Insect Resistance)
                           Corn                        Bt176                    X
                           Corn                        Spodoptera                                        X
                           Corn                        Elasmopalpost                                     X
                           Corn                        Diabrotica                                        X
                           Corn                        Helicoverpa                                       X
                           Corn                        Armyworm
                           Corn                        ECB/Glufosinate          X           X
                           Corn                        CRW/Glufosinate          X           X
                           Sunflower                   Looper                               X
                           Sunflower                   Head Moth                X
                           Sunflower                   Seed Weevil              X
                           Soybean                     Cyst                     X                        X
- -------------------------------------------------------------------------------------------------------------------------------

</TABLE>
 

                                          21
<PAGE>

<TABLE>
<CAPTION> 
MYCOGEN CORPORATION                                                                            VALUATION: SUMMARY OF BUSINESS UNITS
- ------------------------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------------------------
ELEMENTS OF PROJECTED BUSINESS VALUATION (CONT'D)

- -------------------------------------------------------------------------------------------------------------------------------
       BUSINESS                CROP                       TRAIT                          GEOGRAPHICAL REGION
       --------                ----                       -----                          -------------------
                                                                           N. AMERICA    ARGENTINA    BRAZIL           OTHER
- -------------------------------------------------------------------------------------------------------------------------------
       <S>                  <C>                        <C>                  <C>          <C>          <C>            <C>
                           Sorghum                     Midge
                                                       Greenbug Aphid
                           Alfalfa                     Weevil
                                                       Lepidoptera

       Output              Corn                        High Oil                 X           X            X
                                                       High Oil/Evt. 176        X
                                                       Hi Oleic                 X           X            X
                                                       Low Phytate              X           X            X
                                                       Forage Protein           X           X            X
                                                       Green Gene               X           X            X
                           Soybean                     High Nutrition           X                        X
                           Sunflower                   High Oleic               X
                                                       High Palmitic            X
                                                       Quality Protein          X           X
                           Sorghum                     Nutritional              X

       Disease Resistance
                           Corn                        Mold/Mycotoxin                       X            X
                           Sunflower                   Sclerotinia              X           X
                                                       Verticilian                          X
- -------------------------------------------------------------------------------------------------------------------------------

</TABLE>
 

                                          22
<PAGE>

<TABLE>
<CAPTION> 
MYCOGEN CORPORATION                                                                            VALUATION: SUMMARY OF BUSINESS UNITS
- ------------------------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------------------------
ELEMENTS OF PROJECTED BUSINESS VALUATION (CONT'D)

- -------------------------------------------------------------------------------------------------------------------------------
       BUSINESS                  CROP                       TRAIT                          GEOGRAPHICAL REGION
       --------                  ----                       -----                          -------------------
                                                                             N. AMERICA    ARGENTINA    BRAZIL           OTHER
- -------------------------------------------------------------------------------------------------------------------------------
       <S>                    <C>                        <C>                  <C>          <C>          <C>            <C>
       JV/Partner Royalties
                              VMO                        Conventional                                                  Europe
                                                         Early Traits                                                  Europe
                                                         Output Traits                                                 Europe
                              Cotton                     Conventional             X           X
                                                         Bud/Bollworm             X           X                        Australia
                                                         Boll Weevil              X           X                          and
                                                         Lygus                    X                                    Greece
                              Oilseed/Humko                  --                   X           X
                              Oilseed/DAS                    --                   X
                              Rice                       Stem Borer                                                    Japan
                                                         Plant Hopper                                                  Japan
                              Turf                       White Grub               X
                                                         Army/Cutworm             X
                                                         Webworm                  X
- -------------------------------------------------------------------------------------------------------------------------------

                           --------------------------------------------------------------------------------------------------
                           PRODUCTS VALUED (BY REGION)                             38            19         14             7

                           TOTAL PRODUCT LINES VALUED                              78
                           --------------------------------------------------------------------------------------------------

                           -----------------------------------------------------------
                           CONVENTIONAL AND OTHER                                  14
                           EARLY TRAITS                                            33
                           OUTPUT TRAITS                                           25
                           DISEASE RESISTANCE                                       5
                           -----------------------------------------------------------

</TABLE>
 

                                          23
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                      -----------------------------------


                         RESULTS OF DISCOUNTED CASH 
                               FLOW VALUATION


                      -----------------------------------


                                      24
<PAGE>

<TABLE>
<CAPTION>
MYCOGEN CORPORATION                                                                 VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- ----------------------------------------------------------------------------------------------------------------------------------
SUMMARY OF VALUATION


   ------------------------------------------------------------------------------------------------------------
     BUSINESS                   CROP                REGION                DISCOUNT            GROWTH RATE     
                                                                             RATE             /EBIT MULTIPLE   
   ------------------------------------------------------------------------------------------------------------
<S>                           <C>                 <C>                   <C>                  <C>          <C>  
     Biopesticides            --                     --                11.0% - 14.0%           6 -       10    
     SoilServ                 --                     --                11.0% - 14.0%           6 -       10    
     Conven. Seed
                                  Corn            N. America           12.0% - 14.0%           8 -       12    
                                                  Argentina            12.0% - 14.0%           8 -       12    
                                                  Brazil               12.0% - 14.0%           8 -       12    
                                  Soybeans        N. America           12.0% - 14.0%           8 -       12
                                                  Brazil               12.0% - 14.0%           8 -       12
                                  Sorghum         N. America           12.0% - 14.0%           8 -       12    
                                  Alfalfa         N. America           12.0% - 14.0%           8 -       12    
                                  Sunflower       N. America           12.0% - 14.0%           8 -       12    
                                                  Argentina            12.0% - 14.0%           8 -       12    
                                  All             N. America           12.0% - 14.0%           8 -       12    
                                                  Argentina            12.0% - 14.0%           8 -       12    
                                                  Brazil               12.0% - 14.0%           8 -       12    
                                                                                                               

     Early / Input Traits
                                  Corn            N. America           20.0% - 24.0%        5.0% -     8.5%    
                                                  Argentina            20.0% - 24.0%        0.0% -     6.5%    
                                                  Brazil               20.0% - 24.0%        5.0% -     6.5%    
                                  Soybeans        N. America           20.0% - 24.0%        5.0% -     6.5%    
                                                  Brazil               20.0% - 24.0%        5.0% -     6.5%    
                                  Sunflower       N. America           20.0% - 24.0%        5.0% -     6.5%    
                                                  Argentina            20.0% - 24.0%        0.0% -     6.5%    
                                  All             N. America           20.0% - 24.0%        5.0% -     6.5%    
                                                  Argentina            20.0% - 24.0%        0.0% -     6.5%    
                                                  Brazil               20.0% - 24.0%        5.0% -     6.5%    
                                                                                                               

     Output Traits
                                  Corn            N. America           25.0% - 30.0%        5.0% -     6.5%    
                                                  Argentina            25.0% - 30.0%        5.0% -     6.5%    
                                                  Brazil               25.0% - 30.0%        5.0% -     6.5%    
                                  Soybean         N. America           25.0% - 30.0%        5.0% -     6.5%    
                                                  Brazil               25.0% - 30.0%        5.0% -     6.5%    
                                  Sunflower       N. America           25.0% - 30.0%        5.0% -     6.5%    
                                                  Argentina            25.0% - 30.0%        5.0% -     6.5%    
                                  All             N. America           25.0% - 30.0%        5.0% -     6.5%    
                                                  Argentina            25.0% - 30.0%        5.0% -     6.5%    
                                                  Brazil               25.0% - 30.0%        5.0% -     6.5%    
                                                                                                               

     Disease Resistance
                                                  N. America           31.0% -  50.0%       8.0% -    10.0%    
                                                  Argentina            31.0% -  50.0%       8.0% -    10.0%    
                                                  Brazil               31.0% -  50.0%       8.0% -    10.0%    
                                                                                                               
                                  All Other Crops                      45.0% - $50.0%       8.0% -    10.0%    
                                  Rice (Japan Tobacco)                 31.0% - $50.0%       8.0% -    10.0%    
                                                                                                               

     JV/Royalties
        VMO                       Conventional Seed                    12.0% -  14.0%          6 -       10    
                                  Early / Input Traits                 20.0% -  24.0%       5.0% -     6.5%    
                                  Output Traits                        25.0% -  30.0%       5.0% -     6.5%    
                                  Disease-Res.                         31.0% -  30.0%       8.0% -    10.0%    
                                                                                                     Total VMO 
        JG Boswell                Cotton                               12.0% -  14.0%          8 -       12    

        Humko                     Oilseed         N. America           12.0% -  14.0%          6 -       10    
                                                  Argentina            12.0% -  14.0%          6 -       10    
                                                                                                 Total Oilseed 
        DAS Canada                Canola                               20.0% -  24.0%          8 -       12    
        PHB Bt Royalties                                               20.0% -  20.0%                          
        Other Partner Royalties                                        20.0% -  24.0%       1.0% -      25%    
        Other Pests / Crops                                            31.0% - $ 0.0%       5.0% -     6.3%    

     Miscellaneous (1)

                              Synergy with Third Party (common Illinois Foundation Seed)                       
                              Cost Savings                                                                     
                              NOL-Current (est)                                                                
                              NOL-Projected (est)                                                              
                              Monsanto Settlement (80%-100% Probability)         
                              35% in Vermont (at cost)                                                         
                              Oral Immunity (est.)                                                           
                              Bt Blocking (50% Probability)            20.0% - 24.0%                           
                              Corporate A&D                            22.0% - 14.0%                           
                              Litigation Expense (Net of Interest)     12.8% - 14.0%                           
                              Net Debt                                                                         
                                                                                                               

                                                                                                               
                                                                                                               

     Total
        Shares Outstand (MM)      36.26
        Options Outstand (MM)      3.59
     Final Outstanding (Treasury Method, MM)                                                                        

                                                                                             Value/Share       
   ------------------------------------------------------------------------------------------------------------

<CAPTION>

   ---------------------------------------------------------------------------------------- 
            VALUATION                                     GEOGRAPHIC         SUB-     VALUE/ 
       LO            HI        AVERAGE         TOTAL        TOTAL           TOTALS    SHARE 
   ---------------------------------------------------------------------------------------- 
       <C>          <C>        <C>         <C>             <C>          <C>                 
         $3 -         $4           $4             $4          $4        $0.09 - $0.12       
        $28 -        $40          $34            $34         $34        $0.72 - $1.02       
                                                                                            
        $94 -       $210         $152                                                       
        $37 -        $56          $47                                                       
       $101 -       $175         $138
       ($10)-        $18           $4                                                       
         $0 -         $0           $0                                                       
         $9 -        $15          $12                                                       
         $3 -         $9           $6
        ($4)-        ($4)         ($4)                                                       
        $14 -        $22          $18                                                       
        $97 -       $254                        $176                    $2.54 - $6.53       
        $49 -        $79                         $64                    $1.29 - $2.02       
       $101 -       $175                        $138                    $2.65 - $4.50       
              Total Conventional Seed                       $378                            
                                                                                            
                                                                                            
        $72 -       $126          $99                                                       
         $1 -         $5           $3                                                       
        $29 -        $53          $41                                                       
        $45 -        $73          $59                                                       
        ($0)-         $1           $0                                                       
        ($1)-        ($1)         ($1)                                                       
        ($1)-         $2           $1                                                       
       $115 -       $198                        $156                    $3.01 - $5.08       
        ($0)-         $7                          $3                   $-0.01 - $0.18      
        $29 -        $54                         $41                    $0.75 - $1.39       
                    Total Early Traits                      $201                            
                                                                                            
                                                                                            
         $7 -        $17          $12                                                       
        ($2)-        ($2)         ($2)                                                       
         $5 -        $11           $8                                                       
       $144 -       $266         $205                                                       
         $7 -        $14          $11                                                       
         $4 -         $8           $6                                                       
        $13 -        $23          $18                                                       
       $156 -       $291                        $223                    $4.08 - $7.47       
        $11 -        $21                         $16                    $0.28 - $0.55       
        $14 -        $27                         $20                    $0.35 - $0.70       
                   Total Output Traits                      $260                            
                                                                                            
                                                                                            
        ($2)-         $0          ($1)           ($1)                  $-0.05 - $0.00      
        ($0)-         $2           $1             $1                    $0.00 - $0.04       
        ($0)-        ($0)         ($0)           ($0)                  $-0.01 - $-0.01     
     Total Disease Resistance (Current)                      ($1)
       $119 -       $154         $136           $136                    $3.10 - $3.96       
        ($2)-         $2          ($0)           ($0)                  $-0.06 - $0.04      
       Total Disease Resistance (Other)                     $136                            
                                                                                            
                                                                                         
         $7 -        $10           $9                                   $0.18 - $0.27       
        ($1)-        ($2)         ($2)                                  $-0.04 - $-0.04     
         $2 -         $4           $3                                   $0.06 - $0.11       
        ($0)-         $0           $0                                   $0.00 - $0.01       
         $8          $14                         $11         $11
        $39 -        $86          $73            $73         $73        $1.54 - $2.22       
                                                                                            
         $0 -         $0           $0             $0                    $0.00 - $0.00       
         $2 -         $3           $2             $2                    $0.06 - $0.07       
         $0 -         $0                                      $3
        $13 -        $21          $17            $17         $17        $0.34 - $0.54       
        $35          $38          $36            $36         $36        $0.90 - $0.97       
        $14 -        $21          $17            $17         $17        $0.35 - $0.54       
        $20 -       $104          $62            $62         $62        $0.53 - $2.67       
                                                                                         
                                                                                         
                                                                                         
        $29          $45          $37            $37                    $0.75 - $1.15       
         $9          $13          $11            $11                    $0.23 - $0.34       
        $80 -        $80          $80            $80                    $2.09 - $2.06       
        $30 -        $30          $30            $30                    $0.77 - $0.76       
        $82 -       $103          $92            $92                    $2.15 - $2.64       
         $9 -         $9           $9             $9                    $0.25 - $0.24       
        $20 -        $30          $30            $30                    $0.52 - $0.77       
       $111 -       $131         $121           $121                    $2.91 - $3.36       
       ($80)-       ($77)        ($79)          ($79)                  $-2.10 - $-1.99     
       ($37)-       ($34)        ($36)          ($36)                  $-0.97 - $-0.92     
       ($75)-       ($75)        ($75)          ($75)                  $-1.96 - $-1.93     
                                                            $220                            
                                                                                         
    ---------    ---------   ---------      ---------    --------                           
      $1,847      $1,841       $1,444         $1,482      $1,482                            
                                                                                         
                                                                                         
                                                                                         
                                                                                         
       38.27       38.93        38.40          38.75                                        
                                                                                         
      $27.37      $47.29       $37.32         $37.82                                        
   ---------------------------------------------------------------------------------------- 
</TABLE>

(1) Additional opportunities remaining to be quantified include biotech reagent
    and protocol licensed royalties and oral immunity.

Note: Initial value excludes contribution from revenue synergies, cost 
savings, and other economies of scale from consolidation with DAS.  Value per 
share calculated based on outstanding common shares, includes 3.593 million 
outstanding options with an average exercise price of $12.03

                                      25
<PAGE>


MYCOGEN                          VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- -------------------------------------------------------------------------------
VALUATION OF BUSINESSES (AVERAGE OF PROJECTED RANGE)


                                  [GRAPH]




                                       26
<PAGE>

MYCOGEN                          VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- -------------------------------------------------------------------------------
SENSITIVITY OF VALUATION TO CONVENTIONAL SEED MARKET SHARE

<TABLE>
<CAPTION>

                                          BASE CASE                                 SENSITIVITY ANALYSIS
                                          ---------                                 -------------------- 
                                 CONVENTIONAL                           NEW CONVENTIONAL            NEW CONVENTIONAL
                                 SEED MARKET      CONTRIBUTION          2007 SEED SHARE @           2007 SEED SHARE @
                                 1997   2007        TO VALUE             75% OF FORECAST             125% OF FORECAST
                                --------------   --------------     -----------------------      ----------------------
KEY BUSINESSES                                                                      CHANGE                      CHANGE
- --------------
<S>                             <C>     <C>      <C>                 <C>            <C>          <C>            <C>
CONVENTIONAL SEEDS

Corn             N. America       3.4%    13.6%    $2.46 - $5.40     $0.98 - $2.87  (60.2%)      $3.93 - $7.92   59.8%
 
                 Brazil          11.0%    29.0%    $2.65 - $4.50     $2.34 - $3.91  (11.7%)      $2.97 - $5.09   12.1%

EARLY TRAITS

Corn              N. America      3.4%    13.6%    $1.88 - $3.25     $1.60 - $2.76  (14.9%)      $2.16 - $3.72   14.9%

Soybean           N. America      1.8%     7.8%    $1.16 - $1.86     $0.86 - $1.36  (25.9%)      $1.22 - $1.96    5.2%

OUTPUT TRAITS

Soybean           N. America      1.8%     7.8%    $3.77 - $6.83     $3.55 - $6.40   (5.8%)      $3.99 - $7.24    5.8%



PERCENTAGE OF TOTAL VALUE (1)                             45.3%          40.6%                         48.7%

TOTAL  VALUATION/SHARE                              $27.37 - $47.29  $23.98 - $41.51             $30.25 - $52.38
</TABLE>

<TABLE>
<S>                                                                                   <C>
(1) Total valuation includes 35 additional business units.                             WASSERSTEIN PERELLA & CO.
- ----------------------------------------------------------------------------------------------------------------
</TABLE>


                                       27
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------
PROBABILITY-WEIGHTED VALUATION METHODOLOGY

- -    AN ALTERNATIVE METHOD OF VALUATION, RATHER THAN VARYING THE DISCOUNT RATES
     FOR VARIOUS PROJECTS, USES PROBABILISTIC WEIGHTING OF EVENTS WITH A
     CONSTANT RISK-ADJUSTED COST OF CAPITAL

- -    INSTEAD OF USING VARIABLE DISCOUNT RATES FOR BUSINESSES TO REFLECT THE
     VARYING ASSOCIATED RISK, THE RISK OF A GIVEN BUSINESS IS MADE EXPLICIT
     THROUGH DEFINED GO/NO GO DECISION STAGES

     -    The development pipeline for new products is defined in terms of
          discrete stages with associated cost requirements.  Each stage is also
          examined in terms of success rate of various categories of projects
          through the relevant go/no go decision points

     -    Scientific expert opinion is collectively applied to estimate the
          projected probability for successfully developing new projects.  Early
          stages receive a low probability due to scientific risks, and later
          stages receive a higher probability due to commercialization risks

- -    THE RESULTING PRODUCT ATTRITION AND SPENDING PROFILES ARE APPLIED TO
     ESTIMATE THE PROBABILITY THAT A GIVEN PROJECT WILL PASS THROUGH SUCCESSIVE
     STAGES OF THE DEVELOPMENT PIPELINE UNTIL COMMERCIALIZATION.  THESE
     PROBABILITY-WEIGHTED EXPENSE AND REVENUE STREAMS ARE THEN USED TO ESTIMATE
     THE FREE CASH FLOW AND ASSOCIATED VALUATION

- -    WP&CO. HAS LOWERED MANAGEMENT PROBABILITY ESTIMATES TO REFLECT EXECUTION
     AND COMMERCIALIZATION RISK IN LIGHT OF SIZE AND FINANCIAL RESOURCES OF
     COMPETITORS

                                      MANAGEMENT      WP&CO. MODIFIED
                                      ----------      ---------------
                                      ESTIMATES          ESTIMATES
                                      ---------          ---------

            EARLY TRAITS                 100%               90%

            OUTPUT TRAITS                100%               81%

            DISEASE RESISTANCE           100%               72%


                                      28
<PAGE>

MYCOGEN CORPORATION                       VALUATION: PROBABILITY-WEIGHTED METHOD
- --------------------------------------------------------------------------------
PRODUCT ATTRITION PROFILE FOR PROBABILITY-WEIGHTED VALUATION METHOD

- --------------------------------------------------------------------------------
- - THE PROBABILITY-WEIGHTED METHOD INCORPORATES ESTIMATED PROBABILITIES OF KEY 
  EVENTS IN THE COMMERCIALIZATION OF NEW PRODUCTS TO WEIGHT THE ASSOCIATED 
  REVENUES AND EXPENSES

- - BASED ON INPUT FROM KEY SCIENTIFIC PERSONNEL AT MYCOGEN, THE FOLLOWING 
  PROBABILITIES HAVE BEEN USED IN THIS VALUATION
- --------------------------------------------------------------------------------


                                       
            [GRAPH]                 [GRAPH]                 [GRAPH]



<TABLE>
<CAPTION>

     COST ($/MM)            T-5      T-4        T-3        T-2        T-1      T=0
                           -----    -----      -----      -----     ------   (LAUNCH)
<S>                        <C>      <C>        <C>        <C>       <C>      <C>

ACTIVITIES                 $2.00     $0.5       $0.0
Gene characterization                $1.0       $0.5
Expression/Screening                            $0.5      $0.1
Optimization                                              $0.6        $0.6
Event Breeding

</TABLE>


                                       29
<PAGE>

MYCOGEN CORPORATION              VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- -------------------------------------------------------------------------------
SUMMARY OF VALUATION

<TABLE>
<CAPTION>
- --------------------------------------------------------------------------------------------------------------------
                                            Discount     Growth Rate     Valuations                Geographic Sub-  
Business            Crop       Region         Rate     /EBIT Multiple   Lo         Hi     Average     Total   Totals
- --------------------------------------------------------------------------------------------------------------------
<S>                <C>         <C>         <C>            <C>           <C>       <C>      <C>       <C>      <C>   
BIO-PESTICIDES       -           -         10.0%-14.0%       6 -  10    $    3 -  $    5   $    4    $    4   $    4
SOILSERV             -           -         10.0%-14.0%       6 -  10    $   27 -  $   41   $   34    $   34   $   34
CONVEN. SEED       Corn        N. America  11.0%-14.0%       8 -  10    $   95 -  $  185   $  140  
                               Argentina   11.0%-14.0%       8 -  10    $   37 -  $   55   $   46  
                               Brazil      11.0%-14.0%       8 -  10    $  112 -  $  178   $  145  
                   Soybeans    N. America  11.0%-14.0%       8 -  10    $  (11)-  $    9   $   (1)  
                               Brazil      11.0%-14.0%       8 -  10    $    0 -  $    0   $    0  
                   Sorghum     N. America  11.0%-14.0%       8 -  10    $    9 -  $   14   $   12  
                   Alfalfa     N. America  11.0%-14.0%       8 -  10    $    3 -  $    8   $    5  
                   Sunflower   N. America  11.0%-14.0%       8 -  10    $   (4)-  $   (4)  $   (4) 
                               Argentina   11.0%-14.0%       8 -  10    $   15 -  $   22   $   18  
                   All         N. America  11.0%-14.0%       8 -  10    $  101 -  $  221             $  161         
                               Argentina   11.0%-14.0%       8 -  10    $   34 -  $   81             $   68         
                               Brazil      11.0%-14.0%       8 -  10    $  112 -  $  178             $  145         
                                                                                  TOTAL CONVENTIONAL SEED     $  374
                                                                                 
EARLY/INPUT TRAITS                                                               
                   Corn        N. America  11.0%-14.0%    5.0% - 6.5%   $   63 -  $  150   $  106
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $    1 -  $    6   $    4
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $   22 -  $   56   $   39
                   Soybeans    N. America  11.0%-14.0%    5.0% - 6.5%   $   87 -  $  189   $  138
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $   (0)-  $    1   $    0
                   Sunflower   N. America  11.0%-14.0%    5.0% - 6.5%   $   (2)-  $   (0)  $   (1)
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $   (0)-  $    4   $    2
                   All         N. America  11.0%-14.0%    5.0% - 6.5%   $  149 -  $  339             $  244         
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $    1 -  $   10             $    6         
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $   22 -  $   57             $   40         
                                                                                       TOTAL EARLY TRAITS     $  289
                                                                               
OUTPUT TRAITS                                                                  
                   Corn        N. America  11.0%-14.0%    5.0% - 6.5%   $    6 -  $   23   $   14
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $   (1)-  $   (0)  $   (1)
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $    2 -  $    9   $    5
                   Soybean     N. America  11.0%-14.0%    5.0% - 6.5%   $  110 -  $  276   $  193
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $    8 -  $   16   $   11
                   Sunflower   N. America  11.0%-14.0%    5.0% - 6.5%   $    3 -  $    7   $    5
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $    8 -  $   18   $   13
                   All         N. America  11.0%-14.0%    5.0% - 6.5%   $  120 -  $  306             $  213         
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $    6 -  $   18             $   12         
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $   10 -  $   27             $   18         
                                                                                      TOTAL OUTPUT TRAITS     $  243
                                                                                 
DISEASE RESISTANCE                                                               
                               N. America  11.0%-14.0%    8.0% - 10.0%  $   (2)-  $   11   $   (4)   $   (4)        
                               Argentina   11.0%-14.0%    8.0% - 10.0%  $    1 -  $   10   $    6    $    6         
                               Brazil      11.0%-14.0%    8.0% - 10.0%  $   (1)-  $   (1)  $   (1)   $   (1)        
                                                                       TOTAL DISEASE RESISTANCE (CURRENT)     $    9

 DISEASE RESISTANCE - All Other Crops      11.0%-14.0%    5.0% -  6.5%  $   86 -  $  176   $  131    $  136         
                    - Rice (Japan Tobacoo) 11.0%-14.0%    5.0% -  6.5%  $    3 -  $   14   $    8    $    8        
                                                                         TOTAL DISEASE RESISTANCE (OTHER)     $  139

JV/ROYALTIES
    VMO            Conventional Seed       11.0%-14.0%      6  -  12    $    7 -  $   13   $   10                   
                   Early/Input Traits      11.0%-14.0%    5.0% - 6.5 %  $   (1)-  $   (1)  $   (1)                  
                   Output Traits           11.0%-14.0%    5.0% - 6.5 %  $    2 -  $    4   $    3                   
                   Disease Res.            11.0%-14.0%    5.0% - 10.0%  $   (0)-  $    4   $    2                   
                                                             TOTAL VMO  $    8    $   21             $   14   $   14
                                                                                                    
    JG BOSWELL     Cotton                  11.0%-14.0%       6 -   12   $   51 -  $   93   $   72    $   72   $   72
                                                                                                    
    HUMKO          Oilseed     N. America  11.0%-14.0%       8 -   10   $    0 -  $    0   $    0    $    0         
                               Argentina   11.0%-14.0%       8 -   10   $    2 -  $    3   $    2    $    2         
                                                         TOTAL OILSEED  $    0 -  $    0                      $    3
                                                                                                    
    DAS CANADA     Canola                  11.0%-14.0%       6 -   10   $   19 -  $   40   $   29    $   29   $   29
    PHB BT ROYALTIES                       11.0%-14.0%                  $   43 -  $   48   $   46    $   46   $   46
    OTHER PARTNER ROYALTIES                11.0%-14.0%    5.0% - 6.5%   $   10 -  $   22   $   16    $   16   $   16
    Other Pests/Crops                      11.0%-14.0%    5.0% - 6.5%   $  137 -  $  334   $  236    $  236   $  236
                                                                                 
MISCELLANEOUS(1)                                                                 
                                                                                 
      Synergy with Third Party (including Illinois Foundation Seed)     $   28 -  $   53   $   40    $   40
      Cost Savings                                                      $    9 -  $   13   $   11    $   11
      NOL-Current (est)                                                 $   80 -  $   80   $   80    $   80         
      NOL-Projects (est)                                                $   35 -  $   35   $   35    $   35         
      Monsanto Settlement (80%-100% Probability)                        $   82 -  $  103   $   92    $   92         
      35% in Vermont (at cost)                                          $    9 -  $    9   $    9    $    9         
      Oral Immunity                                                     $   20 -  $   30   $   30    $   30
      Bt Blocking (50% probability)        11.0%-14.0%                  $  175 -  $  203   $  189    $  189         
      Corporate R&D                        12.0%-14.0%                  $ (124)-  $ (117)  $ (120)   $ (120)
      Litigation Expense (Net of Interest) 11.0%-14.0%                  $  (37)-  $  (35)  $  (34)   $  (34)        
      Net Debt                                                          $  (75)-  $  (75)  $  (75)   $  (75)  $  (75)
                                                                                                              $  330
                                                                        ------    ------   ------    ------   ------
TOTAL                                                                   $1,663    $2,146   $1,748    $1,755   $1,755
                                                                                                     

    Shares Outstand (MM)       36.26
    Options Outstand (MM)       3.59
Final Outstanding (Treasury Method, MM)                                  38.29     39.86    38.88     38.89

                                                          Value Share   $27.77    $54.92   $44.76    $46.13


- --------------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Additional opportunities remaining to be quantified include biotech 
reagent and protocol licensed royalties and oral immunity.

Note:  Initial value excludes contribution from revenue synergies, cost 
savings, and other economies of scale from consolidation with DAS.  Value per 
share calculated based on outstanding common shares, includes 3.593 million 
outstanding options with an average exercise price of $12.03

                                      30
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------
IMPACT OF RECENT SEED OPERATION RESULTS

- -    UPON COMPLETION OF THE FY 1998 SETTLEMENT PROCESS, THE NORTH AMERICAN SEED
     BUSINESS HAS POSTED RESULTS IN LINE WITH PROJECTIONS FOR ALL BUT THE CORN
     SEED OPERATIONS

     -    Corn seed is expected to post a decline in volume of approximately 10%
          relative to FY 1997

     -    Corn prices also have shown a less robust increase than expected

     -    As a result, seed sales are expected to be 24% below 1998 plan and 8%
          below 3Q 1998 forecasts

- -    THE OBSERVED DECLINE IN VOLUME AND UNIT SALES PRICE IS DUE TO AGGRESSIVE
     DISCOUNTING BY DEKALB AND PIONEER.  SUCH DISCOUNTING TO GAIN MARKET SHARE
     IS NOT A SUSTAINABLE LONG-TERM STRATEGY.  HOWEVER, THE RESULTING LOSSES IN
     MARKET SHARE MAY ADVERSELY IMPACT MYCOGEN'S LONG-TERM GROWTH PROJECTIONS

- -    IN ARGENTINA, BECAUSE THE FISCAL YEAR EXTENDS THROUGH JANUARY, ONLY
     PRELIMINARY RESULTS ARE AVAILABLE.  THESE RESULTS SUGGEST THAT SALES WILL
     BE $4 MM SHORT (ABOUT 10% BELOW PROJECTIONS) AND GROSS PROFITS WILL BE 30%
     BELOW PROJECTED LEVELS OF $12 MM

- -    ASSUMING THAT THE RECENT MARKET SHARE EROSION IMPACTS PROJECTED MARKET
     SHARE GROWTH IN A CONSTANT FASHION, TOTAL VALUE WOULD BE REDUCED BY
     APPROXIMATELY $40 MM OR APPROXIMATELY $1 PER MYCOGEN SHARE

<TABLE>
<CAPTION>
                                        Current Range         Reduced Growth Range
                                        -------------         --------------------
         <S>                           <C>                    <C>
         Variable Discount Rate        $27.37 - $47.29           $26.22 - $45.44

         Probability Weighted Method   $27.82 - $54.97           $26.83 - $53.28
</TABLE>


                                      31
<PAGE>

MYCOGEN CORPORATION              VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- -------------------------------------------------------------------------------
SUMMARY OF VALUATION

<TABLE>
<CAPTION>

BUSINESSES             CROPS     REGIONS    DISCOUNT     GROWTH RATE         VALUATION             GEOGRAPHIC  SUB-       VALUE/
                                              RATE      /EBIT MULTIPLE     LO       HI     AVERAGE   TOTAL    TOTALS      SHARE
- ------------------------------------------------------------------------------------------------------------------------------------
<S>                  <C>       <C>        <C>           <C>              <C>               <C>     <C>        <C>    <C>
Biopesticides            -          -     11.0% - 14.0%    6 -    10         $3  -     $4      $4      $4         $4   $0.09 - $0.12
SoilServ                 -          -     11.0% - 14.0%    6 -    10        $28  -    $40     $34     $34        $34   $0.73 - $1.02
Conven. Seed
                     Corn      N. America 12.0% - 14.0%    8 -    12        $42  -   $156    $109
                               Argentina  12.0% - 14.0%    8 -    12        $37  -    $58     $47
                               Brazil     12.0% - 14.0%    8 -    12       $101  -   $175    $138
                     Soybeans  N. America 12.0% - 14.0%    8 -    12       ($10) -    $18      $4
                               Brazil     12.0% - 14.0%    8 -    12         $0  -     $0      $0
                     Sorghum   N. America 12.0% - 14.0%    8 -    12         $9  -    $15     $12
                     Alfalfa   N. America 12.0% - 14.0%    8 -    12         $3  -     $9      $5
                     Sunflower N. America 12.0% - 14.0%    8 -    12        ($4) -    ($4)    ($4)
                               Argentina  12.0% - 14.0%    8 -    12        $14  -    $22     $18
                     All       N. America 12.0% - 14.0%    8 -    12        $63  -   $198            $130              $1.65 - $5.09
                               Argentina  12.0% - 14.0%    8 -    12        $49  -    $79             $64              $1.29 - $2.02
                               Brazil     12.0% - 14.0%    8 -    12       $101  -   $175            $138              $2.66 - $4.50
                                                                           Total Conventional Seed            $333

Early / Input Traits 
                     Corn      N. America 20.0% - 24.0% 5.0% -  6.5%        $66  -   $116     $91
                               Argentina  20.0% - 24.0% 0.0% -  6.5%         $1  -     $5      $3
                               Brazil     20.0% - 24.0% 5.0% -  6.5%        $29  -    $53     $41
                     Soybeans  N. America 20.0% - 24.0% 5.0% -  6.5%        $45  -    $73     $59
                               Brazil     20.0% - 24.0% 5.0% -  6.5%        ($0) -     $1      $0
                     Sunflower N. America 20.0% - 24.0% 5.0% -  6.5%        ($1) -    ($1)    ($1) 
                               Argentina  20.0% - 24.0% 0.0% -  6.5%        ($1) -     $2      $1
                     All       N. America 20.0% - 24.0% 5.0% -  6.5%       $109  -   $187            $143              $2.84 - $4.81
                               Argentina  20.0% - 24.0% 5.0% -  6.5%        ($0) -     $7              $3             $-0.01 - $0.18
                               Brazil     20.0% - 24.0% 5.0% -  6.5%        $29  -    $54             $41              $0.75 - $1.39
                                                                                Total Early Traits            $192

Output Traits 
                     Corn      N. America 25.0% - 30.0% 5.0% -  6.5%         $6  -    $15     $10
                               Argentina  25.0% - 30.0% 5.0% -  6.5%        ($2) -    ($2)    ($2)
                               Brazil     25.0% - 30.0% 5.0% -  6.5%         $5  -    $11      $8
                     Soybeans  N. America 25.0% - 30.0% 5.0% -  6.5%       $144  -   $266    $205
                               Brazil     25.0% - 30.0% 5.0% -  6.5%         $7  -    $14     $11
                     Sunflower N. America 25.0% - 30.0% 5.0% -  6.5%         $4  -     $8      $6
                               Argentina  25.0% - 30.0% 5.0% -  6.5%        $13  -    $23     $18
                     All       N. America 25.0% - 30.0% 5.0% -  6.5%       $155  -   $289            $222              $4.05 - $7.42
                               Argentina  25.0% - 30.0% 5.0% -  6.5%        $11  -    $21             $16              $0.28 - $0.55
                               Brazil     25.0% - 30.0% 5.0% -  6.5%        $14  -   $ 27             $20              $0.35 - $0.70
                                                                               Total Output Traits            $258

Disease Resistance
                               N. America 31.0% - 50.0% 8.0% - 10.0%        ($2) -    ($0)    ($1)    ($1)            $-0.05 - $0.00
                               Argentina  31.0% - 50.0% 8.0% - 10.0%        ($0) -     $2      $1      $1              $0.00 - $0.04
                               Brazil     31.0% - 50.0% 8.0% - 10.0%        ($0) -    ($0)    ($0)    ($0)           $-0.01 - $-0.01
                                                                Total Disease Resistance (Current)             ($1)
                     All Other            
                      Crops               45.0% - 50.0% 8.0% - 10.0%       $119  -   $154    $136    $136              $3.11 - $3.96
                     Rice (Japan Tobacco) 31.0% - 50.0% 8.0% - 10.0%        ($2) -     $2     ($0)    ($0)            $-0.06 - $0.04
                                                                  Total Disease Resistance (Other)            $136

JV / Royalties
    VMO              Conventional Seed    12.0% - 14.0%    6 -    10         $7  -    $10      $9                      $0.18 - $0.27
                     Early / Input Traits 20.0% - 24.0% 5.0% -  6.5%        ($1) -    ($2)    ($2)                   $-0.04 - $-0.04
                     Output Traits        25.0% - 30.0% 5.0% -  6.5%         $2  -     $4      $3                      $0.04 - $0.11
                     Disease-Res.         31.0% - 50.0% 8.0% - 10.0%        ($0) -     $0      $0                      $0.00 - $0.01
                                                              Total VMO      $8  -    $14             $11      $11
    JG Boswell       Cotton               12.0% - 14.0%    8 -    12        $39  -    $86     $73     $73      $73     $1.55 - $2.22

    ???????          Oilseed   N. America 12.0% - 14.0%    6 -    10         $0  -     $0      $0      $0              $0.00 - $0.00
                               Argentina  12.0% - 14.0%    6 -    10         $2  -     $3      $2      $2              $0.06 - $0.07
                                                           Total Oilseed     $0  -     $0                       $3
    DAS Canada       Canola               20.0% - 24.0%    8 -    12        $13  -    $21     $17     $17      $17     $0.34 - $0.54
    PHD B? Royalties                      20.0% - 24.0%                     $35  -    $38     $36     $36      $36     $0.91 - $0.97
    Other Partner Royalties               20.0% - 24.0% 1.0% -  2.5%        $14  -    $21     $17     $17      $17     $0.35 - $0.54
    Other P??? / Crops                    31.0% - 50.0% 5.0% -  6.5%        $20  -   $104     $62     $62      $62     $0.53 - $2.68

Miscellaneous*

        Synergy with Third Party (???????? Illinois Productions S???)       $29       $45     $37     $37              $0.75 - $1.15
        Cost Savings                                                         $9       $13     $11     $11              $0.23 - $0.34
        NOL-Current (est)                                                   $80  -    $80     $80     $80              $2.10 - $2.06
        NOL-Projected (est)                                                 $26  -    $26     $26     $26              $0.67 - $0.66
        Monsanto Settlement (???-100% Probability                           $82  -   $103     $92     $92              $2.15 - $2.64
        35% in Ver???? (at cost)                                             $9  -     $9      $9      $9              $0.25 - $0.24
        Oral Imm???????? (est)                                              $20  -    $30     $30     $30              $0.52 - $0.77
        ?? Blocking (50% Probability)         20.0% - 24.0%                $111  -   $131    $121    $121              $2.92 - $3.36
        Corporate R&D                         12.0% - 14.0%                ($80) -   ($77)   ($78)   ($78)           $-2.09 - $-1.98
        Litigation Expenses (Net of Interest) 12.0% - 14.0%                ($37) -   ($36)   ($36)   ($36)           $-0.98 - $-0.92
        Net Debt                                                           ($75) -   ($75)   ($75)   ($75)           $-1.96 - $-1.93
                                                                                                              $217
                                                                         ------    ------  ------  ------   ------
Total                                                                    $1,??2    $1,7??  $1,??7  $1,392   $1,??3

    Shares Outstand. (MM)      36.26
    Options Outstand. (MM)      3.??
Final Outstanding (Treasury Method, MM)                                   38.20     38.90   36.66   38.68

                                                        Value/Share      $26.23    $48.44  $36.??  $34.?2
- ------------------------------------------------------------------------------------------------------------------------------------
</TABLE>

[ILLEGIBLE]


                                      32
<PAGE>

MYCOGEN CORPORATION       VALUATION: PROBABILITY - WEIGHTED METHOD DCF ANALYSIS
- -------------------------------------------------------------------------------
SUMMARY OF VALUATION

<TABLE>
<CAPTION>
- --------------------------------------------------------------------------------------------------------------------
                                            Discount     Growth Rate     Valuation                 Geographic Sub-  
Business            Crop       Region         Rate     /EBIT Multiple   Lo         Hi     Average     Total   Totals
- --------------------------------------------------------------------------------------------------------------------
<S>                <C>         <C>         <C>            <C>           <C>       <C>      <C>       <C>      <C>   
BIO-PESTICIDES       -           -         10.0%-14.0%       6 -  10    $    3 -  $    5   $    4    $    4   $    4
SOILSERV             -           -         10.0%-14.0%       6 -  10    $   27 -  $   41   $   34    $   34   $   34
CONVEN. SEED       Corn        N. America  11.0%-14.0%       8 -  10    $   63 -  $  135   $   99  
                               Argentina   11.0%-14.0%       8 -  10    $   37 -  $   55   $   46  
                               Brazil      11.0%-14.0%       8 -  10    $  112 -  $  178   $  145  
                   Soybean     N. America  11.0%-14.0%       8 -  10    $  (10)-  $    9   $   (1)  
                               Brazil      11.0%-14.0%       8 -  10    $    0 -  $    0   $    0  
                   Sorghum     N. America  11.0%-14.0%       8 -  10    $    9 -  $   14   $   12  
                   Alfalfa     N. America  11.0%-14.0%       8 -  10    $    3 -  $    8   $    5  
                   Sunflower   N. America  11.0%-14.0%       8 -  10    $   (4)-  $   (4)  $   (4) 
                               Argentina   11.0%-14.0%       8 -  10    $   15 -  $   22   $   18  
                   All         N. America  11.0%-14.0%       8 -  10    $   69 -  $  171             $  120         
                               Argentina   11.0%-14.0%       8 -  10    $   34 -  $   81             $   68         
                               Brazil      11.0%-14.0%       8 -  10    $  112 -  $  178             $  145         
                                                                                  TOTAL CONVENTIONAL SEED     $  332
                                                                                 
EARLY / INPUT TRAITS
                   Corn        N. America  11.0%-14.0%    5.0% - 6.5%   $   57 -  $  137   $   97
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $    1 -  $    6   $    4
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $   22 -  $   34   $   39
                   Soybean     N. America  11.0%-14.0%    5.0% - 6.5%   $   87 -  $  189   $  138
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $   (0)-  $    1   $    0
                   Sunflower   N. America  11.0%-14.0%    5.0% - 6.5%   $   (2)-  $   (0)  $   (1)
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $   (0)-  $    4   $    2
                   All         N. America  11.0%-14.0%    5.0% - 6.5%   $  143 -  $  326             $  235         
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $    1 -  $   10             $    4         
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $   22 -  $   57             $   40         
                                                                                       TOTAL EARLY TRAITS     $  280
                                                                               
OUTPUT TRAITS                                                                  
                   Corn        N. America  11.0%-14.0%    5.0% - 6.5%   $    5 -  $   20   $   12
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $   (1)-  $   (0)  $   (1)
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $    2 -  $    9   $    5
                   Soybean     N. America  11.0%-14.0%    5.0% - 6.5%   $  110 -  $  276   $  193
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $    6 -  $   16   $   11
                   Sunflower   N. America  11.0%-14.0%    5.0% - 6.5%   $    3 -  $    7   $    5
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $    8 -  $   18   $   13
                   All         N. America  11.0%-14.0%    5.0% - 6.5%   $  118 -  $  303             $  211         
                               Argentina   11.0%-14.0%    5.0% - 6.5%   $    6 -  $   18             $   12         
                               Brazil      11.0%-14.0%    5.0% - 6.5%   $   10 -  $   27             $   18         
                                                                                      TOTAL OUTPUT TRAITS     $  241
                                                                                 
DISEASE RESISTANCE                                                               
                               N. America  11.0%-14.0%    5.0% - 10.0%  $   (3)-  $   10   $    4    $    4        
                               Argentina   11.0%-14.0%    5.0% - 10.0%  $    1 -  $   10   $    6    $    6         
                               Brazil      11.0%-14.0%    5.0% - 10.0%  $   (1)-  $   (1)  $   (1)   $   (1)        
                                                                       TOTAL DISEASE RESISTANCE (CURRENT)     $    9

 DISEASE RESISTANCE - All Other Crops      11.0%-14.0%    5.0% -  6.5%  $   86 -  $  176   $  131    $  131         
                    - Rice (Japan Tobacco) 11.0%-14.0%    5.0% -  6.5%  $    3 -  $   14   $    8    $    8        
                                                                         TOTAL DISEASE RESISTANCE (OTHER)     $  139

JV/ROYALTIES
    VMO            Conventional Seed       11.0%-14.0%      6  -  12    $    7 -  $   13   $   10                   
                   Early / Input Traits    11.0%-14.0%    5.0% - 6.5 %  $   (1)-  $   (1)  $   (1)                  
                   Output Traits           11.0%-14.0%    5.0% - 6.5 %  $    2 -  $    4   $    3                   
                   Disease-Res.            11.0%-14.0%    5.0% - 10.0%  $    0 -  $    4   $    2                   
                                                             TOTAL VMO  $    8    $   21             $   14   $   14
                                                                                                    
    JG BOSWELL     Cotton                  11.0%-14.0%       6 -   12   $   51 -  $   93   $   72    $   72   $   72
                                                                                                    
    HUMKO          Oilseed     N. America  11.0%-14.0%       8 -   10   $    0 -  $    0   $    0    $    0         
                               Argentina   11.0%-14.0%       8 -   10   $    2 -  $    3   $    2    $    2         
                                                         TOTAL OILSEED  $    0 -  $    0                      $    3
                                                                                                    
    DAS CANADA     Canola                  10.0%-14.0%       6 -   10   $   19 -  $   40   $   29    $   29   $   29
    PHB BT ROYALTIES                       10.0%-14.0%                  $   43 -  $   48   $   46    $   46   $   46
    OTHER PARTNER ROYALTIES                11.0%-14.0%    5.0% - 6.5%   $   10 -  $   22   $   16    $   16   $   16
    Other Pests / Crops                    11.0%-14.0%    5.0% - 6.5%   $  137 -  $  334   $  236    $  236   $  236
                                                                                 
MISCELLANEOUS(1)                                                                 
                                                                                 
      Syngergy with Third Party (including Illinois Foundation Seed)    $   28 -  $   53   $   40    $   40
      Cost Savings                                                      $    9 -  $   13   $   11    $   11
      NOL-Current (est)                                                 $   80 -  $   80   $   80    $   80         
      NOL-Projected (est)                                               $   36 -  $   36   $   36    $   36         
      Monsanto Settlement (80%-100% Probability)                        $   82 -  $  103   $   92    $   92         
      35% in Vermont (at cost)                                          $    9 -  $    9   $    9    $    9         
      Oral Immunity                                                     $   20 -  $   30   $   30    $   30
      Bt Blocking (50% probability)        11.0%-14.0%                  $  175 -  $  203   $  189    $  189         
      Corporate R&D                        12.0%-14.0%                  $ (124)-  $ (116)  $ (120)   $ (120)
      Litigation Expense (Net of Interest) 11.0%-14.0%                  $  (37)-  $  (35)  $  (36)   $  (36)        
      Net Debt                                                          $  (75)-  $  (75)  $  (75)   $  (75)  $  (75)
                                                                                                              $  332
                                                                        ------    ------   ------    ------   ------
TOTAL                                                                   $1,826    $2,000   $1,689    $1,764   $1,764
                                                                                                     

    Shares Outstand. (MM)      36.26
    Options Outstand. (MM)      3.59
FINAL OUTSTANDING (TREASURY METHOD, MM)                                  38.24     39.04    38.96     38.86

                                                          Value Share   $26.83    $53.29   $41.48    $43.83


- --------------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Additional opportunities remaining to be quantified include biotech 
reagent and protocol licensed royalties and oral immunity.

Note:  Initial value excludes contribution from revenue synergies, cost 
savings, and other economies of scale from consolidation with DAS.  Value per 
share calculated based on outstanding common shares, includes 3.593 million 
outstanding options with an average exercise price of $12.03

                                      33
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                      -----------------------------------


                             COMPARABLE ANALYSIS


                      -----------------------------------


                                      34
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
COMPARABLE SEED COMPANIES

- -    MYCOGEN'S VALUE IS A COMBINATION OF ITS CONVENTIONAL SEED BUSINESS AND THE
     VALUE DERIVED FROM ACTIVITIES IN THE AGROBIOTECH AREA

- -    MYCOGEN'S CONVENTIONAL SEED BUSINESS IS A VALUABLE ASSET BUT HAS NO CLEAR
     SIMILARLY SIZED AND SCOPED COMPARABLES

     -    Within the past twelve months nearly every public U.S. seed company
          has either been acquired or received a strategic minority investment. 
          As a result, these stocks trade based on their pending acquisition or
          in the case of Pioneer and AgriBiotech on speculation of some future
          transaction
     
     -    Publicly traded seed companies are a scarce asset.  Private seed 
          companies appear to be an alternative to Mycogen, but most are too 
          small, with the larger companies operating as cooperatives and limited
          in their ability to offer control to a third party

     -    Market share remains a key determinant of value, both because of the
          critical effect of size in determining profitability and the ability
          to drive adoption of new hybrids in the market.  However, a share of
          the larger market for major row crops, e.g. corn and soybean, is more
          highly valued than similar shares in other smaller crop segments

     -    While Mycogen's seed business is smaller than both Pioneer and DeKalb
          Genetics, these are the most comparable businesses in their leadership
          roles in seed distribution, germplasm quality and commitment to R&D

- -    OFFSETTING MYCOGEN'S SIZE RELATIVE TO SEED COMPETITORS IS ITS CLEARLY
     SUPERIOR POSITION RELATIVE TO MOST COMPARABLE AGROBIOTECH COMPANIES

     -    Mycogen has a technology and product development portfolio that is
          comparable to larger competitors.  Mycogen dominates the attractive Bt
          market.  Mycogen holds more than four times the number of Bt patents
          held by its closest competitor
     
     -    Mycogen's network of alliances and licensing rights provide ready 
          access to a critical mass of biotech tools and intellectual property.
          In addition, Mycogen has gained exclusive access to certain highly 
          attractive new growth platforms such as Ahlquist technology for insect
          and disease resistance and oral immunity through transgenic plants

- -    MYCOGEN'S BIOTECH CAPABILITIES ARE UNIQUE.  THERE IS NO COMPARABLE PUBLIC
     COMPANY OF ANY SIZE.  HOWEVER, A GOOD HISTORICAL COMPARABLE IS PROVIDED BY
     PGS.  THIS BUSINESS, WITH NO SALES, LARGE LOSSES AND AN IP POSITION
     CONSIDERABLY WEAKER THAN MYCOGEN'S, WAS ACQUIRED BY AGREVO FOR $733 MILLION


                                      35
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
COMPARABLE COMPANY ACQUISITIONS

- -    THE RECENT ACQUISITION OF CARGILL'S INTERNATIONAL SEED BUSINESS CONTRADICTS
     THE NOTION THAT LOSS-MAKING MYCOGEN DIFFERS FROM OTHER COMPARABLE
     ACQUISITIONS SINCE OTHER COMPANIES ARE ALL PROFITABLE.  CARGILL'S 
     LOSS-MAKING SEED BUSINESS (~$-20 MILLION IN 1997) WAS RECENTLY ACQUIRED BY
     MONSANTO FOR $1.4 BILLION

- -    THERE ARE NO COMPARABLE ACQUISITIONS OF SEED COMPANIES WITH A SIMILAR
     MARKET SHARE AND PRESENCE IN CROP SEGMENTS TO MYCOGEN.  HOWEVER, THE
     ACQUISITION OF MINORITY STAKES IN PIONEER AND THE ACQUISITION OF DELTA AND
     PINE LAND PROVIDE SOME SIMILARITY IN TERMS OF CROP PRESENCE AND MARKET
     SHARE, RESPECTIVELY

- -    DOW'S 68.8% OWNERSHIP OF MYCOGEN WAS BOUGHT AT AN AGGREGATE ACQUISITION
     PRICE OF $16.78 PER SHARE.  ALTHOUGH THE INITIAL PURCHASE OF 4.45 MILLION
     SHARES FROM LUBRIZOL TOOK PLACE AT A 25% PREMIUM TO THE MARKET, THE
     SUBSEQUENT SHARES PURCHASED BY DOW HAVE BEEN ACQUIRED AT A MINIMAL PREMIUM
     (LESS THAN 5% IN AGGREGATE)

- -    COMPARABLE "SQUEEZE-OUT" TRANSACTIONS IN THE BIOTECH INDUSTRY HAVE REQUIRED
     PREMIUM TO THE CURRENT SHAREHOLDERS OF OVER 50%.  ACQUIRING THE REMAINING
     SHARES OF MYCOGEN IN THE RANGE OF THE CURRENT VALUATION OR AT A SIMILAR
     PREMIUM TO THE MARKET WILL STILL PROVIDE DOW WITH THE COMPLETE ACQUISITION
     OF MYCOGEN AT AN AGGREGATE PURCHASE PRICE AT OR BELOW CURRENT TRADING
     VALUES


                                      36
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
PREMIUM ANALYSIS - MONSANTO/DEKALB GENETICS


<TABLE>
<CAPTION>

                                                                                  PREMIUM TO PRIOR PRICE
                                                                    --------------------------------------------------
ANNC. DATE     SHARES(3)    % TOTAL   CUMM %      PRICE/SHARE(3)     1-DAY          1-WEEK        4-WEEKS      8-WEEKS
- ----------     ----------   -------   ------      --------------     -----          ------        -------      -------
<S>            <C>          <C>       <C>         <C>               <C>             <C>            <C>         <C>
 2/11/96          0.49        1.4%      1.4%          $10.83        $11.42  (5%)    $10.96  (1%)   $7.83  38%    $7.58   43%
 2/11/96          2.27        6.6%      8.0%          $10.83        $11.42  (5%)    $10.96  (1%)   $7.83  38%    $7.58   43%
 2/11/96         10.34       29.9%     37.8%          $11.83        $11.42   4%     $10.96   8%    $7.83  51%    $7.58   56%
   NA             0.71        2.1%     39.9%          $38.26(4)
 5/9/98          20.81       60.1%    100.0%         $100.00        $74.13  35%     $69.50  44%   $70.81  41%   $70.19   42%
                ------
  TOTAL          34.61

</TABLE>

<TABLE>
<CAPTION>

                                                             WEIGHTED AVG.      LATEST ACQ.
                                                             -------------      -----------
<S>                                                          <C>                <C>
              PURCHASE PRICE PER SHARE                           $65.29            $100.00
              Shares Outstanding(2)                                36.3               36.3
                                                                   ----               ----
              Aggregate Purchase Value                         $2,371.9           $3,632.7
              Net Debt (2/98)                                     110.0              110.0
                                                                  -----              -----
              ADJUSTED AGGREGATE PURCHASE VALUE                $2,481.9           $3,742.7

              LTM Sales (2/98)                                   $468.6             $468.6
              ADJUSTED AGGREGATE PURCHASE VALUE / SALES           5.30x              7.99x

</TABLE>

- --------------------------------
(1) ESTIMATED BASED ON ANALYST ESTIMATES AND NEWS ARTICLES
(2) REPRESENTS COMMON EQUIVALENT SHARES BASED ON RESPECTIVE PRICES
(3) SPLIT ADJUSTED
(4) ESTIMATED AVERAGE SHARE PRICE. SPECIFIC DATES WERE NOT AVAILABLE



- -------------------------------------------------------------------------------

                                       37
<PAGE>


MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------

<TABLE>
<CAPTION>
                              TOTAL%
                        -----------------                                        PREMIUM TO PRIOR PRICE
                         PRE       POST                    ------------------------------------------------------------
ANNC. DATE    SHARES    TRANS.     TRANS.    PRICE/SHARE           1-DAY     1-WEEK        4-WEEKS        8-WEEKS
- ----------    ------    ------     ------    -----------           -----     ------        -------        -------
<S>           <C>       <C>        <C>       <C>              <C>            <C>           <C>            <C>
 1/15/96       4.45      18.1%      12.3%      $16.27         $16.00    2%   $14.25  14%    $13.88   17%   $13.00  25%
 1/15/96       9.50      38.6%      26.3%      $13.28         $16.00  (17%)  $14.25  (7%)   $13.88   (4%)  $13.00   2%
   1996        0.85       3.4%       2.3%      $17.21(1) 
 12/3/96       1.00       4.1%       2.8%      $16.75         $16.75    0%   $16.75   0%    $15.75    6%   $14.38  17%
   1997        2.29       9.3%       6.3%      $23.20(2)
  1/9/98       0.48       2.0%       1.3%      $19.46         $19.25    1%   $19.13   2%    $19.75   (1%)  $19.94  (2%)
 1/16/98       3.76      15.3%      10.4%      $19.94         $18.75    6%   $19.13   4%    $19.13    4%   $19.88   0%
   1998        0.30       1.2%       0.8%      $19.48 
 3/13/98       2.00       8.1%       5.5%      $20.06         $18.31   10%   $18.75   7%    $20.63   (3%)  $21.75  (8%)
             ------       ----       ----      ------
SUBTOTAL      24.63     100.0%      68.2%      $16.78
Final         11.48                 31.8% 
             ------                 -----
Total         36.11                100.0% 

</TABLE>

<TABLE>
<S>                                            <C>           <C>           <C>           <C>           <C>
ASSUMED FINAL PURCHASE PRICE / SHARE            $20.50        $25.00        $30.00        $35.00        $40.00

Cum. Wtd. Avg. Price                            $17.96        $19.39        $20.98        $22.57        $24.16
Shares Outstanding (3)                           37.9          38.4          38.8          39.0          39.2
                                                 ----          ----          ---           ----          ----
Aggregate Purchase Value                       $681.6        $744.9        $813.5        $880.8        $947.4
Net Debt (2/98)                                  13.7          13.7          13.7          13.7          13.7  
                                                 ----          ----          ----          ----          ----
ADJUSTED AGGREGATE PURCHASE VALUE              $695.2        $758.6        $827.1        $894.5        $961.1

LTM Sales (2/98)                               $214.0        $214.0        $214.0        $214.0        $214.0
ADJUSTED AGGREGATE PURCHASE VALUE / SALES         3.25x         3.55x         3.87x         4.18x         4.49x
</TABLE>


- ------------------------------
(1) WEIGHTED AVERAGE PRICE OF VARIOUS OPEN MARKET PURCHASES MADE DURING 1996
(2) WEIGHTED AVERAGE PRICE OF VARIOUS OPEN MARKET PURCHASES MADE DURING 1997
(3) REPRESENTS COMMON EQUIVALENT SHARES BASED ON RESPECTIVE PURCHASE PRICES FOR 
    FINAL SHARE BLOCKS



                                       38
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
PREMIUM ANALYSIS FOR BIOTECH ACQUISITIONS BY MAJOR SHAREHOLDERS (1)



<TABLE>
<CAPTION>
                                                                                                       Seller Closing Price/
                                                                                                  Pre-Ann. Acquisition Premium
                                                             Ann. Deal   Per Share           ------------------------------------
                                                   Ann.        Value        Acq.    $ Being       1-Day     30-Day     60-Day
Acquiror               Seller                      Date        ($MM)       Price    Acquired      Prem.      Prem.      Prem.
- --------               ------                      ----        -----       -----    --------      -----      -----      -----
<S>                    <C>                        <C>        <C>         <C>        <C>          <C>        <C>        <C>
Monsanto Co.           Calgene Inc. (Biotech)     1/28/97      242.6       $8.00      43.7%       45.5%      60.0%      45.5%


Novartis AG            SyStemix Inc. (Biotech)    5/27/96      119.4      $19.50      26.8%       77.3%      59.2%      48.6%


Monsanto Co.           DeKalb Genetics             5/9/98    3,426.2      $100.00    60.11%      34.91%     41.22%     42.47%

</TABLE>

<TABLE>
<CAPTION>
- ----------------------------------------------------------------------------------------------------------------------------------
<S>                                                                                  <C>         <C>        <C>        <C>
Mean                                                                                  43.5%       52.5%      53.5%      45.5%

Median                                                                                43.7%       45.5%      59.2%      45.5%

Maximum                                                                               60.1%       77.3%      60.0%      48.6%

Minimum                                                                               26.8%       34.9%      41.2%      42.5%

Mycogen Corp. Data                                                                               $20.50     $18.25     $17.00

Implied Share Price Based on Median for Biotech Transactions                                     $29.82     $29.85     $24.73

Implied Share Price Based on Mean for Biotech Transactions                                       $31.27     $28.01     $24.74

- ----------------------------------------------------------------------------------------------------------------------------------
</TABLE>


- ------------------------------------
(1) Source: Securities Data Company

Note: Unless noted, days referred to are calendar days.


                                       39
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                      -----------------------------------


                                 CONCLUSIONS


                      -----------------------------------


                                      40
<PAGE>

MYCOGEN CORPORATION                                                 CONCLUSIONS
- -------------------------------------------------------------------------------
SUMMARY OF VALUATION RESULTS



<TABLE>
<CAPTION>



                                                                 LOW        MEAN       HIGH
                                                                 ---        ----       ----
           <S>                                                  <C>       <C>         <C>
           DISCOUNTED CASH FLOW

                   Variable Discount Rate (Reduced Growth)      $26.22                $45.44
                   Probability-Weighted  (Reduced Growth)       $26.83                $53.28


           COMPARABLE TRADING COMPANIES(1)

                   Premium of 10%, Implied Multiple: 5.4x                  $30.22
                   Premium of 30%, Implied Multiple: 5.7x                  $31.93
                   Premium of 50%, Implied Multiple: 6.0x                  $33.64


           COMPARABLE ACQUISITIONS(2)

                   Range with and without DKB(3)                $33.24                $38.85


           BIOTECH SQUEEZE OUT
           (Comparable Range of Premiums)

                   Based on Price 1 Day Prior                   $27.66                $36.34
                   Based on Price 60 Days Prior                 $24.22                $25.26

</TABLE>


(1) Comparable Companies: Pioneer, DeKalb, Delta and Pine Land, and 
    Agribiotech. Acquisition premiums only applied to sales multiples for 
    Pioneer and Agribiotech.

(2) Comparable acquisitions included: DeKalb(60%)/Monsanto; 
    Calgene(49.9%/Monsanto); Pioneer Hi-Bred(20%)/DuPont and Delta and Pine 
    Land/Monsanto.

(3) Delta and Pine Land acquisition not directly comparable due to dominant 
    DPL position in cotton market.



                                    41
<PAGE>

MYCOGEN                                                             CONCLUSIONS
- -------------------------------------------------------------------------------
GRAPHICAL SUMMARY OF VALUATION RESULTS


<TABLE>
<CAPTION>


METHOD                                                  $20.00         $30.00       $40.00      $50.00       $60.00
- ------                                                    |              |            |           |            |
                                                          ------------------------------------------------------
<S>                                                     <C>            <C>          <C>         <C>          <C>
- -  DISCOUNTED CASH FLOW
   -  Variable Discount Rate (Reduced Growth)               $26.22 ----------------------------$45.44
   -  Probability-Weighted (Reduced Growth)                  $26.83 --------------------------------------$53.28


- -  COMPARABLE TRADING COMPANIES
   (Premiums only apply to PHB and AgroBiotech)
   -  Premium 10%                                                        --
   -  Premium 30%                                                           --
   -  Premium 50%                                                              --


- -  COMPARABLE ACQUISITIONS
   -  DKB, PHB, Calgene (49.9%)                                          $33.24 ----------$38.85
      (with and without DPL)


- -  BIOTECH SQUEEZE OUT
   (Range of Biotech Premiums)
   -  Based on Price 1 Day Prior                                   $27.66 -------------$36.34
   -  Based on Price 60 Days Prior                            $24.22 -- $25.26

</TABLE>


                                    42
<PAGE>

MYCOGEN                                                             CONCLUSIONS
- -------------------------------------------------------------------------------
IMPLIED AGGREGATE DOW PURCHASE PRICE FOR MYCOGEN


<TABLE>
<CAPTION>


VALUATION APPROACH                                      $10.00         $20.00       $30.00      $40.00       $50.00     $60.00
- ------------------                                        |              |            |           |            |          |
                                                          -----------------------------------------------------------------
<S>                                                     <C>            <C>          <C>         <C>          <C>        <C>
   -  VARIABLE DISCOUNT RATE (REDUCED GROWTH)                              $26.22 ------------------------$45.44
   -  PROBABILITY-WEIGHTED (REDUCED GROWTH)                                 $26.83 ---------------------------------$53.28
   -  COMPARABLE TRADING/ACQUISITIONS                                              $31.06 ------ $38.85
   -  BIOTECH SQUEEZE OUT                                               $24.22 ------------- $36.34


IMPLIED AGGREGATE PURCHASE
- --------------------------
(REMAINING BLOCK PURCHASED AT ABOVE VALUATION)

- -  VARIABLE DISCOUNT RATE (REDUCED GROWTH)                        $19.78 ------- $25.89

- -  PROBABILITY-WEIGHTED (REDUCED GROWTH)                           $19.98 ---------$28.37

- -  COMPARABLE TRADING/ACQUISITIONS                                  $21.17 ---- $23.60

- -  BIOTECH SQUEEZE OUT                                           $19.15 ------ $23.00


                                                                     MYCO [$21.31]
</TABLE>


                                    43
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                      -----------------------------------


                                   APPENDIX
                            A. SUMMARY FINANCIALS
                            B. COMPARABLE ANALYSES


                      -----------------------------------


                                      44
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                      -----------------------------------


                               SUMMARY FINANCIALS


                      -----------------------------------


                                      45
<PAGE>


MYCOGEN CORPORATION               VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE INCOME STATEMENT PROJECTIONS ($MM)

<TABLE>
<CAPTION>

                       1998       1999       2000       2001       2002       2003       2004       2005       2006       2007
                    ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------
<S>                  <C>        <C>        <C>        <C>        <C>        <C>        <C>       <C>        <C>         <C>
REVENUES                $256.5    $298.5     $355.9     $418.8     $492.9     $577.8      $705.0    $1,061.5   $1,503.8  $2,034.0
     SoilSer v           $34.2     $33.4      $33.4      $33.4      $33.4      $33.4       $33.4       $33.4      $33.4     $33.4
     Biopesticides        $8.3      $7.8       $7.8       $7.8       $7.8       $7.8        $7.8        $7.8       $7.8      $7.8
     Seeds              $186.4     221.0     $273.4     $330.3     $402.1     $486.0      $607.9      $961.1   $1,398.9  $1,923.5
     VMO                  $5.9      $7.4       $8.1       $9.1      $10.2      $11.5       $17.0       $20.5      $25.2     $30.7
     Oilseed             $21.7     $28.8      $33.2      $38.1      $39.3      $39.1       $38.9       $38.7      $38.5     $38.5
COGS                    $147.6    $175.3     $200.1     $226.8     $252.6     $278.7      $312.7      $361.5     $408.9    $464.1
    SoilServ             $22.0     $22.3      $22.3      $22.3      $22.3      $22.3       $22.3       $22.3      $22.3     $22.3
    Biopesticides         $4.5      $4.9       $4.9       $4.9       $4.9       $4.9        $4.9        $4.9       $4.9      $4.9
    Seeds                $96.3    $115.8     $135.9     $157.3     $180.9     $206.1      $239.3      $287.1     $333.3    $387.2
    VMO                   $3.9      $4.9       $5.4       $6.1       $6.8       $7.6        $8.5        $9.6      $10.7     $12.0
    Oilseed              $20.9     $27.5      $31.7      $36.3      $37.8      $37.8       $37.8       $37.8      $37.8     $37.8
GROSS PROFIT            $109.0    $123.2     $155.8     $192.0     $240.3     $299.1      $392.2      $700.0   $1,094.9  $1,569.8
SG&A                     $68.6     $81.6      $88.9      $95.7     $105.0     $114.1      $127.9      $147.0     $173.0    $204.9
R&D                      $32.5     $46.0      $59.0      $71.0      $91.0      $98.0      $105.0      $119.8     $164.6    $215.5
    SoilServ              $0.0      $0.0       $0.0       $0.0       $0.0       $0.0        $0.0        $0.0       $0.0      $0.0
    Biopesticides         $1.1      $0.8       $0.8       $0.8       $0.8       $0.8        $0.8        $0.8       $0.8      $0.8
    Seeds                $30.8     $44.0      $53.9      $60.9      $67.0      $72.9       $83.2      $116.9     $161.2    $211.6
    VMO                   $0.6      $0.7       $1.7       $2.8       $3.6       $3.6        $2.9        $2.1       $2.5      $3.1
    Oilseed               $0.0      $0.0       $0.0       $0.0       $0.0       $0.0        $0.0        $0.0       $0.0      $0.0
    Corporate             $0.0      $0.5       $2.6       $6.5      $19.6      $20.7       $18.0        $0.0       $0.0      $0.0
EBITDA                    $7.9     ($4.5)      $7.9      $25.3      $44.3      $87.0      $159.4      $433.1     $756.9  $1,149.5
Depreciation              $4.5      $5.1       $6.0       $7.0       $8.1       $9.3       $10.8       $13.1      $15.3     $17.9
Amortization              $1.3      $1.3       $1.3       $1.3       $1.3       $1.3        $1.3        $1.3       $1.2      $1.2
                     ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------
EBIT                      $2.0    ($10.9)      $0.5      $16.9      $34.8      $76.4      $147.2      $418.8     $740.4  $1,130.4
Royalty and Venture 
Income                   ($4.1)    ($5.0)     ($4.8)     ($2.7)      $2.4      $12.0       $20.6       $29.9      $37.0     $48.2
TOTAL OPERATING INCOME   ($2.1)   ($15.9)     ($4.3)     $14.2      $37.2      $88.4      $167.8      $448.7     $777.4  $1,178.6
LITIGATION EXPENSES     ($20.0)   ($15.0)    ($10.0)     ($5.0)     ($2.0)     ($2.0)      ($2.0)
INTEREST EXP./REV.       ($2.8)    ($7.6)    ($11.8)    ($15.9)    ($18.6)    ($17.9)     ($15.6)      ($7.2)     $10.2     $36.6
PRE-TAX INCOME (TOTAL)  ($24.9)   ($38.5)    ($26.1)     ($6.7)     $16.6      $68.4      $150.2      $441.5     $787.7  $1,215.2
TAXES (@41%)               0.0       0.0        0.0        0.0       (6.8)     (28.1)      (61.6)     (181.0)    (322.9)   (498.2)
NOL Utilization            0.0       0.0        0.0        0.0        6.8       28.1         4.6         0.0        0.0       0.0
NET INCOME               (24.9)    (38.5)     (26.1)      (6.7)      16.6       68.4        93.2       260.5      464.7     717.0
E.P.S. (38.27MM SHARES) ($0.65)   ($1.01)    ($0.68)    ($0.17)     $0.43       $1.79      $2.44       $6.81     $12.14    $18.73
</TABLE>

                                      46
<PAGE>
MYCOGEN CORPORATION               VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE BALANCE SHEET PROJECTIONS ($MM)
<TABLE>
<CAPTION>
                                      1998     1999     2000     2001     2002     2003     2004     2005      2006      2007
                                     -------  -------  -------  -------  -------  -------  -------  -------  --------  --------
<S>                                  <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>       <C>
Cash and Equivalents                    $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2    $408.2  $1,005.7
Accounts Receivable                    $59.7    $70.2    $82.9    $97.4   $112.9   $128.9   $149.7   $179.4    $209.0    $244.3
Inventories                            $65.9    $79.3    $92.2   $106.1   $121.2   $137.4   $158.2   $187.5    $216.6    $250.7
PP&E                                  $105.0   $107.8   $115.1   $138.3   $147.0   $155.0   $186.4   $204.8    $214.8    $227.2
Intangibles                            $31.6    $30.3    $29.0    $27.6    $26.3    $24.9    $23.6    $22.3     $21.1     $19.9
Prepaid Expenses                       $18.1    $18.1    $18.1    $18.1    $18.1    $18.1    $18.1    $18.1     $18.1     $18.1
                                     -------  -------  -------  -------  -------  -------  -------  -------  --------  --------
TOTAL ASSETS                         $ 282.5   $307.8   $339.4   $389.7   $427.6   $466.4   $538.1   $614.2  $1,087.8  $1,815.9
                                     -------  -------  -------  -------  -------  -------  -------  -------  --------  --------
                                     -------  -------  -------  -------  -------  -------  -------  -------  --------  --------
Advances from DAS                      $13.5    $13.5    $13.5    $13.5    $13.5    $13.5    $13.5    $13.5     $13.5     $13.5
Short-term Borrowings                  $73.1   $132.0   $186.7   $240.8   $257.9   $223.0   $194.6     $0.7      $0.0      $0.0
A/P & Accruals                         $19.3    $24.2    $27.1    $30.1    $34.3    $39.6    $46.4    $56.0     $65.5     $76.7
Accrued Compensation                    $6.1     $6.1     $6.1     $6.1     $6.1     $6.1     $6.1     $6.1      $6.1      $6.1
Deferred Revenues                       $8.2     $8.2     $8.2     $8.2     $8.2     $8.2     $8.2     $8.2      $8.2      $8.2
Other Current Liabilities              $12.9    $12.9    $12.9    $12.9    $12.9    $12.9    $12.9    $12.9     $12.9     $12.9
TOTAL CURRENT LIABILITIES             $133.1   $196.9   $254.6   $311.6   $332.9   $303.3   $281.8    $97.4    $106.2    $117.4
 
Long-term Liabilities                  $17.1    $17.1    $17.1    $17.1    $17.1    $17.1    $17.1    $17.1     $17.1     $17.1
 
Paid-In Capital                        0.031    0.031    0.031    0.031    0.031    0.031    0.031    0.031     0.031     0.031
Additional PIC                        $344.7   $344.7   $344.7   $344.7   $344.7   $344.7   $344.7   $344.7    $344.7    $344.7
Retained Earning (Deficit)           ($212.4) ($250.9) ($277.0) ($283.7) ($267.2) ($198.7) ($105.5)  $155.0    $619.7  $1,336.7
STOCKHOLDERS EQUITY                   $132.3    $93.8    $67.7    $61.0    $77.5   $146.0   $239.2   $499.7    $964.5  $1,681.4
                                     -------  -------  -------  -------  -------  -------  -------  -------  --------  --------
TOTAL S.H. EQUITY AND LIAB.           $282.5   $307.8   $339.4   $389.7   $427.6   $466.4   $538.1   $614.2  $1,087.8  $1,815.9
                                     -------  -------  -------  -------  -------  -------  -------  -------  --------  --------
                                     -------  -------  -------  -------  -------  -------  -------  -------  --------  --------
NET WORKING CAPITAL                    $93.4   $112.4   $135.1   $160.5   $186.9   $213.8   $248.6   $298.0    $347.2    $405.5
NET ASSETS                            $198.5   $220.2   $250.1   $298.8   $333.9   $368.8   $435.0   $502.8    $562.1    $632.7
 
Net Operating Income                  ($24.9)  ($38.5)  ($26.1)   ($6.7)   $16.6    $68.4   $150.2   $441.5    $787.7  $1,215.2
Less: Taxes Paid                        $0.0     $0.0     $0.0     $0.0    ($0.0)   ($0.0)  ($57.0) ($181.0)  ($322.9)  ($498.2)
Plus: D&A                               $5.9     $6.5     $7.4     $8.3     $9.5    $10.6    $12.2    $14.3     $16.5     $19.1
Less: Capital Expenditure             ($22.4)   ($7.9)  ($13.3)  ($30.2)  ($16.8)  ($17.2)  ($42.3)  ($31.5)   ($25.3)   ($30.3)
Less: Increase in NWC                 ($28.1)  ($19.0)  ($22.6)  ($25.5)  ($26.3)  ($26.9)  ($34.8)  ($49.4)   ($49.2)   ($58.3)
 
FREE CASH FLOW                        ($69.6)  ($58.9)  ($54.7)  ($54.0)  ($17.1)   $34.9    $28.3   $194.0    $406.6    $647.5
</TABLE>

                                       47
<PAGE>

MYCOGEN CORPORATION               VALUATION: VARIABLE DISCOUNT RATE DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE CASH FLOW STATEMENT ($MM)

<TABLE>
<CAPTION>
                                   1998     1999     2000     2001     2002     2003     2004     2005     2006       2007
                                  ------   ------   ------   ------   ------   ------   ------   ------   ------     ------
<S>                               <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>      <C>        <C>
Net Income                        ($24.9)  ($38.5)  ($26.1)   ($6.7)   $16.6    $68.4    $93.2   $260.5   $464.7     $717.0
Depreciation                         4.5      5.1      6.0      7.0      8.1      9.3     10.8     13.1     15.3       17.9
Amortization                         1.3      1.3      1.3      1.3      1.3      1.3      1.3      1.3      1.2        1.2
Change in Working Capital:
(INC.) DEC. IN ACCTS. REC.         (17.6)   (10.5)   (12.7)   (14.5)   (15.4)   (16.0)   (20.8)   (29.7)   (29.6)     (35.4)
(INC.) DEC. IN INVENTORY            (8.8)   (13.4)   (12.9)   (13.9)   (15.1)   (16.2)   (20.8)   (29.3)   (29.1)     (34.1)
(INC.) DEC. IN PPD. EXPENSES         -        -        -        -        -        -        -        -        -          -   
INC. (DEC.) IN ACC. PAY/ACC.        (1.8)     4.9      2.9      2.9      4.2      5.3      6.8      9.6      9.5       11.2
INC. (DEC.) IN ACCRUED COMPENSA      -        -        -        -        -        -        -        -        -          -   
INC. (DEC.) IN DEFERRED REVENUES     -        -        -        -        -        -        -        -        -          -   
INC. (DEC.) IN OTHER CURR. LIAB.     -        -        -        -        -        -        -        -        -          -   
INC. (DEC.) IN LT LIABILITIES        1.6      -        -        -        -        -        -        -        -          -   

CASH FLOW FROM OPERATIONS          (45.6)   (51.0)   (41.4)   (23.8)    (0.3)    52.1     70.6    225.5    432.0      677.8

Capital Expenditures               (22.4)    (7.9)   (13.3)   (30.2)   (16.8)   (17.2)   (42.3)   (31.5)   (25.3)     (30.3)
CASH FLOW FROM INVESTMENTS         (22.4)    (7.9)   (13.3)   (30.2)   (16.8)   (17.2)   (42.3)   (31.5)   (25.3)     (30.3)
Net Cash Flow                      (68.0)   (58.9)   (54.7)   (54.0)   (17.1)    34.9     28.3    194.0    406.6      647.5

Debt Issuance (Paydown)
ADVANCES FROM DAS                    -        -        -        -        -        -        -        -        -          -   
SHORT-TERM BORROWINGS               68.0     58.9     54.7     54.0     17.1    (34.9)   (28.3)  (194.0)    (0.7)       -   
Equity Issuance                      -        -        -        -        -        -        -        -        -          -   
CASH FLOW (FINANCING)               68.0     58.9     54.7     54.0     17.1    (34.9)   (28.3)  (194.0)    (0.7)       -   

NET INC./DEC. IN CASH               $0.0    ($0.0)    $0.0    ($0.0)    $0.0     $0.0     $0.0     $0.0   $406.0     $647.5

Cash & Equivalents BOY              $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $408.2
Cash & Equivalents EOY              $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2     $2.2   $408.2   $1,055.7

</TABLE>


                                      48
<PAGE>

MYCOGEN CORPORATION            VALUATION:  VARIABLE DISCOUNT RATE DCF ANALYSIS
- ------------------------------------------------------------------------------
CORPORATE NET OPERATING LOSS CARRYFORWARDS / DEBT SCHEDULE ($MM)

<TABLE>
<CAPTION>
                             1998      1999      2000      2001      2002      2003      2004      2005     2006      2007
                             ----      ----      ----      ----      ----      ----      ----      ----     ----      ----
<S>                          <C>      <C>       <C>        <C>      <C>       <C>       <C>      <C>       <C>       <C>
NOL SCHEDULE
- ------------

Start New NOL Carry (1)      $10.2    $ 26.0    $ 36.7     $ 39.5   $ 39.5    $ 32.7    $  4.6   $   0.0   $   0.0   $   0.0
Taxes Due                    $ 0.0    $  0.0    $  0.0     $  0.0   $ (6.8)   $(28.1)   $(61.6)  $(181.0)  $(322.9)  $(498.2)
Total New NOL Utilized       $ 0.0    $  0.0    $  0.0     $  0.0   $  6.8    $ 28.1    $  4.6   $   0.0   $   0.0   $   0.0

Balance Current NOL Carry    $10.2    $ 26.0    $ 36.7     $ 39.5   $ 32.7    $  4.6    $  0.0   $   0.0   $   0.0   $   0.0
New NOL YTD                  $10.2    $ 15.8    $ 10.7     $  2.7   $  0.0    $  0.0    $  0.0   $   0.0   $   0.0   $   0.0



DEBT SCHEDULE
- -------------

Advances from DAS            $13.5    $ 13.5    $ 13.5     $ 13.5   $ 13.5    $ 13.5    $ 13.5   $  13.5   $  13.5   $  13.5

BOY Short Term Borrowings      5.1      73.1     132.0      186.7    240.8     257.9     223.0     194.6       0.7      --
Addn. Short-Term Borrow.      68.0      58.9      54.7       54.0     17.1       --        --        --        --       --
Debt Paid Down                 --        --        --         --       --      (34.9)    (28.3)   (194.0)     (0.7)     --
                             -----    ------    ------     ------   ------    ------    ------   -------   -------   -------
EOY Short-term Borrowings    $73.1    $132.0    $186.7     $240.8   $257.9    $223.0    $194.6   $   0.7   $   0.0   $   0.0
</TABLE>

(1) Excludes existing NOL's existing prior to 1998. Prior NOL's valued
    separately subject to existing utilization limitations.

(2) NOL's generated in 1998-2007 period valued assuming accelerated
    utilization due to consolidation with larger entity.

                                      49
<PAGE>

<TABLE>
<CAPTION>

CURRENT as of:                                                                                      Estimated Present Value of NOLs
                   7/21/98                                                                                                Option 1
                                                              Option 1        FY 1999        FY 2000        Fy 2001        Fy 2002
                                                          ------------------------------------------------------------------------
<S>                                                       <C>              <C>            <C>            <C>           <C>        
Estimated NOL at 8/31/98 (federal)                         228,001,545     18,732,548     18,732,548     18,732,548     18,732,548
Estimated Annual Limitation(1)                              53,521,566
Estimated R&D Credit                                         2,071,000                                                            
Estimated State NOLs                                                        2,052,014      2,052,014      2,052,014      2,052,014
                                                                                                                                  
                                                                                                                                  

Discount rate used for PV Calculation                            6.06%                                            
                                                                                                                                  
April 1998 federal tax exempt rate:                              5.05%                    St. Price=      $   30.00               
Estimated Value - # of shares plus options                  39,850,340
times buyout price=                                      1,195,510,200
Est. Contributions During Past 2 Years                     135,677,204               Est. Contributions Prior 2 Years
                                                         -------------               DAS                                75,000,000
382 Valuation                                            1,059,832,996               Exercised                          11,899,244
2002/1099 option income - exercises thru above date         12,109,587               To be Exercised                    48,777,960
2002/1099 option income - est. exercises at buyout          58,737,120                                                 -----------
Restricted Stock taxable inc - vested thru above date        2,074,838                Estimated contributions          135,677,204
Restricted Stock inc. est - not vested thru above date       1,080,000
Estimated 8/31/98 Other Oper. Loss                          30,000,000
Estimated NOL from 8/31/97                                 124,000,000
                                                         -------------
Estimated NOL                                              228,001,545




                                                                 FY 2003        FY 2004       Present Value 
                                                         -------------------------------------------------- 
<S>                                                            <C>            <C>            <C>            
Estimated NOL at 8/31/98                                       4,870,348              -      $   68,446,166 
Estimated Annual Limitation(1)                                                                              
Estimated R&D Credit                                                          2,071,000      $ 1,543,017.32 
Estimated State NOLs                                           2,052,014      2,052,014      $10,070,633.87 
                                                                                             -------------- 
                                                                     PV=                     $           80 
                                                                                                            
                                                             WHEN ITALICIZED AMOUNT FOR FY2003              
                                                             TURNS NEGATIVE, THE FORMULAS                   
                                                             NEED TO BE MODIFIED.                           
</TABLE>


Comments:

The available R&D Credit was adjusted down to an estimate of what will 
actually be available for use.

The value of the state NOL is a rough estimate.

The capital Loss Carryforward of 2,618,115 was ignored because of the 
uncertainty of its use.

Foreign tax credits have been ignored because of the relatively small value.

1) Limitation may be higher for acquiror other than Dow. Also, some portion 
of carryover is not subject to current limitation.

                                        50
<PAGE>

<TABLE>
<CAPTION>

MYCOGEN CORPORATION                                                             VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- -----------------------------------------------------------------------------------------------------------------------------------
CORPORATE INCOME STATEMENT PROJECTIONS ($MM)
                      1998      1999      2000      2001      2002      2003      2004      2005       2006        2007
                    --------- --------- --------- --------- --------- --------- --------- --------- ----------  -------------
<S>                 <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>         <C>
REVENUES            $256.5    $298.5    $355.4    $416.6    $484.5    $554.3    $641.3    $780.1    $929.9      $1,111.5
   SoilServ          $34.2     $33.4     $33.4     $33.4     $33.4     $33.4     $33.4     $33.4     $33.4         $33.4
   BioPesticides      $8.3      $7.8      $7.8      $7.8      $7.8      $7.8      $7.8      $7.8      $7.8          $7.8
   Seeds               $186.4    $221.0    $272.9    $328.2    $393.8    $462.6    $548.0    $685.3    $833.3        $1,012.7
   VMO                   $5.9      $7.4      $8.1      $9.1     $10.2     $11.4     $13.2     $14.9     $16.9           $19.1
   Oilseed              $21.7     $28.8     $33.2     $38.1     $39.3     $39.1     $38.9     $38.7     $38.5           $38.5
COGS                 $147.6    $175.3    $200.1    $226.8    $252.6    $278.7    $312.7    $361.5    $408.9            $464.1
   SoilServ             $22.0     $22.3     $22.3     $22.3     $22.3     $22.3     $22.3     $22.3     $22.3           $22.3
   Biopesticides         $4.5      $4.9      $4.9      $4.9      $4.9      $4.9      $4.9      $4.9      $4.9            $4.9
   Seeds                $96.3    $115.8    $135.9    $157.3    $180.9    $206.1    $239.3    $287.1    $333.3          $387.2
   VMO                   $3.9      $4.9      $5.4      $6.1      $6.8      $7.6      $8.5      $9.6     $10.7           $12.0
   Oilseed              $20.9     $27.5     $31.7     $36.3     $37.8     $37.8     $37.8     $37.8     $37.8           $37.8
GROSS PROFIT           $109.0    $123.2    $155.3    $189.8    $231.9    $275.7    $328.6    $418.5    $521.0          $647.4
SG&A                    $68.6     $81.6     $88.9     $95.7    $105.0    $114.1    $127.9    $147.0    $173.4          $204.9
R&D                   $36.5     $46.0     $59.0     $71.0     $91.0     $98.0    $105.0    $105.0    $105.0          $123.5
   SoilServ              $0.0      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0            $0.0
   Biopesticides         $1.1      $0.8      $0.8      $0.8      $0.8      $0.8      $0.8      $0.8      $0.8            $0.8
   Seeds                $34.7     $39.3     $46.1     $48.9     $54.7     $60.6     $69.4     $85.7    $101.4          $120.7
   VMO                   $0.7      $0.6      $1.1      $1.1      $1.4      $1.4      $1.5      $1.6      $1.7            $1.9
   Oilseed               $0.0      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0            $0.0
   Corporate             $0.0      $5.2     $11.0     $20.2     $34.1     $35.1     $33.3     $16.8      $1.1            $0.0
EBITDA                   $3.9     ($4.5)     $7.4     $23.1     $35.9     $63.6     $95.7    $166.5    $242.6          $319.0
Depreciation             $3.6      $4.0      $4.6      $5.2      $6.1      $7.1      $8.3     $10.0     $11.8           $14.0
Amortization             $2.6      $2.6      $2.6      $2.6      $2.6      $2.6      $1.8      $1.3      $1.2            $1.2
                    --------- --------- --------- --------- --------- --------- --------- --------- ----------  -------------
EBIT                    ($2.4)   ($11.1)     $0.2     $15.2     $27.2     $53.9     $85.6    $155.3    $229.6          $303.8
Royalty and Venture
   Income               ($4.1)    ($5.0)    ($4.8)    ($1.5)     $3.4     $11.8     $16.4     $22.7     $24.9           $30.3
TOTAL OPERATING
   INCOME               ($6.5)   ($16.1)    ($4.6)    $13.7     $30.6     $65.7    $102.0    $177.9    $254.5          $334.1
LITIGATION EXPENSES    ($20.0)   ($15.0)   ($10.0)    ($5.0)    ($2.0)    ($2.0)
INTEREST EXP./REV       ($3.0)    ($7.9)   ($12.2)   ($16.3)   ($19.1)   ($19.6)   ($19.0)   ($17.7)   ($13.5)          ($5.7)
PRE-TAX INCOME (TOTAL) ($29.5)   ($38.9)   ($26.8)    ($7.6)     $9.5     $44.0     $83.0    $160.3    $241.0          $328.4
TAXES (@41%)              0.0       0.0       0.0       0.0      (3.9)    (18.0)    (34.0)    (65.7)    (98.8)         (134.7)
NOL Utilization           0.0       0.0       0.0       0.0       3.9      18.0      20.2       0.0       0.0             0.0
NET INCOME              (29.5)    (38.9)    (26.8)     (7.6)      9.5      44.0      69.2      94.5     142.2           193.8
E.P.S.(38.29MM SHARES) ($0.77)   ($1.02)   ($0.70)   ($0.20)    $0.25     $1.15     $1.81     $2.47     $3.71           $5.06

</TABLE>


                                      51
<PAGE>

MYCOGEN CORPORATION        VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- ------------------------------------------------------------------------------
CORPORATE BALANCE SHEET PROJECTIONS ($MM)

<TABLE>
<CAPTION>
                               1998      1999      2000      2001      2002      2003      2004      2005      2006      2007
                               ----      ----      ----      ----      ----      ----      ----      ----      ----      ----
<S>                          <C>       <C>       <C>       <C>        <C>      <C>       <C>        <C>      <C>        <C>
Cash and Equivalents         $   2.2   $   2.2   $   2.2   $   2.2    $   2.2  $   2.2   $   2.2    $  2.2   $   2.2    $   2.2
Accounts Receivable          $  60.1   $  70.7   $  83.3   $  97.9    $ 113.3  $ 129.4   $ 150.2    $179.9   $ 209.5    $ 244.9
Inventories                  $  66.5   $  79.9   $  92.8   $ 106.7    $ 121.9  $ 138.1   $ 158.9    $188.2   $ 217.4    $ 251.6
PP&E                         $ 105.1   $ 108.1   $ 119.4   $ 139.2    $ 148.3  $ 160.4   $ 188.1    $206.8   $ 217.1    $ 229.7
Intangibles                  $  30.3   $  27.7   $  25.1   $  22.4    $  19.8  $  17.1   $  15.3    $ 14.0   $  12.8    $  11.6
Prepaid Expenses             $  18.1   $  18.1   $  18.1   $  18.1    $  18.1  $  18.1   $  18.1    $ 18.1   $  18.1    $  18.1
                             -------   -------   -------   -------    -------  -------   -------    ------   -------    -------
TOTAL ASSETS                 $ 282.3   $ 306.6   $ 340.9   $ 386.5    $ 423.5  $ 465.2   $ 532.8    $609.2   $ 677.1    $ 758.0
                             -------   -------   -------   -------    -------  -------   -------    ------   -------    -------
                             -------   -------   -------   -------    -------  -------   -------    ------   -------    -------
Advances from DAS            $  13.5   $  13.5   $  13.5   $  13.5    $  13.5  $  13.5   $  13.5    $ 13.5   $  13.5    $  13.5
Short-term Borrowings        $  77.3   $ 135.6   $ 193.7   $ 243.9    $ 267.3  $ 259.7   $ 251.2    $223.5   $ 139.7    $  15.7
A/P & Accruals               $  19.5   $  24.4   $  27.4   $  30.3    $  34.5  $  39.8   $  46.6    $ 56.2   $  65.7    $  76.9
Accrued Compensation         $   6.1   $   6.1   $   6.1   $   6.1    $   6.1  $   6.1   $   6.1    $  6.1   $   6.1    $   6.1
Deferred Revenues            $   8.2   $   8.2   $   8.2   $   8.2    $   8.2  $   8.2   $   8.2    $  8.2   $   8.2    $   8.2
Other Current Liabilities    $  12.9   $  12.9   $  12.9   $  12.9    $  12.9  $  12.9   $  12.9    $ 12.9   $  12.9    $  12.9
TOTAL CURRENT LIABILITIES    $ 137.5   $ 200.7   $ 261.8   $ 315.0    $ 342.5  $ 340.2   $ 338.6    $320.4   $ 246.2    $ 133.3

Long-term Liabilities        $  17.1   $  17.1   $  17.1   $  17.1    $  17.1  $  17.1   $  17.1    $ 17.1   $  17.1    $  17.1

Paid-In Capital                0.031     0.031     0.031     0.031      0.031    0.031     0.031     0.031     0.031      0.031
Additional PIC               $ 344.7   $ 344.7   $ 344.7   $ 344.7    $ 344.7  $ 344.7   $ 344.7    $344.7   $ 344.7    $ 344.7
Retained Earning (Deficit)   $(217.0)  $(256.0)  $(282.8)  $(290.3)   $(280.8) $(236.8)  $(167.6)   $(73.1)  $  69.1    $ 262.8
STOCKHOLDERS EQUITY          $ 127.7   $  88.8   $  61.9   $  54.4    $  63.9  $ 107.9   $ 177.1    $271.6   $ 413.8    $ 607.6
                             -------   -------   -------   -------    -------  -------   -------    ------   -------    -------

TOTAL S.H. EQUITY AND LIAB.  $ 282.3   $ 306.6   $ 340.9   $ 386.5    $ 423.5  $ 465.2   $ 532.8    $609.2   $ 677.1    $ 758.0
                             -------   -------   -------   -------    -------  -------   -------    ------   -------    -------
                             -------   -------   -------   -------    -------  -------   -------    ------   -------    -------

NET WORKING CAPITAL          $  94.3   $ 113.3   $ 136.0   $ 161.4    $ 187.8  $ 214.8   $ 249.6    $299.8   $ 348.3    $ 406.6
NET ASSETS                   $ 199.3   $ 221.4   $ 255.3   $ 300.6    $ 336.1  $ 375.1   $ 437.7    $505.8   $ 565.4    $ 636.3

Net Operating Income         $ (29.5)  $ (38.9)  $ (26.8)  $  (7.6)   $   9.5  $  44.0   $  83.0    $160.3   $ 241.0    $ 328.4
Less: Taxes Paid             $   0.0   $   0.0   $   0.0   $   0.0    $  (0.0) $   0.0   $ (13.8)   $(65.7)  $ (98.8)   $(134.7)
Plus: D&A                    $   6.3   $   6.6   $   7.2   $   7.9    $   8.8  $   9.7   $  10.1    $ 11.2   $  13.0    $  15.2
Less: Capital Expenditure    $ (21.5)  $  (7.0)  $ (15.9)  $ (25.0)   $ (15.2) $ (19.2)  $ (36.0)   $(28.7)  $ (22.1)   $ (26.6)
Less: Increase in NWC        $ (29.0)  $ (19.0)  $ (22.7)  $ (25.5)   $ (26.4) $ (27.0)  $ (34.9)   $(49.4)  $ (49.3)   $ (58.4)

FREE CASH FLOW               $ (73.7)  $ (58.3)  $ (58.1)  $ (50.2)   $ (23.3) $   7.6   $   8.5    $ 27.7   $  83.8    $ 124.0
</TABLE>


                                   52
<PAGE>

<TABLE>
<CAPTION> 
MYCOGEN CORPORATION                                                             VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- ------------------------------------------------------------------------------------------------------------------------------------
- ------------------------------------------------------------------------------------------------------------------------------------
CORPORATE CASH FLOW STATEMENT ($MM)

                                   1998      1999      2000       2001      2002      2003      2004      2005     2006      2007
                                 --------  --------  --------   --------  --------  --------  --------  --------  ------   --------
<S>                              <C>       <C>       <C>        <C>       <C>       <C>       <C>       <C>       <C>      <C>
Net Income                        ($29.5)   ($38.9)   ($26.8)    ($7.6)     $9.5     $44.0     $69.2     $94.5    $142.2    $193.8
Depreciation                         3.6       4.0       4.6       5.2       6.1       7.1       8.3      10.0      11.8      14.0
Amortization                         2.6       2.6       2.6       2.6       2.6       2.6       1.8       1.3       1.2       1.2
Change in Working Capital:
(INC.) DEC. IN ACCTS. REC.         (18.0)    (10.5)    (12.7)    (14.5)    (15.5)    (16.0)    (20.8)    (29.7)    (29.6)    (35.4)
(INC.) DEC. IN INVENTORY            (9.4)    (13.4)    (12.9)    (13.9)    (15.1)    (16.2)    (20.8)    (29.3)    (29.2)    (34.2)
(INC.) DEC. IN PPD. EXPENSES        -         -         -         -         -         -         -         -         -         -
INC. (DEC.) IN ACC. PAY/ACC.        (1.6)      4.9       2.9       3.0       4.2       5.3       6.8       9.6       9.5      11.2
INC. (DEC.) IN ACCRUED COMPENSA     -         -         -         -         -         -         -         -         -         -
INC. (DEC.) IN DEFERRED REVENUES    -         -         -         -         -         -         -         -         -         -
INC. (DEC.) IN OTHER CURR. LIAB.    -         -         -         -         -         -         -         -         -         -
INC. (DEC.) IN LT LIABILITIES        1.6      -         -         -         -         -         -         -         -         -
CASH FLOW FROM OPERATIONS          (50.6)    (51.3)    (42.3)    (25.2)     (8.1)     26.7      44.5      56.4     105.9     150.6

Capital Expenditures               (21.5)     (7.0)    (15.9)    (25.0)    (15.2)    (19.2)    (36.0)    (28.7)    (22.1)    (26.6)
CASH FLOW FROM INVESTMENTS         (21.5)     (7.0)    (15.9)    (25.0)    (15.2)    (19.2)    (36.0)    (28.7)    (22.1)    (26.6)
NET CASH FLOW                      (72.2)    (58.3)    (58.1)    (50.2)    (23.3)      7.6       8.5      27.7      83.8     124.0

Debt Issuance (Paydown)
ADVANCES FROM DAS                   -         -         -         -         -         -         -         -         -         -
SHORT-TERM BORROWINGS               72.2      58.3      58.1      50.2      23.3      (7.6)     (8.5)    (27.7)    (83.8)   (124.0)
Equity Issuance                     -         -         -         -         -         -         -         -         -         -
CASH FLOW (FINANCING)               72.2      58.3      58.1      50.2      23.3      (7.6)     (8.5)    (27.7)    (83.8)   (124.0)

NET INC./DEC. IN CASH              ($0.0)    ($0.0)     $0.0     ($0.0)     $0.0     ($0.0)    ($0.0)    ($0.0)     $0.0      $0.0

Cash & Equivalents BOY              $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2
Cash & Equivalents EOY              $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2      $2.2
</TABLE>
 


                                          53
<PAGE>

MYCOGEN CORPORATION          VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- --------------------------------------------------------------------------------
CORPORATE NET OPERATING LOSS CARRYFORWARDS / DEBT SCHEDULE ($MM)

<TABLE>
<CAPTION>
 

                               1998      1999      2000      2001      2002      2003      2004      2005      2006      2007
                             --------  --------  --------  --------  --------  --------  --------  --------  --------  --------
<S>                          <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>
NOL SCHEDULE

Start New NOL Carry(1)          $12.1     $28.1     $39.1     $42.2     $42.2     $38.3     $20.2      $0.0      $0.0      $0.0
Taxes Due                        $0.0      $0.0      $0.0      $0.0     ($3.9)   ($18.0)   ($34.0)   ($65.7)   ($98.8)  ($134.7)
Total New NOL Utilized           $0.0      $0.0      $0.0      $0.0      $3.9     $18.0     $20.2      $0.0      $0.0      $0.0

Balance Current NOL Carry       $12.1     $28.1     $39.1     $42.2     $38.3     $20.2      $0.0      $0.0      $0.0      $0.0
New NOL YTD                     $12.1     $16.0     $11.0      $3.1      $0.0      $0.0      $0.0      $0.0      $0.0      $0.0


DEBT SCHEDULE

Advances from DAS               $13.5     $13.5     $13.5     $13.5     $13.5     $13.5     $13.5     $13.5     $13.5     $13.5

BOY Short Term Borrowings         5.1      77.3     135.6     193.7     243.9     267.3     259.7     251.2     223.5     139.7
Addn. Short-Term Borrow.         72.2      58.3      58.1      50.2      23.2         -         -         -         -         -
Debt Paid Down                      -         -         -         -         -      (7.6)     (8.5)    (27.7)    (83.8)   (124.0)
                             --------  --------  --------  --------  --------  --------  --------  --------  --------  --------
BOY Short-term Borrowings       $77.3    $135.6    $193.7    $243.9    $267.3    $259.7    $251.2    $223.5    $139.7     $15.7

</TABLE>
 


(1)  Excluded existing NOL's existing prior to 1998. Prior NOL's valued
     separately subject to existing utilization limitations
(2)  NOL's generated in 1998-2007 period valued assuming accelerated utilization
     due to consolidation with larger entity



                                          54
<PAGE>

<TABLE>
<CAPTION>

MYCOGEN CORPORATION                                                         VALUATION: PROBABILITY-WEIGHTED METHOD DCF ANALYSIS
- -------------------------------------------------------------------------------------------------------------------------------
CORPORATE FINANCIAL RATIO PROJECTIONS ($MM)

                              1998       1999      2000      2001      2002      2003      2004      2005      2006      2007
                             ------     ------    ------    ------    ------    -------   ------    ------    -------   ------

<S>                          <C>        <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C> 
COGS/SALES                   58.5%      59.7%     57.1%     54.6%     51.8%     49.2%     47.5%     45.0%     42.8%     40.6%
SG&A/SALES                   27.2%      27.8%     25.4%     23.1%     21.5%     20.2%     19.4%     18.3%     18.2%     17.9%
R&D/SALES                    14.5%      15.7%     16.8%     17.1%     18.7%     17.3%     16.0%     13.1%     11.0%     10.8%
ROYALTY/SALES                -1.6%      -1.7%     -1.4%     -0.4%      0.7%      2.1%      2.6%      2.9%      2.7%      2.7%
OPERATING MARGIN              1.3%      -1.9%      2.1%      6.5%      9.3%     14.6%     18.3%     24.8%     29.2%     31.8%

EBITDA/SALES                  1.5%      -1.5%      2.1%      5.6%      7.4%     11.2%     14.6%     20.7%     25.4%     27.9%
EBIT/SALES                   -0.9%      -3.8%      0.1%      3.7%      5.6%      9.5%     13.0%     19.3%     24.0%     26.6%
NET INC./SALES              -11.7%     -13.3%     -7.7%     -1.8%      1.9%      7.8%     10.5%     11.8%     14.9%     17.0%

WORKING CAP/SALES            37.4%      38.6%     38.8%     38.9%     38.5%     37.9%     38.0%     37.2%     36.5%     35.6%
DEPRECIATION/PP&E             3.5%       3.7%      3.8%      3.8%      4.1%      4.4%      4.4%      4.8%      5.4%      6.1%
DEPRECIATION/SALES            1.4%       1.4%      1.3%      1.3%      1.3%      1.2%      1.3%      1.2%      1.2%      1.2%
PPE/SALES                    41.6%      36.8%     34.0%     33.5%     30.4%     28.3%     28.6%     25.8%     22.7%     20.1%

DEBT/ASSETS                  38.8%      61.3%     75.9%     81.1%     79.5%     69.2%     57.4%     44.2%     24.7%      2.5%

COVERAGE (EBIT/INTEREST)     -0.8x      -1.4x      0.0x      0.9x      1.4x      2.7x      4.5x      8.8x     17.0x     53.2x
DEBT/TOTAL CAP.              38.8%      61.3%     75.9%     81.1%     79.5%     69.2%     57.4%     44.2%     24.7%      2.5%
</TABLE>

                                          55
<PAGE>

MYCOGEN CORPORATION
- -------------------------------------------------------------------------------




                      -----------------------------------


                              COMPARABLE ANALYSIS


                      -----------------------------------


                                      56
<PAGE>
MYCOGEN CORPORATION                                          COMPARABLE ANALYSIS
- --------------------------------------------------------------------------------
SELECTED SEED COMPARABLE COMPANIES ANALYSIS

TRADING STATISTICS

<TABLE>
<CAPTION>
                                                                                                             
                         CURRENT     EQUITY    ADJUSTED    PRICE/EARNINGS    EST. 3-5   98E P/E/             
                          PRICE      MARKET     MARKET     --------------    YR. EPS    3-5 YEAR    PRICE/   
COMPANY                  8/26/98     VALUE      VALUE       1997    1998E     GTH.     EPS GTH.(1)   BOOK    
- -------------            -------    -------    --------    -----    -----    --------  -----------  ------
<S>                      <C>       <C>         <C>         <C>      <C>      <C>       <C>          <C>
                         (in $)    (in $ MM)   (in $ MM)     (a)     (a)       (%)       (a)         (a)

Mycogen                   21.75       823.6       904.9       NM       NM     22.5         NM        4.1     
Pioneer Hi-Bred           36.88     8,908.3     8,710.3     37.5     32.2     15.0       2.14        6.4     
Dekalb Genetics(2)        70.07     2,525.0     2,765.0     87.0     89.8     25.0       3.59       11.2     
Delta & Pine Land         46.11     1,823.0     1,890.3     93.4     72.1     30.0       2.40       18.3     
Agribiotech(3)            11.13       371.9       370.5       NM     46.4     40.0       1.16        4.6     
                                                --------------------------------------------------------------
                                                Mean        72.6     60.1     27.5       2.32       10.1     
                                                Median      87.0     59.2     27.5       2.27        8.8     
                                                High        93.4     89.8     40.0       3.59       18.3     
                                                Low         37.5     32.2     15.0       1.16        4.6     
                                                --------------------------------------------------------------

<CAPTION>

                                                          ADJUSTED MARKET VALUE /                                                
                     -------------------------------------------------------------------------------------------------  NET DEBT/
                      1997     LTM    1998E   1999E   1997     LTM     1998E    1999E    1997    LTM    1998E   1999E    MARKET  
COMPANY              SALES   SALES    SALES   SALES  EBITDA   EBITDA   EBITDA   EBITDA   EBIT    EBIT    EBIT    EBIT     CAP.   
- -------------        -----   -----    -----   -----  ------   ------   ------   ------   ----    ----   -----   -----   ---------
<S>                  <C>     <C>      <C>     <C>    <C>      <C>      <C>      <C>      <C>     <C>    <C>     <C>     <C>
                      (a)     (a)     (a)     (a)      (a)      (a)      (a)      (a)     (a)     (a)    (a)      (a)     (%)

Mycogen               4.29    4.15    3.53    3.03      NM       NM       NM       NM      NM      NM     NM       NM     9.9    
Pioneer Hi-Bred       4.88    4.73    4.49    4.20    19.3     18.9     16.8     14.3    24.0    23.4   20.1     16.8    (2.3)   
Dekalb Genetics(2)    6.13    5.42    5.80    5.22    45.3     56.5     44.6     35.4    58.5    83.0   58.8     46.1     9.5    
Delta & Pine Land    10.32    9.33    7.13    5.33    50.8     57.5     33.3     22.4    58.9    71.4   37.2     24.1     3.6    
Agribiotech(3)        1.34    1.34    1.45    0.72    32.3     32.3     32.4     12.6    62.6    62.6   42.9     14.2    (0.4)   
- ---------------------------------------------------------------------------------------------------------------------------------
Mean                  5.64    5.20    4.72    3.87    36.9     41.3     31.8     21.2    51.0    60.1   39.8     25.3     2.6    
Median                5.50    5.08    5.15    4.71    38.8     44.4     32.9     18.4    50.7    67.0   40.1     20.5     1.6    
High                 10.32    9.33    7.13    5.33    50.8     57.5     44.6     35.4    62.6    83.0   58.8     46.1     9.5    
Low                   1.34    1.34    1.45    0.72    19.3     18.9     16.8     12.6    24.0    23.4   20.1     14.2    (2.3)   
- ---------------------------------------------------------------------------------------------------------------------------------

</TABLE>

OPERATING STATISTICS

<TABLE>
<CAPTION>

                             TOTAL REVENUES                                                                                   
                      ------------------------------             EBITDA MARGIN                       EBIT MARGIN
                         LTM      97/96 %   98E/97 %   -------------------------------     ---------------------------------- 
COMPANY                 AMOUNT     GROWTH     GROWTH    1997      LTM    1998E    1999E     1997      LTM     1998E      1999E 
- -------------         ---------   -------   --------   ----     ----    -----    -----     ----     ----     -----      ----- 
<S>                   <C>         <C>       <C>        <C>      <C>     <C>      <C>       <C>      <C>      <C>        <C>   
                      (IN $ MM)     (%)        (%)      (%)      (%)      (%)      (%)      (%)      (%)      (%)        (%)  

Mycogen                  218       35.6      21.6       3.4      1.2      3.1       NM       NM       NM      0.8         NM  
Pioneer Hi-Bred        1,840        3.7       8.7      25.3     25.1     26.8     29.4     20.3     20.2     22.4       25.1  
Dekalb Genetics(2)       510       16.5       5.7      13.5      9.6     13.0     14.7     10.5      6.5      9.9       11.3  
Delta & Pine 
 Land(2)                 203       19.6      44.8      20.3     16.2     21.4     23.8     17.5     13.1     19.1       22.1  
Agribiotech(3)           277         NA      (8.1)      4.1      4.1      4.5      5.8      2.1      2.1      3.4        5.1  
                   -----------------------------------------------------------------------------------------------------------
                   Mean            13.2      12.8      15.8     13.7     16.4     18.4     12.6     10.5     13.7       15.9  
                   Median          16.5       7.2      16.9     12.9     17.2     19.2     14.0      9.8     14.5       16.7  
                   High            19.6      44.8      25.3     25.1     26.8     29.4     20.3     20.2     22.4       25.1  
                   Low              3.7      (8.1)      4.1      4.1      4.5      5.8      2.1      2.1      3.4        5.1  
                   -----------------------------------------------------------------------------------------------------------


<CAPTION>
                                 NET INCOME MARGIN               R&D/TOTAL REVENUES     
                          --------------------------------    -----------------------  
                          1997      LTM     1998E    1999E    1997     1998E    1999E  
                          ----     ----     -----    -----    ----     -----    -----  
<S>                       <C>      <C>      <C>      <C>      <C>      <C>      <C>    
                           (%)      (%)      (%)      (%)      (%)      (%)       (%)  
                                                                                       
Mycogen                     NM       NM       NM       NM     11.4     12.7      15.3  
Pioneer Hi-Bred           13.6     14.6     15.0     16.9      8.2      7.7       7.8  
Dekalb Genetics(2)         6.4      4.3      6.1      7.1     12.7     12.6      15.1  
Delta & Pine 
 Land(2)                  10.7      6.9     10.1     11.8      7.4      6.1       4.7  
Agribiotech(3)              NM       NM      1.9      2.3       NA       NA        NA  
- ---------------------------------------------------------------------------------------
Mean                      10.2      8.6      8.3      9.5      9.4      8.8       9.2  
Median                    10.7      6.9      8.1      9.4      8.2      7.7       7.8  
High                      13.6     14.6     15.0     16.9     12.7     12.6      15.1  
Low                        6.4      4.3      1.9      2.3      7.4      6.1       4.7  
- ---------------------------------------------------------------------------------------

</TABLE>

- ---------------------

1997 data refers to FYE 8/31/97, etc. All means and medians exclude Mycogen.
Currency are converted at current exchange rates.
EPS projections are based on I/B/E/S consensus; other projections are based 
on selected brokers' research except Mycogen projections are provided by the 
management
When not available, depreciation and amortization are estimated as a 
percentage of sales based on the latest released data.
When not available, LTM data is based on selected brokers' research.
(1) Represents ratio of the 1998E P/E ratio to the estimated 3-5 year 
earnings growth rate.
(2) Stock price is calculated at the average of 30-day stock prices before 
the announcement of Monsanto transactions.
(3) Agribiotech fiscal year end 6/30. LTM data represents financials for 1997 
fiscal year end pro forma for acquisitions, EBITDA estimated per analyst 
projections of D&A margins.


                                        57
<PAGE>

MYCOGEN CORPORATION                                          COMPARABLE ANALYSIS
- --------------------------------------------------------------------------------
SELECTED COMPARABLE COMPANIES QUARTERLY ANALYSIS FOR FISCAL YEAR 1997

<TABLE>
<CAPTION>
 

                                         EBITDA MARGIN                                EBIT MARGIN
                            -------------------------------------       --------------------------------------
                              1-QTR     2-QTR     3-QTR     4-QTR          1-QTR     2-QTR     3-QTR     4-QTR
                              -----     -----     -----     -----          -----     -----     -----     -----
<S>                         <C>        <C>        <C>     <C>           <C>         <C>        <C>     <C>
Mycogen                     (44.7%)      8.3%     13.5%    (6.2%)        (55.4%)      5.5%     10.6%   (16.4%)

Pioneer Hi-Bred             (57.8%)      6.1%     41.8%   (35.2%)        (78.9%)    (2.3%)     40.0%   (52.8%)
DeKalb Genetics               11.0%     16.1%     14.2%   (19.4%)           6.4%     14.5%     12.5%   (53.0%)
Delta & Pine Land           (82.8%)     25.2%     29.5%        NM       (101.6%)     23.3%     28.4%        NM
Agribiotech(1)              (14.0%)    (4.1%)      8.6%    (2.3%)        (16.4%)    (6.1%)      7.0%    (3.8%)
           ---------------------------------------------------------------------------------------------------
           Mean             (35.9%)     10.8%     23.5%   (19.0%)        (47.6%)      7.4%     22.0%   (36.5%)
           Median           (35.9%)     11.1%     21.8%   (19.4%)        (47.7%)      6.1%     20.4%   (52.8%)
           ---------------------------------------------------------------------------------------------------

<CAPTION>

                                       NET INCOME MARGIN                          R&D/TOTAL REVENUES
                            -------------------------------------       --------------------------------------
                              1-QTR     2-QTR     3-QTR     4-QTR          1-QTR     2-QTR     3-QTR     4-QTR
                              -----     -----     -----     -----          -----     -----     -----     -----
<S>                         <C>        <C>        <C>     <C>              <C>       <C>       <C>       <C>
Mycogen                     (54.7%)      3.7%      6.8%   (48.4%)          26.3%      7.8%      6.9%     22.3%

Pioneer Hi-Bred             (50.0%)    (0.8%)     25.8%   (29.6%)          33.3%     12.5%      3.1%     30.3%
DeKalb Genetics                3.1%      8.5%      7.3%   (20.1%)           8.9%     13.2%     12.8%     23.1%
Delta & Pine Land           (65.5%)     14.1%     17.9%        NM          41.0%      5.2%      3.3%        NM
Agribiotech(1)              (16.9%)    (8.9%)      6.4%    (6.2%)           1.2%      2.1%      1.4%      2.0%
           ---------------------------------------------------------------------------------------------------
           Mean             (32.3%)      3.2%     14.3%   (18.6%)          21.1%      8.3%      5.2%     18.5%
           Median           (33.5%)      3.9%     12.6%   (20.1%)          21.1%      8.8%      3.2%     23.1%
           ---------------------------------------------------------------------------------------------------

</TABLE>



<TABLE>
<CAPTION>

                                        DAYS RECEIVABLE                             DAYS OF INVENTORY
                            -------------------------------------       --------------------------------------
                              1-QTR     2-QTR     3-QTR     4-QTR          1-QTR     2-QTR     3-QTR     4-QTR
                              -----     -----     -----     -----          -----     -----     -----     -----
<S>                           <C>       <C>       <C>       <C>            <C>       <C>       <C>       <C>
Mycogen(2)(3)                   129        61        85       109            761       145        89       257

Pioneer Hi-Bred(2)              178        79        34       162          1,490       515        68       558
DeKalb Genetics(2)(4)            69        33        79       357            526       147        97     1,361
Delta & Pine Land                92        99        99        NM          1,067       144        50        NM
Agribiotech(1)                   97        61        81        64            289       189       122       113
           ---------------------------------------------------------------------------------------------------
           Mean                 109        68        73       194            843       249        84       677
           Median                94        70        80       162            796       168        83       558
           ---------------------------------------------------------------------------------------------------

<CAPTION>

                                         DAYS PAYABLE                           NET DEBT/BOOK EQUITY
                            -------------------------------------       --------------------------------------
                              1-QTR     2-QTR     3-QTR     4-QTR          1-QTR     2-QTR     3-QTR     4-QTR
                              -----     -----     -----     -----          -----     -----     -----     -----
<S>                          <C>        <C>       <C>       <C>          <C>       <C>        <C>        <C>
Mycogen(2)(3)                   216        40        25        95         (3.4%)      8.4%     24.5%     19.5%

Pioneer Hi-Bred(2)              718       147        29       108          19.3%   (30.8%)    (9.7%)      1.7%
DeKalb Genetics(2)(4)           249        44        11       153          71.8%     35.7%     72.4%     60.8%
Delta & Pine Land               314        38        12        NM          66.1%    103.1%     34.7%     39.9%
Agribiotech(1)                  104        92        64        52        (16.8%)     60.4%     64.3%     56.4%
           ---------------------------------------------------------------------------------------------------
           Mean                 346        80        29       104          35.1%     42.1%     40.4%     39.7%
           Median               281        68        21       108          42.7%     48.0%     49.5%     48.2%
           ---------------------------------------------------------------------------------------------------
</TABLE>
 




- --------------------
NOTE: DAYS CALCULATION ASSUMES 360-DAY A YEAR AND ALL MEANS AND MEDIANS EXCLUDE
MYCOGEN DATA
(1)  Agribiotech data are not pro forma of acquisition
(2)  Data not available to separate notes receivable from accounts receivable
     for quarterly data
(3)  2nd and 3rd quarter net debts include $14.25 million unsecured note payable
     to bank that was specified in the 10-K
(4)  Accounts Payable includes only trade accounts payable



                                          58
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- -------------------------------------------------------------------------------
SELECTED SEED COMPARABLE COMPANIES ANALYSIS FOR FISCAL YEAR 1994-1997

<TABLE>
<CAPTION>
                                EBITDA Margin                         EBIT Margin                       Net Income  Margin
                       -------------------------------     ----------------------------------    -------------------------------- 
                        1994     1995    1996    1997       1994      1995     1996    1997       1994     1995    1996    1997   
                        ----     ----    ----    ----       ----      ----     ----    ----       ----     ----    ----    ----   
<S>                    <C>      <C>     <C>     <C>        <C>       <C>      <C>      <C>       <C>      <C>     <C>      <C>    
Mycogen                (5.3%)    (5.8%)  (8.7%)   3.4%      (11.0%)  (13.7%)  (14.5%)  (1.3%)    (8.8%)   (14.1%) (19.6%)  (8.5%) 

Pioneer Hi-Bred        25.4%     23.1%   24.6%   25.3%       20.4%    18.3%    20.2%   20.3%     12.4%     11.9%   13.0%   13.6%  
Dekalb Genetics        10.2%     11.1%   11.4%   13.5%        6.6%     7.6%     8.5%   10.5%      3.5%      3.0%    4.4%    6.4%  
Delta & Pine Land      19.3%     22.5%   20.4%   20.3%       16.1%    19.4%    17.7%   17.5%      9.7%     11.1%   10.5%   10.7%  
Agribiotech (1)          NM     (27.0%)  (9.0%)  (0.7%)        NM    (29.9%)  (11.2%)  (2.4%)      NM     (29.6%) (12.8%)  (4.1%) 

               -------------------------------------------------------------------------------------------------------------------
               Mean    18.3%      7.4%   11.8%   14.6%       14.4%     3.8%     8.8%   11.5%      8.6%     (0.9%)   3.8%    6.7%  
               Median  19.3%     16.8%   15.9%   16.9%       16.1%    12.9%    13.1%   14.0%      9.7%      7.0%    7.4%    8.6%  
               -------------------------------------------------------------------------------------------------------------------

                                 R&D/Total Revenues     
                          ------------------------------
                           1994     1995    1996    1997
                           ----     ----    ----    ----
                          <C>      <C>     <C>     <C>  
Mycogen                   16.1%    18.7%   15.2%   11.4%
                                                        
Pioneer Hi-Bred            7.7%     8.5%    7.9%    8.2%
Dekalb Genetics           13.8%    13.3%   12.3%   12.7%
Delta & Pine Land          6.8%     6.7%    6.4%    7.4%
Agribiotech (1)             NM      1.2%    0.2%    1.8%
                                                        
               -----------------------------------------
               Mean        9.4%     7.4%    6.7%    7.5%
               Median      7.7%     7.6%    7.1%    7.8%
               -----------------------------------------

</TABLE>

<TABLE>
<CAPTION>
                           Selling/Total Revenues                      G&A Margin
                       ------------------------------      --------------------------------
                        1994     1995    1996    1997       1994      1995     1996    1997 
                        ----     ----    ----    ----       ----      ----     ----    ---- 
<S>                    <C>      <C>     <C>     <C>        <C>       <C>      <C>      <C>  
Mycogen                22.4%    20.8%   24.3%   19.8%      14.9%     11.7%    12.7%    8.5% 

Pioneer Hi-Bred        22.7%    23.1%   22.2%   21.0%       8.3%      8.2%     7.5%    7.3% 
Dekalb Genetics        19.3%    20.2%   18.8%   18.2%       5.7%      8.1%     8.3%    7.6% 
Delta & Pine Land       7.2%     7.7%    6.2%    6.0%      10.1%      9.7%     6.1%    5.5% 
Agribiotech (1)          NA       NA      NA      NA         NA        NA       NA      NA

               -----------------------------------------------------------------------------
               Mean    16.4%    17.0%   15.7%   15.1%       8.0%      8.7%     7.3%    6.8%
               Median  19.3%    20.2%   18.8%   18.2%       8.3%      8.2%     7.5%    7.3%
               -----------------------------------------------------------------------------
</TABLE>


<TABLE>
<CAPTION>
                        Days Receivable       Days of Inventory         Days Payable            Net Debt/Book Equity 
                     -------------------     -------------------    -------------------    -----------------------------
                     1994 1995 1996 1997     1994 1995 1996 1997    1994 1995 1996 1997    1994    1995    1996    1997 
                     ---- ---- ---- ----     ---- ---- ---- ----    ---- ---- ---- ----    ----    ----    ----    ---- 
<S>                  <C>  <C>  <C>  <C>      <C>  <C>  <C>  <C>     <C>  <C>  <C>  <C>     <C>     <C>     <C>     <C>  
Mycogen               86   89   70   70       182  181  143  162     22   36    33   60    (30.2%) (13.5%) (36.7%) 19.5%
                                                                                                                        
Pioneer Hi-Bred       39   38   44   52       213  239  189  205     48   33    44   40     (6.1%)   4.9%   (4.8%)  1.7%
Dekalb Genetics(2)(3) 53   65   48   42       218  235  177  217     14   15    24   24    102.1%   98.8%   36.6%  60.8%
Delta & Pine Land     11   19  157  187       144  130  153  133     28   40    55   59     31.8%   11.0%   48.3%  39.9%
Agribiotech (1)       NM   54  104   95        NM  145  136  170     NM   56    82   77    (45.4%)  (9.3%)  29.9%  56.4%
                                                                                                                        
             -----------------------------------------------------------------------------------------------------------
             Mean     34   44   88   94       192  187  164  181     30   36    51   50     20.6%   26.4%   27.5%  39.7%
             Median   39   46   76   74       213  190  165  188     28   36    50   49     12.8%    8.0%   33.2%  48.2%
             -----------------------------------------------------------------------------------------------------------
</TABLE>

- ----------------------------
NOTE: DAYS CALCULATION ASSUMES 360-DAY A YEAR AND ALL MEANS AND MEDIANS EXCLUDE 
      MYCOGEN DATA

(1)   Agribiotech changed its fiscal year end in 1995. 1995 data are based on 
      nine-month period ended 6/30/95. 1997 data are not pro forma of 
      acquisition because no pro forma balance sheet number available for ratio 
      calculations

(2)   Data not available to separate trade receivables from note receivables

(3)   Accounts Payable includes only trade accounts payable


                                      59
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- --------------------------------------------------------------------------------
SELECTED COMPARABLE ACQUISITION / VALUATION MULTIPLES

<TABLE>
<CAPTION>

                                                                                                       ADJUSTED PURCHASE PRICE/
                                                                                                 ----------------------------------
                                                                  IMPLIED VALUE    ADJUSTED        LTM        LTM            LTM
TARGET                             ACQUIRER           CLOSE DATE    OF EQUITY   PURCHASE PRICE    SALES      EBITDA          EBIT
- ------------------------------     -----------------  ----------  ------------- --------------   -------     ------         -------
<S>                                <C>                 <C>         <C>           <C>              <C>         <C>            <C>
SEED COMPANIES
- --------------
DELTA & PINE LAND                  MONSANTO            PENDING     $1,832.5      $1,906.7          9.87 X    69.8 X         89.6 X
Sunseeds                           AgrEvo              10/6/97           NA            NA          2.20 X    13.1 X         18.0 X
PIONEER HI-BRED (16.6% STAKE)      DUPONT              9/18/97     $1,700.0      $1,700.0          4.60 X    18.4 X         22.6 X
Holden's Foundation Seeds          Monsanto             9/4/97           NA        $975.0 (1)     21.67 X      NA X           NA X
Asgrow Corn & Seed                 Monsanto             2/4/97           NA        $240.0          1.41 X      NA             NA
Morgan Seeds                       Mycogen Corp.       10/1/96        $40.9         $40.9          1.10 X      NA             NA
Agracetus (W.R. Grace)             Monsanto            5/21/96       $150.0        $150.0            NA        NA             NA
Sure Grow                          Delta & Pine Land   5/21/96        $70.0         $78.9          3.47      17.5           19.1
Jacobs Hertz Seed (Monsanto)       Delta & Pine Land    2/5/96           NA            NA            NA        NA             NA
Cargill - Cotton & Seed            Delta & Pine Land    5/3/94           NA            NA            NA        NA             NA


<CAPTION>

                                     IMPLIED VALUE OF EQUITY/
                                     -------------------------
                                          NET         BOOK
                                        INCOME        VALUE
                                     ------------  -----------
SEED COMPANIES
- --------------
DELTA & PINE LAND                         NM X         25.1 X
Sunseeds                                  NA X           NA X
PIONEER HI-BRED (16.6% STAKE)           33.9 X          8.9 X
Holden's Foundation Seeds                 NA X           NA X
Asgrow Corn & Seed                        NA             NA
Morgan Seeds                              NA             NA
Agracetus (W.R. Grace)                    NA             NA
Sure Grow                               29.9            3.2
Jacobs Hertz Seed (Monsanto)              NA             NA
Cargill - Cotton & Seed                   NA             NA
</TABLE>




- ------------------
(1) Final terms not disclosed; purchase price assumes maximum expected price.

                                      60
<PAGE>

MYCOGEN CORPORATION                                         COMPARABLE ANALYSIS
- --------------------------------------------------------------------------------
SELECTED COMPARABLE ACQUISITION / VALUATION MULTIPLES (CONT'D)

<TABLE>
<CAPTION>



                                                                                                         ADJUSTED PURCHASE PRICE/
                                                                                                     ------------------------------
                                                                     IMPLIED VALUE      ADJUSTED          LTM         LTM       LTM
TARGET                               ACQUIRER          CLOSE DATE      OF EQUITY     PURCHASE PRICE      SALES      EBITDA     EBIT
- ------------------------------       ---------------   ----------    -------------   --------------     -------     ------   -------
<S>                                  <C>               <C>           <C>             <C>                <C>         <C>      <C>
BIOTECH COMPANIES (MAJORITY STAKES)
- --------------
Monsanto                             American Home        Pending(1)    $35,563.7      $39,134.7        5.09 X    36.4 X    70.8 X
                                     Products
Plant Breeding Int'l (Unilever)      Monsanto             Pending          $523.0         $523.0       19.96 (2)    NA        NA
DEKALB GENETICS                      MONSANTO             PENDING        $3,771.2(3)    $3,881.2(3)     8.28 X    61.2 X    79.7 X
Zeneca                               Mogen                5/13/97           $73.6          $73.6       12.80 X      NM X      NM X
Bionova (ELM)                        DNA Plant Tech.      9/27/96           $63.4          $67.9          NM X      NM X      NM X
Plant Genetic Systems                AgrEvo                8/30/9          $733.0         $733.0          NM X      NM X      NM X
CALGENE INC.                         MONSANTO              4/1/96          $299.8(3)      $268.0(3)     4.80 X      NM X      NM X
(49.9% SHARES) 
Mycogen                              DowElanco             3/8/96          $444.7(3)      $358.1(3)     2.90 X      NM X      NM X
(9.5mm shares)
United Agriseeds Inc.                Mycogen              2/28/96           $72.4          $72.4          NA        NA        NA
Lubrizol                             Mycogen              1/15/96              NA             NA          NA        NA        NA



<CAPTION>

                                     IMPLIED VALUE OF EQUITY/
                                     -------------------------
                                          NET         BOOK
                                        INCOME        VALUE
                                     ------------  -----------

BIOTECH COMPANIES (MAJORITY STAKES)
- --------------
Monsanto                                 NM X          8.1 X
                                     
Plant Breeding Int'l (Unilever)          NA             NA
DEKALB GENETICS                          NM X         16.9 X
Zeneca                                   NM X           NA
Bionova (ELM)                            NM X           NA
Plant Genetic Systems                    NM X           NA
CALGENE INC.                             NM X          3.1 X
(49.9% SHARES)                       
Mycogen                                  NM X          2.3 X
(9.5mm shares)                       
United Agriseeds Inc.                    NA             NA
Lubrizol                                 NA             NA
</TABLE>




- ------------------
(1)  Monsanto operating data are not pro forma of all announced acquisitions and
     acquisitions Monsanto is currently bidding
(2)  Sales multiple calculated based on PBIC's royalty revenue
(3)  Calculated by translating the price that acquiror paid for part of the
     target into price for the entire company

                                      61

<PAGE>

                          July 16, 1998


The Dow Chemical Company
2030 Dow Center
Midland, Michigan 48674
Attention: Brian J. Taylorson

Dow AgroSciences LLC
9330 Zionsville Road
Indianapolis, Indiana 46268
Attention:  Louis M. Pribila

Dear Mr. Taylorson and Mr. Pribila:

     In order to evaluate the request by Dow AgroSciences LLC ("DAS") that 
the Board of Directors of Mycogen Corporation ("MYCOGEN") consider amending 
(the "PROPOSED AMENDMENT") the Exchange and Purchase Agreement dated as of 
January 15, 1996 among Mycogen, Agrigenetics, Inc., DAS and United Agriseeds, 
Inc., the Special Committee of independent directors (the "SPECIAL 
COMMITTEE") appointed on April 30, 1998 by the Board of Directors of Mycogen 
to consider the advisability of entering into the Proposed Amendment has 
requested that The Dow Chemical Company ("TDCC") and DAS provide the Special 
Committee and its representatives access to certain non-public, confidential, 
proprietary and/or privileged TDCC and DAS information relating to Mycogen, 
DAS or TDCC (the "CONFIDENTIAL INFORMATION").  As a condition to being 
furnished the Confidential Information, the Special Committee and its 
representatives, and any other person who receives Confidential Information 
pursuant to this letter agreement, each agree to treat such Confidential 
Information in accordance with the terms of this letter agreement.

     The term "Confidential Information" includes information which has been 
provided to the Special Committee and its representatives since April 30, 
1998 as well as information which will be provided on or after the date of 
this letter agreement.  The term "Confidential Information" does not include 
information which (i) was or becomes generally available to the public other 
than as a result of a disclosure in violation of the terms of this letter 
agreement, or (ii) was or becomes available to the Special Committee or its 
representatives on a non-confidential basis from a source other than DAS or 
TDCC, provided that the Special Committee or its representatives, as the case 
may be, reasonably believes that such source has obtained such information 
lawfully and is not under any obligation of confidentiality to DAS or TDCC.

     The Special Committee agrees that the Confidential Information will be 
kept confidential and will be used only for evaluating the Proposed Amendment 
and, in the event the Proposed Amendment is entered into by Mycogen and DAS 
subsequently makes an offer to purchase all of 

<PAGE>

Mycogen's capital stock (a "PROPOSED TRANSACTION"), for evaluating any 
Proposed Transaction.  The Special Committee further agrees that the 
Confidential Information shall not be shown, made available or communicated 
in any way to anyone other than members of the Special Committee, its 
attorneys, Altheimer & Gray, and its financial advisor, Wasserstein Perella & 
Co., Inc. (including, if determined by the Special Committee, Dr. Alan J. 
Biloski, formerly of Wasserstein Perella & Co.).  DAS, TDCC and the Special 
Committee acknowledge that the Special Committee may believe it appropriate 
to disclose Confidential Information to other parties in connection with its 
deliberations.  If the Special Committee desires to disclose any Confidential 
Information to any other person(s), the Special Committee shall identify to 
DAS and TDCC the person(s) and the Confidential Information desired to be 
disclosed to such person(s) and request DAS' and TDCC's approval to such 
disclosure, and may not disclose such Confidential Information without DAS's 
and TDCC's prior written approval.  Wasserstein Perella & Co., Inc., Dr. 
Biloski (if the Special Committee determines to provide him with any 
Confidential Information) and any other person approved by DAS and TDCC to 
receive Confidential Information shall execute a copy of and agree to be 
bound by the terms of this letter.  All Confidential Information will remain 
subject to the terms of this letter for ten years from the letterhead date.

     In the event the Special Committee or its representatives, or any other 
person who receives Confidential Information pursuant to this letter, receive 
a subpoena or other legal administrative, regulatory (including 
self-regulatory) or judicial process or notice requesting Confidential 
Information, the person receiving such request shall, to the extent permitted 
under such legal, administrative, regulatory or judicial process or notice, 
provide prompt notice to TDCC and DAS of such request to allow TDCC and DAS 
an opportunity to prevent disclosure of the Confidential Information, and 
shall also reasonably cooperate with TDCC and DAS to prevent disclosure of 
such Confidential Information.  Except as provided in the immediately 
preceding sentence, nothing in this letter shall restrict any use or 
disclosure of Confidential Information required by law or required by or in 
response to applicable legal, administrative, regulatory or judicial process 
or rules or as required consistent with fiduciary duties of the directors or 
officers of Mycogen in their capacities as such, in each case as advised by 
counsel.

     Without prejudice to the rights and remedies otherwise available to 
them, TDCC and DAS  shall each be entitled to equitable relief by way of 
specific performance, injunction or otherwise in the event of any actual or 
threatened breach of any provision of this letter agreement.

     It is further understood and agreed that no failure or delay by TDCC or 
DAS in exercising any right, power or privilege under this letter agreement 
shall operate as a waiver thereof, nor shall any single or partial exercise 
thereof preclude any other or further exercise thereof or the exercise of any 
right, power or privilege under this letter agreement.

     This letter agreement shall be governed by, and construed in accordance 
with, the laws of the State of Delaware, without reference to conflicts of 
laws principles.

                               *      *      *

                                      2
<PAGE>

     Please confirm your agreement with the foregoing by signing
and returning to the undersigned a duplicate copy of this letter.

                              Very truly yours,

                              Special Committee of the Board of 
                              Directors of Mycogen Corporation

                              By:                              
                                  ---------------------------------
                                  Peter Lieberman
                                  Altheimer & Gray
                                  10 S. Wacker Drive
                                  Suite 4000
                                  Chicago, IL 60606

                              Counsel for the Special Committee
     
                              Wasserstein, Perella & Co., Inc.

                              By:                                 
                                  ---------------------------------
                                  John Simpson
                                  Managing Director


Accepted and Agreed

THE DOW CHEMICAL COMPANY



By:                                    
    ----------------------------                
Name:
Title:

DOW AGROSCIENCES LLC



By:                                             
    ----------------------------                       
Name:
Title:

                                      3



<PAGE>
                                       
                    BRASSICA LICENSE AND RESEARCH AGREEMENT

This Agreement is between DowElanco Canada (hereinafter DEC) a Canadian 
Corporation and Mycogen Corporation (hereinafter Mycogen), a California 
Corporation.

WHEREAS Mycogen owns certain rights to i) BACILLUS THURINGIENSIS technology, 
ii) BACILLUS THURINGIENSIS patents and patent applications, iii) owns 
BRASSICA germplasm, which is listed in Appendix A, and can further develop 
BRASSICA germplasm;

WHEREAS DEC is interested in having another party develop BRASSICA germplasm 
for its use;

WHEREAS, the parties have previously entered into a Memorandum of 
Understanding dated March 13, 1996 for an oilseed BRASSICA program to develop 
improved cultivars and incorporate insect resistance traits based on use of 
BACILLUS THURINGIENSIS technology;

WHEREAS, the parties recognize that certain basic assumptions and facts which 
the BRASSICA program was based upon have changed,

NOW THEREFORE, in consideration of the mutual covenants and agreements set 
forth below, the parties covenant and agree as follows:

ARTICLES

ARTICLE I - DEFINITIONS

SECTION 1.01 BRASSICA: "BRASSICA" means species, germplasm and cultures of 
OILSEED BRASSICA, including but not limited to BRASSICA NAPUS, BRASSICA RAPA, 
BRASSICA CARINATA, BRASSICA JUNCEA and SINAPIS ALBA.

SECTION 1.02 Bt PROGRAM VARIETIES: "Bt Program Varieties" means Program 
Varieties which have incorporated Bt Traits.

SECTION 1.03 Bt VARIETIES: "Bt Varieties" means Varieties which have 
incorporated Bt Traits.

SECTION 1.04 Bt TRAITS: "Bt Traits" means BACILLUS THURINGIENSIS genes or 
transgenic plant containing BT genes (events) developed from the 
Pioneer/Mycogen Bt Collaboration, developed solely by Mycogen or developed by 
Mycogen and another collaborator, and any Bt genes or events which Mycogen 
may have access to through licenses with third-parties, but only to the 
extent such genes are available for sublicensing to DEC for purposes of this 
Agreement. Bt Traits with activity against Flea Beetle (primary target) and 
Bertha Armyworm/Diamondback Moth (secondary target) are included, as are 
other Bt Traits for other targets, which may be identified by DEC to Mycogen 
in writing from time to time.

                                       1
<PAGE>

SECTION 1.05 CONFIDENTIAL INFORMATION: "Confidential Information" means 
either party's information and includes, but is not limited to, all 
information contained in unpublished patent application(s), Developmental 
Targets, Product Goals and any information related thereto, Intellectual 
Property, Technology and any information related to business relationships, 
strategies, surveys, forecasts, marketing research, product concepts and 
product development processes.

SECTION 1.06 DEC AFFILIATES: "DEC Affiliates" mean DowElanco or DowElanco 
B.V., any company which owns, directly or indirectly, an equity interest in 
DowElanco (the Indiana Partnership) or DowElanco B.V., and any company which 
DowElanco Canada, DowElanco (the Indiana partnership) or DowElanco B.V., now 
or hereafter owns, directly or indirectly, at least twenty-five percent (25%) 
of the company's outstanding equity. For purposes of this Agreement, Mycogen 
and Mycogen Affiliates will not be considered DEC Affiliates.

SECTION 1.07 DEC TRANSGENIC TRAITS: "DEC Transgenic Traits" means any trait 
which is derived or produced via molecular methods other than markers.

SECTION 1.08 DEVELOPMENTAL TARGETS: "Developmental Targets" means the 
quantitative target for the agronomic, oil and meal traits that are defined 
as Product Goal, i.e., one such agronomic trait is yield (see definition of 
Product Goals) and the Developmental Target for this trait could be for 
example yield more than or at least equal to the variety Quannum.

SECTION 1.09 HIGH OLEIC: "High Oleic" means oleic acid content in seed oil 
greater than seventy percent (70%) on a weight percent basis.

SECTION 1.10 INTELLECTUAL PROPERTY: "Intellectual Property" means all PVP(s), 
and Patent(s) and patent know-how owned or controlled by Mycogen, filed or 
developed prior to the execution of this Agreement, related to Varieties, 
Product Goals and Developmental Targets and any continuation, divisional, 
continuation-in-part, reexaminations reissue application(s) thereof, and any 
corresponding foreign patent application(s) thereof and any patents derived 
from any of the foregoing, and any other U.S. or foreign patent/patent 
application(s) owned or licensed by Mycogen to the extent that the PVP(s) and 
Patent(s)/patent application(s) claim any of the Varieties, Product Goals or 
Developmental Targets.

SECTION 1.11 MANAGEMENT DEVELOPMENT TEAM: "Management Development Team or 
MDT" means a team comprising two (2) Mycogen and three (3) DEC and/or DEC 
Affiliate employees.

SECTION 1.12 MYCOGEN AFFILIATES: "Mycogen Affiliates" means any company which 
Mycogen owns directly or indirectly at least twenty-five percent (25%) of the 
company's outstanding equity.

                                       2
<PAGE>

SECTION 1.13 NET SALES: "Net Sales" means the invoice price of any sale, 
lease, transfer or other disposition of Planting Seeds to customers less (i) 
value added tax, sales or turnover tax, excise taxes and duties which are 
included in the price, (ii) trade, quantity and cash discounts actually 
allowed and taken, (iii) allowances for credits given for rejected or 
returned Planting Seeds, (iv) rebates, and (v) freight and insurance if 
included in the price. If Planting Seeds are transferred among DEC 
Affiliates, such transfers shall not be considered to be included in Net 
Sales and subject to a royalty under this Agreement, unless the transferee 
uses the Planting Seeds without transferring such Planting Seeds to a non-DEC 
Affiliate for consideration. Any subsequent transfer by a DEC Affiliate to a 
non-DEC Affiliate shall be included in the Net Sales subject to a royalty 
under this Agreement, and the invoice price used in determining Net Sales for 
the transfer shall be the invoice price for the transfer by the DEC Affiliate 
to the non-DEC Affiliate.

SECTION 1.12 PATENT(S): "Patent(s)" shall mean all patent(s) and patent 
application(s) owned or controlled by Mycogen, including any application(s) 
and patent(s) which were filed prior to the execution of this Agreement, any 
continuation, divisional, continuations-in-part, reexamination, reissue 
patent(s) and patent application(s), as well as foreign patent(s) and patent 
application(s) claiming Varieties or products produced by Varieties which 
meet Product Goals, such as oils having High Oleic content and include, but 
not limited to, US Patent Application No. 08/374402 entitled "75% Oleate 
Canola Oil with Improved Stability" and any continuation, divisional, 
continuations-in-part, reexamination, reissue patent(s) and patent 
application(s), as well as foreign patent(s) thereof.

SECTION 1.15 PLANTING SEEDS: "Planting Seeds" means seeds of Varieties which 
are sold for commercial production of canola or other BRASSICA species.

SECTION 1.16 PRODUCTS: "Products" means materials developed from processing of 
commercial crop grown from Planting Seeds or Program Planting Seeds.

SECTION 1.17 PRODUCT GOALS: "Product Goals" means a) agronomic traits, such 
as, but not limited to: yield, maturity, lodging resistance and disease 
resistance, such as blackleg; b) oil traits, such as, but not limited to: oil 
percentage on a seed weight basis, erocic acid level, oleic acid level and 
linolenic acid level; and c) meal traits, such as, but not limited to: fiber 
percentage, glucosinolate content, sinapine content, phytic acid content, and 
protein content. The Product Goals may be further defined by the Management 
Development Team. However, Product Goals will exclude transgenic traits, 
including but not limited to Bt Traits and Roundup Ready Traits, except as to 
the extent that such traits become available to DEC under the provisions of 
this Agreement, or by other written agreement of the parties.

                                       3


<PAGE>

SECTION 1.18 PROGRAM: "Program" means development via traditional breeding and
mutation techniques of BRASSICA germplasm and cultivars and the production of
Program Varieties to meet Product Goals and Development Targets.

SECTION 1.19 PROGRAM PLANTING SEEDS: "Program Planting Seeds" means seeds of
Program Varieties which are sold for commercial production of canola or other
BRASSICA species.

SECTION 1.20 PROGRAM PVP(s): "Program PVP(s)" means Plant Variety Protection 
applications(s) and certificate(s) claiming Porgram Varieties.

SECTION 1.21 PROGRAM REPORTS: "Programs Reports" means written reports
containing information on progress of research and development, field data, 
along with the costs and expenditures of the Program. The costs and expenditures
shall be reported in sufficient detail such that a third party audit could be 
completed if necessary. Research and development information shall include but 
shall not be limited to information about results from laboratory analysis of 
oil and meal traits identified as Developmental Targets and Product Goals. Field
data shall include all results from nurseries and yield trials for agronomic 
traits identified as Product Goals and Developmental Targets.

SECTION 1.22 PROGRAM VARIETIES: "Program Varieties" means varieties developed
under the Program using Mycogen germplasm, licensed germplasm and germplasm in
the public domain.

SECTION 1.23 PVP(S): "PVP(S)" means Plant Variety Protection applications(s) and
certificate(s) owned or controlled by Mycogen covering Varieties.

SECTION 1.24 ROUND-UP READY VARIETIES: "Round-up Ready Varieties" means
Varieties, Program Varieties, Bt Varieties, Bt Program Varieties that contain
the Round-up Ready gene.

SECTION 1.25 SEEDS: "Seeds" shall mean an organ of the plant which is harvested
and sown in a successive growing season to produce the next generation of
plants, where such Seeds are not Planting Seeds or Program Planting Seeds.

SECTION 1.26 TECHNOLOGY: "Technology" means Varieties, and Intellectual
Property, breeding techniques and any know-how that is related to the Program,
but was developed prior to the effective date of this agreement, but only to the
extent that such technology is used in the program.

SECTION 1.27 THIRD PARTY VARIETIES: "Third Party Varieties" means Varieties
developed solely from third-party germplasm outside the Program.

SECTION 1.28 VARIETIES: "Varieties" means oilseed BRASSICA germplasm and
cultivars developed by Mycogen prior to the Program as listed in Appendix A.

                                          4
<PAGE>

ARTICLE 2 - OILSEED BRASSICA VARIETY AND BREEDING LINES DEVELOPMENT PROGRAM

SECTION 2.01 BRASSICA VARIETY DEVELOPMENT SCHEDULE: BRASSICA Variety Development
Schedule is defined in Appendix B and is incorporated in full by reference. The
MDT, as defined in the Section below, will agree upon Product Goals and
Developmental Targets for the Program. Thereafter on a yearly basis, the MDT
shall establish and modify the benchmarks and monitor the progress of the
Program. Modifications to the Developmental Targets and Program Goals shall be
made yearly on or by February 15th by the MDT. Mycogen will use reasonably
diligent efforts to develop by March 15th of year four (4) at least twenty (20)
Program Varieties containing Developmental Targets for DEC evaluation. The
objective of the Program is to commercialize at least one (1) Program Variety in
year seven (7) of the Program.

SECTION 2.02 BRASSICA VARIETY MANAGEMENT DEVELOPMENT TEAM: A Management
Development Team (MDT) will meet within thirty (30) days of receipt of Program
Reports. The location of the meetings shall be determined by the MDT. The MDT
shall annually up date Appendix C, listing the Varieties that are developed
under the Program. The MDT shall be comprised of two (2) Mycogen and three (3)
DEC employees, and ad hoc a DEC and a Mycogen attorney. The MDT shall review the
Program Reports and make recommendations regarding modification of the Program
so that the Program meets its Product Goals and Developmental Targets.

SECTION 2.03 BRASSICA VARIETY DEVELOPMENT PROGRAM:
A) DEVELOPMENTAL TARGETS: Mycogen shall incorporate Developmental Targets into
germplasm according to the BRASSICA Variety Development Schedule in Section 1
above.

SECTION 2.04 PROGRAM REPORTS: Mycogen shall provide Program Reports on a
quarterly basis according to a schedule established by the MDT, which schedule
may be changed from time to time.

SECTION 2.05 MAINTENANCE OF ADVANCED SEED: Mycogen shall be responsible for
maintaining at least five (5) pounds of pre-breeder seed of all advanced
relevant Varieties and Program Varieties as determined by the MDT. At the
request of DEC a breeder seed increase will be performed by Mycogen.

SECTION 2.06 DEC FIELD TESTING: At DEC's discretion, DEC may conduct
testing/field testing of Varieties or Program Varieties. DEC shall share data
from such testing/field testing with Mycogen.

SECTION 2.07 MYCOGEN FIELD TESTING: Mycogen shall obtain data which supports
advancement of Varieties or Program Varieties according to the BRASSICA Variety

                                          5
<PAGE>

Development Schedule-attached hereto as Appendix B. This data shall be included
in Program Reports.

SECTION 2.08 FUNDING AND PAYMENTS: DEC shall pay only the actual costs of the
Program, which in any event, at least U.S. $750,000 per year. Costs and
expenditures of the Program shall be included in Program Reports. DEC shall pay
Mycogen for the cost of Program within thirty (30) days of receipt of Program
Report. Payments for the Program shall be made to the following address:

                    Mycogen Corporation
                    5501 Berlin Drive
                    San Diego, California 92121

SECTION 2.09 INVENTIONS: Subject to Articles 3 and 4, DEC shall own all Program
Varieties. The Parties shall be responsible for filing and/or maintaining
Patent(s) as specified in Section 2.10.

SECTION 2.10 FILING AND MAINTAINING PATENT(S) AND PVP(S): Mycogen warrants that
it will use its best efforts to prosecute and maintain any Patent(s) or PVP(s)
which exist at the execution of this agreement. Mycogen warrants that it shall
pay any taxes and maintenance fees to keep Patent(s) or PVP(s) in full force and
effect during the term of this Agreement. However, if Mycogen decides not to
make such payments or abandon prosecution of Patent(s) or PVP(s), Mycogen shall
give DEC at least sixty (60) days notice so that DEC may talk over the
prosecution of Patent(s) or PVP(s) or make such payments to keep Patent(s) or
PVP(s) in force.  DE shall be solely reponsible for filing, prosecuting and 
maintaining patent(s) or PVPs which are filed after the execution of this 
Agreement and which are developed under the Program. If DEC decides no to file 
patent(s) or PVP(s) claiming Program Varieties, Mycogen may file such patent(s) 
or PVP(s). If DEC decides to abandon or fails to pay maintenance fees or taxes, 
Mycogen may take over payment of fees or taxes for patent(s) or PVP(s). However,
even if Mycogen takes over the filing or maintenance of patent(s) or PVP(s), DEC
shall have a license as described in Sections 3.01 and 4.01 hereunder.

ARTICLE 3 - RIGHTS AND GRANTS

SECTION 3.01 MYCOGEN GRANTS REGARDING VARIETIES: Mycogen grants DEC a sole,
irrevocable, exclusive right to develop, make, have made, use, sublicense sell
and have sold the Planting Seeds and Program Planting Seeds and products
therefrom. No right is granted under this Agreement to sublicense the use of 
Varieties or Program Varieties for breeding or the development of new planting
materials.

SECTION 3.02 DEC OPTION REGARDING Bt PATENT(S) AND ACCESS TO ROUND-UP READY
TRAITS: If Mycogen grants a Bt license in BRASSICA to a third party, the DEC may
license Bt's from Mycogen to produce Planting Seed of Bt Varieties or Program
Planting Seed of Bt

                                          6
<PAGE>

Program Varieties under terms and conditions no less favorable than other
licensees of Bt in BRASSICA. If Mycogen obtains access to Round-up Ready traits
for BRASSICA and can sublicense such rights, DEC shall have an option to license
the traits for producing Planting  Seed of Round-up Ready Varieties or Program
Planting Seed of Round-up Ready Program Varieties. The terms and conditions of
the license shall be no less favorable than the terms and conditions of other
Mycogen Round-up Ready licenses.

SECTION 3.03 MYCOGEN OPTION REGARDING PLANTING SEED AND PROGRAM PLANTING SEED OF
VARIETIES AND PROGRAM VARIETIES: If DEC licenses Planting Seed or Program
Planting Seed of Varieties or Program Varieties to third parties, then Mycogen
will have the right to obtain a license from DEC to make, have made, use and
sell such Planting Seeds and Program Planting Seeds of such Varieties or Program
Varieties from DEC under terms and conditions no less favorable than those
granted by DEC to such third Parties.

SECTION 3.04 DEC OPTION REGARDING FUTURE TRAITS: If Mycogen grants a license to
a third party for future traits or technology related to BRASSICA, then DEC may
license such traits or technology under terms and conditions no less favorable
than other licensees; however, if Mycogen obtains a license to Rutgers
University low saturation technology for use in oilseed BRASSICA, Mycogen will
license the technology to DEC for use in BRASSICA. DEC and Mycogen shall agree
to negotiate licensing terms and conditions for the Rutgers University low
saturation technology in good faith.

SECTION 3.05 MYCOGEN OPTION TO PRODUCE SEED: Mycogen and Mycogen Affiliates will
have the first option to produce Planting Seeds for DEC and  DEC Affiliates,
provided that Mycogen or a Mycogen Affiliate is able to offer such production on
a competitive basis in terms of quality, quantity and price.

ARTICLE 4 - ROYALTIES

SECTION 4.01 ROYALTIES PAID BY DEC FOR VARIETIES: DEC shall pay Mycogen a five
percent (5%) royalty in U.S. dollars based on Net Sales of Planting Seed of
Varieties and Program Planting Seed of Program Varieties. If Varieties or
Program Varieties are High Oleic, then DEC shall pay Mycogen an additional
royalty of twenty percent (20%) of any premium that is earned when compared to
canola oil which is not High Oleic. The price for canola oil shall be determined
by the closing price of canola on the Canadian Commodities Exchange based on the
volume sold and the date of sale. Royalties will not be paid to Mycogen for
the commercialization of Third Party Varieties. Royalties will not be paid on
value-added to Planting Seeds or Program Planting Seeds by the incorporation of
DEC Transgenic Traits. No royalties will be due under this provision on any Net
Sales of Planting Seed of Varieties or Program Planting of Program Varieties by
Mycogen or Mycogen Affiliates.

                                          7

<PAGE>

SECTION 4.02 TERM OF ROYALTIES PAID:    DEC shall pay the five percent (5%)
royalties, as described in Sections 4.01, for the commercial lifetime of the
Varieties or Program Varieties.

ARTICLE 5 -  REGISTRATION

SECTION 5.01 CANADIAN REGISTRATION FOR VARIETIES, PROGRAM VARIETIES, BT PROGRAM
VARIETIES AND BT VARIETIES:   DEC shall develop registration data packages for
obtaining Canadian regulatory approval for the sale of any Bt Traits in Bt
Varieties or Bt Program Varieties and for the registration of Varieties or
Program Varieties. DEC shall have access and be able to use any Mycogen
regulatory data and information without additional compensation to Mycogen. At
the request of DEC, Mycogen shall use reasonable efforts to provide data needed
for registration, including but not limited to data related to Product Goals,
morphological traits and the like.

ARTICLE 6 - RECORDS AND TAXES

SECTION 6.01 RECORDS:    The parties agree to maintain complete and accurate
books and records in accordance with normal accounting practice in respect to
all Varieties and Program Varieties sold under this Agreement.

SECTION 6.02 TAXES: In the event that withholding taxes are due on any royalties
payable under this Agreement, the party paying the royalty shall withhold the
withholding taxes required and promptly remit such taxes to the appropriate tax
authority. DEC shall be entitled to deduct such withheld taxes from the
royalties otherwise payable to the other party hereunder. The party paying the
taxes shall promptly provide the other party with documentation evidencing the
payment of such taxes.

SECTION 6.03 ADDRESS OF ROYALTIES PAYMENTS:

Mycogen, to:        Mycogen Seeds
                    1340 Corporate Ctr Curve
                    St. Paul, MN 55121
                    Attention: Finance Department


DEC, to:            DowElanco
                    9330 Zionsville  Road
                    Indianapolis, Indiana
                    Attention:

or to such other address provided in writing.

                                          8
<PAGE>

ARTICLE 7 - WARRANTIES, INFRINGEMENT & PRODUCT LIABILITY

SECTION 7.01 WARRANTIES OF OWNERSHIP AND MERCHANTABILITY:
A. Mycogen warrants that it has the right to license Varieties and has the 
right to enter into this Agreement. If, after the execution of this 
Agreement, any licenses are obtained by either party from third parties to 
varieties, both Mycogen and DEC warrant they will use their best efforts to 
obtain terms of the license which permits utilization of such license within 
the scope of this license. However, nothing in this Agreement shall be 
construed as:

(i) a warranty as to the validity or scope of any Patent(s) or PVP(s);

(ii) a warranty or representation that anything made, used, sold or otherwise
disposed of under the licenses granted in this Agreement will or will not
infringe patents or plant variety protection certificates of third paries; and


(iii) an obligation to bring or prosecute actions or suits against third parties
for infringement of patent(s) or plant variety protection certificate(s), except
as agreed herein under Section 5.02 hereof.

B. MYCOGEN MAKES NO REPRESENTATIONS, EXTENDS NO WARRANTIES OF ANY KIND, EITHER
EXPRESS OR IMPLIED, INCLUDING WARRANTIES FOR MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE, AND ASSUMES NO RESPONSIBILITIES WHATSOEVER WITH RESPECT TO
ANY MATERIALS PROVIDED TO DEC RELATING TO THE TECHNOLOGY OR TO THE USE, SALE, OR
OTHER DISPOSITION BY DEC OR ITS VENDEES OR OTHER TRANSFEREES OF PLANTING SEEDS
OR PROGRAM PLANTING SEEDS INCORPORATING OF MADE BY USE OF INTELLECTUAL PROPERTY
LICENSED UNDER THIS AGREEMENT.

SECTION 7.02 INFRINGEMENT OF PATENT(S):
A. DEC may pursue actions to abate infringement of the Patent(s) or PVP(s) and
DEC shall incur all costs associated with abatement of the infringing activity.
Mycogen shall reasonably assist DEC in such litigation, provided  DEC reasonably
compensates Mycogen for such assistance. If there is a commercially significant
third party infringement of any claim(s) in any Patent(s) or PVP(s) and DEC does
not wish to bring an infringement action, then DEC shall execute whatever
documents are necessary to enable Mycogen to pursue such infringement action in
their name if so desired. DEC shall provide reasonable assistance to Mycogen;
however, Mycogen shall reimburse DEC for reasonable expenses associated with
such assistance. If a party declines to participate in the litigation, other
than reasonable assistance, then the party filing the litigation shall have the
right to control such litigation. If the interested party prevails, any damages
and/or costs awarded shall belong to the interested party provided that during
such litigation, the interested party acted in good faith to preserve the right,
title and interest in

                                          9
<PAGE>

and to the Patent(s) or PVP(s). If DEC files actions to abate infringement of
patent(s) or PVP(s) developed under the Program and filed after the execution of
this Agreement, Mycogen shall provide reasonable assistance to DEC. DEC shall
reimburse Mycogen for reasonable expenses associated with such assistance.

B. In the event that DEC or its sublicensees are sued by a third party for
infringement of a third party's patent with respect to activities performed in
accordance with the licenses granted to DEC under this Agreement, DEC may
request from Mycogen reasonable assistance in defending such infringement
allegations. DEC shall reimburse Mycogen for any out-of-pocket expenses incurred
by Mycogen with respect to such assistance, provided that such suit is not due
to a breach of the Warranties provided in Section 5.01 hereof, or is due to
gross negligence by Mycogen or its representatives. If DEC or its sublicensees
negotiate a license from the third party to practice under the third party's
patent(s) or plant variety protection certificate(s), Mycogen shall in good
faith renegotiated the royalty rates set forth in  Section 4.01 and 4.02 hereof,
to reflect the additional expenditures required by DEC to practice the licenses
granted herein.

C. The A and B provisions above will not apply to intellectual property rights
relating to any Mycogen transgenic traits, including but not limited to Bt
Traits, Round-up Ready Traits and transgenic disease resistance traits. The
enforcement and defense of these rights will be controlled by Mycogen, except to
the extent otherwise agreed by the parties.

SECTION 7.03 PRODUCT LIABILITY: DEC shall indemnify Mycogen for any liabilities
related to claims and expenses, including legal expenses and reasonable
attorney's fees, arising out of the death of or injury to any person or persons
or out of any damage to property and against any other claim, proceeding,
demand, expense and liability of any kind whatsoever resulting from the
production, manufacture, sale, use, lease, consumption or advertisement of
Planting Seeds or Program Planting Seeds, except where negligent conduct on the
part of Mycogen is the sole cause of the claim.


ARTICLE 8 - CONFIDENTIALITY

SECTION 8.01 CONFIDENTIAL INFORMATION: The parties shall hold all Confidential
Information in confidence and shall use their best efforts to protect the
confidentiality of the information. The parties shall not publish, disclose, or
allow a third party access to, nor use for any purpose the other party's
Confidential Information. The parties may disclose confidential Information to
consultants and third parties provided: a) a secrecy agreement is obtained that
is at least as restrictive as the confidentiality provisions in this Agreement,
and b) each party notifies the other party of such disclosure and provides a
copy of the executed secrecy agreement with the consultant or third party:
however under no circumstances shall Mycogen disclose information to Pioneer
International Hi-bred without the written consent of DEC. The term for
confidentiality between the parties hereto shall continue until five (5) years
after the termination of this Agreement.

                                          10
<PAGE>

SECTION 8.02 EXCEPTIONS: The obligations of confidentiality of Section 8.01
hereof shall not apply to Confidential Information that the receiving party can
show;

     A) by written records was in its possession prior to disclosure under this
Agreement and which has not been previously acquired from the disclosing party:

     B) is or becomes part of the public domain through no fault of the
receiving party;

     C) is lawfully received without an obligation of confidence from a third
party legally entitled to disclose the information.

     D) is required by law to be disclosed but only to the extent it is so
required; or

     E) is required to be disclosed to a governmental agency to obtain the
necessary approvals for the sale of Planting Seeds and Program Planting Seeds
and such information cannot be claimed as "business confidential".

ARTICLE 9 -  RECORD KEEPING

SECTION 9.01 BOOKS AND RECORDS: The parties shall keep books and records
sufficient to verify the accuracy and completeness of payments under Article 4
hereof. Such books and records shall be preserved for a period not less than
three (3) years after they are created during and after the term of this
Agreement.

SECTION 9.02 AUDIT: On thirty (30) days notice, during regular business hours
and at a single location, a party shall have the right to have an independent
auditor examine the other party's sales records and books of accounts to verify
the accuracy of royalty payments. The costs for any audit shall be paid by the
party requesting the audit.

ARTICLE 10 - TERM & TERMINATION

SECTION 10.01 EXPIRATION OF LICENSE: The term of this License Agreement shall
begin on May 15, 1996 and continue until the last commercial sale of Varieties.

SECTION 10.02 PROGRAM TERM: The term of the Program is retroactive and begins
five (5) years from May 15, 1996. The Program may be extended in writing upon
mutual agreement between the parties.

SECTION 10.03 TERMINATION: If the parties are unable to agree on the initial
Product Goals and Development Targets by April 30th of year one (1), DEC may
terminate this Agreement within thirty (30) days written notice of April 30th.
Thereafter, DEC may terminate the Program at any time for any reason by giving
at least six(6) months

                                          11


<PAGE>

unambiguous, written notice of such termination to Mycogen.  Termination of 
the PRogram shall not effect the licenses gratned herein.

SECTION 10.04 DEFAULT:  If either party at any time defaults in the timely 
payment of any moneys due to the other party, or if Mycogen fails to actively 
pursue the Program, or if either party fails to remedy any such breach or 
default within ninety (90) days after written notice thereof by the other 
party, the non-breaching party may, at its option, terminate this Agreement by 
giving notice of termination to the breaching party.  However, if there is any 
disagreement as to the sufficiency of the brreaching party's remedy, the 
praties agree to settle the controversy through a mutually agreed upon third- 
party mediator no later than sexty (60) days after the aforementioned ninety 
(90) day period has ended.

SECTION 10.05 ACCOUNTING UPON TERMINATIOIN OR EXPIRATION:  On the termination
or expiration of this License Agreement, the parties shall remain obligated
to provide an accounting for and to pay royalties earned up to the date of the
termination or expiration.


ARTICLE 11 - MISCELLANEOUS

SECTION 11.01 PUBLIC ANNOUNCEMENTS:  No public announcement or press release 
concerning this Agreement or the transactions contemplated herein shall be 
made by either of the parties hereto without the prior consent and approval 
of the other party (which consent shall not be unreasonably withheld or 
delayed), except to the extent required by law.

SECTION 11.02 ASSIGNMENT AND TRANSFERABILTIY OF THE AGREEMENT:  This 
Agreement may be assigned to DEC Affiliates, or to a purchaser of 
substantially all of the business interests of DEC.  Mycogen may not assign 
this Agreement under any circumstances without the written consent of DEC.


Section 11.03  ENTIRE AGREEMENT:  This Agreement constitutes the entire 
agreement between the parties hereto with respect to the subject matter 
hereof and cancels and supersedes any prior understandings and agreements 
between the parties hereto with respect to the subject matter of this 
Agreement.  There are no rerepresentations, warranties, terms, conditions, 
undertakintgs or collateral agreements, express, implied or statutory, between 
the parties other than as expressly set forth in this Agreement.

Section 11.04 AMENDMENTS AND WAIVER:  No modification of or amendment to this 
Agreement shall be valid or binding unless set forth in writing and duly 
executed by the parties hereto and no waiver of any breach of any term or 
provision of this Agreement shall be effective or binding unless made in 
writing and signed by the party purporting to give the same and, unless 
otherwise provided, shall be limited to the specific breach waived.


                                       12
<PAGE>

SECTION 11.05 NOTICES:  Any demand, notice or other communication to be given 
in connecion with this Agreement shall be given in writing and shall be given 
by personal delivery or by electronic means addressed to the recipeient as 
follow:

To Mycogen:             Mycogen Seeds
                        1340 Corporate Ctr Curve
                        St. Paul, MN 55121
                        Attention: Larry Sernyk

with written copy to    Mycogen Seeds
                        5501 Oberlin Drive
                        San Diego, CA 92121
                        Attention: Legal Department

To DEC:                 General Patent Counsel
                        Patent Department
                        DowElanco
                        9330 Zionsville Road
                        Indianapolis, Indiana 46265-1054

or to such other address, individual or electronic communication number as 
may be desgnated by notice given by either pary to the other.  Any demand, 
notice or other communication given by personal delivery shall be 
conclusively deemed to have been given on the day of actual delivery thereof 
and, if given by electronic communication.  On the day of transmittal thereof 
if given during the normal business hours next occur if not given during such 
hours on any day.  IF the pary giving any demand, notice or other 
communication knows or ought reasonable to know of any difficulties with the 
postal system which might affect the delivery of mail, any such demand, 
notice or other communication shall not be mailed but shall be given by 
personal delivery or by electronic communication.

SECTION 11.06 GOVERNING LAW:  This Agreement shall be governed by and 
construed in accordance with the laws of the State of California, USA.

SECTION 11.07  HEADINGS:  The Headings of Articles and SEctions used in this 
Agreement are for reference purpose only and will not be considered as padrt 
of this Agreement for purposes of interpretation.

SECTION 11.08 PROVISIONS OF THE AGREEMENT:  If any one or more of the 
provisions of tlhis Agreement should for any reason be held by a Court of 
competent jurisdiction to be invalid, illegal or unenfoceable , the remainder 
of this Agreement will nevertheless remain in full force and efect unless 
such provision(s) go to the essence and substance of this Agreement.


                                       13
<PAGE>

SECTION 11.09 SCHEDULES:  Mycogen shall provide Schedules A,B, and C within 
thirty (30) days of the last signature hereto.  The schedules shall not 
affect the effective date of this Agreement.

IN WITNESS WHEREOF, the parties hereto have duly executed this Agreement on 
the dates indicated below.

MYCOGEN CORPORATION

By: /s/ Carl Eibl
   --------------------------------
Name:   Carl Eibl

Title: President
Date:  11/3/97
     ------------------------------


DOWELANCO CANADA, INC.

By: /s/ John L. Hagaman
   --------------------------------
Name:   John L. Hagaman

Title: President and CEO

Date: October 30, 1997
     ------------------------------



                                       14
<PAGE>

Appendix A
- -----------

Brassica germplasm

(Schedule to be provided by Mycogen within thiry (30) days of signing)


                                       15

<PAGE>

                                      SCHEDULE A
                 MYCOGEN SEEDS BRASSICA AND RELATED SPECIES GERMPLASM


                          BRASSICA NAPUS L. ADVANCED STRAINS

<TABLE>
<CAPTION>

- --------------------------------------------------------------------------------
Variety/Strain           Description
<S>                      <C>
- --------------------------------------------------------------------------------
 AG019                   HOLLY Canole-!st HOLLY Canola developed by Agrigenetics
                         and basis for HOLLY oil patent applications
- --------------------------------------------------------------------------------
 EXP94-03                HOLLY Canola
- --------------------------------------------------------------------------------
 EXP94-06                HOLLY Canola-registered in 1997 for contract production
                         in Canada uner the designation DMS100
- --------------------------------------------------------------------------------
 SVO95-08                HOLLY Canola
- --------------------------------------------------------------------------------
 SVO95-13                HOLLY Canola with very low C18;3
- --------------------------------------------------------------------------------
 EXP95-06                High oleic Canola
- --------------------------------------------------------------------------------
 EXP95-09                High oleic Canola
- --------------------------------------------------------------------------------
 EXP95-10                High oleic Canola
- --------------------------------------------------------------------------------
 MPS96-01                High erucic/low glucosinolates with high oil content
- --------------------------------------------------------------------------------
 MPS96-02                High erucic/low glucosinolates with high oil content
- --------------------------------------------------------------------------------
 MPS96-03                High erucic/low glucosinolates with high oil content
- --------------------------------------------------------------------------------
 MPS96-04                High erucic/low glucosinolates with high oil content
- --------------------------------------------------------------------------------
 MPS96-05                High erucic/low glucosinolates with high oil content
- --------------------------------------------------------------------------------
 MPS96-06                High palmitic/high erucic/low glucosinolates
- --------------------------------------------------------------------------------
 MPS96-07                High palmitic/high erucic/low glucosinolates
- --------------------------------------------------------------------------------
</TABLE>


                        BRASSICA NAPUS L. BREEDING POPULATIONS

As described in the Mycogen/Agrigentics laboratory notebooks listed below:

<TABLE>
<CAPTION>
- ----------------------------------------------------------------------
     Volume         Notebook Number          Issued To
  <S>               <C>                    <C>
- ----------------------------------------------------------------------
  Rapeseed V!             2007             Larry Sernyk
  Rapeseed V2             2155             Larry Sernyk
  Rapeseed V3             2293             Larry Sernyk
  Rapeseed V4             2343               Jay Laing
- ----------------------------------------------------------------------
</TABLE>



<PAGE>




Appendix B
- ----------

Variety Development Schedule








<PAGE>



Appendix C


Program Varieties







<PAGE>





                    VARIETY DEVELOPMENT FLOWCHART - RAPESEED
                             CONTRACT REGISTRATION


<TABLE>
<CAPTION>

                                                                     Mycogen Seeds

                  YEAR        1                          2                         3                          4
                 STAGE        Oa                        ob                         1                          2
                            Produce                  Othaplod
                            Crosses                 Production                  Nursery                     Prelim
                           (1 year)                  (1 year)                   (1 year)                    (1 year)
           <S>            <C>                     <C>                        <C>                      <C>
                          ------------------------------------------------------------------------------------------------------
                   STAGE  Plan and make           Produce dihaploids       Nursery screening of     Replicated trials at 4
             DESCRIPTION  crosses according to    using microscope         dihaploids at 2          location (3 replicates)
                          product goals           culture                  locations                of best dilhaploids from
                                                                                                    nursery screen
                          ------------------------------------------------------------------------------------------------------

       NUMBER OF STRAINS                                           2000                     250                              25
         AT END OF STAGE                                                                   12.5%                           10.0%

       RESPONSIBILITIIES
                          ------------------------------------------------------------------------------------------------------
               RESEARCH
               (MYCOGEN)  1. Plan F1 crosses      1. Produce dihaploids    1. Conduct dihaploids    1. Conduct replicated trials
                             According to            strains                  nurseries                (In house and contract)
                             product goals
                          2. Make F1 crosses      2. Analytical screen     2. Analyze results       2. Analyize results and
                                                     for product goal         and make selections      make selection for
                                                                              for advancement          advancement
                                                                                                    3. probreeder seed
                                                                                                       production (winter
                                                                                                       greenhouse)
                          --------------------------------------------------------------------------------------------------------
PRODUCT CHARACTERIZATION
            LEADER (PCL)
      (DOWELANCO CANADA)
                                                                           1. Monitor strain        1. Monitor strain
                                                                              advancement              advancement process
                                                                              process

                          --------------------------------------------------------------------------------------------------------
   PRODUCT SUCESS LEADER
                   (PSL)
      (DOWELANCO CANADA)
                          1. Delias product                                                         1. Review strain performance
                             goals
                                                                                                    2. Communicate product lineup
                                                                                                       needs with research
</TABLE>



<TABLE>
<CAPTION>

                                            DowElenco

                    YEAR      5                          6                         7                          8
                   STAGE      3a                        3b                         4                          5
                            Contract                 Contract
                          Registration 1           Registration 2              Pre-Launch                    Launch
                           (1 year)                  (1 year)
             <S>          <C>                     <C>                      <C>                      <C>
                          --------------------------------------------------------------------------------------------------------

                   STAGE First year contract      Second year contract     Validale varieial        One variety every two years
             DESCRIPTION registration trials      registration trials      characteristics with     in each of mid season and
                         at 6-E locations of      at 6-E location of       growers and end          long season maturity
                         best dilhaploids         dilhaploids from         users                    groups
                         from prelim              first year contract
                         trials                   registration trials

                          --------------------------------------------------------------------------------------------------------

       NUMBER OF STRAINS                     4                       1                          1
         AT END OF STAGE                  18.0%                   25.0%                     100.0%

       RESPONSIBILITIIES
                          --------------------------------------------------------------------------------------------------------
               RESEARCH
               (MYCOGEN) 1. Greeder seed          1. Collect               1. Provid's support to   1. Provide support to PCL and
                            production (year         Information in           PCL and PSL as           PSL as required
                            in 4-5 winter)           contract                 required
                                                     regulation for and
                                                     file PVP
                         2. Collect
                            information in
                            contract
                            registration trials
                            for PVP
                          --------------------------------------------------------------------------------------------------------
PRODUCT CHARACTERIZATION  1. Conduct contract     1. Conduct contract      1. Provide support to    1. Provide support to PSL as
            LEADER (PCL)     registration            registration             PSL as required          required
      (DOWELANCO CANADA)     trials (In house        trials (In house
                             and contract)           contract
                          2. Analze results       2. Analyze results and   2. Organize agronomic
                             and make                prepare submission       and quality
                             selections for          for variety              validation trials
                             advancement             registration             thoughout target
                                                                              area
                                                  3. Foundation seed
                                                     production
                          --------------------------------------------------------------------------------------------------------
   PRODUCT SUCESS LEADER  1. Review strain        1. Review strain         1. Certified seed        1. Lauch variety
                   (PSL)     performance             performance              production
      (DOWELANCO CANADA)  2. Participate in       2. Participate in                                 2. Commercial
                             strain                  strain                                            production
                             advancement             advancement
                             discussions             discussions
                          3. Project seed         3. Develop commercial
                             requirement for         strategy for
                             launch                  strains
                          --------------------------------------------------------------------------------------------------------
</TABLE>






<PAGE>


                             RESTATED LOAN AGREEMENT

This Restated Loan Agreement ("Agreement") is made as of April 16, 1998 between
Dow AgroSciences LLC, a Delaware limited liability company (the "Lender"), and
Mycoyen S.A., an Argentine corporation (the "Borrower") (together, the
"parties").

WHEREAS, Mycogen Corporation has executed an Assignment of Loan dated April 16,
1998, assigning to Lender all of its rights, title and interest to a certain
Revolving Loan Agreement dated January 1, 1997, between Mycogen Corporation,
successor in interest to Agrigenetics, Inc., and Borrower, and

WHEREAS, the parties agree to restate the Revolving Loan Agreement in its
entirety;

NOW, THEREFORE, the parties hereto have agreed and do hereby agree as follows:

1.   THE LOAN

     1.1  The Advance

          From the above date to December 31, 1998, the Lender agrees to make
          from time to time advances to the Borrower ("Advances"), in an
          aggregate amount not exceeding $50,000,000 (fifty million U.S.
          dollars), at any time outstanding ("Commitment"). Advances repaid
          prior to December 31, 1998, may be reborrowed. This Agreement involves
          U.S. dollars only. The term "Termination Date" shall mean December 31,
          1998. Borrower must give notice to Lender by 9:00 a.m. Eastern
          Standard Time on any Business Day if Advances are requested for that
          day.

     1.2  Repayment

          (a)  The unpaid principal amount of each Advance shall be due and
               payable on the last Business Day of the term of each Advance
               (each, a "Maturity Date"). Notwithstanding the foregoing, the
               unpaid principal amount of the Loan shall be due and payable on
               the Termination Date.

          (b)  Interest on the unpaid principal amount of the Loan shall be
               capitalized and added to the unpaid principal amount of the Loan
               on the first Business Day of each month. Notwithstanding the
               foregoing, all accrued and unpaid interest is due and payable on
               the Repayment date.

          (c)  Repayment may be made at any time, provided that the final
               repayment be made on or prior to December 31, 1998. Borrower must
               receive Lender's request for repayment by 9:00 a.m. Eastern


                                       -1-
<PAGE>

               Standard Time on an Business Day if repayment is to be made that
               day.

     1.3  Cancellation/Reduction

          As provided under 2, EVENTS OF DEFAULT, Lender may at any time
          permanently reduce the Commitment and the unpaid principal and all
          interest shall be due and payable immediately.

     1.4  Evidence of Debt

          The Lender shall maintain in accordance with its usual practice an
          account or accounts evidencing the indebtedness of the Borrower
          resulting from the Loan and the amounts of principal and interest
          payable and paid from time to time hereunder. In any legal action or
          proceeding in respect of the Agreement, the entries made in such
          account or accounts shall, unless in case of obvious or manifest
          error, be conclusive evidence of the existence and amounts of the
          obligations of the Borrower therein recorded.

     1.5  Interest

          (a)  The Loan shall bear interest from day to day at an interest rate
               per annum

               (i)  From the date of this Agreement until the Maturity Date
                    equal to the lesser of

                    (x)  LIBOR, as defined below, plus 0.375%, or

                    (y)  the maximum rate allowable by law (the "Interest
                         Rate").

               (ii) "LIBOR" means the rate of deposits in U.S. dollars for a
                    period of one month which appears on the Telerate page 3750
                    as of 11:00 a.m., London time, on the date that is two
                    Business days prior to the first day of the Interest Period.
                    Interest accrues on the unpaid principal amount of each
                    Advance from the date of each Advance and is payable in
                    accordance with Section 1.2.

          (b)  The Interest Rate for each Interest Period is calculated by
               Lender prior to each interest Period. Such calculation is
               conclusive and binding absent manifest error.

          (c)  Interest is calculated on the basis of a 360-day year for actual
               days occurring during the Interest Period.


                                       -2-
<PAGE>


          (d)  "Interest Period" means the period commencing on the first
               Business Day of each month and ending on the day immediately
               preceding the first Business Day of the succeeding month.

2.   EVENTS OF DEFAULT

     In the event that:

     (A)  The Borrower fails to pay any sum payable hereunder when due; or

     (B)  The Borrower defaults in the due performance and observance of any
          other term of this Agreement and such default is not remedied within
          15 days after notice of such default; or

     (C)  The Borrower goes bankrupt or becomes insolvent or is subject to a
          receivership either voluntary or compulsory; or

     (D)  Any order is made or law, decree, regulation or resolution passed for
          the liquidation, winding up or dissolution of the Borrower; or

     (E)  All or any substantial part of the business or assets of the Borrower
          is expropriated, nationalized, compulsorily acquired or taken into
          public ownership or the Borrower ceases to be able or entitled to
          exercise the rights of control or ownership of the same; or

     (F)  The Borrower ceases to be directly or indirectly controlled by Lender,

     then and in any such event, and at any time thereafter if any such event
     shall then be continuing, the Lender may, by written notice to the Borrower
     declare the Loan immediately due and payable together with all interest
     accrued thereon and all other amounts payable hereunder, including all
     interest accrued on any past due principal, to the extent permitted by law.

3.   REPRESENTATIONS AND WARRANTIES OF BORROWER, The Borrower represent and
     warrants as follows:

     (A)  The Borrower is a corporation duly organized, validly existing and in
          good standing under the laws of the Republic of Argentina;

     (B)  The execution, delivery and performance by the Borrower of this
          Agreement are within the Borrower's corporate powers, have been duly
          authorized by all necessary corporate action, and do not contravene
          (i) the Borrower's Articles of Formation or By-laws or (ii) any law or
          any judgment or contractual restriction binding on or affecting the
          Borrower;



                                       -3-

<PAGE>

     (C) No authorization or approval or other action by, and no notice to or 
         filing with, any governmental authority or regulatory body which has 
         not already been obtained or made is required for the due execution, 
         delivery and performance by the Borrower of this Agreement; and 

     (D) This Agreement is the legal, valid and binding obligation of the 
         Borrower enforceable against Borrower in accordance with its terms.

4.   COVENANTS OF THE BORROWER; REPORTING REQUIREMENTS. So long as the Loan 
     shall remain unpaid, the Borrower will, unless the Lender shall otherwise 
     consent in writing, furnish to the Lender:

     (A) As soon as practicable, in any event within five Business Days after 
         the occurrence of each Event of Default, or each event which with 
         notice or lapse of time or both would become an Event of Default, 
         which is continuing on the date of such statement, a statement of an 
         authorized representative of the Borrower setting forth details of 
         such Event of Default or event and the action which the Borrower 
         proposes to take with respect thereto; and

     (B) Such other information respecting the business, properties or the 
         condition or operations, financial or otherwise, of the Borrower as 
         the Lender may from time to time reasonably request.

5.   COSTS AND EXPENSES

     The Borrower agrees to pay on demand all losses and all costs and 
     expenses, if any, in connection with the enforcement of this Agreement 
     and any instruments or other documents delivered hereunder, including, 
     without limitation, losses, costs and expenses sustained as a result of 
     a default by the Borrower in the performance of its obligations 
     contained in this Agreement or any instrument or document delivered 
     hereunder.
     
6.   ALTERNATIVE DISPUTE RESOLUTION

     The parties shall negotiate in good faith to resolve any dispute arising 
     out of or relating to this Agreement. In the event that the parties fail 
     to resolve a dispute by good faith negotiations, or if either party 
     deems a resolution by such means to be improbable, either party may 
     initiate mediation of the dispute upon written notice to the other 
     party. Such mediation shall be conducted promptly in accordance with the 
     Center for Public Resources Model Procedure for Mediation of Business 
     Disputes. If, within 60 days after notice of mediation, the parties have 
     failed to resolve the dispute by mediation, either party may propose 
     binding arbitration or initiate litigation. If either party requests 
     mediation, it shall occur in Indianapolis, Indiana.


                                      -4-

<PAGE>

7.   CHANGE OF CONTROL. After any change of Control (as defined below) of the 
     Borrower, the Lender may, at its option, upon notice to the Borrower 
     declare all principal, interest, and other amounts payable under this 
     Agreement to be immediately due and payable, whereupon the same shall 
     become immediately due and payable.

8.   DEFINITIONS. Capitalized terms as to which such capitalization would not
     be required in accordance with standard rules of grammar shall have the 
     meanings specified below.

     "Affiliate" means, with respect to each party hereto, a party that 
     directly, or indirectly, through one or more intermediaries, controls 
     or is controlled by, or is under common control with, the party 
     specified. The term "control" is defined below. For purposes of this 
     Agreement, Borrower is not an Affiliate of Lender.

     "Business Day" means any day other than a Saturday, Sunday or other day 
     on which banking institutions in Indianapolis, Indiana are required or 
     authorized by law to suspend operations.

     "Control" means the possession, directly or indirectly, of the power to 
     direct or cause the direction of the management and policies of any 
     individual, corporation, partnership, unincorporated association or 
     other entity, whether through the ownership of voting stock, by contract 
     or otherwise. A person who is the owner of 20% or more of a 
     corporation's outstanding voting stock shall be deemed to have Control 
     of such corporation.

9.   MISCELLANEOUS

     The Borrower agrees to take all such steps and actions and to execute 
     and to deliver and/or cause to be delivered all such further documents 
     and instruments as may be necessary in the opinion of the Lender to 
     establish, maintain and protect the rights of the Lender hereunder and 
     generally to carry out the true intent of this Agreement.

10.  ASSIGNMENT

     This Agreement may not be assigned in whole or in part by Borrower 
     without the express written consent of the other party. This Agreement 
     may be assigned by Lender to any Affiliate.

11.  SUCCESSORS

     This Agreement and any instrument or document executed in accordance 
     herewith shall be binding upon and shall inure to the benefit of the 
     parties hereto and their respective successors and assignees.


                                      -5-

<PAGE>

12.  GOVERNING LAW

     This Agreement and any instruments or other documents executed in 
     accordance herewith shall be governed by and construed in accordance 
     with the laws of the State of Indiana.

13.  AMENDMENTS, ETC.

     No amendment or waiver of any provision of this Agreement or any 
     instrument delivered hereunder, nor consent to any departure by the 
     Borrower therefrom, shall in any event be effective unless the same 
     shall be in writing and signed by an authorized representative of the 
     Lender.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly 
executed on the date first written above.

LENDER:                                     BORROWER:

Dow AgroSciences LLC                        Mycoyen S.A.


By: /s/ Sean S. Skinner                     By: [Illegible]
   ----------------------------                ---------------------------

Printed: Sean S. Skinner                    Printed: [Illegible]
        -----------------------                     ----------------------

Title: Treasurer                            Title: Vice President
      -------------------------                   ------------------------

Date: 5/15/98                               Date: 
     --------------------------                  -------------------------
                                                         [Illegible]


                                      -6-





<PAGE>


                               LOAN AGREEMENT

This Loan Agreement ("Agreement") is made as of April 1, 1997 between 
DowElanco, an Indiana general partnership (the "Lender"), and Mycogen 
Corporation, a California corporation (the "Borrower").

The parties hereto have agreed and do hereby agree as follows:

1.   THE LOAN

     1.1  The Advance

          From the above date to April 1, 1998, the Lender agrees to make 
          from time to time advances to the Borrower ("Advances"), in an 
          aggregate amount not exceeding $50,000,000 (fifty million U.S. 
          dollars), at any time outstanding ("Commitment"). Advances repaid 
          prior to April 1, 1998, may be reborrowed.  This Agreement involves 
          U.S. dollars only.

     1.2  Repayment

          Repayment may be made at any time, provided that the final 
          repayment be made on or prior to April 1, 1998.  Borrower must 
          receive Lender's request for repayment by 9:00 a.m. Eastern 
          Standard Time on any Business Day if repayment is to be made that 
          day.

     1.3  Cancellation/Reduction

          From time to time and upon 30 days written notice, except as 
          provided under 2. EVENTS OF DEFAULT, the Borrower or Lender may at 
          any time permanently reduce the Commitment and the unpaid principal 
          and all interest shall be due and payable immediately.
          
     1.4  Evidence of Debt

          The Lender shall maintain in accordance with its usual practice an 
          account or accounts evidencing the indebtedness of the Borrower 
          resulting from the Loan and the amounts of principal and interest 
          payable and paid from time to time hereunder.  In any legal action 
          or proceeding in respect of the Agreement, the entries made in such 
          account or accounts shall, unless in case of obvious or manifest 
          error, be conclusive evidence of the existence and amounts of the 
          obligations of the Borrower therein recorded.
          
                                  -1-
<PAGE>

     1.5  Interest

          The Loan shall bear interest from day to day at Lender's cost of 
          borrowing, as advised from time to time by Lender, plus 1/8% per 
          annum payable every three months from the date hereof to maturity 
          on the outstanding balance.

2.   EVENTS OF DEFAULT

     In the event that:

     (A)  The Borrower fails to pay any sum payable hereunder when due; or

     (B)  The Borrower defaults in the due performance and observance of 
          any other term of this Agreement and such default is not 
          remedied within 15 days after notice of such default; or

     (C)  The Borrower goes bankrupt or becomes insolvent or is subject 
          to a receivership either voluntary or compulsory; or

     (D)  Any order is made or law, decree, regulation or resolution 
          passed for the liquidation, winding up or dissolution of the 
          Borrower; or

     (E)  All or any substantial part of the business or assets of the 
          Borrower is expropriated, nationalized, compulsorily acquired 
          or taken into public ownership or the Borrower ceases to be 
          able or entitled to exercise the rights of control or 
          ownership of the same; or

     (F)  The Borrower ceases to be directly or indirectly controlled by 
          Lender.

     then and in any such event, and at any time thereafter if any such event 
     shall then be continuing, the Lender may, by written notice to the Borrower
     declare the Loan immediately due and payable together with all interest 
     accrued thereon and all other amounts payable hereunder, including all 
     interest accrued on any past due principal, to the extent permitted by law.

3.   REPRESENTATIONS AND WARRANTIES OF BORROWER.  The Borrower represents and 
     warrants as follows:

     (A)  The Borrower is a corporation duly organized, validly existing 
          and in good standing under the laws of the State of California;

     (B)  The execution, delivery and performance by the Borrower of 
          this Agreement are within the Borrower's corporate powers, 
          have been duly authorized by all necessary corporate action, 
          and do not contravene (i) the Borrower's Articles of 
          Incorporation or By-laws or (ii) any law or any judgment or 
          contractual restriction binding on or affecting the Borrower;

                                       -2-
<PAGE>

     (C)  No authorization or approval or other action by, and no notice 
          to or filing with, any governmental authority or regulatory 
          body which has not already been obtained or made is required 
          for the due execution, delivery and performance by the 
          Borrower of this Agreement; and

     (D)  This Agreement is the legal, valid and binding obligation of 
          the Borrower enforceable against the Borrower in accordance 
          with its terms.

4.   COVENANTS OF THE BORROWER; REPORTING REQUIREMENTS.  So long as the Loan 
     shall remain unpaid, the Borrower will, unless the Lender shall otherwise
     consent in writing, furnish to the Lender:

     (A)  As soon as practicable, in any event within five Business Days 
          after the occurrence of each Event of Default, or each event 
          which with notice or lapse of time or both would become an 
          Event of Default, which is continuing on the date of such 
          statement, a statement of an authorized representative of the 
          Borrower setting forth details of such Event of Default or 
          event and the the action which the Borrower proposes to take 
          with respect thereto; and

     (B)  Such other information respecting the business, properties or 
          the condition or operations, financial or otherwise, of the 
          Borrower as the Lender may from time to time reasonably 
          request.

5.   COSTS AND EXPENSES

     The Borrower agrees to pay on demand all losses and all costs and 
     expenses, if any, in connection with the enforcement of this Agreement 
     and any instruments or other documents delivered hereunder, including, 
     without limitation, losses, costs and expenses sustained as a result of 
     a default by the Borrower in the performance of its obligations 
     contained in this Agreement or any instrument or document delivered 
     hereunder.

6.   ALTERNATIVE DISPUTE RESOLUTION

     The parties shall negotiate in good faith to resolve any dispute arising 
     out of or relating to this Agreement.  In the event that the parties 
     fail to resolve a dispute by good faith negotiations, or if either party 
     deems a resolution by such means to be improbable, either party may 
     initiate mediation of the dispute upon written notice to the other 
     party.  Such mediation shall be conducted promptly in accordance with 
     the Center for Public Resources Model Procedure for Mediation of 
     Business Disputes.  If, within 60 days after notice of mediation, the 
     parties have failed to resolve the dispute by mediation, either party 
     may propose binding arbitration or initiate litigation.  If either party 
     requests mediation, it shall occur in Indianapolis, Indiana.

                                       -3-

<PAGE>

7.   CHANGE OF CONTROL. After any change of Control (as defined below) of the 
     Borrower, the Lender may, at its option, upon notice to the Borrower 
     declare all principal, interest, and other amounts payable under this 
     Agreement to be immediately due and payable, whereupon the same shall 
     become immediately due and payable.

8.   DEFINITIONS. Capitalized terms as to which such capitalization would not 
     be required in accordance with standard rules of grammar shall have the 
     meanings specified below.

     "Affiliate" means, with respect to each party hereto, a party that 
     directly, or indirectly, through one or more intermediaries, controls or 
     is controlled by, or is under common control with, the party specified. 
     The term "control" is defined below. For purposes of this Agreement, 
     Borrower is not an Affiliate of Lender.

     "Business Day" means any day other than a Saturday, Sunday or other day 
     on which banking institutions in Indianapolis, Indiana are required or 
     authorized by law to suspend operations.

     "Control" means the possession, directly or indirectly, of the power to 
     direct or cause the direction of the management and policies of any 
     individual, corporation, partnership, unincorporated association or 
     other entity, whether through the ownership of voting stock, by contract 
     or otherwise. A person who is the owner of 20% or more of a 
     corporation's outstanding voting stock shall be deemed to have Control 
     of such corporation.

9.   MISCELLANEOUS

     The Borrower agrees to take all such steps and actions and to execute 
     and to deliver and/or cause to be delivered all such further documents 
     and instruments as may be necessary in the opinion of the Lender to 
     establish, maintain and protect the rights of the Lender hereunder and 
     generally to carry out the true intent of this Agreement.

10.  ASSIGNMENT

     This agreement may not be assigned in whole or in part by Borrower 
     without the express written consent of the other party. This Agreement 
     may be assigned by Lender to any Affiliate.

11.  SUCCESSORS

     This Agreement and any instrument or document executed in accordance 
     herewith shall be binding upon and shall inure to the benefit of the 
     parties hereto and their respective successors and assignees.


                                      -4-

<PAGE>

12.  GOVERNING LAW

     This Agreement and any instruments or other documents executed in 
     accordance herewith shall be governed by and construed in accordance 
     with the laws of the State of Indiana.

13.  AMENDMENTS, ETC.

     No amendment of waiver of any provision of this Agreement or any 
     instrument delivered hereunder, nor consent to any departure by the 
     Borrower therefrom, shall in any event be effective unless the same 
     shall be in writing and signed by an authorized representative of the 
     Lender.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly 
executed on the date first written above.

LENDER:                                     BORROWER:

DowElanco                                   Mycogen Corporation


By: /s/ Sean S. Skinner                     By: James A. Baumker
   ----------------------------                ---------------------------

Printed: Sean S. Skinner                    Printed: James A. Baumker
        -----------------------                     ----------------------

Title: Treasurer                            Title: VP CFO
      -------------------------                   ------------------------

Date: 5/20/97                               Date: 6/10/97
     --------------------------                  -------------------------
                                                         [Illegible]


                                      -5-


<PAGE>

                         AMENDMENT NO. 1 TO LOAN AGREEMENT

This Amendment No. 1 to Loan Agreement ("Amendment") is made as of September 
29, 1997 between DowElanco LLC, a Delaware corporation, f/k/a DowElanco, an 
Indiana general partnership (the "Lender"), and Mycogen Corporation, a 
California corporation (the "Borrower") (together, the "parties").

WHEREAS, the parties executed a Loan Agreement as of April 1, 1997 (the 
"Agreement"); and

WHEREAS, the parties wish to amend the Agreement;

NOW THEREFORE, the parties hereto have agreed and do hereby agree to amend the 
Agreement as follows:

     Section 1.3 Cancellation/Reduction is hereby deleted in its entirety and 
     replaced with the following:

     1.3 Cancellation/Reduction
         As provided under 2. EVENTS OF DEFAULT the Borrower or Lender may at 
         any time permanently reduce the Commitment and the unpaid principal and
         all interest shall be due and payable immediately.

     All other terms and conditions of the Agreement shall remain in full 
     force and effect.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly 
executed on the date first written above.

LENDER:                                  BORROWER:

DowElanco LLC                            Mycogen Corporation


By: /s/ Sean S. Skinner                  By: /s/ James A. Baumker
   -----------------------------            -------------------------------

Printed: Sean S. Skinner                    Printed: James A. Baumker
        -----------------------                     ----------------------

Title: Treasurer                            Title: VP CFO
      -------------------------                   ------------------------

Date: 9/23/97                               Date: 9/29/97
     --------------------------                  -------------------------




<PAGE>

                         AMENDMENT NO.2 TO LOAN AGREEMENT

This Amendment No. 2 to Loan Agreement ("Amendment") is made as of November 
14, 1997 between DowElanco LLC, a Delaware corporation, f/k/a DowElanco, an 
Indiana general partnership (the "Lender"), and Mycogen Corporation, a 
California corporation (the "Borrower") (together, the "parties").

WHEREAS, the parties executed a Loan Agreement as of April 1, 1997, and 
Amendment No. 1 as of September 29, 1997 (the "Agreement"); and

WHEREAS, the parties wish to amend the Agreement;

NOW THEREFORE, the parties hereto have agreed and do hereby agree to amend 
the Agreement as follows:

     Section 1.1 The Advance is hereby deleted in its entirety and 
     replaced with the following:

     1.1 The Advance
         From the date of this Amendment No. 2 to April 1, 1998, the Lender 
         agrees to make from time to time advances to the Borrower ("Advances"),
         in an aggregate amount not exceeding $75,000,000 (seventy-five million
         U.S. dollars), at any time outstanding ("Commitment"). Lender must 
         receive Borrower's request for an advance by 9:00 a.m. Eastern Standard
         Time if the advance is to be made that day. Advances repaid prior to 
         April 1, 1998, may be reborrowed. This Agreement involves U.S. dollars 
         only.

     All other terms and conditions of the Agreement shall remain in full 
     force and effect.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly 
executed on the date first written above.

LENDER:                                  BORROWER:

DowElanco LLC                            Mycogen Corporation


By: /s/ Sean S. Skinner                  By: /s/ James A. Baumker
   -----------------------------            -------------------------------

Printed: Sean S. Skinner                    Printed: James A. Baumker
        -----------------------                     ----------------------

Title: Treasurer                            Title: VP CFO
      -------------------------                   ------------------------

Date: 11/14/97                               Date: 11/17/97
     --------------------------                  -------------------------




<PAGE>

                         AMENDMENT NO. 3 TO LOAN AGREEMENT

This Amendment No. 3 to Loan Agreement ("Amendment") is made as of November 
18, 1997 between DowElanco LLC, a Delaware corporation, f/k/a DowElanco, an 
Indiana general partnership (the "Lender"), and Mycogen Corporation, a 
California corporation (the "Borrower") (together, the "parties").

WHEREAS, Lender and Borrower are parties to that certain Loan Agreement dated 
as of April 1, 1997, as amended by Amendment No. 1 as of September 29, 1997, 
and Amendment No. 2 as of November 14, 1997 (the "Agreement"); and

WHEREAS, the parties wish to further amend the Agreement;

NOW THEREFORE, the parties hereto have agreed and do hereby agree to amend the 
Agreement as follows:

     Section 1.2 is hereby deleted in its entirety and replaced with the      
following:

     1.2 Repayment

         Repayment may be made at any time, provided that the final repayment 
         be made on or prior to September 30, 1998.

     All other terms and conditions of the Agreement shall remain in full 
     force and effect.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly 
executed on the date first written above.

LENDER:                                  BORROWER:

DowElanco LLC                            Mycogen Corporation


By: /s/ Sean S. Skinner                  By: /s/ James A. Baumker
   -----------------------------            -------------------------------

Printed: Sean S. Skinner                    Printed: James A. Baumker
        -----------------------                     ----------------------

Title: Treasurer                            Title: VP CFO
      -------------------------                   ------------------------

Date: 11/18/97                               Date: 11/19/97
     --------------------------                  -------------------------



<PAGE>

                         AMENDMENT NO. 4 TO LOAN AGREEMENT

This Amendment No. 4 to Loan Agreement ("Amendment") is made as of April 6, 
1998 between Dow AgroSciences LLC, formerly known as DowElanco LLC, a 
Delaware limited liability company (the "Lender"), and Mycogen Corporation, a 
California corporation (the "Borrower") (together, the "parties").

WHEREAS, Lender and Borrower are parties to that certain Loan Agreement dated 
as of April 1, 1997, as amended by Amendment No. 1 as of September 29, 1997, 
Amendment No. 2 as of November 14, 1997, and Amendment No. 3 as of November 18, 
1997 (the "Agreement"); and

WHEREAS, the parties wish to further amend the Agreement;

NOW THEREFORE, the parties hereto have agreed and do hereby agree to amend the 
Agreement as follows:

     Section 1.2 Repayment is hereby deleted in its entirety and      
replaced with the following:

     1.2 Repayment

         Repayment may be made at any time, provided that the final repayment 
         be made on or prior to September 30, 1999.

     All other terms and conditions of the Agreement shall remain in full 
force and effect.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly 
executed on the date first written above.

LENDER:                                  BORROWER:

Dow AgroSciences LLC                     Mycogen Corporation


By: /s/ Sean S. Skinner                  By: /s/ James A. Baumker
   -----------------------------            -------------------------------

Printed: Sean S. Skinner                    Printed: James A. Baumker
        -----------------------                     ----------------------

Title: Treasurer                            Title:  CEO
      -------------------------                   ------------------------

Date: 4/7/98                               Date: 4/8/98
     --------------------------                  -------------------------



<PAGE>


                      AMENDMENT NO. 5 TO LOAN AGREEMENT

This Amendment No. 5 to Loan Agreement ("Amendment") is made as of ___________,
1997 between Dow AgroScience LLC, formerly known as DowElanco LLC, a Delaware
limited liability company (the "Lender"), and Mycogen Corporation, a 
California corporation (the "Borrower") (together, the "parties").

WHEREAS, Lender and Borrower are parties to that certain Loan Agreement dated 
as of April 1, 1997, as amended by Amendment No. 1 as of September 29, 1997, 
Amendment No. 2 as of November 14, 1997, Amendment No. 3 as of November 18, 
1997, and Amendment No. 4 as of April 6, 1998 (the "Agreement"); and

WHEREAS, the parties wish to further amend the Agreement;

NOW THEREFORE, the parties hereto have agreed and do hereby agree to amend 
the Agreement as follows:

1.   Section 1.2 Repayment is hereby deleted in its entirety and replaced 
with the following:

     1.2  Repayment

          (a)  The unpaid principal amount of each Advance shall be due and 
               payable on the Repayment Date.

          (b)  Interest on the unpaid principal amount of the Loan is due and 
               payable as it accrues on the first Business Day of each 
               calendar quarter until December 31, 1997; thereafter, interest 
               on the unpaid principal amount of the Loan shall be 
               capitalized and added to the unpaid principal amount of the 
               Loan on the first Business Day of each month.  Notwithstanding 
               the foregoing, all accrued and unpaid interest is due and 
               payable on the Repayment Date.

          (c)  Repayment may be made at any time, provided that the final 
               repayment be made on or prior to the Repayment Date.  Borrower
               must receive Lender's request for repayment by 9:00 a.m. Eastern
               Standard Time on any Business Day if repayment is to be made 
               that day.

2.   Section 1.5 Interest is hereby deleted in its entirety and replaced with 
the following:

     1.5  Interest

          (a)  The Loan shall bear interest from day to day at an interest 
               rate per annum

                                       1
<PAGE>

               (i)    From October 1, 1997 through March 31, 1998, equal to 
                      LIBOR, as defined below, plus 0.25%, and

               (ii)   From April 1, 1998, until the Repayment Date equal to 
                      LIBOR, as defined below, plus 0.375%.

               (iii)  From October 1, 1997 until December 31, 1997, "LIBOR" 
                      means the rate of deposits in U.S. dollars for a period 
                      of three months which appears on the Telerate page 3750 
                      as of 11:00 a.m., London time, on the date that is two 
                      Business days prior to the first day of the Interest 
                      Period.  Effective January 1, 1998, "LIBOR" means the 
                      rate for deposits in U.S. dollars for a period of one 
                      month which appears on the Telerate Page 3750 as of 
                      11:00 a.m., London time, on the date that is two 
                      Business Days prior to the first date of the Interest 
                      Period.  Interest accrues on the unpaid principal amount
                      of each Advance from the date of each Advance and is 
                      payable in accordance with Section 1.2.

          (b)  The Interest Rate for each Interest Period is calculated by 
               Lender prior to each Interest Period.  Such calculation is 
               conclusive and binding absent manifest error.

          (c)  Interest is calculated on the basis of a 360-day year for 
               actual days occurring during the Interest Period.

          (d)  "Interest Period" means each calendar quarter, or part of each 
               calendar quarter, during which the Loan or any Advance is 
               outstanding between the date of this Amendment and December 
               31, 1997.  Thereafter, "Interest Period" means the period 
               commencing on the first Business Day of each month and ending 
               on the day immediately preceding the first Business Day of 
               the succeeding month.

All other terms and conditions of the Agreement shall remain in full force 
and effect.

                                       2
<PAGE>

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly 
executed on the date first written above.

LENDER:                                BORROWER:

Dow AgroSciences LLC                   Mycogen Corporation


By:  /s/ Sean S. Skinner               By:  /s/ J.A. Baumker
   ----------------------------           ----------------------------
Printed:  Sean S. Skinner              Printed:  J.A. Baumker
        -----------------------                -----------------------
Title:  Treasurer                      Title:  CEO
      -------------------------              -------------------------
Date:  4/13/98                         Date:  4/15/98
     --------------------------             --------------------------


                                       3



<PAGE>



                               LOAN AGREEMENT

This Loan Agreement ("Agreement") is made as of April 1, 1997 between Mycogen
Corporation, a California corporation (the "Lender"), and DowElanco, an 
Indiana general partnership (the "Borrower").

The parties hereto have agreed and do hereby agree as follows:

1.   THE LOAN

     1.1  The Advance

          From the above date to April 1, 1998, the Lender agrees to make 
          from time to time advances to the Borrower ("Advances"), in an 
          aggregate amount not exceeding $50,000,000 (fifty million U.S. 
          dollars), at any time outstanding ("Commitment").  Lender must 
          receive Borrower's request for an advance by 9:00 a.m. Eastern
          Standard Time if the advance is to be made that day.  Advances
          repaid prior to April 1, 1998, may be reborrowed.  This Agreement
          involves U.S. dollars only.

     1.2  Repayment

          Repayment may be made at any time, provided that the final 
          repayment be made on or prior to April 1, 1998.

     1.3  Cancellation/Reduction

          From time to time and upon 30 days written notice, the Borrower or 
          Lender may at any time permanently reduce the Commitment and the 
          unpaid principal and all interest shall be due and payable 
          immediately.
          
     1.4  Evidence of Debt

          The Lender shall maintain in accordance with its usual practice an 
          account or accounts evidencing the indebtedness of the Borrower 
          resulting from the Loan and the amounts of principal and interest 
          payable and paid from time to time hereunder.  In any legal action 
          or proceeding in respect of the Agreement, the entries made in such 
          account or accounts shall, unless in case of obvious or manifest 
          error, be conclusive evidence of the existence and amounts of the 
          obligations of the Borrower therein recorded.
          
                                  -1-
<PAGE>

     1.5  Interest

          The Loan shall bear interest from day to day at Borrower's rate of 
          deposit, as advised from time to time by Borrower, minus 1/8% per 
          annum payable every three months from the date hereof to maturity 
          on the outstanding balance.

2.   EVENTS OF DEFAULT

     In the event that:

     (A)  The Borrower fails to pay any sum payable hereunder when due; or

     (B)  The Borrower defaults in the due performance and observance of 
          any other term of this Agreement and such default is not 
          remedied within 15 days after notice of such default; or

     (C)  The Borrower goes bankrupt or becomes insolvent or is subject 
          to a receivership either voluntary or compulsory; or

     (D)  Any order is made or law, decree, regulation or resolution 
          passed for the liquidation, winding up or dissolution of the 
          Borrower; or

     (E)  All or any substantial part of the business or assets of the 
          Borrower is expropriated, nationalized, compulsorily acquired 
          or taken into public ownership or the Borrower ceases to be 
          able or entitled to exercise the rights of control or 
          ownership of the same; or

     (F)  The Borrower ceases to be directly or indirectly controlled by 
          The Dow Chemical Company, Midland, Michigan, U.S.A.,

     then and in any such event, and at any time thereafter if any such event 
     shall then be continuing, the Lender may, by written notice to the Borrower
     declare the Loan immediately due and payable whereupon the same shall 
     become immediately due and payable together with all interest accrued 
     thereon and all other amounts payable hereunder, including all interest 
     accrued on any past due principal, to the extent permitted by law.

3.   REPRESENTATIONS AND WARRANTIES OF BORROWER.  The Borrower represents and 
     warrants as follows:

     (A)  The Borrower is an Indiana general partnership;

     (B)  The execution, delivery and performance by the Borrower of 
          this Agreement are within the Borrower's powers, have been duly 
          authorized by all necessary action, and do not contravene (i) the 
          Borrower's 

                                       -2-
<PAGE>

          Partnership Agreement or Authorization Policy or (ii) any law or
          any judgment or contractual restriction binding on or affecting
          the Borrower;

     (C)  No authorization or approval or other action by, and no notice 
          to or filing with, any governmental authority or regulatory 
          body which has not already been obtained or made is required 
          for the due execution, delivery and performance by the 
          Borrower of this Agreement; and

     (D)  This Agreement is the legal, valid and binding obligation of 
          the Borrower enforceable against the Borrower in accordance 
          with its terms.

4.   COVENANTS OF THE BORROWER; REPORTING REQUIREMENTS.  So long as the Loan 
     shall remain unpaid, the Borrower will, unless the Lender shall otherwise
     consent in writing, furnish to the Lender:

     (A)  As soon as practicable, in any event within five Business Days 
          after the occurrence of each Event of Default, or each event 
          which with notice or lapse of time or both would become an 
          Event of Default, which is continuing on the date of such 
          statement, a statement of an authorized representative of the 
          Borrower setting forth details of such Event of Default or 
          event and the action which the Borrower proposes to take with 
          respect thereto; and

     (B)  Such other information respecting the business, properties or 
          the condition or operations, financial or otherwise, of the 
          Borrower as the Lender may from time to time reasonably 
          request.

5.   COSTS AND EXPENSES

     The Borrower agrees to pay on demand all losses and all costs and 
     expenses, if any, in connection with the enforcement of this Agreement 
     and any instruments or other documents delivered hereunder, including, 
     without limitation, losses, costs and expenses sustained as a result of 
     a default by the Borrower in the performance of its obligations 
     contained in this Agreement or any instrument or document delivered 
     hereunder.

6.   ALTERNATIVE DISPUTE RESOLUTION

     The parties shall negotiate in good faith to resolve any dispute arising 
     out of or relating to this Agreement.  In the event that the parties 
     fail to resolve a dispute by good faith negotiations, or if either party 
     deems a resolution by such means to be improbable, either party may 
     initiate mediation of the dispute upon written notice to the other 
     party.  Such mediation shall be conducted promptly in accordance with 
     the Center for Public Resources Model Procedure for Mediation of 
     Business Disputes.  If, within 60 days after notice of mediation, the 
     parties have failed to resolve the dispute by mediation, either party 
     may propose binding arbitration or 

                                       -3-

<PAGE>

     initiate litigation. If either party requests mediation, it shall occur 
     in Indianapolis, Indiana.

7.   CHANGE OF CONTROL. After any change of Control (as defined below) of the 
     Borrower, the Lender may, at its option, upon notice to the Borrower 
     declare all principal, interest, and other amounts payable under this 
     Agreement to be immediately due and payable, whereupon the same shall 
     become immediately due and payable.

8.   DEFINITIONS. Capitalized terms as to which such capitalization would not 
     be required in accordance with standard rules of grammar shall have the 
     meanings specified below.

     "Affiliate" means, with respect to each party hereto, a party that 
     directly, or indirectly, through one or more intermediaries, controls or 
     is controlled by, or is under common control with, the party specified. 
     The term "control" is defined below. For purposes of this Agreement, 
     Lender is not an Affiliate of Borrower.

     "Business Day" means any day other than a Saturday, Sunday or other day 
     on which banking institutions in Indianapolis, Indiana are required or 
     authorized by law to suspend operations.

     "Control" means the possession, directly or indirectly, of the power to 
     direct or cause the direction of the management and policies of any 
     individual, corporation, partnership, unincorporated association or 
     other entity, whether through the ownership of voting stock, by contract 
     or otherwise. A person who is the owner of 20% or more of a 
     corporation's outstanding voting stock shall be deemed to have Control 
     of such corporation.

9.   MISCELLANEOUS

     The Borrower agrees to take all such steps and actions and to execute 
     and to deliver and/or cause to be delivered all such further documents 
     and instruments as may be necessary at any time or times in the 
     reasonable opinion of the Lender to establish, maintain and protect the 
     rights of the Lender hereunder and generally to carry out the true intent 
     of this Agreement.

10.  ASSIGNMENT

     This agreement may not be assigned in whole or in part by Lender 
     without the express written consent of the other party. This Agreement 
     may be assigned by Borrower to any Affiliate.


                                      -4-

<PAGE>

11.  SUCCESSORS

     This Agreement and any instrument or document executed in accordance 
     herewith shall be binding upon and shall inure to the benefit of the 
     parties hereto and their respective successors and assignees.

12.  GOVERNING LAW

     This Agreement and any instruments or other documents executed in 
     accordance herewith shall be governed by and construed in accordance 
     with the laws of the State of Indiana.

13.  AMENDMENTS, ETC.

     No amendment or waiver of any provision of this Agreement or any 
     instrument delivered hereunder, nor consent to any departure by the 
     Borrower therefrom, shall in any event be effective unless the same 
     shall be in writing and signed by an authorized representative of the 
     Lender and then such waiver or consent shall be effective only in the 
     specific instance and for the specific purpose for which given.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly 
executed on the date first written above.

LENDER:                                     BORROWER:

DowElanco                                   Mycogen Corporation


By: /s/ Sean S. Skinner                     By: /s/ James A. Baumker
   ----------------------------                ---------------------------

Printed: Sean S. Skinner                    Printed: James A. Baumker
        -----------------------                     ----------------------

Title: Treasurer                            Title: VP CFO
      -------------------------                   ------------------------

Date: 5/20/97                               Date: 6/10/97
     --------------------------                  -------------------------
                                                         [Illegible]


                                      -5-





<PAGE>

                         AMENDMENT NO. 1 TO LOAN AGREEMENT

This Amendment No. 1 to Loan Agreement ("Amendment") is made as of April 6, 
1998 between Mycogen Corporation, a California corporation (the "Lender"), and 
Dow AgroSciences LLC, formerly known as DowElanco LLC, a Delaware limited 
liability company (the "Borrower") (together, the "parties").

WHEREAS, Lender and Borrower are parties to that certain Loan Agreement dated 
as of April 1, 1997 (the "Agreement"); and

WHEREAS, the parties wish to amend the Agreement;

NOW THEREFORE, the parties hereto have agreed and do hereby agree to amend the 
Agreement as follows:

     Section 1.2 Repayment is hereby deleted in its entirety and replaced 
with the following:

     1.2 Repayment

         Repayment may be made at any time, provided that the final repayment 
         be made on or prior to September 30, 1999.


     All other terms and conditions of the Agreement shall remain in full 
force and effect.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly 
executed on the date first written above.

LENDER:                                      BORROWER:                   
                                                                            
Mycogen Corporation                          Dow AgroSciences LLC      
                                                                              
                                                                              
By: /s/ James A. Baumker                     By: /s/ Sean S. Skinner          
   ------------------------------               -----------------------------
                                                                              
   Printed: James A. Baumker                 Printed: Sean S. Skinner         
           ----------------------                    -----------------------  
                                                                              
   Title: CEO                                Title: Treasurer                 
         ------------------------                  -------------------------  
                                                                              
   Date: 4/8/98                             Date: 4/7/98                    
        -------------------------                 --------------------------  
                                                                             


                                      i


<PAGE>

                         AMENDMENT NO. 2 TO LOAN AGREEMENT

This Amendment No. 2 to Loan Agreement ("Amendment") is made as of October 1, 
1997 between Mycogen Corporation, a California corporation (the "Lender"), and 
Dow AgroSciences LLC, formerly known as DowElanco LLC, a Delaware limited 
liability company (the "Borrower") (together, the "parties").

WHEREAS, Lender and Borrower are parties to that certain Loan Agreement dated 
as of April 1, 1997, as amended by Amendment No. 1 as of April 6, 1998 (the 
"Agreement"); and

WHEREAS, the parties wish to amend the Agreement;

NOW THEREFORE, the parties hereto have agreed and do hereby agree to amend the 
Agreement as follows:

1.   Section 1.2 Repayment is hereby deleted in its entirety and replaced 
with the following:

     1.2 Repayment

         (a)  The unpaid principal amount of each Advance shall be due and 
              payable on the Repayment Date.

         (b)  Interest on the unpaid principal amount of the Loan is due and 
              payable as it accrues on the first Business Day of each 
              calendar quarter until December 31, 1997; thereafter, interest 
              on the unpaid principal amount of the Loan shall be capitalized 
              and added to the unpaid principal amount of the Loan on the 
              first Business Day of each month. Notwithstanding the 
              foregoing, all accrued and unpaid interest is due and payable 
              on the Repayment Date.

         (c)  Repayment may be made at any time, provided that the final 
              repayment be made on or prior to the Repayment Date. Borrower 
              must receive Lender's request for repayment by 9:00 a.m. 
              Eastern Standard Time on any Business Day if repayment is to be 
              made that day.

2.   Section 1.5 Interest is hereby deleted in its entirety and replaced with 
the following:

     1.5 Interest

         (a)  From October 1, 1997 until the Repayment Date, the Loan shall 
              bear interest at a rate equal to LIBID, as defined below, minus 
              0.25%.


                                      1

<PAGE>

          (b)  "LIBID" means LIBOR minus 0.125%.  From October 1, 1997 until 
               December 31, 1997, "LIBOR" means the rate of deposits in U.S. 
               dollars for a period of three months which appears on the 
               Telerate page 3750 as of 11:00 a.m., London time, on the date 
               that is two Business days prior to the first day of the 
               Interest Period.  Effective January 1, 1998, "LIBOR" means the 
               rate for deposits in U.S. dollars for a period of one month 
               which appears on the Telerate Page 3750 as of 11:00 a.m., 
               London time, on the date that is two Business Days prior to 
               the first date of the Interest Period.  Interest accrues on 
               the unpaid principal amount of each Advance from the date of
               each Advance and is payable in accordance with Section 1.2.

          (c)  The Interest Rate for each Interest Period is calculated by 
               Lender prior to each Interest Period.  Such calculation is 
               conclusive and binding absent manifest error.

          (d)  Interest is calculated on the basis of a 360-day year for 
               actual days occurring during the Interest Period.

          (e)  "Interest Period" means each calendar quarter, or part of each 
               calendar quarter, during which the Loan or any Advance is 
               outstanding between the date of this Amendment and December 
               31, 1997.  Thereafter, "Interest Period" means the period 
               commencing on the first Business Day of each month and ending 
               on the day immediately preceding the first Business Day of 
               the succeeding month.

     All other terms and conditions of the Agreement shall remain in full
     force and effect.


IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be duly 
executed on the date first written above.

LENDER:                                  BORROWER:
                                         
Mycogen Corporation                      Dow AgroSciences LLC           
                                         
                                         
By:  /s/ J.A. Baumker                    By:  /s/ Sean S. Skinner       
   ----------------------------             ----------------------------
Printed:  J.A. Baumker                   Printed:  Sean S. Skinner      
        -----------------------                  -----------------------
Title:  CEO                              Title:  Treasurer              
      -------------------------                -------------------------
Date:  4/15/98                           Date:  4/13/98                 
     --------------------------               --------------------------


                                       2



<PAGE>

                       MEMORANDUM OF UNDERSTANDING

     WHEREAS, there are now pending several consolidated putative class 
action lawsuits in the Superior Court for the State of California, for the 
County of San Diego (the "Court"), consolidated under the lead case of LESLIE 
SUSSER V. MYCOGEN CORPORATION, ET AL., Case No. 720255 (the "Litigation"), 
brought on behalf of the public, minority shareholders of Mycogen Corporation 
("Mycogen" or the "Company");

     WHEREAS, the Complaint in the Litigation challenges certain actions 
allegedly taken or not taken by defendant Dow Agrosciences LLC ("DAS") the 
majority shareholder of Mycogen, The Dow Chemical Company ("TDCC"), DAS's 
parent, and certain members of Mycogen's Board of Directors, some of whom 
are also affiliated with DAS and TDCC, in connection with DAS's April 30, 
1998, request to the board of directors of Mycogen to execute a contractual 
amendment to permit Mycogen to enter discussions with DAS regarding the 
possible acquisition by DAS of all of the outstanding shares of Mycogen common 
stock held by persons and entities other than DAS at a price of $20.50 per 
share (the "Proposed Transaction");

     WHEREAS, following announcement of the Proposed Transaction, the board 
of directors of Mycogen formed a Special Committee of disinterested directors 
to negotiate with TDCC and DAS regarding the Proposed Transaction, which 
Special Committee retained legal and financial advisors to assist in 
evaluations and negotiations regarding the Proposed Transaction;

     WHEREAS, following the commencement of the Litigation and the filing of 
the complaints, plaintiffs' attorneys continued their investigative efforts, 
communicated at various times with counsel for the defendants, and, together 
with their independent financial advisor, were provided by defendants' 
counsel with, INTER ALIA, confidential financial evaluations,

                                      
<PAGE>

analyses and projections prepared by DAS's financial advisor, Salomon Smith 
Barney, and the Special Committee's financial advisor, Wasserstein Perella 
and Company, pertaining to Mycogen and the Proposed Transaction, so that 
plaintiffs, through their counsel, could convey their position as to a fair 
price for Mycogen shares. Plaintiffs attorneys and their independent 
financial advisor reviewed these materials and other publicly available 
materials filed with the Securities and Exchange Commission with respect to 
Mycogen in connection with their communications with defendants' counsel and 
their financial advisors;

     WHEREAS, the documents provided by defendants' counsel to plaintiffs' 
counsel included a draft letter written in August 1997 by Dr. Jerry Caulder, 
who had resigned in May 1997 as Chairman of the Board and Chief Executive 
Officer of Mycogen, and Thomas J. Cable, a director of the Company, alleging 
that TDCC and DAS had not acted in the best interest of the Company with 
regard to certain transactions, and various other documents relating to the 
matters discussed in the draft letter (collectively, the "Caulder 
documents");

     WHEREAS, after review of the materials provided by the defendants to 
plaintiffs' counsel and their independent financial advisor, and plaintiffs' 
counsel's independent review of other pertinent materials, plaintiffs' 
counsel and their independent financial advisor, at the request of attorneys 
for the defendants, met in person with attorneys and financial advisors for 
TDCC, DAS and the Special Committee to discuss the Proposed Transaction and 
the ongoing negotiations between TDCC and DAS and the Special Committee and 
to present their views;

     WHEREAS, the pendency of the Litigation and the communications between 
counsel for plaintiffs and defendants and their respective financial advisors 
with respect to the above matters, were among the material causal factors 
that TDCC, DAS and the Special 


                                       2

<PAGE>

Committee took into account in the course of the negotiations regarding 
enhancement of the terms of the Proposed Transaction;

     WHEREAS, on August 31, 1998, Mycogen and DAS jointly announced the 
execution of a definitive merger agreement (the "Merger Agreement") whereby 
DAS, through an acquisition subsidiary, will make a tender offer to acquire 
all of the shares of Mycogen common stock that DAS does not already own for a 
price of $28.00 per share (the "Tender Offer") and, following the Tender 
Offer, if DAS and the acquisition subsidiary obtain at least 90% of the total 
shares of Mycogen (on a fully diluted basis), the acquisition subsidiary will 
be merged into Mycogen and each remaining shareholder will receive $28.00 per 
share for each remaining share of Mycogen common stock;

     WHEREAS, plaintiffs' counsel, after consultation with their independent 
financial advisor, and after a candid exchange of views with defendants and 
their financial advisors, have agreed in principle, subject to the review of 
final transaction documents and confirmatory discovery as further set forth 
herein, that the enhanced terms of the transaction set forth in the Merger 
Agreement result in a transaction that is fair to and in the best interests 
of the plaintiffs and the minority shareholders of Mycogen, taking into 
account all factors affecting or potentially affected the value and business 
prospects of Mycogen;

     WHEREAS, defendants deny that they have committed any wrongdoing but 
nevertheless believe that is in their best interests to resolve the 
Litigation on the basis set forth herein,

     WHEREAS, counsel for the parties have reached an agreement in principle, 
subject to confirmatory discovery by plaintiffs in the Litigation and the 
other terms hereof,


                                       3

<PAGE>

providing for the settlement of the Litigation (the "Settlement") between and 
among plaintiffs, on behalf of themselves and the putative class of persons 
on behalf of whom plaintiffs have brought the Litigation, and all defendants, 
on the terms and subject to the conditions set forth below;

     NOW THEREFORE, as a result of the foregoing and the negotiations among 
counsel to the parties, the parties to the Litigation hereby agree as follows:

     1.   INCORPORATION OF RECITALS: The foregoing recitals are incorporated 
into and expressly made a part of this Memorandum of Understanding.

     2.   STIPULATION AND OTHER SETTLEMENT DOCUMENTS: The parties to the 
Litigation will attempt in good faith to agree upon and to execute as soon as 
practicable an appropriate stipulation of settlement (the "Stipulation") and 
such other documentation as may be required in order to obtain any and all 
necessary or appropriate court approvals of the Stipulation and the 
Settlement, upon and consistent with the terms set forth in this Memorandum 
of Understanding. The Stipulation will expressly provide, INTER ALIA:

          (1)   CLASS CERTIFICATION: for class certification, conditional on 
final Court approval (as defined herein) of the Settlement, pursuant to 
Section 382 of the California Code of Civil Procedure of a class consisting 
of all persons (other than defendants and their affiliates) who owned common 
stock of Mycogen on April 30, 1998, and their successors in interest and 
transferees, immediate and remote through and including the closing of the 
Merger (the "Class");

          (2)   NO ADMISSION OF WRONGDOING: that all defendants have denied, 
and continue to deny, that they have committed any violations of law and that 
they are entering into


                                       4

<PAGE>

the Stipulation because the proposed Settlement would eliminate the burden 
and expense of further litigation;

          (3)   RELEASE OF ALL CLAIMS: for the release of all claims that 
were asserted or could have been asserted in the Litigation by members of the 
Class, or any or all of them, and any and all other or additional such claims 
by or on behalf of Mycogen itself or the stockholders of Mycogen, against 
TDCC, DAS, Mycogen, the Special Committee, each of the members thereof, each 
of the current directors of Mycogen and any and all other defendants, as well 
as each of their present or former officers, directors, employees, agents, 
attorneys, accountants, financial advisors, commercial bank lenders, 
investment bankers, representatives, affiliates, associates, parents, 
subsidiaries, general and limited partners and partnerships, heirs, 
executors, administrators, successors and assigns, whether known or unknown, 
under state or federal law, and whether directly, derivatively, 
representatively or in any other capacity, arising out of, relating to, or in 
connection with, in whole or in part, the Proposed Transaction, the Tender 
Offer, the Merger, the Merger Agreement, the Caulder documents or any of the 
matters alleged in them, any disclosures made in connection with any of 
these, or any other matter affecting or alleged to affect the sufficiency or 
fairness of the consideration offered or paid in the Tender Offer or the 
Merger on any basis whatsoever, except for statutory appraisal rights (the 
"Settled Claims"). In addition, Mycogen shall release TDCC, DAS and each of 
their present or former officers, directors, employees, agents, 
representatives, affiliates, parents, subsidiaries, successors and assigns, 
from any and all claims arising out of, relating to, or in connection with, 
in whole or in part, their fiduciary duties as majority or controlling 
shareholders or directors of Mycogen, including without limitation any of the 
matters alleged in the Caulder documents.


                                       5


<PAGE>


          (4)  DISMISSAL: for the dismissal of the Litigation and all Settled 
Claims with prejudice and without costs to any party (except as set forth 
below);

          (5)  OPT OUTS: that the defendants shall in their sole discretion 
have the option to terminate the Settlement if potential class members 
holding in excess of a certain number of shares of Mycogen (to be agreed upon 
in advance by the parties and set forth in the Stipulation) request exclusion 
from the class.

     3.   SUBMISSION TO THE COURT. The parties to the Litigation, through 
their counsel, will present the Stipulation and Settlement to the Court for 
hearing and approval as soon as practicable following appropriate notice to 
the members of the Class and will use their best efforts to final Court 
approval of the Stipulation and Settlement, including dismissal of the 
Litigation with prejudice and the release of all claims as set forth above.  
It is expressly acknowledged that the Tender Offer and the Merger may be 
closed prior to final Court approval of the Settlement.  As used in this 
Memorandum of Understanding, "final COURT approval" of the Settlement means 
that the Court has entered an Order approving the Settlement in accordance 
with the Stipulation and that Order is finally affirmed on appeal or is no 
longer subject to appeal.

     4.   SUSPENSION OF PROCEEDINGS. Pending the preparation of the 
Stipulation and other documents and their presentation to the Court for its 
approval, the plaintiffs agree that they shall not move for preliminary 
injunction in the Litigation and all parties agree that all proceedings in the 
Litigation shall be suspended, except for the confirmatory discovery provided 
herein and any other matters as to which the parties may expressly agree.

     5.   CONFIRMATORY DISCOVERY. The parties shall conduct as expeditiously 
as possible such reasonable additional discovery as the parties agree or the 
Court orders is

                                       6

<PAGE>


necessary and appropriate to confirm the fairness and reasonableness of the 
terms of the Settlement.  Plaintiffs presently anticipate that up to four 
depositions will be required in addition to relevant document production in 
response to the Request for Production of Documents previously served by 
plaintiff's counsel. Plaintiffs reserve the right to withdraw from the terms 
of this Memorandum of Understanding and the proposed Settlement in the event 
that such discovery reveals that the Settlement is not fair and reasonable.

     6.   ATTORNEYS' FEES.  Conditional upon a Stipulation of Settlement 
being executed, Court approval of the Settlement (including the class 
certification and release) being granted, and the Court dismissing the 
Litigation with prejudice, all in accordance with the Stipulation of 
Settlement, plaintiffs' counsel of record in the Litigation will jointly 
apply at the settlement hearing to the Court for an award of attorneys' fees 
and expenses (including, but not limited to, fees and expenses of plaintiffs' 
counsels' independent financial advisor).  The parties shall attempt in good 
faith to agree on a maximum dollar amount of plaintiffs' counsel's fees 
application and, in the event they so agree the fee application shall not 
exceed that maximum dollar amount and the defendants will not oppose the 
application.  In the event the parties are unable to agree on a maximum 
dollar amount, plaintiffs' counsel may make a fee petition in any amount, 
without limitation, but the defendants shall reserve the rights to make any 
and all objections to the petition, or any part thereof, on any relevant 
grounds, plaintiffs shall reserve the right to oppose any and all such 
objections and pursue any additional relevant discovery pertaining thereto, 
and defendants shall reserve the right to oppose such discovery on any 
applicable ground.  Subject to the conditions set forth in this Memorandum of 
Understanding and any order of the Court, any and all attorneys' fees and 
expenses awarded by the Court to

                                       7

<PAGE>

plaintiffs' counsel may be paid by any combination of TDCC, DAS, Mycogen 
and/or their successors in interest on behalf of all defendants to the order 
of Milberg Weiss Bershad Hynes & Lerach LLP, as receiving agent for 
plaintiffs' counsel, within ten days after final Court approval of the 
Settlement (as defined in paragraph 3 hereof) and dismissal, with prejudice 
and without costs or fees (except as otherwise set forth in this paragraph), 
of the Litigation.  TDCC, DAS and/or Mycogen or their successors in interest 
shall also cause the dissemination of notice of the Settlement to the Class 
in such manner as the Court determines to be appropriate, and shall pay all 
costs and expenses incurred in providing such notice to the members of the 
Class.

     7.   CONDITIONS TO SETTLEMENT.  The consummation of the Settlement is 
subject to (a) the completion by plaintiffs' counsel of confirmatory 
discovery as provided above; (b) confirmation by plaintiffs' counsel 
following such confirmatory discovery that the Settlement is fair and 
reasonable, (c) drafting and execution of the Stipulation and such other 
documentation as may be required to obtain final Court approval of the 
Settlement in a form satisfactory to the parties; (d) consummation of the 
Tender Offer, and (e) final Court approval of the Settlement and the 
Stipulation, including class certification, release, and dismissal with 
prejudice as set forth above.  The consummation of the Merger shall not be a 
condition of this Memorandum of Understanding or of the Settlement.  In the 
event that the Settlement is not consummated for any reason, neither this 
Memorandum of Understanding, anything contained herein, nor anything done or 
disclosed by any person or party in connection herewith shall be deemed to 
prejudice in any way the positions of any party with respect to the 
Litigation.  In such event, neither the existence of this Memorandum of 
Understanding nor its contents shall be admissible in evidence or shall be 
referred to for any purpose in the Litigation or in any other litigation or 
proceeding.

                                       8

<PAGE>

     8.   COUNTERPARTS.  This Memorandum of Understanding may be executed in 
counterpart by any of the signatories hereto, including by telecopier, and as 
so executed shall constitute one agreement.

     9.   GOVERNING LAW.  This Memorandum of Understanding and the Settlement 
contemplated by it shall be governed by, and construed in accordance with, 
the laws of the State of California, without regard to California's conflict 
of law rules.

    10.   MODIFICATION.  This Memorandum of Understanding may be modified or 
amended only by a writing signed by the signatories hereto.

    11.   BINDING EFFECT.  This Memorandum of Understanding shall be binding 
upon and inure to the benefit of the parties and their respective agents, 
executors, heirs, successors and assigns.



                                       9


<PAGE>


          12.     CONFIDENTIALITY OF INFORMATION. All agreements by, between 
or among the parties, their counsel and their other advisors as to the 
confidentiality of information exchanged between or among them shall remain 
in full force and effect, and shall survive the execution of this Memorandum 
of Understanding and the consummation of the Settlement, if consummated, 
without regard to any of the conditions of the Settlement.


Dated:  September __, 1998             MILBERG WEISS BERSHAD HYNES &
                                       LERACH LLP


                                  By:  _______________________________________
                                       STEVEN G. SCHULMAN
                                       SETH OTTENSOSER
                                       One Pennsylvania Plaza, 49th Floor
                                       New York, New York 10119
                                       (212) 594-5300



                                       MILBERG WEISS BERSHAD HYNES &
                                         LERACH LLP
                                       WILLIAM S. LERACH
                                       STEVEN W. PEPICH
                                       RANDALL J. BARON
                                       600 West Broadway, Suite 1800
                                       San Diego, CA 92101
                                       Telephone: 619/231-1058


                                       ABBEY, GARDY & SQUITIERI, LLP


DATED: September __, 1998         By:  _______________________________________
                                       ARTHUR ABBEY
                                       MARK C. GARDY
                                       JAMES S. NOTIS
                                       212 East 39th Street
                                       New York, NY 10016
                                       Telephone: 212/889-3700

                                       CO-LEAD COUNSEL FOR PLAINTIFFS

                                       10

<PAGE>

                                       MAYER, BROWN & PLATT


DATED: September 3, 1998          By:  /s/ Bennett W. Lasko
                                       _______________________________________
                                       HERBERT L. ZAROV
                                       BENNETT W. LASKO
                                       190 South La Salle Street
                                       Chicago, IL 60603-3411
                                       Telephone: 312/782-0600

                                       MAYER, BROWN & PLATT
                                       FREDERICK S. LEVIN
                                       350 South Grand Avenue
                                       25th Floor
                                       Los Angeles, CA 90071
                                       Telephone: 213/229-9500

                                       ATTORNEYS FOR DEFENDANTS
                                       DOW AGROSCIENCES, THE DOW CHEMICAL CO.
                                       CARLTON J. EIBL, JOHN L. HAGAMAN, 
                                       NICKOLAS D. HEIN, LOUIS W. PRIBILA, G. 
                                       WILLIAM TOLBERT, J. PEDRO REINHARD, 
                                       ROY M. BARBEE, WILLIAM C. SCHMIDT AND 
                                       PERRY J. GEHRING

                                       ALTHEIMER & GRAY


DATED: September 3, 1998          By:  illegible
                                       __________________________________
                                       THEODORE J. LOW
                                       10 South Wacker Drive
                                       Suite 4000
                                       Chicago, IL 60606
                                       Telephone: 312/715-4000


                                       GRAY, CARY, WARE & FREIDENRICH
                                       ROBERT W. BROWNLIE
                                       401 B Street, Suite 1700
                                       San Diego, CA 92101-4297
                                       Telephone: 619/699-2700


                                       ATTORNEYS FOR DEFENDANTS
                                       MYCOGEN CORP., JOSEPH P. SULLIVAN, AND
                                       GEORGE KHACHATOURIANS

                                       11





<PAGE>
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
                              MYCOGEN CORPORATION
                                       AT
                              $28.00 NET PER SHARE
                                       BY
                         AGROSCIENCES ACQUISITION INC.
                         A MAJORITY-OWNED SUBSIDIARY OF
                              DOW AGROSCIENCES LLC
                   AND A WHOLLY OWNED INDIRECT SUBSIDIARY OF
                            THE DOW CHEMICAL COMPANY
 
 THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME,
           ON FRIDAY, OCTOBER 2, 1998, UNLESS THE OFFER IS EXTENDED.
 
    THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT PROPERLY WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER A
NUMBER OF SHARES OF COMMON STOCK, PAR VALUE $0.001 PER SHARE (INCLUDING THE
ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS) (THE "SHARES"), OF MYCOGEN
CORPORATION (THE "COMPANY") SUCH THAT, UPON PURCHASE OF SUCH SHARES BY
AGROSCIENCES ACQUISITION INC. ("PURCHASER"), PURCHASER AND DOW AGROSCIENCES LLC
("PARENT"), COLLECTIVELY, WILL BE THE OWNERS OF SHARES REPRESENTING AT LEAST 90%
OF THE FULLY DILUTED SHARES (AS DEFINED IN THE INTRODUCTION OF THIS OFFER TO
PURCHASE). THE OFFER IS ALSO SUBJECT TO OTHER TERMS AND CONDITIONS CONTAINED IN
THIS OFFER TO PURCHASE. SEE THE INTRODUCTION AND SECTIONS 1 AND 13 HEREOF.
 
    THE OFFER IS BEING MADE PURSUANT TO THE AGREEMENT AND PLAN OF MERGER (THE
"MERGER AGREEMENT") DATED AS OF AUGUST 31, 1998, AMONG THE COMPANY, PARENT,
PURCHASER, AND, FOR THE LIMITED PURPOSE SET FORTH IN THE MERGER AGREEMENT, THE
DOW CHEMICAL COMPANY ("TDCC"). UNDER THE MERGER AGREEMENT, FOLLOWING THE
CONSUMMATION OF THE OFFER AND SUBJECT TO CERTAIN CONDITIONS, PURCHASER WILL BE
MERGED WITH AND INTO THE COMPANY (THE "MERGER"). IN THE MERGER, EACH OUTSTANDING
SHARE (OTHER THAN SHARES HELD BY PARENT, PURCHASER OR THE COMPANY, WHICH SHALL
BE CANCELED, AND SHARES HELD BY STOCKHOLDERS WHO PROPERLY EXERCISE DISSENTERS'
RIGHTS UNDER CALIFORNIA LAW) WOULD BE CONVERTED INTO THE RIGHT TO RECEIVE $28.00
PER SHARE, AND THE COMPANY WOULD BECOME AN INDIRECT WHOLLY OWNED SUBSIDIARY OF
TDCC.
 
    A SPECIAL COMMITTEE OF TWO OF THE COMPANY'S DIRECTORS INDEPENDENT OF TDCC,
PARENT, PURCHASER AND MANAGEMENT OF THE COMPANY (THE "SPECIAL COMMITTEE")
UNANIMOUSLY RECOMMENDED TO THE COMPANY'S BOARD OF DIRECTORS THAT IT ENTER INTO
THE MERGER AGREEMENT AND APPROVE THE OFFER. THE COMPANY'S BOARD OF DIRECTORS
UNANIMOUSLY HAS APPROVED THE OFFER AND RECOMMENDS THAT STOCKHOLDERS OF THE
COMPANY ACCEPT THE OFFER AND TENDER THEIR SHARES. THE OFFER IS BEING EFFECTED TO
FACILITATE THE MERGER. SEE "RECOMMENDATION OF THE COMPANY'S BOARD OF DIRECTORS."
 
                               ------------------
 
                                   IMPORTANT
 
    Any stockholder desiring to tender all or any portion of such stockholder's
Shares, should either (1) complete and sign the Letter of Transmittal (or a
facsimile thereof) in accordance with the instructions in the Letter of
Transmittal and deliver it and any other required documents to the Depositary
and either deliver the certificate(s) representing such Shares to the Depositary
along with the Letter of Transmittal or tender such Shares pursuant to the
procedure for book-entry transfer set forth in Section 3 hereof or (2) request
such stockholder's broker, dealer, commercial bank, trust company or other
nominee to effect the transaction for such stockholder. Any stockholder whose
Shares are registered in the name of a broker, dealer, commercial bank, trust
company or other nominee must contact such broker, dealer, commercial bank,
trust company or other nominee if such stockholder desires to tender such
Shares.
 
    A stockholder who desires to tender Shares and whose certificates
representing such Shares are not immediately available, or who cannot comply
with the procedure for book-entry transfer on a timely basis, may tender such
Shares by following the procedures for guaranteed delivery set forth in Section
3.
 
    Questions and requests for assistance or additional copies of this Offer to
Purchase, the Letter of Transmittal and the Notice of Guaranteed Delivery may be
directed to Salomon Smith Barney Inc. ("Salomon Smith Barney") or to the
Information Agent, at their respective addresses and telephone numbers set forth
on the back cover of this Offer to Purchase. Additional copies of this Offer to
Purchase, the Letter of Transmittal and the Notice of Guaranteed Delivery may be
obtained from the Information Agent or from brokers, dealers, commercial banks
or trust companies.
 
                               ------------------
 
                      The Dealer Manager for the Offer is:
                           SALOMON SMITH BARNEY INC.
 
                               ------------------
 
            The date of this Offer to Purchase is September 4, 1998.
<PAGE>
                               TABLE OF CONTENTS
 
<TABLE>
<CAPTION>
                                                                                                              PAGE
                                                                                                            ---------
<S>                                                                                                         <C>
INTRODUCTION..............................................................................................          1
 
RECOMMENDATION OF THE COMPANY'S BOARD OF DIRECTORS........................................................          3
 
THE TENDER OFFER..........................................................................................          3
 
   1.  Terms of the Offer; Extension of Tender Period; Termination; Amendment.............................          3
 
   2.  Acceptance for Payment and Payment for Shares......................................................          5
 
   3.  Procedure for Tendering Shares.....................................................................          6
 
   4.  Withdrawal Rights; Statutory Rights................................................................         10
 
   5.  Certain U.S. Federal Income Tax Considerations.....................................................         10
 
   6.  Price Range of the Shares..........................................................................         12
 
   7.  Certain Information Concerning the Company.........................................................         13
 
   8.  Certain Information Concerning Purchaser, Parent and Certain Affiliates of Parent..................         14
 
   9.  Background of the Offer............................................................................         16
 
  10.  Purpose of the Offer; the Merger Agreement.........................................................         41
 
  11.  Source and Amount of Funds.........................................................................         52
 
  12.  Certain Effects of the Offer.......................................................................         52
 
  13.  Certain Conditions of the Offer....................................................................         54
 
  14.  Certain Legal Matters; Regulatory Approvals........................................................         56
 
  15.  Fees and Expenses..................................................................................         56
 
  16.  Miscellaneous......................................................................................         57
 
Schedule I--Information Concerning the Directors and Executive Officers of Parent, Purchaser and Certain
  Affiliates of Parent....................................................................................        I-1
 
Schedule II--Chapter 13 of the California General Corporation Law.........................................       II-1
 
Schedule III--Opinion of Wasserstein Perella & Co., Inc...................................................      III-1
</TABLE>
 
                                       i
<PAGE>
To the Stockholders of Mycogen Corporation:
 
                                  INTRODUCTION
 
    AgroSciences Acquisition Inc., a Delaware corporation ("Purchaser") and a
majority-owned subsidiary of Dow AgroSciences LLC, a Delaware limited liability
company ("Parent"), hereby offers to purchase all of the outstanding shares of
common stock, par value $0.001 per share (including the associated preferred
stock purchase rights) (the "Shares"), of Mycogen Corporation, a California
corporation (the "Company"), at a purchase price of $28.00 per Share (the "Offer
Price"), net to the seller in cash, in accordance with the terms and subject to
the conditions set forth in this Offer to Purchase and in the related Letter of
Transmittal (which, as amended from time to time, collectively constitute the
"Offer"). Parent and Purchaser are each indirect wholly owned subsidiaries of
The Dow Chemical Company, a Delaware corporation ("TDCC").
 
    The Offer is being made in connection with an Agreement and Plan of Merger
(the "Merger Agreement") dated as of August 31, 1998, among the Company,
Purchaser, Parent and, for the limited purpose set forth in the Merger
Agreement, TDCC. The Merger Agreement requires Purchaser, on the terms and
subject to the conditions set forth therein, to offer to purchase all of the
outstanding Shares of the Company pursuant to the Offer.
 
    The Offer is conditioned upon, among other things, there being validly
tendered and not properly withdrawn prior to the expiration of the Offer a
number of Shares such that upon purchase of such Shares by Purchaser, Purchaser
and Parent, collectively, will be the owners of Shares representing at least 90%
of the Fully Diluted Shares (as defined below) (the "Minimum Condition").
Purchaser may not waive the Minimum Condition without the consent of the Special
Committee (as defined below) unless, following the consummation of the Offer,
Purchaser and Parent, collectively, would be the owners of Shares representing
at least 81.07% of the Fully Diluted Shares. Parent and Purchaser would
collectively own at least this percentage of Fully Diluted Shares only if
Purchaser purchased at least a majority of the Fully Diluted Shares which Parent
does not already own and therefore could be purchased by Purchaser pursuant to
the Offer. The Offer is also subject to the other terms and conditions contained
in this Offer to Purchase. See Sections 1 and 13.
 
    "Fully Diluted Shares" as of a particular date means the issued and
outstanding Shares as of such date, plus the Shares that would be issued if all
options to purchase Shares under the Company's option plan ("Options") (whether
or not vested) outstanding as of that date were exercisable and exercised and
all Shares that would be issued if all eligible persons executed and delivered
to the Company valid Stock Purchase Elections (as defined in Section 10 hereof)
under the Company's Stock Purchase Plan.
 
    As of August 31, 1998, there were outstanding 36,275,538 Shares held by
approximately 4,700 holders of record, of which Parent owned 24,766,157 Shares,
or 68.3%. As of August 31, 1998, Options covering a total of 3,568,635 Shares
were outstanding. Unless Parent consents, the Company may not issue additional
Options prior to the consummation of the Offer. Under the Merger Agreement, all
unvested Options will become exercisable immediately prior to the expiration of
the Offer (contingent upon Purchaser purchasing Shares in the Offer), and all
Shares issuable upon the exercise of Options (whether or not previously vested)
may be tendered in the Offer. Under the Merger Agreement, Shares that would be
issuable under the Company's Stock Purchase Plan as of November 30, 1998 may be
purchased immediately prior to the expiration of the Offer (contingent upon
Purchaser purchasing Shares in the Offer) and tendered in the Offer. The Company
anticipates that there will be no more than 24,000 Shares issuable under the
Stock Purchase Plan that would be issued and tendered in the Offer. Under the
Merger Agreement, the Shares outstanding under the Restricted Stock Plan may be
tendered in the Offer (contingent upon Purchaser purchasing Shares in the
Offer). Assuming that no additional Options are issued and that 24,000 Shares
are issued under the Stock Purchase Plan, Purchaser estimates that there must be
approximately 11,115,000 Shares (including Shares tendered after being issued
upon the exercise of Options or under the Stock Purchase Plan and including
Shares of Restricted Stock) validly tendered and not properly withdrawn in order
to satisfy the Minimum Condition.
<PAGE>
    Under the Merger Agreement, following the consummation of the Offer and
subject to certain conditions, Purchaser will merge with and into the Company
(the "Merger"). In the Merger, each outstanding Share of the Company (other than
Shares held by Parent, Purchaser and the Company which will be canceled, and
Shares held by stockholders who properly exercise dissenters' rights under
California Law) will be converted into the right to receive an amount in cash
equal to the Offer Price. Assuming Shares are purchased in the Offer, the
conditions to the Merger, described in more detail in Section 10, include that
Purchaser, assuming the transfer of all Shares owned by Parent to Purchaser, own
at least 90% of the outstanding Shares and that there not be any order, decree,
ruling or other governmental action restraining or prohibiting the Merger.
Following the consummation of the Merger, the Company will continue as the
surviving corporation (the "Surviving Corporation") and will be a majority-owned
subsidiary of Parent and a wholly owned indirect subsidiary of TDCC. If
Purchaser elects to waive the Minimum Condition and purchase Shares pursuant to
the Offer, but, subsequent to the Offer, does not own a sufficient number of
Shares to effect the Merger, then, pursuant to the terms of the Merger
Agreement, the Exchange and Purchase Agreement (as defined in Section 9) would
no longer prevent Purchaser, Parent or their affiliates from acquiring
additional Shares or impose conditions on the acquisition of additional Shares
or increasing their ownership of the Company (whether through any tender offer,
open market purchase, negotiated transaction, merger, consolidation, reverse
stock split or otherwise).
 
    A SPECIAL COMMITTEE OF TWO OF THE COMPANY'S DIRECTORS INDEPENDENT OF TDCC,
PARENT, PURCHASER AND MANAGEMENT OF THE COMPANY (THE "SPECIAL COMMITTEE")
UNANIMOUSLY RECOMMENDED TO THE COMPANY'S BOARD OF DIRECTORS THAT THE COMPANY
ENTER INTO THE MERGER AGREEMENT AND THAT THE BOARD OF DIRECTORS APPROVE THE
OFFER. THE COMPANY'S ENTIRE BOARD OF DIRECTORS ALSO REVIEWED THE OFFER AND,
AFTER RECEIPT OF THE RECOMMENDATION OF THE SPECIAL COMMITTEE, CONCLUDED THAT THE
OFFER IS IN THE BEST INTERESTS OF THE COMPANY AND ITS STOCKHOLDERS (OTHER THAN
TDCC OR ITS AFFILIATES). ACCORDINGLY, THE COMPANY'S BOARD OF DIRECTORS
UNANIMOUSLY HAS DETERMINED THAT EACH OF (1) THE OFFER AND (2) THE MERGER IS FAIR
TO AND IN THE BEST INTERESTS OF THE STOCKHOLDERS OF THE COMPANY (OTHER THAN TDCC
OR ITS AFFILIATES) AND UNANIMOUSLY HAS APPROVED THE OFFER AND RECOMMENDS THAT
STOCKHOLDERS OF THE COMPANY ACCEPT THE OFFER AND TENDER THEIR SHARES. SEE
"RECOMMENDATION OF THE COMPANY'S BOARD OF DIRECTORS."
 
    Tendering stockholders will not be obligated to pay brokerage fees or
commissions or, except as set forth in Instruction 6 of the Letter of
Transmittal, transfer taxes on the transfer and sale of Shares pursuant to the
Offer. Purchaser will pay all fees and expenses of Salomon Smith Barney Inc.
("Salomon Smith Barney"), which is acting as Dealer Manager for the Offer (the
"Dealer Manager"), BankBoston, N.A. (the "Depositary") and Georgeson & Company
Inc. (the "Information Agent") incurred in connection with the Offer. See
Section 15.
 
    The purpose of the Offer is for Parent, through Purchaser, to acquire any
and all outstanding Shares and to facilitate the Merger. On August 31, 1998, the
closing market price of the Company's Shares was $20.00 per Share. Accordingly,
the Offer provides an opportunity to existing stockholders of the Company to
sell Shares at a significant premium over recent trading prices. See Section 6.
 
    THIS OFFER TO PURCHASE DOES NOT CONSTITUTE A SOLICITATION OF A PROXY,
CONSENT OR AUTHORIZATION FOR OR WITH RESPECT TO AN ANNUAL MEETING OR ANY SPECIAL
MEETING OF THE COMPANY'S STOCKHOLDERS OR ANY ACTION IN LIEU THEREOF. ANY SUCH
SOLICITATION, IF REQUIRED, WILL BE MADE ONLY PURSUANT TO SEPARATE PROXY
MATERIALS IN COMPLIANCE WITH THE REQUIREMENTS OF SECTION 14(A) OF THE SECURITIES
EXCHANGE ACT OF 1934, AS AMENDED (THE "EXCHANGE ACT").
 
    Information concerning the Company contained herein has been provided by the
Company unless otherwise stated.
 
                                 *  *  *  *  *
 
                                       2
<PAGE>
    Subject to certain exceptions set forth below, Purchaser expressly reserves
the right to waive any one or more of the conditions to the Offer. See Sections
1 and 13.
 
    Stockholders are urged to read this Offer to Purchase and the related Letter
of Transmittal carefully before deciding whether to tender their Shares.
 
               RECOMMENDATION OF THE COMPANY'S BOARD OF DIRECTORS
 
    The Special Committee unanimously recommended to the Company's Board of
Directors that it approve the Offer. The Company's entire Board of Directors
also reviewed the Offer and, after receipt of the recommendation of the Special
Committee, concluded that the Offer is in the best interests of the Company and
its stockholders (other than TDCC or its affiliates). Accordingly, the Company's
Board of Directors has unanimously (1) determined that the Merger Agreement is
fair to and in the best interests of the stockholders of the Company other than
TDCC or its affiliates (the "Minority Stockholders") (2) approved and adopted
the Merger Agreement, including the Merger and the Offer, and recommends that
the stockholders of the Company accept the Offer, tender their Shares to
Purchaser and, if required by applicable law, approve and adopt the Merger
Agreement and the Merger. The Offer is being effected to acquire any and all
outstanding Shares and to facilitate the Merger. The Offer allows stockholders
to receive cash at a premium over recent trading prices for the Company's
Shares. See Sections 6 and 9.
 
    The Special Committee's financial advisor, Wasserstein Perella & Co., Inc.
("Wasserstein Perella") has delivered to the Special Committee its written
opinion, dated August 31, 1998, to the effect that, subject to the various
assumptions and limitations set forth therein, as of the date of such opinion,
the $28.00 cash price to be received by the holders of Shares (other than TDCC
and its affiliates) pursuant to the Merger Agreement is fair to such holders
from a financial point of view. A copy of the full text of the opinion of
Wasserstein Perella, dated August 31, 1998, which sets forth, among other
things, the opinion expressed, assumptions made, procedures followed, matters
considered and limitations of review undertaken in connection with such opinion,
is attached as Schedule III hereto and should be read in its entirety.
 
                                THE TENDER OFFER
 
1. TERMS OF THE OFFER; EXTENSION OF TENDER PERIOD; TERMINATION; AMENDMENT
 
    Upon the terms and subject to the conditions of the Offer (including, if the
Offer is extended or amended, the terms and conditions of any such extension or
amendment), Purchaser will accept for payment and pay for all Shares validly
tendered and not properly withdrawn on or prior to the Expiration Date (as
hereinafter defined) at a price of $28.00 per Share, net to the seller in cash.
Purchaser may not make a material change to the terms of the Offer other than
pursuant to the Merger Agreement or an amendment thereto. The term "Expiration
Date" means 12:00 Midnight, New York City time, on Friday, October 2, 1998,
unless Purchaser shall have extended the period during which the Offer is open,
in which event the term "Expiration Date" shall mean the latest time and date at
which the Offer, as so extended by Purchaser, shall expire.
 
    The Offer is conditioned upon, among other things, satisfaction of the
Minimum Condition. The Offer is also subject to certain other conditions set
forth in Section 13. Purchaser may waive the Minimum Condition if, following the
consummation of the Offer, Purchaser and Parent collectively would be the owners
of Shares representing at least 81.07% of the Fully Diluted Shares. Parent and
Purchaser would collectively own at least this percentage of Fully Diluted
Shares only if Purchaser purchased at least a majority of the Fully Diluted
Shares which Parent does not already own and therefore could be purchased by
Purchaser pursuant to the Offer. Purchaser may not waive the Minimum Condition
(unless the Special Committee consents) if, following the consummation of the
Offer, Purchaser and Parent, collectively, would be the owners of Shares
representing less than 81.07% of the Fully Diluted Shares.
 
                                       3
<PAGE>
    Purchaser expressly reserves the right, in its reasonable discretion, to
extend the Offer (i) for any period required by any rule, regulation,
interpretation or position of the Securities and Exchange Commission (the
"Commission") or the staff thereof applicable to the Offer, (ii) if at any
scheduled expiration date any of the conditions to the Offer set forth in
paragraphs (a) - (e) of Section 13 have not been satisfied or waived, until such
time as all of such conditions will have been satisfied or waived, (iii) in the
event all of the conditions to the Offer will have been satisfied or waived,
other than the Minimum Condition, for a period or periods aggregating not more
than 40 business days after the later of (A) the initial expiration date of the
Offer and (B) the date on which all of the conditions set forth in paragraphs
(a) - (e) of Section 13 will have been satisfied or waived or (iv) as may
otherwise be permitted pursuant to the Merger Agreement or any amendment to the
Merger Agreement. If at any scheduled expiration date of the Offer, the Minimum
Condition will not have been satisfied, then, at the request of the Company
(acting at the direction of the Special Committee, which request will
subsequently be confirmed in writing), Purchaser will, and Parent will cause
Purchaser to, extend the Offer for a period or periods aggregating not more than
40 business days, subject to the right of Purchaser and Parent to terminate the
Merger Agreement as described herein. In addition, if at any scheduled
expiration date of the Offer, a condition set forth in paragraph (c) or (d) of
Section 13 will not have been satisfied but all of the other conditions set
forth in paragraphs (a) - (e) of Section 13 will then have been satisfied, then,
at the request of the Company (acting at the direction of the Special Committee,
which request will subsequently be confirmed in writing) and so long as the
Company is using its reasonable best efforts to cause such conditions to become
satisfied, Purchaser will, and Parent will cause Purchaser to, extend the Offer
for up to an additional 20 business days, subject to the right of Purchaser and
Parent to terminate the Merger Agreement as described in Section 10. Subject to
the right of Purchaser and Parent to terminate the Merger Agreement as described
in Section 10, Purchaser will not terminate or withdraw the Offer prior to any
scheduled expiration date of the Offer, including as extended as described in
this paragraph; provided, however, that Purchaser may, at its option, terminate
and withdraw the Offer if, after such extensions described in this paragraph,
the Offer has expired in accordance with its terms without Purchaser being
required to accept Shares for payment pursuant to the Merger Agreement.
 
    Purchaser reserves the right to extend, delay, terminate or amend the Offer
or waive satisfaction of any condition to the Offer but only as, when and to the
extent permitted by the Merger Agreement or any amendment to the Merger
Agreement. Any extension, termination or waiver of the Offer will be made by
giving oral or written notice of such extension, termination or waiver to the
Depositary and by causing the Depositary to provide as soon as practicable
thereafter a copy of such notice to all holders of Shares whose Shares have not
been taken up prior to the extension. Purchaser acknowledges that (i) Rule
14e-1(c) under the Exchange Act requires Purchaser to pay the consideration
offered or return the Shares tendered promptly after the termination or
withdrawal of the Offer and (ii) Purchaser may not delay acceptance for payment
of (except as provided by clause (i)) any Shares upon the occurrence of any of
the conditions specified in Section 13 without extending the period of time
during which the Offer is open.
 
    Purchaser may increase the Offer Price and may waive any condition to the
Offer, except that it may not waive the Minimum Condition unless either (i) the
Special Committee consents or (ii) following consummation of the Offer,
Purchaser and Parent collectively would be the owners of at least 81.07% of the
Fully Diluted Shares. In addition, without the consent of the Special Committee,
no change to the Offer may be made that decreases the price per Share payable in
the Offer, changes the form of consideration payable in the Offer, reduces the
maximum number of Shares to be purchased in the Offer or imposes conditions to
the Offer in addition to the conditions set forth in Section 13.
 
    Any such extension, termination or waiver will be followed as promptly as
practicable by public announcement thereof, and such announcement in the case of
an extension will be made no later than 9:00 a.m., New York City time, on the
next business day after the previously scheduled Expiration Date. Without
limiting the manner in which Purchaser may choose to make any public
announcement, except as provided by applicable law (including Rules 14d-4(c) and
14d-6(d) under the Exchange Act, which require
 
                                       4
<PAGE>
that material changes be promptly disseminated to holders of Shares), Purchaser
shall have no obligation to publish, advertise or otherwise communicate any such
announcement other than by issuing a release to the Dow Jones News Service or as
otherwise may be required by law.
 
    If Purchaser makes a material change in the terms of the Offer or if
Purchaser waives a material condition of the Offer, Purchaser will extend the
Offer to the extent required by Rules 14d-4(c) and 14d-6(d) under the Exchange
Act. The minimum period during which an offer must remain open following
material changes in the terms of the Offer, other than a change in price or a
change in the percentages of securities sought, will depend on the facts and
circumstances, including the materiality, of the changes. With respect to a
change in price or, subject to certain limitations, a change in the percentage
of securities sought, a minimum ten business day period from the day of such
change is generally required to allow for adequate dissemination to
stockholders. Accordingly, if prior to the Expiration Date, Purchaser decreases
the number of Shares being sought, increases or decreases the consideration
offered pursuant to the Offer and if the Offer is scheduled to expire at any
time earlier than the period ending on the tenth business day from the date that
notice of such increase or decrease is first published, sent or given to
stockholders, the Offer will be extended at least until the expiration of such
ten business day period. Except as otherwise provided herein, any extension of
the Offer will not constitute a waiver by Purchaser of any of the conditions set
forth in Section 13.
 
2.  ACCEPTANCE FOR PAYMENT AND PAYMENT FOR SHARES
 
    Upon the terms and subject to the conditions of the Offer (including, if the
Offer is extended or amended, the terms and conditions of any such extension or
amendment), Purchaser will accept for payment all Shares validly tendered and
not properly withdrawn on or prior to the Expiration Date as soon as practicable
after the later to occur of (i) the Expiration Date and (ii) the date of
satisfaction or waiver of the conditions set forth in Section 13. As promptly as
practicable after such acceptance, Purchaser shall, subject to applicable law,
pay for such Shares.
 
    For purposes of the Offer, Purchaser shall be deemed to have accepted for
payment and thereby purchased tendered Shares of the Company if, as and when
Purchaser gives oral or written notice to the Depositary of its acceptance of
such Shares for payment pursuant to the Offer. Payment for Shares of the Company
accepted for payment pursuant to the Offer will be made by deposit by Purchaser
of the purchase price to be paid by it with the Depositary, which Depositary
will act as agent for the tendering stockholders for the purpose of receiving
payments from Purchaser and transmitting such payments to tendering
stockholders. Under no circumstances will interest be paid by Purchaser on the
consideration paid for the Shares of the Company pursuant to the Offer,
regardless of any delay in making such payment. Purchaser will pay all stock
transfer taxes, if any, payable on the transfer of Shares of the Company
purchased by it pursuant to the Offer, except as set forth in Instruction 6 of
the Letter of Transmittal.
 
    In all cases, payment for Shares tendered and accepted for payment pursuant
to the Offer will be made only after timely receipt by the Depositary of a
certificate(s) for such Shares or a timely confirmation of a book-entry transfer
of such Shares into the Depositary's account at the Book-Entry Transfer Facility
(as defined in Section 3), a Letter of Transmittal (or a facsimile thereof),
properly completed and duly executed, with any required signature guarantees or
Agent's Message (as defined in Section 3) and any other documents required by
the Letter of Transmittal. For a description of the procedure for tendering
Shares of the Company pursuant to the Offer, see Section 3.
 
    If any tendered Shares are not accepted for payment for any reason or if
certificate(s) are submitted for more Shares than are tendered, certificates
evidencing unpurchased or untendered Shares will be returned without expense to
the tendering stockholder (or, in the case of Shares tendered by book-entry
transfer into the Depositary's account at the Book-Entry Transfer Facility
pursuant to the procedures set forth in Section 3, such Shares will be credited
to an account maintained at the Book-Entry Transfer Facility) as promptly as
practicable following the expiration, termination or withdrawal of the Offer.
 
                                       5
<PAGE>
    If Purchaser increases the consideration offered to stockholders pursuant to
the Offer, such increased consideration will be paid to all stockholders whose
Shares are purchased pursuant to the Offer, whether or not such Shares were
tendered or accepted for payment prior to such increase in consideration.
 
    Purchaser reserves the right to assign, in whole or from time to time in
part, to Parent or an affiliate of Parent, the right to purchase all or any
portion of the Shares tendered pursuant to the Offer, but any such assignment
will not relieve Purchaser of its obligations under the Offer nor will any such
assignment prejudice in any way the rights of tendering stockholders to receive
payment for Shares validly tendered and accepted for payment pursuant to the
Offer.
 
    During the pendency of the Offer, Purchaser will not purchase any Shares,
whether in the open market or otherwise, except pursuant to the Offer.
 
3.  PROCEDURE FOR TENDERING SHARES
 
VALID TENDER OF SHARES
 
    Except as set forth below, in order for Shares to be validly tendered
pursuant to the Offer, the Letter of Transmittal (or a facsimile thereof),
properly completed and duly executed, together with any required signature
guarantees, or an Agent's Message (as defined below) in connection with a
book-entry delivery of Shares as described below, and any other documents
required by the Letter of Transmittal, must be received by the Depositary at one
of its addresses set forth on the back cover of this Offer to Purchase. In
addition, either (i) certificates evidencing tendered Shares must be received by
the Depositary at any such address or such Shares must be tendered pursuant to
the procedure for book-entry transfer (and a confirmation of receipt of such
delivery must be received by the Depositary), in each case, on or prior to the
Expiration Date or (ii) the guaranteed delivery procedures set forth below must
be complied with. The term "Agent's Message" means a message transmitted by The
Depository Trust Company (the "Book-Entry Transfer Facility") to and received by
the Depositary and forming a part of a Book-Entry Confirmation, which states
that the Book-Entry Transfer Facility has received an express acknowledgment
from the participant in the Book-Entry Transfer Facility tendering the Shares
which are the subject of the Book-Entry Confirmation, that such participant has
received and agrees to be bound by the terms of the Letter of Transmittal and
that Purchaser may enforce such agreement against such participant.
 
BOOK-ENTRY TRANSFER
 
    The Depositary will establish an account with respect to the Shares at the
Book-Entry Transfer Facility for purposes of the Offer within two business days
after the date of this Offer to Purchase. Any financial institution that is a
participant in the system of the Book-Entry Transfer Facility may make
book-entry delivery of Shares by causing the Book-Entry Transfer Facility to
transfer such Shares into the Depositary's account in accordance with the
Book-Entry Transfer Facility's procedures for such transfer. Although delivery
of Shares may be effected through book-entry transfer at the Book-Entry Transfer
Facility, the Letter of Transmittal (or a facsimile thereof), properly completed
and duly executed, together with any required signature guarantees, or an
Agent's Message in connection with a book-entry transfer, and any other required
documents, must, in any case, be received by the Depositary at one of its
addresses set forth on the back cover of this Offer to Purchase on or prior to
the Expiration Date, or the guaranteed delivery procedures described below must
be complied with.
 
    DELIVERY OF DOCUMENTS TO THE BOOK-ENTRY TRANSFER FACILITY IN ACCORDANCE WITH
THE BOOK-ENTRY TRANSFER FACILITY'S PROCEDURES DOES NOT CONSTITUTE DELIVERY TO
THE DEPOSITARY.
 
SIGNATURE GUARANTEES
 
    Except as otherwise provided below, signatures on Letters of Transmittal
must be guaranteed by a member firm of a registered national securities
exchange, a member of the National Association of
 
                                       6
<PAGE>
Securities Dealers, Inc. (the "NASD"), or a commercial bank or trust company
having an office, branch, agency or correspondent in the United States (each of
the foregoing constituting an "Eligible Institution"). Signatures on Letters of
Transmittal need not be guaranteed if (i) the Letter of Transmittal is signed by
the registered holder of Shares tendered and such holder has not completed
either the box entitled "Special Delivery Instructions" or the box entitled
"Special Payment Instructions" on the Letter of Transmittal or (ii) such Shares
are tendered for the account of an Eligible Institution. See Instructions 1 and
5 of the Letter of Transmittal.
 
    If the certificates representing Shares are registered in the name of a
person other than the signer of the Letter of Transmittal, or if payment is to
be made or certificates for Shares not accepted for payment or not tendered are
to be returned to a person other than the registered holder, then the tendered
certificates must be endorsed or accompanied by appropriate stock powers, in
either case signed exactly as the name(s) of the registered holder(s) appear(s)
on the certificates, with the signatures on the certificates or stock powers
guaranteed as described above. See Instructions 1 and 5 of the Letter of
Transmittal.
 
GUARANTEED DELIVERY
 
    If a stockholder desires to tender Shares pursuant to the Offer and such
stockholder's certificates are not immediately available, or such stockholder
cannot deliver the certificates and all other required documents to reach the
Depositary on or prior to the Expiration Date, or such stockholder cannot
complete the procedure for book-entry transfer on a timely basis, such Shares
may nevertheless be tendered if the following guaranteed delivery procedures are
satisfied:
 
        (i) such tender is made by or through an Eligible Institution;
 
        (ii) a properly completed and duly executed Notice of Guaranteed
    Delivery, substantially in the form provided by Purchaser, is received by
    the Depositary as provided below on or prior to the Expiration Date; and
 
       (iii) the certificates (or a book-entry transfer confirmation)
    representing all tendered Shares, in proper form for transfer, in each case
    together with the Letter of Transmittal (or a facsimile thereof) properly
    completed and duly executed, with any required signature guarantees (or, in
    the case of a book-entry transfer, an Agent's Message) and any other
    documents required by the Letter of Transmittal are received by the
    Depositary within three NASDAQ National Market System ("NASDAQ NMS") trading
    days after the date of execution of such Notice of Guaranteed Delivery.
 
    The Notice of Guaranteed Delivery may be delivered by hand or transmitted by
telegram, telex, facsimile transmission or mail to the Depositary and must
include a guarantee by an Eligible Institution in the form set forth in such
Notice of Guaranteed Delivery.
 
    THE METHOD OF DELIVERY OF CERTIFICATES AND ALL OTHER REQUIRED DOCUMENTS,
INCLUDING DELIVERY THROUGH THE BOOK-ENTRY TRANSFER FACILITY, IS AT THE OPTION
AND RISK OF THE TENDERING STOCKHOLDER AND THE DELIVERY WILL BE DEEMED MADE ONLY
WHEN ACTUALLY RECEIVED BY THE DEPOSITARY. IF DELIVERY IS BY MAIL, REGISTERED
MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED IS RECOMMENDED. IN ALL
CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO INSURE TIMELY DELIVERY.
 
OPTIONS
 
    Under the Merger Agreement, holders of unvested Options outstanding under
the Mycogen Corporation 1992 Stock Option Plan (which incorporates outstanding
Options under the Mycogen Corporation 1983 Stock Option Plan (the "1992 Plan")
who submit valid Option Elections (as defined in Section 10) to the Company
prior to the expiration of the Offer will be able (contingent on the purchase by
Purchaser of Shares pursuant to the Offer) to exercise their Options immediately
prior to the expiration of the Offer and to tender the Shares issuable upon such
exercise in the Offer. All Option exercises must be effected through the
Company. A holder of Options who wishes to participate in the Offer must submit
to the
 
                                       7
<PAGE>
Company an Option Election pursuant to which such holder will be deemed,
immediately prior to the expiration of the Offer (and conditioned upon the
purchase by Purchaser of Shares pursuant to the Offer), to have (i) exercised
all of such holder's Options to purchase Shares and (ii) then tendered such
Shares pursuant to the Offer. Any such exercise of an Option and tender of
Shares must be in accordance with the terms of the 1992 Plan and the Options.
 
    In no event are any Options or Option Elections to be delivered to the
Depositary, Purchaser, Parent or any other person other than the Company in
connection with a tender of Shares hereunder.
 
    The Company will send or deliver to holders of Options additional materials
concerning the exercise of Options and the tender of Shares issuable upon
exercise of Options, including an Option Election. Holders should use the Option
Election to exercise Options and to tender Shares issuable upon exercise of
Options, as described above. HOLDERS OF OPTIONS MAY NOT USE THE LETTER OF
TRANSMITTAL TO DIRECT THE TENDER OF SHARES ISSUABLE UPON EXERCISE OF OPTIONS.
Questions with respect to tendering Shares issuable upon exercise of Options
should be directed to Mycogen Corporation, AgroSciences Tender Offer, 5501
Oberlin Drive, San Diego, California 92121, Attention: Cheri Manis; telephone
number (800) 745-7475.
 
    IN ORDER TO ASSURE THAT THE COMPANY, ON BEHALF OF HOLDERS OF OPTIONS WHO
EXERCISE THEIR OPTIONS PURSUANT TO OPTION ELECTIONS, CAN TIMELY TENDER SHARES
ISSUABLE UPON EXERCISE OF OPTIONS, HOLDERS OF OPTIONS SHOULD COMPLETE AND RETURN
THE OPTION ELECTION SO THAT IT IS RECEIVED BY THE COMPANY NO LATER THAN 5:00
P.M., SAN DIEGO, CALIFORNIA TIME, ON WEDNESDAY, SEPTEMBER 30, 1998, UNLESS THE
OFFER IS EXTENDED.
 
PURCHASE RIGHTS
 
    Under the Merger Agreement, holders of purchase rights ("Purchase Rights")
under the Mycogen Corporation Employee Stock Purchase Plan (the "Stock Plan")
who submit a Stock Purchase Election to the Company prior to the expiration of
the Offer will be able (contingent on the purchase of Shares in the Offer) to
exercise their Purchase Rights immediately prior to the expiration of the Offer
and to tender the Shares issuable upon such exercise (the "Stock Purchase
Shares") in the Offer.
 
    All Purchase Right exercises must be effected through the Company. A holder
of Purchase Rights who wishes to participate in the Offer must submit to the
Company a Stock Purchase Election to exercise all of such holder's Purchase
Rights to purchase Stock Purchase Shares and then tender such Stock Purchase
Shares pursuant to the Offer; provided, that any such exercise of a Purchase
Rights is in accordance with the terms of the Stock Plan.
 
    In no event are any Purchase Rights or Stock Purchase Elections to be
delivered to the Depositary, Purchaser, Parent or any other person other than
the Company in connection with a tender of Stock Purchase Shares hereunder.
 
    The Company will send or deliver to holders of Purchase Rights additional
materials concerning the exercise of Purchase Rights and the tender of Stock
Purchase Shares, including a Stock Purchase Election. Holders should use the
Stock Purchase Election to exercise Purchase Rights and to tender Stock Purchase
Shares, as described above. HOLDERS OF PURCHASE RIGHTS MAY NOT USE THE LETTER OF
TRANSMITTAL TO DIRECT THE TENDER OF STOCK PURCHASE SHARES. Questions with
respect to tendering Stock Purchase Shares should be directed to Mycogen
Corporation, AgroSciences Tender Offer, 5501 Oberlin Drive, San Diego,
California 92121, Attention: Cheri Manis; telephone number (800) 745-7475.
 
    IN ORDER TO ASSURE THAT THE COMPANY, ON BEHALF OF HOLDERS OF PURCHASE RIGHTS
WHO EXERCISE THEIR PURCHASE RIGHTS PURSUANT TO STOCK PURCHASE ELECTIONS, CAN
TIMELY TENDER STOCK PURCHASE SHARES, HOLDERS OF PURCHASE RIGHTS SHOULD COMPLETE
AND RETURN THE STOCK PURCHASE ELECTION SO THAT IT IS RECEIVED BY THE COMPANY NO
LATER THAN 5:00 P.M., SAN DIEGO, CALIFORNIA TIME, ON WEDNESDAY, SEPTEMBER 30,
1998, UNLESS THE OFFER IS EXTENDED.
 
                                       8
<PAGE>
RESTRICTED SHARES
 
    Under the Merger Agreement, holders of shares of restricted stock of the
Company ("Restricted Stock") which were granted pursuant to the Mycogen
Corporation Restricted Stock Issuance Plan (the "Restricted Stock Plan") who
submit a Restricted Stock Election (as defined in Section 10) to the Company
prior to the expiration of the Offer will be able (contingent on the purchase of
Shares in the Offer) to tender their Restricted Stock in the Offer.
 
    Purchaser is offering, as part of the Offer, to purchase any of the
Restricted Stock granted pursuant to the Restricted Stock Plan. All tenders of
Restricted Stock must be effected through the Company. A holder of Restricted
Stock who wishes to participate in the Offer must submit to the Company a
Restricted Stock Election to vest such Restricted Stock, a Letter of Transmittal
and such holder's Restricted Stock certificates.
 
    In no event are any Restricted Stock Elections and Restricted Stock
certificates to be delivered to the Depositary, Purchaser, Parent or any other
person other than the Company in connection with a tender of Restricted Stock
hereunder.
 
    The Company will send or deliver to holders of Restricted Stock additional
materials concerning the tender of Restricted Stock, including a Restricted
Stock Election. Holders should use the Restricted Stock Election and the Letter
of Transmittal to tender Restricted Stock as described above. Questions with
respect to tendering Restricted Shares should be directed to Mycogen
Corporation, AgroSciences Tender Offer, 5501 Oberlin Drive, San Diego,
California 92121, Attention: Cheri Manis; telephone number (800) 745-7475.
 
    IN ORDER TO ASSURE THAT THE COMPANY CAN PERMIT THE RESTRICTED STOCKS TO VEST
(CONTINGENT UPON THE PURCHASE BY PURCHASER OF SHARES PURSUANT TO THE OFFER) AND
THEREBY PERMIT A TIMELY AND VALID TENDER OF THE RESTRICTED SHARES, HOLDERS OF
RESTRICTED SHARES SHOULD COMPLETE AND RETURN THE RESTRICTED STOCK ELECTION AND
THE LETTER OF TRANSMITTAL ALONG WITH THE RELATED RESTRICTED SHARE CERTIFICATES
SO THAT THEY ARE RECEIVED BY THE COMPANY NO LATER THAT 5:00 P.M., SAN DIEGO,
CALIFORNIA TIME, ON WEDNESDAY, SEPTEMBER 30, 1998, UNLESS THE OFFER IS EXTENDED.
 
BACKUP U.S. FEDERAL INCOME TAX WITHHOLDING
 
    For a discussion of U.S. federal income tax considerations relating to
backup withholding, see Section 5.
 
APPOINTMENT AS PROXY
 
    By executing a Letter of Transmittal, a tendering stockholder irrevocably
appoints designees of Purchaser as such stockholder's proxies in the manner set
forth in the Letter of Transmittal to the full extent of such stockholder's
rights with respect to the Shares tendered by such stockholder and accepted for
payment by Purchaser (and with respect to any and all other Shares or other
securities issued or issuable in respect of such Shares on or after the date of
this Offer to Purchase). All such proxies shall be irrevocable and coupled with
an interest in the tendered Shares. Such appointment will be effective when, and
only to the extent that, Purchaser accepts such Shares for payment. Upon such
acceptance for payment, all prior proxies and consents granted by such
stockholder with respect to such Shares and other securities will be revoked
without further action, and no subsequent proxies may be given nor subsequent
written consents executed (and, if given or executed, such proxies or consents
will not be deemed effective). The designees of Purchaser will be empowered to
exercise all voting and other rights of such stockholder as they, in their sole
discretion, may deem proper at any annual, special or adjourned meeting of the
Company's stockholders, by written consent or otherwise. Purchaser reserves the
right to require that, in order for Shares to be deemed validly tendered,
immediately upon Purchaser's payment for such
 
                                       9
<PAGE>
Shares, Purchaser must be able to exercise full voting rights with respect to
such Shares, including voting at any meeting of stockholders scheduled or acting
by written consent without a meeting.
 
DETERMINATION OF VALIDITY
 
    All questions as to the validity, form, eligibility (including time of
receipt) and acceptance for payment of any tender of Shares will be determined
by Purchaser in its reasonable discretion. Purchaser reserves the absolute right
to reject any and all tenders of Shares determined by it not to be in proper
form or the acceptance for payment of which may, in the opinion of Purchaser's
counsel, be unlawful. Purchaser reserves the absolute right to waive any defect
or irregularity in any tender of Shares of any particular stockholder. None of
Purchaser, Parent, any of their affiliates or assigns, the Dealer Manager, the
Depositary, the Information Agent or any other person will be under any duty to
give notification of any defects or irregularities in tenders or incur any
liability for failure to give any such notification.
 
4.  WITHDRAWAL RIGHTS; STATUTORY RIGHTS
 
    Tenders of Shares pursuant to the Offer may be withdrawn at any time on or
prior to the Expiration Date (or such later date as may apply in case the Offer
is extended). Thereafter, such tenders are irrevocable, except that they may be
withdrawn after November 2, 1998, unless theretofore accepted for payment as
provided in this Offer to Purchase. If Purchaser extends the Offer, is delayed
in accepting for payment or paying for Shares or is unable to accept for payment
or pay for Shares pursuant to the Offer for any reason, then, without prejudice
to Purchaser's rights under the Offer, the Depositary may, on behalf of
Purchaser, retain all Shares tendered, and such Shares may not be withdrawn
except to the extent that tendering stockholders are entitled to withdrawal
rights as set forth in this Section 4.
 
    For a withdrawal to be effective, a written, telegraphic, telex or facsimile
transmission notice of withdrawal must be timely received by the Depositary at
one of its addresses set forth on the back cover of this Offer to Purchase. Any
notice of withdrawal must specify the name of the person who tendered the Shares
to be withdrawn, the number of Shares to be withdrawn and the name of the
registered holder, if different from that of the person who tendered such
Shares. If certificates evidencing Shares to be withdrawn have been delivered or
otherwise identified to the Depositary, then prior to the physical release of
such certificates, the serial numbers shown on such certificates must be
submitted to the Depositary, and the signatures on the notice of withdrawal must
be guaranteed by an Eligible Institution unless such Shares have been tendered
for the account of an Eligible Institution. If Shares have been tendered
pursuant to the procedure for book-entry transfer set forth in Section 3, the
notice of withdrawal must specify the name and number of the account at the
Book-Entry Transfer Facility to be credited with the withdrawn Shares.
 
    Withdrawals may not be rescinded, and Shares withdrawn will thereafter be
deemed not validly tendered for purposes of the Offer. However, withdrawn Shares
of the Company may be retendered at any time prior to the Expiration Date by
again following one of the procedures described in Section 3.
 
    All questions as to the form and validity (including time of receipt) of any
notice of withdrawal will be determined by Purchaser, in its reasonable
discretion. None of Purchaser, Parent, any of their affiliates or assigns, the
Dealer Manager, the Depositary, the Information Agent or any other person will
be under any duty to give notification of any defects or irregularities in any
notice of withdrawal or incur any liability for failure to give such
notification.
 
5. CERTAIN U.S. FEDERAL INCOME TAX CONSIDERATIONS
 
    The following is a summary of the material U.S. federal income tax
consequences of the Offer and the Merger. This summary is based upon the current
provisions of the Internal Revenue Code of 1986, as amended, its legislative
history, Treasury regulations, administrative pronouncements and judicial
decisions, all of which are subject to change, possibly with retroactive effect.
This summary does not purport to
 
                                       10
<PAGE>
be a complete discussion of all U.S. federal income tax consequences relating to
the Offer and the Merger. This summary does not address the tax consequences of
the Offer and the Merger under state, local or non-U.S. tax laws. In addition,
this summary may not apply, in whole or in part, to particular categories of
holders of Shares, such as financial institutions, broker-dealers, life
insurance companies, tax-exempt organizations, investment companies, foreign
taxpayers, individuals who received Shares pursuant to employee stock options,
restricted stock programs or in other compensatory transactions, and other
special status taxpayers. Finally, a tax ruling from the Internal Revenue
Service ("IRS") has not be requested. THIS SUMMARY IS INCLUDED FOR GENERAL
INFORMATION ONLY. ALL HOLDERS OF SHARES ARE URGED TO CONSULT THEIR OWN TAX
ADVISORS TO DETERMINE THE SPECIFIC TAX CONSEQUENCES OF THE OFFER AND THE MERGER,
INCLUDING ANY STATE, LOCAL AND NON-U.S. TAX CONSEQUENCES.
 
    A holder of a Share who receives cash in exchange for his or her Share
pursuant to the Offer or the Merger (including cash received upon the exercise
of dissenters' appraisal rights) will recognize gain or loss for U.S. federal
income tax purposes equal to the difference between the amount of cash received
for such Share and such holder's tax basis in such Share. Such gain or loss will
be a capital gain or loss, provided that such Share was held as a capital asset
of the holder at the time such Share was tendered in the Offer or exchanged for
cash in the Merger, as the case may be. A capital gain or loss will be a
long-term capital gain or loss if the holder's holding period is more than 12
months. For individual holders, long-term capital gains are subject to a maximum
federal income tax rate of 20 percent. The deduction of capital losses may be
subject to limitation.
 
    Certain holders of Shares who receive cash in exchange for their Shares
pursuant to the Offer or the Merger (including cash received upon the exercise
of dissenters' appraisal rights) are required to provide the Depositary (as
payer) with their correct taxpayer identification number ("TIN") on a Substitute
Form W-9 (included as part of the Letter of Transmittal). If the Depositary is
not provided with the correct TIN, a holder may be subject to a $50 penalty
imposed by the IRS. In addition, payments made to such holder may be subject to
backup withholding. If backup withholding applies, the Depositary is required to
withhold 31% of any payment made to a holder. Backup withholding is not an
additional federal income tax. Rather, the federal income tax liability of a
person subject to backup withholding will be reduced by the amount of tax
withheld, provided that the required information is given to the IRS. If backup
withholding results in an overpayment of federal income taxes, a refund may be
obtained from the IRS. See instruction 8 of the Letter of Transmittal for a more
detailed discussion regarding backup withholding.
 
                                       11
<PAGE>
6.  PRICE RANGE OF THE SHARES
 
    The Company's Shares are listed and quoted on the NASDAQ NMS under the
symbol MYCO. The following table sets forth, for the periods indicated, the high
and low sale prices per share for the Shares for the periods indicated. The
Company has not paid dividends with respect to Shares in the past two years and
is not expected to do so in the foreseeable future.
 
<TABLE>
<CAPTION>
                                                                             SHARES
                                                                        -----------------
                                                                         HIGH       LOW
                                                                        -------   -------
 
<S>                                                                     <C>       <C>
Fiscal Year Ended August 31, 1997:
  First Quarter.......................................................  $17 1/8   $13 3/4
  Second Quarter......................................................   29 1/4    16 3/4
  Third Quarter.......................................................   28 1/2    17 1/2
  Fourth Quarter......................................................   25        18 3/4
 
Fiscal Year Ended August 31, 1998:
  First Quarter.......................................................  $25 1/2   $19 1/2
  Second Quarter......................................................   22 1/2    15 7/8
  Third Quarter.......................................................   25 1/4    16 5/8
  Fourth Quarter......................................................   25        20
 
Fiscal Year Ended August 31, 1999:
  First Quarter (through 9/3/98)......................................  $27 3/4   $27
</TABLE>
 
    The following table sets forth for the periods indicated, the purchases of
Shares made by Parent, the range of prices paid for such Shares and the average
purchase price for each quarterly period of the Company during such periods:
 
<TABLE>
<CAPTION>
                                                                    SHARES
                                                 --------------------------------------------
                                                 NUMBER OF
                                                   SHARES      HIGH        LOW       AVERAGE
                                                 ----------  ---------  ----------  ---------
<S>                                              <C>         <C>        <C>         <C>
Fiscal Year Ended August 31, 1997:
  First Quarter................................     297,700  $  16.875  $  15.50    $  16.484
  Second Quarter...............................   1,979,700     25.625     16.75       19.456
  Third Quarter................................     805,077     28.00      21.50       25.429
  Fourth Quarter...............................     226,666     24.00      19.25       23.047
 
Fiscal Year Ended August 31, 1998:
  First Quarter................................     146,400  $  20.75   $  20.5625  $  20.694
  Second Quarter...............................   4,696,512     20.761     19.3333     19.927
  Third Quarter................................   2,000,000     20.059     20.059      20.059
  Fourth Quarter...............................           0     --          --         --
 
Fiscal Year Ended August 31, 1999:
  First Quarter (through 9/3/98)...............           0     --          --         --
</TABLE>
 
    On August 31, 1998, the last full trading day prior to announcement of the
execution of the Merger Agreement and Purchaser's intention to commence the
Offer, the closing sale price of the Shares on the NASDAQ NMS was $20.00 per
Share. On September 3, 1998, the last full trading day prior to the commencement
of the Offer, such closing sale price was $27.5625 per Share. STOCKHOLDERS ARE
URGED TO OBTAIN A CURRENT MARKET QUOTATION FOR THE SHARES.
 
                                       12
<PAGE>
7.  CERTAIN INFORMATION CONCERNING THE COMPANY
 
GENERAL
 
    The Company is a California corporation with its principal office located at
5501 Oberlin Drive, San Diego, California 92121. The Company is a diversified
agribusiness and biotechnology company that develops and markets seed for
improved crop varieties and provides crop protection products and services.
 
FINANCIAL INFORMATION
 
    Set forth below is certain selected consolidated financial information with
respect to the Company and its subsidiaries derived from the Company's public
reports filed with the Commission. More comprehensive financial information is
included in reports and other documents filed by the Company with the
Commission, and the following summary is qualified in its entirety by reference
to such reports and other documents and all of the financial information
(including any related notes) contained therein. Such reports and other
documents are available for inspection and copies thereof are obtainable in the
manner set forth below under "Available Information."
 
                              MYCOGEN CORPORATION
                            SELECTED FINANCIAL DATA
                     (IN THOUSANDS, EXCEPT PER SHARE DATA)
 
<TABLE>
<CAPTION>
                                                                                            NINE MONTHS ENDED
                                                          YEAR ENDED AUGUST 31,                  MAY 31,
                                                  -------------------------------------  ------------------------
                                                    1997(1)      1996(1)       1995         1998         1997
                                                  -----------  -----------  -----------  -----------  -----------
<S>                                               <C>          <C>          <C>          <C>          <C>
Net Operating Revenues..........................  $   202,407  $   146,800  $   106,169  $   177,562  $   170,895
Total Revenue...................................      210,973      155,589      113,218      184,318      177,236
Net Loss Applicable to Common Shares............      (37,683 (2)     (47,636 (2)     (15,946)     (37,757 (2)      (6,981)(2)
Net Loss Per Common Share (Basic)...............        (1.22 (1)       (1.82 (1)       (0.83)       (1.13)       (0.23)
Net Loss Per Common Share (Diluted).............        (1.22 (1)       (1.82 (1)       (0.83)       (1.13)       (0.23)
Cash, Cash Equivalents and Securities
  Available-for-Sale............................        2,211       68,038       17,600        1,514        3,097
Total Assets....................................      239,687      227,469      159,608      342,359      280,622
Long-Term Liabilities...........................       15,544        5,228        3,291       20,266       16,187
Redeemable Preferred Stock......................      --           --           --           --           --
Stockholders' Equity............................      157,214      181,194      113,703      203,232      184,341
</TABLE>
 
- ------------------------
 
(1)   The acquisitions of Morgan Seeds in 1997 and UAS and Mycogen Seeds in 1996
    affect the comparability of the Selected Financial Data.
 
(2)   Net loss in 1997, 1996, the nine months ended May 31, 1998 and the nine
    months ended May 31, 1997 includes other charges of $31.7 million, $27.6
    million, $39.0 million and $14.3 million, respectively, as discussed in
    further detail in the Notes to the Company's Consolidated Financial
    Statements.
 
                                       13
<PAGE>
RECENT DEVELOPMENTS
 
    The Company has advised Parent that the Company's fourth quarter has been
negatively impacted by promotional (free seed) efforts on the part of the
Company's competitors. The Company also has advised Parent that fourth quarter
results have been negatively impacted by high litigation costs. Based on
management's preliminary assessment of the business, fourth quarter revenues are
anticipated by the Company to be approximately $25.5 million with a net loss of
approximately $25 million, or approximately $0.69 per Share.
 
AVAILABLE INFORMATION
 
    The Company is registered under the Exchange Act, and, accordingly, is
subject to the informational filing requirements of the Exchange Act. In
accordance therewith, the Company files periodic reports, proxy statements and
other information with the Commission under the Exchange Act relating to its
business, financial condition and other matters. The Company is required to
disclose in such proxy statements certain information, as of particular dates,
concerning the Company's directors and officers, their remuneration, stock
options granted to them, the principal holders of the Company's securities and
any material interest of such persons in transactions with the Company. Such
reports, proxy statements and other information may be inspected at the
Commission's office at 450 Fifth Street, N.W., Washington, D.C. 20549, and also
should be available for inspection and copying at the regional offices of the
Commission located at 500 West Madison Street, Suite 1400, Chicago, Illinois
60661-2511; and 7 World Trade Center, 13th Floor, New York, New York 10048.
Copies may be obtained by mail from the Public Reference Section of the
Commission, 450 Fifth Street, N.W., Washington, D.C. 20549, at prescribed rates.
The Commission also maintains a World Wide Website on the Internet at
http://www.sec.gov which site contains registration statements, reports, proxy
and information statements and other information regarding registrants that file
electronically with the Commission, including the Company. In addition, such
material should be available for inspection at the NASD, 1735 K Street, N.W.,
Washington, D.C. 20006.
 
8.  CERTAIN INFORMATION CONCERNING PURCHASER, PARENT AND CERTAIN AFFILIATES OF
  PARENT
 
GENERAL
 
    Purchaser, a Delaware corporation with its principal offices at 2030 Dow
Center, Midland, Michigan 48674, was organized in April 1998 for the purpose of
effecting the Offer and the Merger, and has not carried on any activities except
in connection with the Offer and the Merger. Parent owns 69% of the outstanding
common stock of Purchaser and Centen Ag Inc., a Delaware corporation ("Centen"),
owns 31% of the outstanding common stock of Purchaser.
 
    Parent is a Delaware limited liability company with its principal offices
located at 9330 Zionsville Road, Indianapolis, Indiana 46268. Parent's principal
business is the production of agricultural products, such as Broadstrike-TM-
herbicides, Lorsban-TM- insecticides and Dursban-TM- insecticides, used in crop
protection and production and for industrial pest control. Parent is 63% owned
by Rofan Services Inc., a Delaware corporation ("Rofan") and 37% owned by
Centen.
 
    Rofan is a Delaware corporation with its principal offices located at 2030
Dow Center, Midland, Michigan 48674. Rofan's principal business is to hold
investments in other entities, such as Parent. Rofan is a wholly owned
subsidiary of TDCC.
 
    Centen is a Delaware corporation with its principal offices located at 2030
Dow Center, Midland, Michigan 48674. Centen's principal business is to hold a
membership interest in Parent. Centen is a wholly owned subsidiary of TDCC.
 
    TDCC is a Delaware corporation with its principal offices located at 2030
Dow Center, Midland, Michigan 48674. TDCC's principal business is the
manufacture and sale of chemicals, plastic materials,
 
                                       14
<PAGE>
agricultural and other specialized products and services. TDCC is a public
corporation whose stock is traded on various exchanges, including the New York
Stock Exchange, Inc. ("NYSE").
 
    Except as described in this Offer to Purchase, during the last five years,
none of TDCC, Rofan, Centen, Parent, Purchaser or, to the best of their
knowledge, any of the persons listed in Schedule I (i) has been convicted in a
criminal proceeding (excluding traffic violations and similar misdemeanors) or
(ii) was a party to a civil proceeding of a judicial or administrative body of
competent jurisdiction and as a result of such proceeding was or is subject to a
judgment, decree or final order enjoining future violations of, or prohibiting
activities subject to, federal or state securities laws or finding any violation
of such laws. The name, business address, present principal occupation or
employment, five-year employment history and citizenship of each director and
executive officer of TDCC, Rofan, Centen, Parent and Purchaser are set forth in
Schedule I.
 
FINANCIAL INFORMATION
 
    Set forth below is certain selected consolidated financial information with
respect to TDCC and its subsidiaries as of its fiscal years ended December 31,
1997, 1996 and 1995. More comprehensive financial information is included in
reports and in documents filed by TDCC with the Commission, and the following
summary is qualified in its entirety by reference to such reports and other
documents and all of the financial information (including any related notes)
contained therein. Such reports and other documents should be available for
inspection and copies thereof should be obtainable in the manner set forth below
under "Available Information."
 
                   THE DOW CHEMICAL COMPANY AND SUBSIDIARIES
                  SELECTED CONSOLIDATED FINANCIAL INFORMATION
 
<TABLE>
<CAPTION>
                                                                              FISCAL YEARS ENDED DECEMBER 31,
                                                                             ----------------------------------
                                                                                1997        1996        1995
                                                                             ----------  ----------  ----------
                                                                             (IN MILLIONS OF DOLLARS EXCEPT PER
                                                                                       SHARE AMOUNTS)
<S>                                                                          <C>         <C>         <C>
STATEMENT OF EARNINGS DATA:
Net Sales..................................................................  $   20,018  $   20,053  $   20,200
Income from Continuing Operations..........................................       1,802       1,900       1,900
Net Income Available for Common Stockholders...............................       1,802       1,900       2,071
 
PER SHARE DATA:
Earnings per Common Share from Continuing Operations.......................  $     7.81  $     7.71  $     7.03
Earnings per Common Share..................................................        7.81        7.71        7.72
Earnings per Common Share from Continuing Operations -- Assuming
  Dilution.................................................................        7.70        7.60        6.93
Earnings per Common Share -- Assuming Dilution.............................        7.70        7.60        7.61
 
BALANCE SHEET DATA:
Working Capital............................................................  $    1,300  $    3,826  $    4,953
Total Assets...............................................................      24,040      24,673      23,582
Net Stockholders Equity....................................................       7,626       7,954       7,361
 
Weighted-average Common Shares
  Outstanding (in millions)................................................       230.6       246.3       268.2
</TABLE>
 
AVAILABLE INFORMATION
 
    TDCC is registered under the Exchange Act, and, accordingly, is subject to
the informational filing requirements of the Exchange Act. In accordance
therewith, TDCC files periodic reports, proxy statements
 
                                       15
<PAGE>
and other information with the Commission under the Exchange Act relating to its
business, financial condition and other matters. TDCC is required to disclose in
such proxy statements certain information, as of particular dates, concerning
TDCC's directors and officers, their remuneration, stock options granted to
them, the principal holders of TDCC's securities and any material interest of
such persons in transactions with TDCC. Such reports, proxy statements and other
information may be inspected at the Commission's office at 450 Fifth Street,
N.W., Washington, D.C. 20549, and also should be available for inspection and
copying at the regional offices of the Commission located at 500 West Madison
Street, Suite 1400, Chicago, Illinois 60661-2511; and 7 World Trade Center, 13th
Floor, New York, New York 10048. Copies may be obtained by mail from the Public
Reference Section of the Commission, 450 Fifth Street, N.W., Washington, D.C.
20549, at prescribed rates. The Commission also maintains a World Wide Website
on the Internet at http://www.sec.gov which site contains registration
statements, reports, proxy and information statements and other information
regarding registrants that file electronically with the Commission, including
TDCC. In addition, such material should be available for inspection at the NYSE,
20 Broad Street, New York, New York 10005.
 
    Except as described in this Offer to Purchase, (i) none of TDCC, Rofan,
Centen, Parent or Purchaser or, to the best of their knowledge, any of the
persons listed in Schedule I or any associate or majority-owned subsidiary of
any such persons, beneficially owns or has a right to acquire any equity
security of the Company and (ii) none of TDCC, Rofan, Centen, Parent or
Purchaser or, to the best of their knowledge, any of the other persons referred
to above, or any of the respective directors, executive officers or subsidiaries
of any of the foregoing, has effected any transaction in any equity security of
the Company during the past 60 days. Jerry E. Toomer, Vice President-Human
Resources of Parent, directly owns 840 Shares. Purchaser believes that Mr.
Toomer will tender all of his Shares pursuant to the Offer. The designees of
Parent who serve on the Board of the Company have agreements with Parent
pursuant to which such persons agree to forfeit to Parent any Shares issuable
pursuant to Options granted in connection with that service. Accordingly, any
Shares subject to such Options cannot be tendered by such persons in response to
the Offer.
 
    Except as described in this Offer to Purchase, (i) none of TDCC, Rofan,
Centen, Parent or Purchaser or, to the best of their knowledge, any of the
persons listed in Schedule I has any contract, arrangement, understanding or
relationship (whether or not legally enforceable) with any other person with
respect to any securities of the Company, including, but not limited to, any
contract, arrangement, understanding or relationship concerning the transfer of
the voting of any such securities, joint ventures, loan or option arrangements,
puts or calls, guarantees of loans, guarantees against loss, or the giving or
withholding of proxies; (ii) there have been no contacts, negotiations or
transactions between TDCC, Centen, Rofan, Parent, Purchaser or any of their
respective subsidiaries or, to the best of their knowledge, any of the persons
listed on Schedule I on the one hand, and the Company or any of its directors,
officers or affiliates, on the other hand, concerning a merger, consolidation or
acquisition, tender offer or other acquisition of securities, election of
directors, a sale or other transfer of a material amount of assets or concerning
any other transactions with the Company that are required to be disclosed
pursuant to the rules and regulations of the Commission.
 
9.  BACKGROUND OF THE OFFER
 
    As noted above, on January 15, 1996, Parent and the Company entered into the
Exchange and Purchase Agreement. Pursuant to the Exchange and Purchase
Agreement, Parent agreed (i) to acquire 2,707,884 shares of Common Stock and a
$100,000 promissory note of Agrigenetics, Inc. in exchange for all of the
outstanding common stock of United Agriseeds, Inc. and (ii) to purchase
1,745,450 shares of Common Stock for consideration of $26,400,000. In addition,
on January 15, 1996, Parent entered into a Stock Purchase Agreement with The
Lubrizol Corporation to purchase 9,502,348 shares of Common Stock from The
Lubrizol Corporation and an affiliate for $126,217,849. The transactions
contemplated by these agreements closed on February 20, 1996 (the "Measurement
Date").
 
                                       16
<PAGE>
    Pursuant to the Exchange and Purchase Agreement, among other things, Parent
agreed that it would not acquire shares of Common Stock beyond specified levels
at certain periods, and that it would not acquire shares of Common Stock such
that it would hold more than 79.9% of the outstanding Common Stock, unless
certain detailed procedures were undertaken. See Item 3(b)(2) "Exchange and
Purchase Agreement."
 
    During calendar year 1996, Parent continued to acquire shares of Common
Stock in the open market, from employees of the Company in connection with the
exercise of their stock options, and directly from individual sellers. On
December 2, 1996, Parent purchased 1,000,000 shares of Common Stock from Pioneer
Overseas Corporation, which, aggregated with shares already owned by Parent,
gave Parent ownership of greater than 50% of the outstanding shares of Common
Stock and control over the Company's Board of Directors (the "Board").
 
    From December 1996 through November 1997, Parent continued to acquire shares
of Common Stock in the open market and directly from third-party sellers
(including from Dr. Jerry Caulder, who resigned as Chairman of the Board and
Chief Executive Officer of the Company in May 1997, but remained a director of
the Company).
 
    On June 30, 1997, TDCC, through wholly-owned subsidiaries, became the 100%
owner of Parent, purchasing the 40% stake in Parent held by another entity.
 
    During the summer of 1997, three of the Company's directors--Dr. Caulder,
Thomas J. Cable and W. Wayne Withers--alleged that Parent, TDCC and Parent's
designees on the Board had breached their fiduciary duties to the Company and
the Minority Stockholders. Those allegations are discussed below. See "Summary
of Special Committee Investigation of Certain Allegations." TDCC, Parent and
Parent's designees deny that they acted wrongfully.
 
    On November 11, 1997, Parent notified four directors of the Company (Dr.
Caulder, Mr. Cable, Dr. David H. Rammler and Mr. Withers) that Parent would not
vote to reelect them to the Board. Parent stated that, in addition to its own
designees and Carlton J. Eibl, President of the Company, it would nominate three
candidates with special expertise and talents in plant biotechnology, the seed
industry and the financial affairs of growth oriented high technology companies.
At the Company's annual meeting of stockholders held on January 8, 1998, Joseph
P. Sullivan, Dr. George Khachatourians and Roy M. Barbee were elected to fill
those vacancies. During March and April 1997, these three new members of the
Board were appointed as an independent committee to work with the Company's
management in evaluating the best path for the Company.
 
    On April 30, 1998, prior to completion of the work of the independent
committee described above, Parent notified the Company and publicly announced
that it desired to amend the Exchange and Purchase Agreement to allow Parent to
purchase all of the Shares held by the Minority Stockholders (the "Minority
Shares") and stated that, if the Exchange and Purchase Agreement were amended to
permit such discussions, Parent would be prepared to discuss such a transaction
at a price per share of $20.50 (the "Initial Proposal"). On May 6, 1998, the
Company announced that it had received the Initial Proposal and that the Board
had appointed the Special Committee to evaluate Parent's request. The Special
Committee, appointed in light of the conflict of interest, with respect to the
Initial Proposal, of the five member majority of the Board designated by Parent,
consisted of Mr. Sullivan and Dr. Khachatourians.
 
    In early May 1998, the Special Committee retained Altheimer & Gray as its
legal adviser, and made inquiries with, and interviewed, a number of investment
banking firms, including Wasserstein Perella. These contacts were reviewed by
the Special Committee at a meeting on May 18, 1998, at which the Special
Committee also reviewed with Altheimer & Gray the duties of special committees
in similar situations.
 
    On May 22, 1998, the Special Committee met with Wasserstein Perella
regarding Wasserstein Perella's retention and the work Wasserstein Perella would
perform in connection therewith (including due
 
                                       17
<PAGE>
diligence efforts), and on May 26, 1998, the Special Committee announced the
retention of Wasserstein Perella as its financial advisor.
 
    During late May and early June 1998, the Special Committee and its advisors
began extensive due diligence with respect to the Company, including its
financial condition and its intellectual property assets and position, both
through on-site visits to the Company's headquarters in San Diego, California
and by telephone and receipt and review of documents.
 
    During late May and early June 1998, Altheimer & Gray learned from Dr.
Khachatourians that Dr. Khachatourians had provided three days of consulting
services to TDCC and Parent in August 1997 for total consideration of $18,000.
In order to avoid any questions regarding his independence, Dr. Khachatourians
determined that he should resign from the Special Committee. At a meeting on
June 11, 1998, Dr. Khachatourians voluntarily resigned from the Special
Committee, and, in accordance with the recommendation of Mr. Sullivan,
Ambassador Clayton K. Yeutter was appointed to the Board and to the Special
Committee. Mr. Sullivan had considered a number of candidates for the
anticipated vacancy on the Special Committee and selected Mr. Yeutter due to his
extensive experience in the agricultural field (including serving as U.S.
Secretary of Agriculture), his strong negotiating skills and background
(including serving as U.S. ambassador to the Uruguay Round of GATT) and Mr.
Sullivan's view, based on their experience together with The Vigoro Corporation,
where Mr. Sullivan was Chairman of the Board and Mr. Yeutter a director, that
Mr. Yeutter would be able to promptly and effectively step into his role on the
Special Committee and be a strong representative of the Minority Stockholders.
In order to permit Mr. Yeutter's appointment to the Board, Mr. Barbee resigned
from the Board.
 
    In mid-June 1998, through its due diligence investigation, the Special
Committee learned of certain allegations involving actions of Parent and its
designated directors on the Board made by former directors and executive
officers of the Company, which are described in detail below. See "Summary of
Special Committee Investigation of Certain Allegations." These allegations
generally involved whether Parent and its Board designees had treated the
Company as a wholly-owned subsidiary, ignoring the rights of the Minority
Stockholders, and had made decisions based on the benefits of opportunities to
Parent, rather than the Company as an independent entity. As described below,
the Special Committee and its representatives investigated these allegations.
The Special Committee took the results of its investigation into account in its
determinations as to the value of the Company and had frank discussions
regarding such allegations during its negotiations with Parent.
 
    On June 10, 1998, Wasserstein Perella sent a letter to TDCC requesting
information on a number of due diligence matters, including issues raised by
these allegations.
 
    On June 25, 1998, the Special Committee and its legal and financial advisors
met with Parent and its representatives to discuss ongoing due diligence issues,
disclosure issues (including issues relating to the allegations referred to
above) and the anticipated schedule for the process. At this meeting, there was
significant discussion as to the information requested by Wasserstein Perella on
behalf of the Special Committee and the scope of information to be provided to
the Special Committee. At a meeting of the Special Committee later on June 25,
the Special Committee was presented with an initial preliminary report by
Wasserstein Perella and a detailed discussion by Altheimer & Gray of the Special
Committee's duties and issues relating to disclosure by Parent to the Special
Committee of certain information.
 
    Based on the June 25 meetings, on June 26, 1998, Wasserstein Perella sent
another letter to TDCC requesting additional information, particularly with
respect to TDCC's and Parent's analyses of the Company, any material discussions
in which TDCC or Parent might be engaged with respect to transactions in the
biotech area and the issues raised by certain of the Company's former officers
and directors.
 
    As a part of its review of the Company's business, Altheimer & Gray learned
that Parent had performed significant work in two areas relating to the
Company's intellectual property estate. Specifically, attorneys for Parent had
prepared an overview and categorization of the Company's intellectual property
 
                                       18
<PAGE>
assets, including an assessment of pending litigation, and Parent was managing
or participating in a substantial part of the outstanding patent litigation to
which the Company is a party. In response to requests from Altheimer & Gray and
the Special Commitee, on July 9, 1998, Mr. Sullivan and attorneys from Altheimer
& Gray met with Parent and its patent litigation counsel to discuss these due
diligence matters.
 
    On July 21, 1998, the Special Committee met and approved an amendment to the
Exchange and Purchase Agreement, subject to approval by the full Board (which
approval was granted the following day), to allow (i) substantive discussions
and negotiations with respect to a potential buyout transaction and (ii) a
transaction to be formally proposed and consummated if such discussions and
negotiations warranted. At that meeting, Wasserstein Perella informed the
Special Committee that, if asked, Wasserstein Perella would be unable to opine
that a price of $20.50 for such a transaction would be fair to the Minority
Stockholders from a financial point of view. Also at that meeting, the Special
Committee and its advisors discussed strategies with respect to a meeting with
Parent to be held the next day.
 
    On July 22, 1998, the Special Committee, along with Wasserstein Perella and
Altheimer & Gray met with Parent and its legal and financial advisors in
Midland, Michigan. Discussions were held as to certain recently disclosed
information, the historical relationship between the Company and Parent
(including issues raised by the allegations noted above) and other due diligence
matters, including Parent's plans for the Company and the Company's strategic
value to Parent. Later that day, the Board approved the amendment to the
Exchange and Purchase Agreement and the amendment was executed.
 
    On July 24, 1998, the Special Committee received Altheimer & Gray's
preliminary analysis of the Company's intellectual property estate and the
litigation with respect thereto. The final report with respect to these issues
was delivered to the Special Committee on July 31, 1998.
 
    On July 27, 1998, the Special Committee met with Altheimer & Gray and
Wasserstein Perella and received Wasserstein Perella's preliminary presentation
as to the value of the Company, with a view toward a presentation of this
analysis to Parent at a meeting scheduled for August 3, 1998. At this July 27
meeting, the Special Committee and its advisors reviewed the presentation in
detail and held lengthy and significant discussions with Wasserstein Perella as
to its analysis and assumptions. Wasserstein Perella circulated another draft of
its preliminary report, and on July 31, 1998, the Special Committee met by
teleconference with its advisors to review the status of the presentation and
review further modifications.
 
    On August 3, 1998, the Special Committee and Wasserstein Perella met with
Parent and its financial advisor, Salomon Smith Barney Inc. The advisors made
presentations at this meeting as to their respective analyses of the Company's
value, and delivered reports to the parties with respect thereto.
 
    During the succeeding ten days, the parties exchanged correspondence
regarding the presentations and conclusions of the financial advisors. During
this period, Parent questioned the wide discrepancy between the projections
presented by the Company's management to the Board in December 1997 and the
projections included in the Wasserstein Perella materials. Also during this
period, the Special Committee received a report from Mr. Eibl regarding the view
of the Company's management with respect to the financial advisors' reports,
assumptions and conclusions. This report was provided by the Special Committee
to Parent.
 
    On August 14, 1998, the Special Committee met with Parent and discussed the
terms of the proposed transaction. Discussions centered on a range of values,
with Parent, at this meeting, indicating a high value of $26.00 per Share and
the Special Committee, at this meeting, indicating that the low end of its range
was $30.00 per Share. The parties agreed to discuss their positions with their
respective advisors and to meet again on August 26, 1998.
 
    During the succeeding two weeks, the Special Committee and its legal and
financial advisors met several times to finalize and refine their information as
to all of the matters discussed above.
 
                                       19
<PAGE>
    On August 26, 1998, the Special Committee met with Parent and the parties
reached a preliminary and tentative agreement as to price at $28.00 per Share,
subject to agreement as to the terms and conditions of a definitive agreement
and any other material issues that might arise. Parent and the Special Committee
instructed their respective advisors to proceed on this basis. Parent indicated
to the Special Committee that it would need the approval of its governing body.
Following the Special Committee meeting with Parent, the Special Committee asked
Wasserstein Perella to formally determine if it would be prepared to render a
fairness opinion with respect to a price of $28.00 per Share.
 
    On August 27, 1998, counsel for Parent delivered an initial draft merger
agreement to Altheimer & Gray, and over the next four days, the parties and
their representatives negotiated the terms of the Merger Agreement. During this
time, legal counsel for Parent and the Special Committee also entered into
discussions with legal counsel for the Company stockholder plaintiffs in the
putative class action litigation with respect to a possible settlement. As a
result of these discussions, on September 3, 1998, counsel for the plaintiffs,
Parent, TDCC and the Special Committee entered into a "Memorandum of
Understanding" ("MOU"). The MOU provides that, subject to a number of
conditions, including confirmatory discovery, and court approval, the parties
would agree to dismiss the putative class action litigation with prejudice. See
Item 8.
 
    On August 31, 1998, the Special Committee met with Mr. Eibl, Wasserstein
Perella and Altheimer & Gray to review the process undertaken to date, review
the Merger Agreement as finally negotiated, receive reports from Mr. Eibl, on
behalf of management of the Company, from Altheimer & Gray, as to their review
of the Company's intellectual property position, the allegations noted above and
the Special Committee's duties under applicable law, and from Wasserstein
Perella as to its report with respect to the Company from a financial point of
view. At this meeting, Wasserstein Perella delivered its opinion, dated August
31, 1998, to the Special Committee to the effect that, subject to the various
assumptions and limitations set forth therein, the $28.00 cash price to be
received by the Minority Stockholders pursuant to the Merger Agreement is fair
to such stockholders from a financial point of view. A copy of the full text of
the opinion of Wasserstein Perella, dated August 31, 1998, which sets forth,
among other things, the opinion expressed, assumptions made, procedures
followed, matters considered and limitations of review undertaken in connection
with such opinion, is attached hereto as Annex A and should be read in its
entirety. The Special Committee (i) unanimously determined that the Merger
Agreement, the Offer, the Merger and the other transactions contemplated by the
Merger Agreement are advisable and fair to, and in the best interests of, the
Company and the Minority Stockholders, (ii) authorized and approved the
acquisition of Shares by Purchaser in the Offer and the Merger, (iii) approved
and adopted in all respects the Merger Agreement and the performance by the
Company of its obligations thereunder, (iv) recommended acceptance of the Offer
and the tender of shares pursuant thereto, and (v) recommended that the Board
approve and adopt the Merger Agreement, the acquisition of Shares pursuant
thereto and that the Board recommend that the Minority Stockholders tender their
Shares in the Offer and, to the extent required, approve and adopt the Merger
Agreement and the transactions contemplated thereby.
 
    Later on August 31, 1998, at a meeting of the Board, the Special Committee
presented its report to the Board, including its recommendations set forth
above. The Board unanimously (i) determined that the Merger Agreement, the
Offer, the Merger and the other transactions contemplated by the Merger
Agreement are advisable and fair to, and in the best interests of, the Company
and the Minority Stockholders, (ii) authorized and approved the acquisition of
shares by Purchaser in the Offer and the Merger, (iii) approved and adopted in
all respects the Merger Agreement and the performance by the Company of its
obligations thereunder, and (iv) recommended that the Minority Stockholders
tender their Shares in the Offer and, to the extent required, approve and adopt
the Merger Agreement and the transactions contemplated thereby. Finally, the
Compensation Committee of the Board, which governs each of the Mycogen
Corporation 1992 Stock Option Plan, the Mycogen Corporation Restricted Stock
Issuance Plan and the Mycogen Corporation 1995 Stock Purchase Plan, approved the
treatment of the
 
                                       20
<PAGE>
options, purchase rights and restricted stock subject to those plans, as
described in the Merger Agreement, and took actions designed to effect such
treatment.
 
    The Merger Agreement was executed on August 31, 1998, and Parent and the
Company issued a joint press release announcing such execution and delivery on
August 31, 1998 (a copy of which is attached hereto as Exhibit 28).
 
    (b)(2)  Reasons for the Recommendation of the Special Committee and the
Board. In determining that the Offer and the Merger are fair to, and in the best
interests of, the Minority Stockholders, and in making its recommendation to the
Board, the Special Committee considered the following material factors, which
taken as a whole, supported its determination:
 
        (i) the offer of $28.00 per Share represented a premium of approximately
    36.6%, 53.4% and 64.7% over the closing price of the Shares on the NASDAQ
    National Market one full trading day, thirty days and sixty days prior to
    the public announcement of the Initial Proposal on April 30, 1998,
    respectively;
 
        (ii) the Special Committee's review of historical market prices and
    recent trading activity of the Shares, including the fact that prior to
    August 31, 1998, the Shares had not closed above $25.50 per Share since June
    1997, and developments in the stock market since the date of the Initial
    Proposal;
 
       (iii) the Special Committee's consideration of, among other things, (a)
    the business plan and information with respect to the financial condition,
    results of operations, business and prospects of the Company, (b) the
    changes and consolidation occurring in the agricultural biotechnology
    industry, their impact on the Company and the potential implication of these
    changes on the Company's relationship with Parent, (c) the historical
    relationship between the Company and Parent, including with respect to the
    Special Committee's investigation of the allegations described below, (d)
    the fact that the valuation analyses of Wasserstein Perella involved
    potentially speculative valuation of income opportunities which were far in
    the future and involved assumptions of market share in such future periods,
    (e) the inherent uncertainty as to the value of certain intellectual
    property rights of the Company which are subject to a number of
    uncertainties (such as, for example, the litigation to which the
    intellectual property is subject, the need to commercially develop such
    rights, and the inherent speculative nature of commercial development of
    these rights, including the area of oral immunology, and the effect of the
    Company's competition in these fields), and (f) concerns regarding the
    achievability of the Company's projections which formed the basis for the
    discounted cash flow analysis in Wasserstein Perella's report;
 
        (iv) the history of the negotiations between the Special Committee and
    its representatives and Parent's representatives, including the fact that
    (a) the negotiations resulted in an increase in the price at which Parent
    was prepared to acquire the Shares from $20.50 per Share to $28.00 per
    Share, an increase of 36.6%, and (b) the Special Committee believed that
    Parent would not further increase the price payable in the Offer and that
    $28.00 per Share was the highest price that could be obtained from Parent;
 
        (v) the Special Committee's review of presentations by, and discussion
    of the terms of the Merger Agreement (including the Offer and the Merger)
    with, representatives of the Special Committee's legal counsel and its
    financial advisors;
 
        (vi) the terms of the Offer, the Merger and the Merger Agreement,
    including the structural features of the Offer, which provide for a prompt
    cash tender offer for all outstanding Shares held by the Minority
    Stockholders to be followed if certain conditions are satisfied by a merger
    for the same consideration (thereby enabling the Minority Stockholders to
    obtain the benefits of the transaction in exchange for their Shares at the
    earliest possible time);
 
                                       21
<PAGE>
       (vii) other provisions of the Offer and the Merger Agreement, including
    the fact that (a) the Purchaser is not permitted to waive the Minimum
    Condition without the approval of the Special Committee unless, after the
    consummation of the Offer, Parent and Purchaser would own at least 81.07% of
    the Fully Diluted Shares (so that at least a majority of the Minority Shares
    on a fully diluted basis would have been tendered), (b) the Offer is not
    subject to any financing condition and (c) the terms of the Merger Agreement
    may not be amended or waived without the approval of the Special Committee;
 
      (viii) the likelihood that the proposed acquisition would be consummated,
    based in part on the financial condition of Parent and the limited scope of
    conditions (other than the Minimum Condition) to be satisfied prior to the
    consummation of the Merger as provided in the Merger Agreement;
 
        (ix) the written opinion of Wasserstein Perella delivered to the Special
    Committee on August 31, 1998 (the "Wasserstein Perella Opinion") to the
    effect that, subject to the various assumptions and limitations set forth in
    the Wasserstein Perella Opinion, the $28.00 cash price to be received by the
    holders of shares of Common Stock (other than TDCC or its affiliates)
    pursuant to the Merger Agreement is fair to such holders from a financial
    point of view, and the report and analysis presented by Wasserstein Perella.
    The full text of the Wasserstein Perella Opinion, which sets forth among
    other things, assumptions made, matters considered and limitations on the
    review undertaken, is attached hereto as Annex A and is incorporated herein
    by reference. The Wasserstein Perella Opinion is directed to the Special
    Committee, addresses only the fairness of the consideration to be received
    by the Minority Stockholders from a financial point of view and does not
    constitute a recommendation to any such stockholder as to whether such
    stockholder should accept the Offer and tender its Shares. STOCKHOLDERS ARE
    URGED TO CAREFULLY READ THE WASSERSTEIN PERELLA OPINION AND THE "OPINION OF
    WASSERSTEIN PERELLA." SECTION SET FORTH BELOW IN THEIR ENTIRETY;
 
        (x) the risk that the Company would suffer the loss of key employees and
    other adverse consequences if the Company had not accepted Parent's offer to
    engage in the transactions contemplated by the Merger Agreement and had
    pursued other alternatives with the attendant delay inherent in such
    alternatives (in particular, it was noted that a competitor of the Company
    had announced plans to open a facility near the Company's headquarters, and
    that the risk of loss of key employees described above, which management had
    indicated was already high, would be increased thereby);
 
        (xi) the belief of the Special Committee, and the concurrence of the
    Company's management, that, in a rapidly developing competitive market, in
    order for the Company to effectively compete, it would need to be a part of
    a larger strategic organization or fundamentally change to a different
    strategy, whether a niche strategy or otherwise, and the fact that such
    change was unlikely to happen in light of Parent's majority ownership of the
    Company; in this connection, the Special Committee also considered
    management's view that the Company has short term cash needs as well as
    continuing needs over many years to fund certain of its research and
    development opportunities which would be difficult to meet in the absence of
    consummating a buyout of the Minority Stockholders by Parent;
 
       (xii) the fact that Parent owns a majority of the shares of Common Stock,
    control of the Board and the right to maintain such ownership level and
    control, and the stated unwillingness of Parent to sell such shares to a
    third party bidder for the acquisition of the Company and the improbability
    of a third party making such a bid; and in connection therewith, Parent had
    indicated that it was not interested in selling the Company to a third party
    and the Special Committee and Wasserstein Perella were not authorized to,
    and did not, solicit third party indications of interest for the acquisition
    of the Company or its businesses;
 
      (xiii) the Special Committee's determination, and the concurrence of the
    Company's management, that, in light of allegations made and other
    organizational differences between Parent and the Company, a continuation of
    the status quo position of the parties would be highly undesirable and
 
                                       22
<PAGE>
    would present a significant risk of further erosion of the relationship
    between Parent and the Company and of the value of the Company;
 
       (xiv) the Special Committee's view that, in light of factors (x)--(xiii),
    together with continued disappointing operating results, and risks with
    respect to the trading price of the Shares and the stock market in general,
    the consideration that the stockholders of the Company (other than Parent
    and Purchaser) would obtain in a future transaction (including any
    transaction which might be effected by Parent pursuant to the Exchange and
    Purchase Agreement following February 1999) would likely be less
    advantageous than the consideration they would receive pursuant to the Offer
    and the Merger; and
 
       (xv) the ability of the Minority Stockholders to exercise dissenters'
    rights under the California Law in connection with the Merger.
 
    In reaching its determinations referred to above, the Board considered the
recommendation of the Special Committee and a report of the Special Committee,
which, in the view of the Board, supported such determinations.
 
    The members of the Board, including the members of the Special Committee,
evaluated the various factors considered in light of their knowledge of the
business, financial condition and prospects of the Company, and sought and
considered the advice of financial and legal advisors. In light of the number
and variety of factors that the Board and the Special Committee considered in
connection with their evaluation of the Offer and the Merger, neither the Board
nor the Special Committee found it practicable to quantify or otherwise assign
relative weights to any of the foregoing factors, and, accordingly, neither the
Board nor the Special Committee did so. In addition to the factors listed above,
the Special Committee considered the fact that consummation of the Offer and the
Merger would eliminate the opportunity of the Minority Stockholders to
participate in any potential future growth in the value of the Company, but
believed that this loss of opportunity was appropriately reflected by the price
of $28.00 per Share to be paid in the Offer and the Merger.
 
    The Board, including the Special Committee, believes that the Offer and the
Merger are procedurally fair because, among other things: (i) the Special
Committee consisted of independent directors (unaffiliated with Parent,
Purchaser or their affiliates or the Company's management) appointed to
represent the interests of the Minority Stockholders; (ii) the Special Committee
retained and was advised by independent legal counsel; (iii) the Special
Committee retained and was advised by independent financial advisors, who
assisted the Special Committee in evaluating the Offer and the Merger and
rendered a fairness opinion, as described herein; (iv) the detailed review by
the Special Committee and its advisors of the business, financial condition and
intellectual property estate of the Company and the review of the allegations of
improprieties by Parent in its relationship with the Company; (iv) the
deliberations pursuant to which the Special Committee evaluated the Offer and
the Merger and alternatives thereto; (v) the $28.00 per Share price and the
other terms and conditions of the Merger Agreement resulted from active
arms'-length bargaining between members of the Special Committee, on the one
hand, and Parent, on the other; and (vi) Purchaser is not permitted to waive the
Minimum Condition without the consent of the Special Committee unless, after the
consummation of the Offer, Parent and Purchaser would own at least 81.07% of the
Fully Diluted Shares (which would constitute the tender of a majority of the
Minority Shares, on a fully diluted basis).
 
    On August 31, 1998, the Board held a meeting and, based upon, among other
things, the unanimous recommendation of the Special Committee, determined that
the Merger Agreement and the transactions contemplated thereby, including the
Offer and the Merger, upon the terms and subject to the conditions set forth in
the Merger Agreement are fair to, and in the best interests of, the Company and
its Minority Stockholders and approved the Offer, the Merger and the Merger
Agreement and recommends that the Minority Stockholders of the Company accept
the Offer and tender their Shares to Purchaser pursuant to the Offer.
 
                                       23
<PAGE>
THE BOARD OF DIRECTORS OF THE COMPANY BELIEVES THAT THE MERGER IS FAIR TO AND IN
THE BEST INTEREST OF THE COMPANY AND THE MINORITY STOCKHOLDERS, AND, UPON THE
RECOMMENDATION OF THE SPECIAL COMMITTEE, RECOMMENDS THAT MINORITY STOCKHOLDERS
ACCEPT THE OFFER AND TENDER THEIR SHARES TO PURCHASER.
 
SUMMARY OF SPECIAL COMMITTEE INVESTIGATION OF CERTAIN ALLEGATIONS
 
    During the course of the Special Committee's due diligence efforts, the
Special Committee learned of certain allegations made by former officers and
directors of the Company. These allegations essentially alleged that Parent and
Parent's nominees to the Board had breached fiduciary duties owed to the Company
and the Minority Stockholders. The allegations, although involving numerous
specifics, fit into five general categories: (i) that Parent and its nominees
had inhibited, blocked or prevented the Company from entering into certain
transactions (such as mergers, acquisitions, joint development agreements and
the like) with third parties that allegedly would have been beneficial to the
Company; (ii) that Parent and its nominees had prevented the Company from making
a public offering; (iii) that Parent provided equity financing to the Company on
terms that were unfair to the Company; (iv), that Parent and its nominees had
offered the Company's technology to others in exchange for technology of little
or no interest to the Company, but of value to Parent; and (v) that Parent had
passed up opportunities to sell the Company as a whole for a favorable price.
 
    These allegations have been principally made by Dr. Jerry Caulder, Chief
Executive Officer of the Company until May 1997 and Thomas Cable, a director of
the Company until January 1998. In November 1997, Parent determined not to vote
for the re-election to the Board of Dr. Caulder (who had remained a member of
the Board after his resignation as Chief Executive Officer), Mr. Cable, David
Rammler, the founder of the Company, and W. Wayne Withers, formerly of Monsanto
Corporation and currently General Counsel of Emerson Electric Company.
 
    In the summer of 1997, while still members of the Board of the Company (but
after Dr. Caulder had resigned as Chief Executive Officer), Dr. Caulder and Mr.
Cable sent an unsigned letter (marked "draft") to Pedro Reinhard, Chief
Financial Officer of TDCC, cataloging a number of complaints about the way TDCC
and Parent had managed the Company. Mr. Withers sent a letter to TDCC around the
same time period requesting that the Company hire an independent law firm to
advise the independent members of the Board concerning alleged conflicts of
interest between Parent and the Company. TDCC and Parent denied the complaints
set forth in the draft letter; there is no known response to Mr. Withers' letter
and no counsel was hired. In approximately April 1998, officers of the Company
prepared two chronologies, one of which described the history of the discussions
concerning raising public equity in 1997 and Parent's ultimate refusal to permit
additional shares to be sold to the public and the other cataloging a number of
transactions with third parties that were said to have been blocked by Parent.
 
    During its due diligence review of the Company, the Special Committee
(neither of whose members had been on the Board at the time of the events in
question) learned of the Caulder/Cable draft letter and the chronologies
described above. Altheimer & Gray, as counsel to the Special Committee, assisted
the Special Committee in an investigation into these matters. Following is a
summary of the Special Committee's analysis of these documents and the
allegations set forth therein.
 
    1.  Both the Caulder/Cable draft letter and one of the management
chronologies, as well as other sources, document cases in which the Company's
management wished to pursue various business opportunities--some in the form of
acquisitions, some structured as licenses, some as joint development agreements
or otherwise--but was purportedly unable to obtain Parent's approval to do so.
These transactions involved a large range of differing circumstances. Only one
of these transactions was ever actually presented to the Board, which rejected
it by a 5-4 vote in February 1997, all of the Parent designees voting against
and all of the other directors voting in favor. Other transactions that were
favored by the
 
                                       24
<PAGE>
Company's management were not approved by the Company's "Technology Committee"
(dominated by Parent), but were not submitted to the Board. The transactions in
question were also at various stages of completion. The largest and most
ambitious projects were never close to consummation. The Special Committee had
significant questions regarding whether these transactions could have been
accomplished even with the enthusiastic support of Parent. Other potential
business deals were more advanced in their development, even at the final
contract stage. In general, the Special Committee found it impossible to tell
whether and to what extent the Company would be better off had any or all of
these transactions been accomplished. Many were in the nature of long term trait
development transactions and it would have been several years before it would be
clear whether they would have been profitable.
 
    2.  As set forth in the Caulder/Cable draft letter and the other chronology,
the Company had been considering means of financing its operations for much of
1997. The Board looked into raising money through the public sale of shares of
Common Stock. During the summer of 1997, Parent decided that it would not permit
the Company to issue new shares to anyone other than Parent, which Parent had a
right to do under the Exchange and Purchase Agreement. The Special Committee
determined that Parent's contractual rights, which had been extensively
bargained for at arms' length, supported its actions in this case. In addition,
Parent has maintained its belief that the raising of funds through outside
equity would be too expensive for the Company. Moreover, there is no assurance
that the Company could have successfully completed a public sale of shares of
Common Stock, or at what price.
 
    3.  In approximately October 1997, in connection with a proposed but
ultimately unsuccessful acquisition, Parent was prepared to purchase
approximately $150 million in value of Common Stock at $24.00 per share. A
fairness opinion for that price had been obtained. After the collapse of that
transaction, in November 1997, Parent agreed to purchase $75 million in value of
Common Stock at a contractually stipulated price of the 90 day trailing average.
This transaction was approved unanimously by the Board, including by Dr. Caulder
and Messrs. Cable, Rammler and Withers. No fairness opinion was obtained for
this transaction. During the two-month period between the time the Board
approved the transaction and when it was consummated, the 90 day trailing
average price declined from $23.02 to $19.94. Because the stock price was
falling at that time, the considerable period of time it took for Parent to
formally approve and consumate the transaction resulted in lowering the cost of
acquisition for Parent.
 
    4.  In the Caulder/Cable draft letter, the allegation is made that Parent
had offered to trade (presumably by way of a cross license) the Company's
technology to others in exchange for technology that was of little or no
interest to the Company but was of value to TDCC and Parent. However, neither
Dr. Caulder, Mr. Cable nor current management of the Company were aware of any
instance in which such a technology trade was in fact consummated.
 
    5.  Finally, Dr. Caulder has maintained that Parent could have arranged for
the sale of all of the Company's stock (including the Shares held by the
Minority Stockholders) at a considerable premium over the market price if it had
chosen to do so. The Special Committee recognized that as a matter of law,
Parent was and is under no obligation to agree to sell its own shares of Common
Stock, even if it might have been in the best interests of the Minority
Stockholders that Parent do so.
 
    TDCC, Parent and Parent's designees have denied that they acted wrongfully
with respect to any of the matters raised in these allegations.
 
    As described above, the Special Committee took these matters and the results
of its investigation into account in making its determinations described above
and in making its recommendations to the Board.
 
VALUATION BY THE FINANCIAL ADVISOR TO TDCC
 
    As noted above, Salomon Smith Barney, as financial advisor to TDCC, made a
presentation to the Special Committee on August 3, 1998, regarding its updated
views on the stand-alone valuation of the
 
                                       25
<PAGE>
Company, which presentation had previously been prepared and delivered to TDCC
(the "Salomon Smith Barney Valuation").
 
    In connection with its preparation of the Salomon Smith Barney Valuation,
Salomon Smith Barney reviewed certain publicly available information concerning
the Company and certain other financial information concerning the Company,
including financial forecasts that were developed by the managements of the
Company and Parent, respectively, and provided to Salomon Smith Barney by
Parent. Salomon Smith Barney discussed the past and current business operations,
financial condition and prospects of the Company with certain officers and
employees of Parent and TDCC. Salomon Smith Barney also considered such other
information, financial studies, analyses, investigations and financial, economic
and market criteria that it deemed relevant.
 
    In its review and analysis, and in arriving at the Salomon Smith Barney
Valuation, Salomon Smith Barney assumed and relied upon the accuracy and
completeness of the information reviewed by it for purposes of the Salomon Smith
Barney Valuation, and Salomon Smith Barney did not assume any responsibility for
independent verification of such information. With respect to the financial
forecasts of the Company, Salomon Smith Barney assumed that they had been
reasonably prepared and reflected the best currently available estimates and
judgments of the Company and Parent, and Salomon Smith Barney expressed no view
with respect to such forecasts or the assumptions upon which they were based.
Salomon Smith Barney did not assume any responsibility for making or obtaining
any independent evaluations or appraisals of any of the assets (including
properties and facilities) or liabilities of the Company, nor was it provided
with any such evaluation or appraisal.
 
    The Salomon Smith Barney Valuation was necessarily based upon conditions as
they existed and could be evaluated as of such date. The Salomon Smith Barney
Valuation is comprised of two sets of analyses: a review of a preliminary
valuation analysis prepared for TDCC and delivered on April 28, 1998
("Preliminary Valuation") and a revised valuation analysis, which updated the
Preliminary Valuation, as of August 3, 1998 ("Updated Valuation"). The Salomon
Smith Barney Valuation did not imply any conclusion as to the likely trading
range, if any, of the Shares following the consummation of a TDCC purchase of
the outside shareholders' stock, which may vary depending upon, among other
factors, changes in interest rates, dividend rates, market conditions, liquidity
and float and other factors that generally influence the price of securities.
The Salomon Smith Barney Valuation was only an estimate of the value, from a
financial point of view, of the Shares to be purchased by Parent and did not
constitute a recommendation to TDCC or to any holder of Shares as to whether
such holders should tender Shares in connection with the Offer. The Salomon
Smith Barney Valuation also does not constitute an opinion to TDCC or any other
person as to the fairness of the consideration to be paid or received in
connection with the Offer.
 
    The following is a summary of the material analyses presented and discussed
by Salomon Smith Barney at the meeting on August 3, 1998.
 
    HISTORICAL STOCK PRICE PERFORMANCE.  Salomon Smith Barney reviewed the
trading prices for Shares over the period from July 1, 1997 to July 31, 1998,
which indicated that the stock had traded from a low of approximately $18 per
Share to a high of approximately $24 per Share during such period. Salomon Smith
Barney noted that the Shares had underperformed by comparison to both the S&P
Composite Average and an index of certain of the Company's peer companies.
 
    ANALYSIS OF SELECTED PUBLICLY TRADED AGRICULTURAL BIOTECHNOLOGY
COMPANIES.  Using publicly available information, Salomon Smith Barney compared
the financial, operating and market performance of the Company with those of the
following agricultural biotechnology companies: AgriBioTech Inc., DEKALB
Genetics Corporation ("Dekalb"), Delta and Pine Land Company ("Delta & Pine
Land"), Empresas La Moderna S.A. de C.V., Monsanto Company ("Monsanto"), Pioneer
Hi-Bred International, Inc. ("Pioneer Hi-Bred"), and Vilmorin et Compagnie (the
"Comparable Companies"). Salomon Smith Barney considered the Comparable
Companies to be reasonably similar to the Company insofar as they participate in
business segments similar to the Company's business segments, but none of these
companies has the same
 
                                       26
<PAGE>
management, makeup, size and combination of businesses as the Company.
Accordingly, the analysis described below is not purely mathematical. Rather it
involves complex considerations and judgments concerning differences in
historical and projected financial and operating characteristics of the Company
and the Comparable Companies and other factors that could affect public trading
value.
 
    For the Company and each of the Comparable Companies, Salomon Smith Barney
calculated multiples of firm value to the lastest twelve months ("LTM")
revenues. Other traditional valuation measures such as multiples of firm value
to estimated 1998, 1999, and 2000 earnings as well as firm value to earnings
before interest, taxes, depreciation, and amortization ("EBITDA"), and to
earnings before interest and taxes ("EBIT") were also calculated, but deemed not
to be meaningful due to the Company's negative financial performance. The
multiples of firm value to LTM revenues for the Comparable Companies calculated
in connection with the Preliminary Valuation ranged from 1.1x to 9.2x, with a
median of 2.7x and a mean of 3.6x; while such multiple for the Company was 3.6x.
The multiples of firm value to LTM revenues for the Comparable Companies
calculated in connection with the Updated Valuation ranged from 1.4x to 9.8x,
with a median of 4.2x and a mean of 4.9x; while such multiple for the Company
was 4.2x.
 
    After review of the different sizes, focuses, market shares, and
intellectual property components of the Comparable Companies as well as the
Company's total lack of profitability as compared to the performances achieved
by the Comparable Companies, Salomon Smith Barney determined that the LTM
revenue multiple to be applied in a valuation of the Company would be
significantly less than the median multiple found in the agricultural
biotechnology sector. In addition, especially as of the Updated Valuation, the
agricultural biotechnology sector experienced considerable consolidation which
Salomon Smith Barney believed had had an unusually positive impact on the
stronger Comparable Companies' stock prices, thereby producing inflated
valuation multiples.
 
    By applying an adjusted multiple range of 1.2x to 2.5x to the Company's LTM
revenue, Salomon Smith Barney derived an implied equity value per Share ranging
from $6.34 to $13.68 for the Preliminary Valuation. In connection with the
Updated Valuation, Salomon Smith Barney applied an adjusted multiple range of
1.5x to 2.7x, resulting in an implied equity value per Share of $8.03 to $14.81.
To account for a possible minority acquisition premium associated with the
purchase of the remaining Shares, Salomon Smith Barney applied a 20% to 30%
premium (the "Premium") to the implied equity value per Share to arrive at an
estimated equity value per Share of $7.60 to $17.79 for the Preliminary
Valuation and $9.64 to $19.25 for the Updated Valuation.
 
    Salomon Smith Barney also performed a multiple analysis based upon the
Company's 2002 projected EBITDA in connection with which the implied value per
Share was derived utilizing a 20-30x multiple discounted back to 1998 in an
attempt to capture the impact of the Company's projected future profitability.
In performing this and other analyses, Salomon Smith Barney utilized two sets of
projections. The first set of projections was compiled by the Company management
and presented to Parent's Operating Committee in December 1997 ("Company
Projections"). The second set of projections included Parent's adjustments to
the Company Projections based upon the Company's recent disappointing financial
performance, the Company's poor competitive position, and differing assumptions
pertaining to the corn market ("TDCC Projections"). Using the Company
Projections, Salomon Smith Barney derived an implied value per Share of $5.98 to
$13.12 including the Premium. Using the TDCC Projections, Salomon Smith Barney
derived an implied value per Share range of $3.25 to $7.88 with the Premium.
 
    ANALYSIS OF SELECTED PRECEDENT TRANSACTIONS.  Salomon Smith Barney also
analyzed certain financial, operating and stock market information publicly
available or estimated by Parent for certain selected merger or acquisition
transactions. Since the Company's operations involve both a seed trait business
and an intellectual property business, Salomon Smith Barney reviewed ten
selected seed driven agricultural biotechnology transactions (the "Seed
Transactions") as well as twelve selected intellectual property driven
 
                                       27
<PAGE>
agricultural biotechnology transactions (the "IP Transactions") in order to
derive an implied private market valuation for the Shares.
 
    Salomon Smith Barney derived the firm values implied by the terms of the
transactions and then calculated the resulting multiples of firm value to LTM
revenues. In connection with the Preliminary Valuation, the multiple of firm
value to LTM revenues in the Seed Transactions ranged from 1.1x to 4.8x, with a
median of 2.1x and a mean of 2.3x, while the multiple of firm value to LTM
revenues in the IP Transactions ranged from 3.0x to 96.2x, with a median of
10.3x and a mean of 8.3x. To properly account for the Company's distinct seed
and intellectual property businesses, Salomon Smith Barney utilized various
blended weighted averages of the selected multiple ranges from the Seed
Transactions and IP Transactions to derive a reference valuation range of $15.23
to $19.89 per Share.
 
    The Updated Valuation included five precedent transactions which occurred
after the Preliminary Valuation was complete. By including these five
transactions in the derivation of the Seed Transaction and IP Transaction
multiple ranges and employing the blended weighted averages used in the
Preliminary Valuation, Salomon Smith Barney derived a reference valuation range
of $18.76 to $25.54 per Share.
 
    While Salomon Smith Barney considered the Seed Transactions and the IP
Transactions to be reasonably similar to the Offer and the Merger, no
transaction used in the analysis of the Precedent Transactions summarized above
is identical to such transactions. The Company's lack of profitability and weak
market position, combined with a very limited universe of potential buyers, all
impact the comparability of certain of the precedent transactions.
 
    DISCOUNTED CASH FLOW ANALYSIS.  Salomon Smith Barney also performed a
discounted cash flow analysis in connection with which reference ranges of per
Share equity value were derived based upon the sum of (i) the value, discounted
to present, of a stream of projected unlevered cash flows and (ii) a projected
terminal value.
 
    The Company's seed business and the intellectual property business were
discounted at different discount rates due to their significantly different risk
profiles. For each segment, Salomon Smith Barney conducted an analysis based
upon the Company Projections and the TDCC Projections. Due to the Company's
current negative financial performance there is a considerable impact on values
calculated by utilizing a nine year projected cash flow stream by comparison to
a four year projected cash flow stream in the discounted cash flow analysis.
Therefore, Salomon Smith Barney valued the Company utilizing each set of
projections for each of the two different segments of the business based on both
a four year and nine year set of projected discounted unlevered cash flows. For
the seed business valuations, a weighted average cost of capital ("WACC")
ranging from 12.0% to 14.0% was used and the Company terminal value was
calculated by applying a 12.0x to 18.0x range of multiples to the Company's
projected EBITDA in the final year. For the intellectual property business
valuations, Salomon Smith Barney used a 15% to 25% WACC and applied a 6.0x to
10.0x range of multiples to the Company's projected revenue in the final year to
derive the terminal value.
 
    Salomon Smith Barney calculated an implied per Share equity value for the
Company using the Company Projections ranging from $6.65 to $8.92 when four
years of cash flows were used and ranging from $8.62 to $15.51 when nine years
of projected cash flow were used. When the TDCC Projections were utilized, the
implied per Share equity value for the Company ranged from $5.21 to $6.95 when
four years of cash flows were used to $5.07 to $9.59 when nine years of
projected cash flows were used.
 
    Salomon Smith Barney prepared the Valuation solely in connection with
advising TDCC with respect to Parent's purchase of the outside shareholders'
Shares. Salomon Smith Barney has not rendered an opinion, nor does the Salomon
Smith Barney Valuation constitute its opinion, to the Company, Parent, TDCC or
any other person as to the fairness of the consideration to be paid or received
in the Offer.
 
    The preparation of valuation analyses is a complex process involving
subjective judgments and is not susceptible to partial analysis or summary
descriptions. The summary set forth above does not purport to
 
                                       28
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be a complete description of the analyses underlying the Salomon Smith Barney
Valuation. Salomon Smith Barney believes that its analysis and the summary set
forth above must be considered as a whole and that selecting portions of its
analyses and the factors considered by it, without considering all analyses and
factors, could create an incomplete view of the processes underlying the
analysis set forth in the Salomon Smith Barney Valuation. The ranges of
valuation implied by any particular analysis described above should not be taken
to be the view of Salomon Smith Barney as to the actual value of the Company.
 
    In performing its analyses, Salomon Smith Barney made numerous assumptions
with respect to industry performance, general business, financial, market and
economic conditions and other matters, many of which are beyond the control of
Parent and the Company. Any estimates contained in such analyses are not
necessarily indicative of actual values or predictive of future results, which
may be significantly more or less than such estimates. Estimated values do not
purport to be appraisals and do not necessarily reflect the prices at which
businesses or companies might actually trade or be sold.
 
    Salomon Smith Barney has acted as financial advisor to TDCC in connection
with its purchase of Shares and, as described under "Fees and Expenses" below,
will receive a fee for its services, a substantial portion of which is
contingent upon consummation of the Offer. In the ordinary course of its
business, Salomon Smith Barney and its affiliates may actively trade the equity
securities of TDCC and the Company for their own account and the accounts of
their customers and, accordingly, may at any time hold a long or short position
in such securities. Salomon Smith Barney and its affiliates have previously
rendered certain investment banking and financial advisory services to TDCC for
which they have received customary compensation. Salomon Smith Barney and its
affiliates (including Travelers Group Inc.) may have other business
relationships with TDCC, Parent or the Company in the ordinary course of their
businesses.
 
    Salomon Smith Barney is an internationally recognized investment banking
firm that provides financial services in connection with a wide range of
business transactions. As part of its business, Salomon Smith Barney regularly
engages in the valuation of companies and their securities in connection with
mergers and acquisitions, restructurings, leveraged buyouts, negotiated
underwritings, competitive biddings, secondary distributions of listed and
unlisted securities, private placements and valuations for estate, corporate and
other purposes. TDCC retained Salomon Smith Barney based on Salomon Smith
Barney's expertise in the valuation of companies as well as its familiarity with
companies in the agriculture biotechnology industry.
 
OPINION OF WASSERSTEIN PERELLA
 
    The Special Committee retained Wasserstein Perella to act as its financial
advisor in connection with the Transactions (as defined herein). Wasserstein
Perella has delivered a written opinion to the Special Committee, dated August
31, 1998, to the effect that, subject to the various assumptions and limitations
set forth therein, as of the date thereof, the $28.00 per Share cash
consideration to be received by holders of Shares (other than TDCC and its
affiliates) in the Offer and the Merger pursuant to the Merger Agreement
(collectively, the "Transactions") is fair to such shareholders from a financial
point of view. Wasserstein Perella was engaged and acted solely as an advisor to
the Special Committee and not as an advisor to or agent of any other person,
including the Company. Wasserstein Perella's opinion is for the benefit and use
of the Special Committee in its consideration of the Transactions and may not be
used for any other purpose.
 
    THE FULL TEXT OF THE WRITTEN OPINION OF WASSERSTEIN PERELLA, DATED AUGUST
31, 1998, WHICH SETS FORTH AMONG OTHER THINGS THE OPINIONS EXPRESSED, THE
ASSUMPTIONS MADE, PROCEDURES FOLLOWED, MATTERS CONSIDERED AND LIMITATIONS OF THE
REVIEW UNDERTAKEN IN CONNECTION WITH THE OPINION, IS ATTACHED AS SCHEDULE III
AND HOLDERS OF THE SHARES ARE URGED TO READ IT IN ITS ENTIRETY. WASSERSTEIN
PERELLA'S OPINION DOES NOT CONSTITUTE A RECOMMENDATION TO ANY HOLDER OF SHARES
AS TO WHETHER OR NOT SUCH
 
                                       29
<PAGE>
HOLDER SHOULD TENDER SHARES PURSUANT TO THE OFFER OR HOW SUCH HOLDER SHOULD VOTE
OR OTHERWISE ACT IN RESPECT OF THE OFFER, THE MERGER AGREEMENT OR THE
TRANSACTIONS CONTEMPLATED THEREBY AND SHOULD NOT BE RELIED UPON BY ANY HOLDER IN
RESPECT OF SUCH MATTERS. THE SUMMARY OF THE OPINION OF WASSERSTEIN PERELLA SET
FORTH HEREIN IS QUALIFIED IN ITS ENTIRETY BY REFERENCE TO THE FULL TEXT OF THE
OPINION ATTACHED AS SCHEDULE III.
 
    In connection with rendering its opinion, Wasserstein Perella, among other
things, (i) reviewed the financial terms and provisions of the Merger Agreement;
(ii) reviewed the Exchange and Purchase Agreement, dated January 15, 1996, among
the Company, Agrigenetics, Inc., Parent and United Agriseeds, Inc. (the
"Exchange and Purchase Agreement"), including TDCC's and its affiliates' rights
and obligations thereunder both if the Transactions are completed and not
completed; (iii) reviewed and analyzed certain publicly available business and
financial information relating to the Company for recent years and interim
periods to date, as well as certain internal financial and operating
information, financial forecasts, projections and analyses prepared by or on
behalf of the Company and provided to Wasserstein Perella for purposes of its
analyses; (iv) met with certain representatives of the Company and Parent to
review and discuss such information and, among other matters, the Company's
business, financial condition, results of operations and prospects; (v) reviewed
and considered certain financial and stock market data relating to the Company
and compared that data with similar data for certain other companies, the
securities of which are publicly traded and that Wasserstein Perella believed
might be relevant or comparable in certain respects to the Company or one or
more of its businesses or assets; (vi) reviewed and considered the financial
terms of certain recent acquisitions and business combination transactions in
the seed and agrobiotech industries specifically, and in other industries
generally, which Wasserstein Perella believed to be reasonably comparable to the
Transactions or otherwise relevant to its analysis; and (vii) performed such
other studies, analyses and investigations and reviewed such other information
as Wasserstein Perella considered appropriate.
 
    In its review and analysis and in formulating its opinion, Wasserstein
Perella assumed and relied on the accuracy and completeness of all the financial
and other information provided to or discussed with it or publicly available,
including the financial projections, forecasts, analyses and other information
provided to Wasserstein Perella, without assuming any responsibility for
independent verification of, or expressing an opinion as to, any of such
information. Wasserstein Perella also relied upon the reasonableness and
accuracy of the unadjusted projections, forecasts, analyses and other
information furnished to Wasserstein Perella and assumed, with the Special
Committee's consent, that such projections, forecasts, analyses and other
information were reasonably prepared in good faith and on bases reflecting the
best currently available judgments and estimates of the Company's management as
of August 31, 1998 and that management of the Company is unaware of any facts
that would make the projections, forecasts and other information provided to
Wasserstein Perella incomplete or misleading. Wasserstein Perella expressed no
opinion with respect to such projections, forecasts and analyses or the
assumptions on which they are based. Wasserstein Perella also did not review any
of the books and records of the Company or Parent, and although Wasserstein
Perella visited certain facilities of the Company, Wasserstein Perella was not
retained to conduct, and did not assume any responsibility for conducting, a
physical inspection of the properties or facilities of the Company or Parent, or
for making or obtaining an independent valuation or appraisal of the assets or
liabilities of the Company or Parent, and no such independent valuation or
appraisal was provided to it. Wasserstein Perella's opinion was based on
economic and market conditions and other circumstances as they existed and could
be evaluated by it on August 31, 1998. Although subsequent developments may
affect Wasserstein Perella's opinion, it is under no obligation to update,
revise or reaffirm its opinion. Wasserstein Perella's analysis assumes that the
transactions described in the Merger Agreement will be consummated on the terms
set forth therein, without material waiver or modification.
 
    In the context of its engagement, Wasserstein Perella was not authorized to
solicit and did not solicit alternative offers for the Company or its assets, or
investigate any other alternative transactions which may
 
                                       30
<PAGE>
be available to the Company. Wasserstein Perella expressed no opinion with
respect to the Third Party Sale Value of the Company as such term is defined in
the Exchange and Purchase Agreement.
 
    The following is a summary of the report presented by Wasserstein Perella to
the Special Committee in connection with the delivery of its opinion on August
31, 1998.
 
    DISCOUNTED CASH FLOW ANALYSES. Wasserstein Perella performed two different
discounted cash flow ("DCF") analyses of the Company based on the Company's
financial projections for the 1998-2007 period by business segment: (i) a
variable discount rate DCF analysis and (ii) a probability-weighted method DCF
analysis. The Company's projections for the 1998-2007 period include the impact
of three pending acquisitions in Brazil, including the impact of an increase in
net debt as a result of these acquisitions. Certain synergies that would be
expected in a combination with TDCC such as expense reductions and the Company's
use of net operating losses were included in the projections.
 
    In conducting the variable discount rate DCF analysis, Wasserstein Perella
used a range of discount rates and a range of terminal multiples of earnings
before interest and taxes ("EBIT") for each of the Company's more established,
growing business segments. For the Company's Biopesticides and the SoilServ
business segments, Wasserstein Perella used discount rates ranging from 11.0% to
14.0% and terminal EBIT multiples ranging from 6x to 10x. For the Company's
Conventional Seed business segment, Wasserstein Perella used discount rates
ranging from 12.0% to 14.0% and terminal EBIT multiples ranging from 8x to 12x.
For the Conventional Seed portion of the Company's joint venture with Verneuil
Holding, S.A. ("VMO") and the Company's entire AC Humko joint venture,
Wasserstein Perella used discount rates ranging from 12.0% to 14.0% and terminal
EBIT multiples ranging from 6x to 10x. For the Company's JG Boswell joint
venture, Wasserstein Perella used discount rates ranging from 12.0% to 14.0% and
terminal EBIT multiples ranging from 8x to 12x. For the Company's DAS Canada
joint venture, Wasserstein Perella used discount rates ranging from 20.0% to 24
 .0% and terminal EBIT multiples ranging from 8x to 12x. These analyses yielded
ranges of per share values for each such business segment as follows:
Biopesticides $0.09 to $0.12; SoilServ $0.73 to $1.02; Conventional Seed $6.48
to $13.05; VMO (conventional seed only) $0.18 to $0.27; AC Humko $0.06 to $0.07;
JG Boswell $1.54 to $2.22; and DAS Canada $0.34 to $0.54.
 
    With respect to the Company's less well established business segments or
business segments that rely on unproven technology, Wasserstein Perella used a
range of discount rates and a range of projected unlevered cash flow perpetuity
growth rates. For the Company's Herbicide and Insect Resistence business
segment, Wasserstein Perella used discount rates ranging from 20.0% to 24.0% and
perpetuity growth rates from 0.0% to 6.5%. For the Company's Output Traits
business segment, Wasserstein Perella used discount rates ranging from 25.0% to
30.0% and perpetuity growth rates ranging from 5.0% to 6.5%. For the Company's
Disease Resistence business segment, Wasserstein Perella used discount rates
ranging from 31.0% to 50.0% and perpetuity growth rates ranging from 8.0% to
10.0%. For all portions of the Company's VMO joint venture excluding the
conventional seed portion, Wasserstein Perella used discount rates ranging from
20.0% to 50.0% and perpetuity growth rates ranging from 5.0% to 10.0%.
Wasserstein Perella applied discount rates ranging from 20.0% to 24.0% to
projected Pioneer Hi-Bred royalties. For the Company's other partner royalties,
Wasserstein Perella used discount rates ranging from 20.0% to 24.0% and
perpetuity growth rates ranging from 1.0% to 2.5%. For the Company's other pest
and crop royalties, Wasserstein Perella used discount rates ranging from 31.0%
to 50.0% and perpetuity growth rates ranging from 5.0% to 6.5%. These analyses
yielded ranges of per share values for each business segment as follows:
Herbicide and Insect Resistence $3.75 to $6.65; Output Traits $4.71 to $8.72;
Disease Resistence $2.98 to $4.03; VMO (other than conventional seed) $0.02 to
$0.08; Pioneer Hi-Bred royalties $0.90 to $0.97; other partner royalties $0.35
to $0.54; and other pest and crop royalties $0.53 to $2.67. In addition, the
Wasserstein Perella valued certain miscellaneous items including potential cost
savings and use of net operating losses which yielded, in the aggregate, a range
of per share values from $4.64 to $6.48.
 
                                       31
<PAGE>
    This variable discount rate DCF analyses yielded an aggregate value per
share for the Shares ranging from $27.37 to $47.29. Wasserstein Perella also
noted that recent declines in volume and unit sales price with respect to corn
seed may adversely impact the Company's long term growth projections and that,
assuming the Company's recent market share erosion impacts projected market
share growth in a constant fashion, the range of values per share of the
Company's Shares would be reduced to $26.22 to $45.44.
 
    In addition, Wasserstein Perella performed a sensitivity analysis based on
certain financial forecasts provided to Wasserstein Perella by management of the
Company with respect to certain key business segments of the North America and
Brazil portions of the Company's Conventional Seed, Herbicide and Insect
Resistance and Output Traits business segments. The Base Case for the
sensitivity analysis was predicated on forecasts of the Company's market share
in each key business segment for the period from 1997 through 2007 (the "Base
Case"). The Base Case projections implied that the Company's market share of the
Conventional Seed business for corn in North American will grow from 3.4% in
1997 to 13.6% in 2007 and that such business segment's contribution to the
overall value of the Company ranges from $2.46 to $5.40 and that the Company's
market share of the Conventional Seed business for corn in Brazil will grow from
11.0% in 1997 to 29.0% in 2007 and that such business segment's contribution to
the overall value of the Company ranges from $2.65 to $4.50. The Base Case
projections also implied that the Company's market share of the Herbicide and
Insect Resistance business for corn crops in North America will grow from 3.4%
in 1997 to 13.6% in 2007 and that such business segment's contribution to the
overall value of the Company ranges from $1.88 to $3.25 and that the Company's
market share of the Herbicide and Insect Resistance business for soybean crops
in North America will grow from 1.8% in 1997 to 7.8% in 2007 and that such
business segment's contribution to the overall value of the Company ranges from
$1.16 to $1.86. The Base Case projections further implied that the Company's
market share of the Output Traits business for soybean crops in North America
will grow from 1.8% in 1997 to 7.8% in 2007 and that such business segment's
contribution to the overall value of the Company ranges from $3.77 to $6.83. In
the Base Case, these key business segments comprised 45.3% of the Company's
overall value and the remainder of the Company's value was derived from 35
additional business units and miscellaneous items.
 
    For purposes of its sensitivity analysis only, Wasserstein Perella also
considered two alternative cases (i) a revised Base Case which was predicated on
the Company achieving 75% of its projected growth in market share for the key
business segments through the year 2007 (the "75% Case") and (ii) a revised Base
Case which was predicated on the Company achieving 125% of its projected growth
in market share for the key business segments through the year 2007 (the "125%
Case"). In the 75% Case, the contribution of the Conventional Seed business for
corn in North America to the Company's overall value ranged from $0.98 to $2.87,
a reduction from the Base Case of 60.2% and the contribution of the Company's
Conventional Seed business for corn in Brazil to the Company's overall value
ranged from $2.34 to $3.91, a reduction from the Base Case of 11.7%. In the 75%
Case, the contribution of the Company's Herbicide and Pesticide Resistance
business for corn crops in North America to the Company's overall value ranged
from $1.60 to $2.76, a reduction from the Base Case of 14.9% and the
contribution of the Company's Herbicide and Pesticide Resistance business for
soybean crops in North America to the Company's overall value ranged from $0.86
to $1.36, a reduction from the Base Case of 25.9%. In the 75% Case, the
contribution of the Company's Output Traits business for soybean crops in North
America to the Company's overall value ranged from $3.55 to $6.40, a reduction
from the Base Case of 5.8%. In the 75% Case, these key business segments
comprised 40.6% of the Company's overall value.
 
    In the 125% Case, the contribution of the Conventional Seed business for
corn in North America to the Company's overall value ranged from $3.93 to $7.92,
an increase from the Base Case of 59.8% and the contribution of the Company's
Conventional Seed business for corn in Brazil to the Company's overall value
ranged from $2.97 to $5.09, an increase from the Base Case of 12.1%. In the 125%
Case, the contribution of the Company's Herbicide and Pesticide Resistance
business for corn crops in North America to the Company's overall value ranged
from $2.16 to $3.72, an increase from the Base Case of 14.9% and the Company's
Herbicide and Pesticide Resistance business for soybean crops in North
 
                                       32
<PAGE>
America to the Company's overall value ranged from $1.22 to $1.96, an increase
from the Base Case of 5.2%. In the 125% Case, the contribution of the Company's
Output Traits business for soybean crops in North America to the Company's
overall value ranged from $3.99 to $7.24, an increase from the Base Case of
5.8%. In the 125% Case, the key business segments comprised 48.7% of the
Company's overall value.
 
    The Base Case, the 75% Case, and the 125% Case resulted in per share
valuation ranges for the Shares from $27.37 to $47.29; $23.98 to $41.51 and
$30.25 to $52.38, respectively.
 
    For purposes of the probability-weighted method DCF analysis, Wasserstein
Perella used estimates provided by management of the probability that new
products will proceed through certain stages of the commercialization process
and ultimately be commercialized in order to weigh the expenses anticipated in
connection with commercializing the product and the revenues anticipated to be
generated by the product. These probability-weighted expense and revenue streams
were then used to estimate the free cash flow attributable to such products.
Wasserstein Perella lowered management's probability estimates to reflect
execution and commercialization risk in light of the size and financial
resources available to the Company's competitors as follows: (i) Wasserstein
Perella used 90% of management's probability estimates with respect to Herbicide
and Pesticide Resistance products; (ii) Wasserstein Perella used 81% of
management's probability estimates with respect to Output Traits products, and;
(iii) Wasserstein Perella used 72% of management's probability estimates with
respect to Disease Resistance products.
 
    For the Company's Biopesticides and the SoilServ business segments,
Wasserstein Perella used discount rates ranging from 10.0% to 14.0% and terminal
EBIT multiples ranging from 6x to 10x. For the Company's Conventional Seed
business segment, Wasserstein Perella used discount rates ranging from 11.0% to
14.0% and terminal EBIT multiples ranging from 8x to 10x. For the conventional
seed portion of the Company's VMO joint venture and the Company's entire joint
ventures with AC Humko and JG Boswell, Wasserstein Perella used discount rates
ranging from 11.0% to 14.0% and terminal EBIT multiples ranging from 6x to 12x.
For the Company's DAS Canada joint venture, Wasserstein Perella used discount
rates ranging from 10.0% to 14 .0% and terminal EBIT multiples ranging from 4x
to 10x.
 
    For the Company's Herbicide and Insect Resistence business segment, Output
Traits business segment, other partner royalties business segment and other pest
and crop royalties business segment, Wasserstein Perella used discount rates
ranging from 11.0% to 14.0% and perpetuity growth rates ranging from 5.0% to
6.5%. For the Company's Disease Resistence business segment and VMO joint
venture (excluding the conventional seed portion), Wasserstein Perella applied
discount rates ranging from 11.0% to 14.0% and perpetuity growth rates ranging
from 5.0% to 10.0%. Wasserstein Perella applied discount rates ranging from
10.0% to 14.0% to projected Pioneer Hi-Bred royalties.
 
    The probability-weighted method DCF analyses yielded an aggregate value per
share for the Share ranging from $27.77 to $54.92. Wasserstein Perella also
noted that recent declines in volume and unit sales price with respect to corn
seed may adversely impact the Company's long term growth projections and that,
assuming the Company's recent market share erosion impacts projected market
share growth in a constant fashion, the range of values per share would be
reduced to $26.83 to $53.29.
 
    COMPARABLE TRANSACTION ANALYSIS.  Wasserstein Perella reviewed recent
acquisitions of all the outstanding equity of, or strategic equity investments
in, four publicly traded agrobiotech companies from April 1, 1996 to August 31,
1998 in which the total purchase price for the seller ranged from $268 million
to $3.88 billion (acquiror/seller): Monsanto Company ("Monsanto")/Delta and Pine
Land Company ("Delta"); E. I. du Pont de Nemours and Company/Pioneer Hi-Bred
International, Inc. ("Pioneer"); Monsanto/DeKalb Genetics Corporation
("DeKalb"); and Monsanto/Calgene, Inc. ("Calgene"). In those transactions in
which only a substantial equity investment was made, the purchase price was
adjusted to translate the price the acquiror paid for part of the seller into a
price for the entire company.
 
    For each transaction, Wasserstein Perella calculated the multiple of
announced purchase price (or adjusted purchase price in the case of substantial
equity investments) to the seller's (i) last twelve months
 
                                       33
<PAGE>
("LTM") sales, (ii) LTM earnings before interest, taxes, depreciation and
amortization ("EBITDA") and (iii) LTM EBIT. Wasserstein Perella also calculated
the implied equity value of each seller as a multiple of net income and book
value.
 
    The analysis of the foregoing four transactions, excluding certain multiples
which Wasserstein Perella determined were not meaningful, yielded a range of
multiples of (a) announced or adjusted purchase price to (i) LTM sales of 4.6x
to 9.87x, (ii) LTM EBITDA of 18.4x to 69.8x, (iii) LTM EBIT of 22.6x to 89.6x
and (b) of implied equity value to (i) net income of 33.9x (in the one instance
in which such information was meaningful) and (ii) book value of 3.1x to 25.1x.
Wasserstein Perella used these comparable transaction multiples to calculate
implied values for the shares based on the ranges of multiples derived from such
transactions. The per Share value implied by this analysis ranged from $33.24
per share to $38.85 per share.
 
    PREMIUM ANALYSIS.  As part of its analysis, Wasserstein Perella reviewed
three acquisition transactions by majority shareholders of publicly owned
minority interests in agrobiotech companies with values ranging from $119.4
million to $3,426 million to derive a range of premiums paid over (i) the
seller's market price per share one day prior to the announcement of the
respective transaction (the "1-Day Market Price"); (ii) the seller's market
price per share 30 days prior to the announcement of the respective transaction
(the "30-Day Market Price"); and (iii) the seller's market price per share 60
days prior to the announcement of the respective transaction ("60-Day Market
Price"). The three transactions involved the following pairs of companies
(acquiror/seller): Monsanto/Calgene; Novartis AG/SyStemix, Inc.; and
Monsanto/DeKalb (the "Premium Transactions").
 
    The Premium Transactions yielded a range of acquisition premiums to the
1-Day Market Price of 34.9% to 77.3% with a mean of 52.5% and a median of 45.5%.
The 1-Day Market Price of the Company was $20.50. The median acquisition premium
to the 1-Day Market Price for the Premium Transactions implies a per share price
of $29.82. The mean acquisition premium to the 1-Day Market Price for the
Premium Transactions implies a per share price of $31.27.
 
    The Premium Transactions yielded a range of acquisition premiums to the
30-Day Market Price of 41.2% to 60.0% with a mean of 53.5% and a median of
59.2%. The 30-Day Market Price of the Company was $18.25. The median acquisition
premium to the 30-Day Market Price for the Premium Transactions implies a per
share price of $29.05. The mean acquisition premium to the 30-Day Market Price
for the PremiumTransactions implies a per share price of $28.01.
 
    The Premium Transactions yielded a range of acquisition premiums to the
60-Day Market Price of 42.57% to 48.6% with a mean of 45.5% and a median of
45.5%. The 60-Day Market Price of the Company was $17.00. The median acquisition
premium to the 60-Day Market Price for the Premium Transactions implies a per
share price of $24.73. The mean acquisition premium to the 60-Day Market Price
for the Premium Transactions implies a per share price of $24.74.
 
    COMPARABLE COMPANY ANALYSIS.  Wasserstein Perella reviewed and compared
certain financial information of the Company to corresponding financial
information for four publicly traded companies: Pioneer; DeKalb; Delta and
Agribiotech, Inc. (collectively, the "Comparable Companies"). Such financial
information was used to calculate for each Comparable Company (a) the
price/earnings ratio ("P/E Ratio") for 1997, the estimated P/E ratio for 1998,
the ratio of 1998 estimated P/E Ratio to estimated three to five year earnings
growth rate and the price to book ratio, (b) the multiple of adjusted market
value to 1997, LTM and estimated 1998 and 1999 financial results, including
sales, EBITDA and EBIT and (c) net debt as a percentage of market
capitalization.
 
    Such analysis, excluding certain multiples which Wasserstein Perella
determined were not meaningful, indicated that, (a) the Company had a price to
book ratio of 4.1x, as compared to a range of 4.6x to 18.3x, with a mean of
10.1x and a median of 8.8x, for the Comparable Companies, (b) with respect to
adjusted market value, (i) the Company traded at a multiple of 4.29x 1997 sales,
as compared to a range of 1.34x to
 
                                       34
<PAGE>
10.32x, with a mean of 5.66x and a median of 5.50x, for the Comparable
Companies, (ii) the Company traded at a multiple of 4.15x LTM sales, as compared
to a range of 1.34x to 9.33x, with a mean of 5.20x and a median of 5.08x, for
the Comparable Companies, (iii) the Company traded at a multiple of 3.53x
estimated 1998 sales, as compared to a range of 1.45x to 7.13x, with a mean of
4.72x and a median of 5.15x, for the Comparable Companies, (iv) the Company
traded at a multiple of 3.03x estimated 1999 sales, as compared to a range of
0.72x to 5.33x, with a mean of 3.87x and a median of 4.71x, for the Comparable
Companies and (c) the Company's net debt was 9.9% of its market capitalization,
as compared to a range of (2.3%) to 9.5%, with a mean of 2.6% and a median of
1.6% for the Comparable Companies. The above analysis, when adjusted to account
for control premiums of 10%, 30% and 50%, implied per share values of $30.22,
$31.93 and $33.64, respectively.
 
    COMPOSITE RANGE.  Based on the above analyses, Wasserstein Perella derived a
composite range of per share values of $25.00 to $35.00. In deriving this
composite range, Wasserstein Perella took into account, among other things, that
(i) the Company historically has failed to achieve its operating projections and
the projections provided to Wasserstein Perella by management of the Company
were significantly higher than those included in the Company's 1997 business
plan, (ii) the Company is projecting net operating losses for the next several
years, (iii) due to the fact that the Company is projecting net losses for the
next several years, the inherent uncertainty associated with the success and
timing of scientific research activities and the historical uncertainty
associated with the Company's cash flows, selection of appropriate discount
rates for purposes of the DCF analyses set forth above involved a greater than
usual degree of subjective judgement, and (iv) the Company's competitors
generally are significantly larger, better established companies with much
greater resources, larger market capitalization, greater market share and a
history of profits.
 
    CERTAIN GENERAL MATTERS.  No company or transaction used in the foregoing
analyses is identical to the Company or the Transactions. In addition, those
analyses and the discounted cash flow analyses are based and heavily dependent
upon, among other factors, assumptions as to future performance and other
factors, and are therefore subject to the limitations described in Wasserstein
Perella's opinion. Accordingly, an analysis of the results of the foregoing is
not entirely mathematical; rather, it involves complex considerations and
judgments concerning differences in financial and operating characteristics of
the companies and other factors that could affect the acquisition value or the
public trading value of the companies to which they are being compared and the
Company.
 
    A fairness analysis is a complex process and is not necessarily susceptible
to a partial analysis or summary description. Wasserstein Perella believes that
its analyses must be considered as a whole and that selecting portions of its
analyses, without considering the analyses taken as a whole, would create an
incomplete view of the process underlying the analyses performed in reaching its
opinion. In addition, Wasserstein Perella considered the results of all such
analyses and did not assign relative weights to any of the analyses, so that the
ranges of valuations resulting from any particular analysis described above
should not be taken to be Wasserstein Perella's view of the actual value of the
Company.
 
    In performing its analyses, Wasserstein Perella made numerous assumptions
with respect to industry performance, general business and economic conditions
and other matters, many of which are beyond the control of the Company. The
analyses performed by Wasserstein Perella are not necessarily indicative of
actual values, which may be significantly more or less favorable than suggested
by such analyses. Such analyses were prepared solely as part of Wasserstein
Perella's opinion. The analyses do not purport to be appraisals or to reflect
the prices at which a company might actually be sold.
 
    The Special Committee retained Wasserstein Perella based upon its experience
and expertise. Wasserstein Perella is an internationally recognized investment
banking and advisory firm. Wasserstein Perella, as part of its investment
banking business, is continuously engaged in the valuation of businesses and
securities in connection with mergers and acquisitions, negotiated
underwritings, competitive biddings, secondary distributions of listed and
unlisted securities, private placements and valuations for corporate
 
                                       35
<PAGE>
and other purposes. In the course of its market marking and other trading
activities, Wasserstein Perella and its affiliates may, from time to time, have
a long or short position, and may buy and sell, securities of the Company.
 
ENGAGEMENT AGREEMENTS OF FINANCIAL ADVISORS
 
    Pursuant to the terms of a letter agreement, dated June 11, 1998 between
Wasserstein Perella and the Company (the "Wasserstein Perella Letter
Agreement"), the Special Committee retained Wasserstein Perella to serve as
financial advisor to the Special Committee with respect a proposal received by
the Company from Parent (i) to amend the Exchange and Purchase Agreement and
(ii) following such amendment, to acquire all outstanding Shares held by persons
other than TDCC and its affiliates at a price initially proposed to be $20.50
per share (an "Engagement Transaction").
 
    The Company agreed in the Wasserstein Perella Letter Agreement to pay
Wasserstein Perella $250,000 upon the execution of the Wasserstein Perella
Letter Agreement and an additional fee of $1,000,000 at such time as Wasserstein
Perella advises the Special Committee that it is prepared to render an opinion
to the Special Committee with respect to the fairness from a financial point of
view of the consideration to be received by the public holders of Shares
pursuant to an Engagement Transaction or that, having completed its review of
the proposed Engagement Transaction, it is unable to render such an opinion. In
addition, the Company also agreed to pay Wasserstein Perella upon the
consummation of an Engagement Transaction 0.50% of the aggregate value paid or
payable to the public shareholders of the Company, in excess of $20.50 per share
plus 1.80% of the aggregate value paid or payable to such shareholders in excess
of $24.06. The Company and Wasserstein Perella further agreed that fees paid to
Wasserstein Perella shall in no event be less than $2,250,000 or more than 0.80%
of the aggregate value paid to public shareholders.
 
    Pursuant to the terms of a letter agreement, dated July 31, 1998, between
Merrill Lynch & Co. ("ML") and the Company (the "ML Letter Agreement"), the
Special Committee retained ML to make available to the Special Committee certain
employees of ML formerly employed by Wasserstein Perella. The Company agreed in
the ML Letter Agreement to pay ML $300,000 if a definitive agreement with
respect to the Transactions was executed on or prior to August 29, 1998 or
$500,000 if a definitive agreement with respect to the Transactions was executed
after August 29, 1998.
 
    The Company has also agreed to reimburse Wasserstein Perella and ML, subject
to certain limitations, for all reasonable out-of-pocket expenses incurred by
Wasserstein Perella and ML (including the reasonable fees and disbursements of
counsel) in connection with the matters contemplated by the Wasserstein Perella
Letter Agreement and the ML Letter Agreement. In addition, pursuant to the terms
of an indemnification agreement with Wasserstein Perella, dated June 11, 1998,
and an indemnification agreement with ML, dated July 31, 1998, the Company
agreed to indemnify Wasserstein Perella and ML (and their affiliates, their
respective directors, officers, agents, employees and controlling persons)
against certain liabilities arising out of or in connection with Wasserstein
Perella's and ML's engagements, including liabilities under the federal
securities laws.
 
    Such report, opinion or appraisal shall be made available for inspection and
copying at the principal executive offices of the Company between 9:00 a.m. and
5:00 p.m. Eastern time by any interested stockholder or his representative who
has been so designated in writing. A copy of such report, opinion or appraisal
will be transmitted by the Company to any interested stockholder or his
representative who has been so designated in writing upon written request and at
the expense of the requesting stockholder.
 
POSITION OF PARENT, PURCHASER, ROFAN, CENTEN AND TDCC REGARDING FAIRNESS
  OF THE OFFER AND THE MERGER
 
    Parent, Purchaser, Rofan, Centen and TDCC (the "Dow Entities") believe that
the acquisition of all of the outstanding Shares of the Company is necessary in
order for the Company to sustain its viability in
 
                                       36
<PAGE>
the highly competitive business environment in which it operates. In particular,
the Dow Entities believe that it will be necessary to utilize efficiently the
financial, technological and other resources of the Company and Parent in order
for the Company to effectively compete in the plant genetics biotechnology
industry, which has been undergoing rapid consolidation. The Dow Entities have
concluded that utilizing the resources of the Company and Parent in the most
effective manner will only be possible if the Company becomes a wholly owned
subsidiary of Parent.
 
    The Dow Entities believe that the consideration to be received by the
Company's stockholders pursuant to the Offer and the Merger is fair to the
Minority Stockholders. The Dow Entities base this belief on (i) the fact that
the Company's Board of Directors, acting upon the unanimous recommendation of
the Special Committee, determined that the Merger Agreement and the transactions
contemplated thereby, including the Offer and the Merger, upon the terms and
subject to the conditions set forth in the Merger Agreement are fair to, and in
the best interests of, the Company and its Minority Stockholders, (ii) the fact
that the Dow Entities and their financial and legal advisors negotiated the
Merger Agreement with the Special Committee on an arms'-length basis, (iii) the
financial analysis of Salomon Smith Barney provided to certain senior executives
of the Dow Entities and summarized above, (iv) the current and historical market
prices for the Shares and the fact that the consideration to be paid in the
Offer and the Merger represents a premium of 40% over the closing price for the
Shares on the NASDAQ NMS on August 31, 1998, the last trading day prior to the
public announcement of the execution of the Merger Agreement and (v) the fact
that Parent is not interested under any circumstances in selling its interest in
the Company to a third party. The Dow Entities have reviewed the factors
considered by the Special Committee in support of its decision, as described
above, and have no basis to question their consideration of or reliance on those
factors. None of the Dow Entities found it practicable to assign, nor did any of
them assign, relative weights to the individual factors considered in reaching
their conclusion as to fairness.
 
SHAREHOLDER LITIGATION
 
    In early May 1998, seven putative class action lawsuits were filed in the
Superior Court of California for the County of San Diego by various alleged
shareholders of the Company (the "plaintiffs") against the Company and the
individual directors of the Company (the "defendants"), Parent and TDCC,
purportedly on behalf of themselves and a putative class of all other
shareholders of the Company, excluding the defendants and any affiliates of the
defendants. These cases have been consolidated by the court under the lead case
of LESLIE SUSSER V. MYCOGEN CORP., ET AL., Case No. 720255. Each of the class
action complaints alleged in substance that the original acquisition price of
$20.50 proposed by Parent was inadequate and that it would be a breach of the
defendants' fiduciary duties to the plaintiffs and the members of the putative
class to agree to an acquisition at that price. The defendants deny all of these
allegations. The lawsuits seek an injunction against the acquisition by Parent,
damages and an award of attorneys' fees and expenses.
 
    The court approved the law firms of Milberg Weiss Bershad Hynes & Lerach LLP
and Abbey, Gardy & Squitieri as plaintiffs' co-lead counsel. Parent and the
Special Committee provided financial analyses prepared by their financial
advisors and other documents and information relating to the proposed
transaction to plaintiffs co-lead counsel. Plaintiffs' co-lead counsel retained
an independent financial advisor and, together with that advisor, reviewed these
materials and other publicly available information filed with the Commission
with respect to the Company. Plaintiffs' co-lead counsel and their financial
advisor also met in person with attorneys and financial advisors for Parent,
TDCC and the Special Committee to discuss the proposed transaction and the
ongoing negotiations between Parent and the Special Committee, and to present
their views.
 
    Plaintiffs' co-lead counsel, after consultation with their independent
financial advisor, have agreed in principle that the terms of the Offer and the
Merger are fair to and in the best interests of the plaintiffs and the members
of the putative class. Based on this agreement in principle, plaintiffs' co-lead
counsel and counsel for the defendants entered into a Memorandum of
Understanding on September 3, 1998 providing
 
                                       37
<PAGE>
for settlement of the lawsuits. The settlement is subject to the right of
plaintiffs' co-lead counsel to conduct further investigation and to take further
discovery from the defendants in order to confirm the fairness of the terms of
the Offer and the Merger. The settlement also is conditioned on the closing of
the Offer and subject to the approval of the court. The settlement does not
require any payments by or to any party, except that the defendants will pay
attorneys' fees to the plaintiffs' attorneys in an amount to be determined by
the court. The payment of attorneys' fees will be made by Parent or TDCC and
will not affect the Offer Price or the amount to be paid to any shareholder for
such shareholder's Shares. The Memorandum of Understanding provides for the
members of the putative class to be given notice and the opportunity to be
excluded from the settlement in such manner as the court determines to be
appropriate.
 
    In the event settlement of the above-described actions is not consummated
and plaintiff's counsel continues above-described actions, such litigation could
result in substantial expense to the Company and significant diversion of
efforts of the Company's management team. The Company believes that all of such
lawsuits are without merit, and would vigorously defend such actions. There can
be no assurance, however, that the plaintiffs will not be successful. The above
summary does not purport to be complete and is qualified in its entirety by
reference to the full text of the complaints, the order of consolidation and the
Memorandum of Understanding, which are attached as Exhibits to the Schedule
14D-1 filed by Purchaser, respectively, and which are incorporated herein by
reference in their entirety.
 
CERTAIN RELATIONSHIPS
 
    THE EXCHANGE AND PURCHASE AGREEMENT.  On January 15, 1996, Parent, the
Company, Agrigenetics, Inc. (currently a wholly owned subsidiary of the Company)
and United AgriSeeds, Inc. entered into the Exchange and Purchase Agreement
pursuant to which, among other things, Parent acquired 2,707,884 Shares on
February 20, 1996.
 
    Pursuant to the Exchange and Purchase Agreement, Parent agreed that from
February 20, 1998 to February 20, 1999, Parent would not acquire more than 65%
of the outstanding Shares (excluding Shares purchased directly from the Company
or its employees). Furthermore, Parent agreed not to acquire from any person
more than 79.9% of the total outstanding Shares except pursuant to a Buyout
Transaction as described below.
 
    Under the Exchange and Purchase Agreement, following February 20, 1999,
Parent would be permitted to increase its beneficial ownership of Shares above
79.9% of the total outstanding Shares only pursuant to a Buyout Transaction. A
Buyout Transaction could only be effected if approved by a majority of the
Company's independent directors or if the value to be offered to holders of
Shares were determined by an independent appraiser.
 
    The Exchange and Purchase Agreement also provides that, until February 20,
1999, (a) at any time Parent is the beneficial owner of less than 20% of the
outstanding Shares, Parent will be entitled to designate for nomination one
person to serve on the board of directors of the Company, (b) at any time Parent
is the beneficial owner of 20% or more but less than 30% of the outstanding
Shares, Parent will be entitled to designate for nomination two directors of the
Company, (c) at any time Parent is the beneficial owner of 30% or more but less
than 50% of the outstanding Shares, the Company will cause its Board of
Directors to consist of seven members and Parent will be entitled to designate
for nomination three (or, if the number of directors is other than seven, the
nearest whole number less than one-half times the total number of directors)
directors of the Company and (d) at any time Parent is the beneficial owner or
more than 50% of the outstanding Shares, the Company will cause its Board of
Directors to consist of nine directors and Parent will be entitled to designate
for nomination five (or, if the number of directors is other than nine, the
nearest whole number greater than one-half times the total number of directors)
directors of the Company. Five of the directors of the Company are designees of
Parent at the present time.
 
                                       38
<PAGE>
    Under the terms of the Exchange and Purchase Agreement, so long as Parent
has the right to nominate at least two members to the Company's Board of
Directors, the Company agreed that it would not, without prior approval of
Parent, issue any Shares or any securities exchangeable for or having the same
voting rights as Shares except: (i) Shares authorized and reserved as of January
15, 1996 pursuant to certain existing benefit plans; (ii) new securities
exchangeable for or having the same voting rights as not more than an aggregate
of 2,000,000 Shares pursuant to employee benefit plans approved by the Company
during the three-year period ending February 20, 1999; and (iii) not more than
2,000,000 Shares in exchange for the assets or securities of one or more other
persons. If the Company proposes to issue any Shares pursuant to the above, the
Company is obligated to offer Parent the right to purchase at market value
additional Shares to permit Parent to maintain its total percentage interest in
the Company.
 
    Following February 20, 1998, the Company is not permitted under the Exchange
and Purchase Agreement to issue new securities for cash, other than (i) any
securities issuable upon conversion of any convertible security of the Company
outstanding as of January 15, 1996, (ii) any securities issuable upon exercise
of any option, warrant or other similar security of the Company authorized as of
January 15, 1996, and (iii) any securities issuable to stockholders of the
Company on a proportional basis in connection with any stock split, stock
dividend or recapitalization of the Company, unless the Company affords Parent a
right of first refusal to purchase all of the new securities proposed to be
issued (other than any new securities issued to officers, directors and
employees pursuant to any existing benefit plans or any newly created employee
benefit plan or to Parent and its affiliates.)
 
    The Company also agreed in the Exchange and Purchase Agreement that it (i)
would ensure that the Rights Agreement and the rights thereunder would not
prevent Parent or an affiliate from acquiring or proposing to acquire some or
all of the outstanding Shares and (ii) would not amend, interpret or enforce the
Rights Agreement or adopt any new shareholder rights agreement if such action
would have an adverse effect on Parent or on the ability of Parent or an
affiliate to acquire or propose to acquire some or all of the outstanding
Shares.
 
    Under the terms of the Merger Agreement, the Exchange and Purchase Agreement
was amended to the extent necessary to permit the execution, delivery and
performance of the Merger Agreement and the transactions contemplated thereby,
including the Offer and the Merger. The Merger Agreement also provides that the
Exchange and Purchase Agreement will be deemed to have been canceled and
terminated and no longer binding on the parties except for a section of that
agreement (providing for the continued inapplicability of the Company's
Shareholder Rights Plan to Parent and its affiliates) upon consummation of the
Offer, even if Purchaser waives the Minimum Condition and the Merger cannot be
consummated.
 
    TECHNOLOGY AGREEMENT.  Pursuant to the Exchange and Purchase Agreement, the
Company, Agrigenetics and Parent executed an Agreement (the "Technology
Agreement") providing for the exchange between the parties of certain currently
existing genes and tools and certain new genes and tools developed or acquired
by the parties during the five year period ending February 20, 2001.
 
    LOAN ARRANGEMENTS.  Pursuant to certain loan arrangements, the Company may
borrow up to $75 million from Parent, of which $20.0 million was unused at
August 31, 1998. Such advances from Parent are due September 30, 1999. Pursuant
to certain other loan arrangements, Parent may borrow up to $75 million from the
Company, none of which was outstanding at August 31, 1998. Additionally, the
Company's Argentina subsidiary may borrow up to $50 million from an affiliate of
Parent, of which $38.5 million was unused at August 31, 1998; any of these
borrowings are due December 31, 1998. The Company maintains an $11.3 million
unsecured term loan due February 1, 2002, which bears interest at a rate of 7.5%
through February 1999. Additionally, the Company has a $10.0 million bank line
of credit facility, which expires February 1999, all of which was unused at
August 31, 1998. The Company has advanced to Dow Quimica S.A., a subsidiary of
TDCC, $9.9 million as of August 13, 1998. Any advances to Dow Quimica are due
April 27, 1999.
 
                                       39
<PAGE>
    SERVICES AGREEMENT.  Pursuant to a services agreement, Parent has agreed to
provide certain services to the Company including commercial, finance, treasury,
tax, order entry, logistics, operations planning, information systems, legal,
materials, management, controllers and purchasing services.
 
    VERNEUIL HOLDING S.A.  In January 1998, the Company obtained an additional
16.25% interest in VMO in exchange for the issuance of 483,439 Shares to Parent
valued at $9.4 million. The Company now owns 35% of VMO.
 
    OILSEED BRASSICA AGREEMENT.  Parent's subsidiary, Dow AgroSciences Canada
(DASC), and the Company are parties to a Brassica License and Research
Agreement, effective as of May 15, 1996 the ("Brassica Agreement"). Under the
Brassica Agreement, DASC and the Company has agreed to develop imporved
cultivars and incorporate insect resistance traits in oilseed BRASSICA varieties
in a program to be funded by DASC (the "Brassica Program"). Program product
goals and development targets will be determined by a Management Development
Committee consisting of two employees of the Company and three employees of
DASC. DASC is obligated to fund the Brassica Program at a minimum level of
$750,000 per year for at least 5 years.
 
    Under the Brassica agreement, the Company granted to DASC an exclusive
license to make, use, sell and sublicense BRASSICA varieties developed by the
Company prior to the date of the agreement, as well as BRASSICA varieties
developed under the Brassica Agreement. DASC agreed to pay the Company royalties
on equal to 5% of the Net Sales of any such varieties, plus 20% of the premium
earned for varieties which have an oleic acid content in their oil of 70% or
more. In connection with the above, DASC granted the Company: (i) an option to
obtain a license to any of the foregoing varieties on terms no less favorable
than those offered to any third party licensee (but only to the extent that DASC
has licensed such varieties to third parties), and (ii) a first right of
production of seed of such varieties for DASC and its affiliates.
 
    In addition, pursuant to the Brassica Agreement, the Company granted DASC:
(i) an option to obtain a license to any Round-Up-Registered Trademark- Ready
traits which the Company may obtain for use in BRASSICA, to the extent that the
Company can sublicense such traits, and (ii) an option to obtain a license to Bt
and other future traits for use in BRASSICA, (but only to the extent that the
Company has licensed such traits to third parties); in each case on terms no
less favorable than those offered to any third party.
 
    HIGH OIL CORN AGREEMENT.  Parent and the Company are parties to a Maize High
Oil Breeding and License Agreement effective as of April 1996 (the "Maize High
Agreement").
 
    Under the Maize High Agreement, Parent and the Company agreed to engage in a
maize high oil development program (the "Maize High Program") using their
intellectual property to develop varieties of corn with an oil content of 5% or
more. Under the Maize High Program, using germplasm from both Parent and the
Company, the Company agreed to use diligent efforts to incorporate developmental
targets into maize germplasm. Parent is obligated to pay the direct costs for
the Maize High Program for a minimum of 5 years, up to a total agreegate amount
during that period of $5,300,000.
 
    Under the Maize High Agreement, the Company granted to Parent a
royalty-bearing license to use and sublicense the Company's intellectual
property and inbreds to the extent necessary to make, have made, use, sublicense
and sell high oil inbreds and hybrids. In consideration of this license Parent
agreed to pay the Company royalties ranging from 1.5% to 6.0% of the net sales
of Parent, its affiliates and their sublicensees based on the percentage of
Mycogen germplasm in the parent inbred lines used to produce each variety.
However, no royalty will be due on any high oil variety if the parent inbred
lines for the variety all contain less than 50% of Mycogen germplasm. In
addition, if a variety contains a Bt or other Company value added trait under
rights proprietary to the Company, then Parent will pay an additional royalty,
to be negotiated in good faith by the parties, for a non-exclusive license to
such trait. Parent also granted the Company and its affiliates an option to
produce high oil varieties for itself, and high oil foundation seed for Parent,
its affiliates and their sublicensees provided the Company or its affiliate (i)
is
 
                                       40
<PAGE>
able to offer such production on a competitive basis, and (ii) has the internal
capacity to process said production without contracting with a non-affiliated
party.
 
    FORFEITURE OF DIRECTOR OPTIONS TO PARENT.  Persons who are designated by
Parent to serve on the Board of the Company have agreements with Parent pursuant
to which such persons agree to forfeit to Parent any Shares issuable pursuant to
options granted in connection with such service.
 
10. PURPOSE OF THE OFFER; THE MERGER AGREEMENT
 
PURPOSE OF THE OFFER
 
    The purpose of the Offer is to enable Parent, through Purchaser, to acquire
any and all outstanding Shares. If the Minimum Condition is satisfied and
Purchaser purchases Shares pursuant to the Offer, Purchaser intends to exercise
its right under California Law, if and to the extent available, to acquire all
of the Shares not purchased in the Offer by way of a statutory short-form
merger.
 
THE MERGER AGREEMENT
 
    The following is a brief summary of certain provisions of the Merger
Agreement. This summary does not purport to be complete and is qualified in its
entirety by reference to the Merger Agreement which has been filed as an exhibit
to the Schedule 14D-1.
 
THE OFFER
 
    Pursuant to the terms of the Merger Agreement, Purchaser was required to
commence the Offer no later than the fifth business day following the public
announcement of the terms of the Merger Agreement. Purchaser will, and Parent
will cause Purchaser to, subject only to the prior satisfaction or waiver of the
conditions of the Offer, accept for payment Shares validly tendered as soon as
it is legally permitted to do so under applicable law. As promptly as
practicable after such acceptance, Purchaser will, subject to applicable law,
pay for such Shares. The Offer Price payable in the Offer will be paid net to
the seller in cash, upon the terms and subject to the conditions of the Offer,
including the Minimum Condition and the other conditions described in Section
13. Purchaser may not waive the Minimum Condition without the consent of the
Special Committee unless, following the consummation of the Offer, Purchaser and
Parent, collectively, would be the owners of Shares representing at least 81.07%
of the Fully Diluted Shares. Parent and Purchaser would collectively own at
least this percentage of Fully Diluted Shares only if Purchaser purchased a
majority of the Fully Diluted Shares which Parent does not already own and
therefore could be purchased by Purchaser pursuant to the Offer. Purchaser may
increase the cash Offer Price, provided that no change may be made that
decreases the Offer Price, changes the form of consideration payable in the
Offer, reduces the maximum number of Shares to be purchased in the Offer or
imposes conditions to the Offer in addition to those set forth in Section 13.
 
    The initial expiration date of the Offer will be midnight on Friday, October
2, 1998, the 20th business day following commencement of the Offer. The
foregoing notwithstanding, Purchaser may, without the consent of the Company,
extend the Offer (i) for any period required by any rule, regulation,
interpretation or position of the Commission or the staff thereof applicable to
the Offer, (ii) if at any scheduled expiration date any of the conditions to the
Offer set forth in paragraphs (a) - (e) of Section 13 have not been satisfied or
waived, until such time as all of such conditions will have been satisfied or
waived, or (iii) in the event all of the conditions to the Offer will have been
satisfied or waived, other than the Minimum Condition, for a period or periods
aggregating not more than 40 business days after the later of (A) the initial
expiration date of the Offer and (B) the date on which all of the conditions set
forth in paragraphs (a) - (e) of Section 13 will have been satisfied or waived.
If at any scheduled expiration date of the Offer, the Minimum Condition will not
have been satisfied, then, at the request of the Company (acting at the
direction of the Special Committee, which request will subsequently be confirmed
in writing), Purchaser will, and Parent will cause Purchaser to, extend the
Offer for a period or periods aggregating not
 
                                       41
<PAGE>
more than 40 business days, subject to the right of Purchaser and Parent to
terminate the Merger Agreement as described herein. In addition, if at any
scheduled expiration date of the Offer, a condition set forth in paragraph (c)
or (d) of Section 13 will not have been satisfied but all of the other
conditions set forth in paragraphs (a) - (e) of Section 13 will then have been
satisfied, then, at the request of the Company (acting at the direction of the
Special Committee, which request will subsequently be confirmed in writing) and
so long as the Company is using its reasonable best efforts to cause such
conditions to become satisfied, Purchaser will, and Parent will cause Purchaser
to, extend the Offer for up to an additional 20 business days, subject to the
right of Purchaser and Parent to terminate the Merger Agreement as described in
"Termination" below. Subject to the right of Purchaser and Parent to terminate
the Merger Agreement as described in "Termination" below, Purchaser will not
terminate or withdraw the Offer prior to any scheduled expiration date of the
Offer, including as extended as described in this paragraph; provided, however,
that Purchaser may, at its option, terminate and withdraw the Offer if, after
such required extensions described in this paragraph, the Offer has expired in
accordance with its terms without Purchaser being required to accept Shares for
payment pursuant to the Merger Agreement.
 
    The Merger Agreement requires, as soon as practicable on the date of
commencement of the Offer, (a) Parent and Purchaser to file with the Commission
(i) a Tender Offer Statement on Schedule 14D-1 with respect to the Offer, which
will contain the Offer to Purchase and form of the related Letter of Transmittal
and (ii) a Rule 13e-3 Transaction Statement with respect to the Offer and the
other transactions contemplated thereby and (b) the Company to file a
Solicitation/Recommendation Statement on Schedule 14D-9, which it will mail to
stockholders promptly after the commencement of the Offer. Purchaser and the
Company also agreed to take all steps necessary to cause the Offer to Purchase
and form of the related Letter of Transmittal to be disseminated to holders of
Shares as and to the extent required by applicable law.
 
OPTIONS
 
    If the conditions set forth in "Conditions to the Consummation of the
Merger" below are satisfied, the Company will use its best efforts to cause all
Options still outstanding immediately prior to the Effective Time (as defined
below) to become exercisable immediately prior to the Effective Time and to
terminate and cease to be outstanding as of the Effective Time; provided,
however, that arrangement will be made so that each holder of such an Option who
consents to the termination of Options (either before the Effective Time or
within a reasonable time thereafter) will be entitled to receive in respect of
such Option an amount in cash equal to (x) the Offer Price less the exercise
price per Share under such Option multiplied by (y) the number of Shares covered
by such Option. Without limiting the generality of the foregoing, the Company's
best efforts will, if necessary, be deemed to include the Company's Board of
Directors amending the 1992 Plan to provide that the term "Corporate
Transaction" shall be deemed to include the Merger.
 
    As soon as practicable after the commencement of the Offer, the Company will
use its reasonable best efforts to cause each holder of Options (whether or not
such Options are vested) to execute and deliver to the Company, prior to the
expiration of the Offer, an agreement (an "Option Election") under which such
holder would agree, contingent upon the purchase of Shares by Purchaser pursuant
to the Offer, to cause, immediately prior to the expiration of the Offer, such
Option to be exercised and the Shares issued as a result of that exercise to be
tendered in the Offer. The Company and Purchaser will reflect on their books and
records the transactions effected pursuant to the Option Elections. Subject to
the terms of the Option Elections and contingent upon the purchase of Shares by
Purchaser pursuant to the Offer, the Company will make available to each holder
of Options the funds necessary to exercise such Options, and Parent will advance
such funds to the Company. The funds advanced to any Option holders in
accordance with the preceding sentence will be deducted from the amount payable
to such Option holder pursuant to the Offer, and the Option Election and the
Offer shall so provide. The funds so deducted will be retained by Purchaser as
repayment of the amount advanced to the Company by Parent. The Plan
Administrator of the
 
                                       42
<PAGE>
1992 Plan has taken action to provide that each outstanding Option as to which a
valid Option Election with respect to such Option is executed (and not revoked)
and delivered to the Company will become exercisable immediately prior to the
purchase of Shares (and contingent upon such purchase) by Purchaser pursuant to
the Offer. The parties to the Merger Agreement consented to the action of the
Plan Administrator of the 1992 Plan referenced in the immediately preceding
sentence, agreed that they will not cause the revocation of such action and will
use their best efforts to take whatever steps are necessary to make it possible
for Shares issuable upon the exercise of Options resulting from the execution
and delivery of valid Option Elections to be tendered in the Offer.
 
EMPLOYEE STOCK PURCHASE PLAN
 
    The Company will use its best efforts to effectuate the provisions described
in the next following paragraph, to provide for termination of the Stock
Purchase Plan, effective no later than the Effective Time and to provide that,
upon termination of the Stock Purchase Plan and contingent upon the purchase by
Purchaser of Shares pursuant to the Offer, any payroll deductions accumulated
under the Stock Purchase Plan and not used to purchase Shares under the Stock
Purchase Plan for tender in the Offer as described in the next following
paragraph will be returned to the applicable participants; provided, however,
that arrangement will be made so that each holder of Purchase Rights as
described in the next following paragraph who consents to the termination of all
Purchase Rights (either before the Effective Time or within a reasonable time
thereafter) will be entitled to receive an amount in cash equal to the net
amount such holder of Purchase Rights would have received as described in the
next following paragraph if such holder had made a Stock Purchase Election.
 
    As soon as practicable after the commencement of the Offer, the Company will
use its reasonable best efforts to cause each individual who has Purchase Rights
outstanding under the Stock Purchase Plan to execute and deliver to the Company,
prior to the expiration of the Offer, an agreement (a "Stock Purchase Election")
under which such holder would agree, contingent upon the purchase of Shares by
Purchaser pursuant to the Offer, to cause, immediately prior to the expiration
of the Offer, such Purchase Rights to be exercised (the date on which the Shares
are purchased by a holder of Purchase Rights being a "Purchase Date" for
purposes of the Stock Purchase Plan) and the Shares issued as a result of such
exercise to be tendered in the Offer. The Company and Purchaser will reflect on
their books and records the transactions effected pursuant to the Stock Purchase
Elections. Subject to the terms of the Stock Purchase Elections and contingent
upon the purchase of Shares by Purchaser pursuant to the Offer, the Company will
make available to each holder of Purchase Rights who has delivered to the
Company an executed Stock Purchase Election (and has not revoked such election)
the funds necessary to exercise such Purchase Rights for the amount of Shares
that would have been purchased upon such exercise if the purchase period under
the Stock Purchase Plan had expired on November 30, 1998 (assuming that the Fair
Market Value (as defined in the Stock Purchase Plan) for November 30, 1998 for
purposes of calculating the purchase price (within the meaning of the Stock
Purchase Plan) would be the Per Share Amount and that payroll deductions had
continued at the same level through November 30, 1998), less any payroll
deductions accumulated with respect to the holder pursuant to normal operation
of the Stock Purchase Plan through the date on which the Offer terminates, and
Parent will advance such funds to the Company. The funds advanced to any holder
of Purchase Rights in accordance with the preceding sentence will be deducted
from the amount payable to such holder of Purchase Rights pursuant to the Offer.
The funds so deducted will be retained by Purchaser as repayment of the amount
advanced to the Company by Parent. The parties to the Merger Agreement will use
their best efforts to take whatever steps are necessary to make it possible for
Shares issuable upon the exercise of Purchase Rights resulting from the
execution and delivery of valid Stock Purchase Elections to be tendered in the
Offer.
 
                                       43
<PAGE>
RESTRICTED STOCK
 
    The Company represents that the Plan Administrator of the Restricted Stock
Plan has taken action to provide that each share of Restricted Stock outstanding
under the Restricted Stock Plan as to which a valid Restricted Stock Election
(as defined below) with respect to such Restricted Stock is executed (and not
revoked) and delivered to the Company will become fully vested and
nonforfeitable immediately prior to the purchase of Shares (and contingent upon
such purchase) by Purchaser pursuant to the Offer. The parties to the Merger
Agreement consent to the action of the Plan Administrator of the Restricted
Stock Plan referenced in the immediately preceding sentence, agree that they
will not cause the revocation of such action and will use their best efforts to
take whatever steps are necessary to make it possible for the Restricted Stock
as to which a valid Restricted Stock Election has been made to be tendered in
the Offer. As soon as practicable after the commencement of the Offer, the
Company will use its reasonable best efforts to cause each holder of shares of
Restricted Stock to execute and deliver to the Company, prior to the expiration
of the Offer, an agreement (a "Restricted Stock Election") under which such
holder would agree, contingent upon the purchase of Shares by Purchaser pursuant
to the Offer, to cause, immediately prior to the expiration of the Offer, the
shares of Restricted Stock (which would be vested in accordance with the
foregoing provisions as described in this paragraph) to be tendered in the
Offer. Immediately prior to the Effective Time, if the Conditions set forth in
"Conditions to the Consummation of the Merger" below are satisfied, the Company
will cause the Plan Administrator of the Restricted Stock Plan to cause all
shares of Restricted Stock outstanding as of the Effective Time to be fully
vested and nonforfeitable.
 
THE MERGER
 
    Immediately following the satisfaction or waiver of all conditions set forth
in "Conditions to the Consummation of the Merger" below (assuming the transfer
of all of Parent's Shares to Purchaser), Parent will cause Purchaser to become
the beneficial and record owner of all Shares then owned of record by Parent
(the time immediately following such action is referred to herein as the
"Designated Time").
 
    At the Designated Time, the parties will (i) file a certificate of ownership
with the Secretary of State of the State of California in accordance with
California Law (the "California Filing") and (ii) file a certificate of
ownership and merger with the Secretary of State of the State of Delaware in
accordance with Delaware Law (the "Delaware Filing"). The Merger will become
effective at such time as the California Filing and the Delaware Filing are duly
filed in accordance with California Law and Delaware Law, respectively, or at
such later time as is agreed upon by the parties and specified in the California
Filing and the Delaware Filing (the "Effective Time").
 
    At the Effective Time, upon the terms and subject to the conditions of the
Merger Agreement and in accordance with California Law and Delaware Law,
Purchaser will be merged with and into the Company, whereupon the separate
corporate existence of Purchaser will cease and the Company will continue as the
Surviving Corporation.
 
    The Articles of Incorporation of the Company in effect immediately prior to
the Effective Time will be the Articles of Incorporation of the Surviving
Corporation until amended in accordance with applicable law. The First Amended
and Restated Bylaws of the Company in effect at the Effective Time will be the
Bylaws of the Surviving Corporation until amended in accordance with applicable
law. The directors of Purchaser at the Effective Time will be the initial
directors of the Surviving Corporation, each to hold office in accordance with
the Articles of Incorporation and Bylaws of the Surviving Corporation and until
his or her successor is duly elected and qualified. The officers of the Company
at the Effective Time, and any additional individuals designated by Parent, will
be the initial officers of the Surviving Corporation, each to hold office in
accordance with the Articles of Incorporation and Bylaws of the Surviving
Corporation and until his or her successor is duly appointed and qualified.
 
                                       44
<PAGE>
    At the Effective Time, by virtue of the Merger and without any action on the
part of Parent, Purchaser (except as required by California Law), the Company or
the holder of any of the following securities:
 
        (i) Each Share issued and outstanding immediately prior to the Effective
    Time (other than Shares to be canceled as described in the next following
    clause and Dissenting Shares (as defined in "Dissenting Shares" below)),
    will by virtue of the Merger and without any action on the part of the
    holder thereof be canceled and extinguished and be converted into the right
    to receive an amount in cash equal to the Offer Price;
 
        (ii) Each Share issued and outstanding immediately prior to the
    Effective Time and owned by Parent or Purchaser or any direct or indirect
    wholly owned subsidiary of Parent or Purchaser, or which is held in the
    treasury of the Company or by any of the Company's subsidiaries, will be
    canceled and retired and no payment of any consideration will be made with
    respect thereto;
 
       (iii) Each share of common stock of Purchaser issued and outstanding
    immediately prior to the Effective Time will be converted into and become
    one validly issued, fully paid and nonassessable share of common stock of
    the Surviving Corporation.
 
    Promptly after the Effective Time, the Surviving Corporation will cause to
be mailed to each record holder, as of the Effective Time, of a certificate or
certificates that, prior to the Effective Time, represented Shares, a form of
letter of transmittal and instructions for use in effecting the surrender of the
certificates in exchange for the Offer Price therefor. Subject to the provision
described in the next following paragraph, upon the surrender of each such
certificate formerly representing Shares, together with such letter of
transmittal, duly completed and validly executed in accordance with the
instructions thereto, the Depositary will deliver to the holder of such
certificate the Offer Price multiplied by the number of Shares formerly
represented by such certificate in exchange therefor, and such certificate will
forthwith be canceled. Until so surrendered and exchanged, each such certificate
(other than certificates representing Dissenting Shares or Shares held by
Parent, Purchaser or the Company, or any direct or indirect subsidiary thereof)
will represent solely the right to receive the Offer Price. No interest will be
paid or accrue on the Offer Price. If the Offer Price (or any portion thereof)
is to be delivered to any person other than the person in whose name the
certificate formerly representing Shares surrendered in exchange therefor is
registered, the certificate so surrendered will be properly endorsed or
otherwise be in proper form for transfer and that the person requesting such
exchange must pay to the Depositary any transfer or other taxes required by
reason of the payment of the Offer Price to a person other than the registered
holder of the certificate surrendered, or must establish to the satisfaction of
the Depositary that such tax has been paid or is not applicable.
 
    Following the date which is six months after the Effective Time, each holder
of a certificate formerly representing a Share may surrender such certificate to
the Surviving Corporation and (subject to applicable abandoned property, escheat
and similar laws) receive in exchange therefor the Offer Price, without any
interest thereon.
 
    After the Effective Time, there will be no transfers on the stock transfer
books of the Surviving Corporation of any Shares. If, after the Effective Time,
certificates formerly representing Shares are presented to the Surviving
Corporation or the Depositary, such certificates will be canceled and exchanged
for the Offer Price, as described above, subject to applicable law in the case
of Dissenting Shares.
 
DISSENTING SHARES
 
    Holders of Shares do not have dissenters' rights as a result of the Offer.
However, in connection with the Merger, holders of Shares, by complying with the
provisions of Chapter 13 of California Law, may have certain rights to dissent
and to require the Company to purchase their Shares for cash at fair market
value. In general, holders of Shares will be entitled to exercise "dissenters'
rights" under California Law only if the holders of five percent or more of the
outstanding Shares properly file demands for payment or if the
 
                                       45
<PAGE>
Shares held by such holders are subject to any restriction on transfer imposed
by the Company or any law or regulation ("Restricted Shares"). Accordingly, any
holder of Restricted Shares and, if the holders of five percent or more of the
Shares properly file demands for payment, all other such holders who fully
comply with all other applicable provisions of Chapter 13 of California Law
("Dissenting Shares") will be entitled to require the Company to purchase their
Shares for cash at their fair market value if the Merger is consummated. In
addition, if, immediately prior to the Effective Time, the Shares are not listed
on a national securities exchange or on the list of OTC margin stocks issued by
the Board of Governors of the Federal Reserve System (the "Federal Reserve
Board"), holders of Shares may likewise exercise their dissenters' rights as to
any or all of their Shares entitled to such rights. If the statutory procedures
under California Law relating to dissenters' rights were complied with, such
rights could lead to a judicial determination of the fair market value of the
Shares. The "fair market value" would be determined as of the day before the
first announcement of the terms of the proposed Merger, excluding any
appreciation or depreciation in consequence of the Merger. The value so
determined could be more or less than the Offer Price.
 
    THE FOREGOING SUMMARY OF THE RIGHTS OF DISSENTING STOCKHOLDERS DOES NOT
PURPORT TO BE A COMPLETE STATEMENT OF THE PROCEDURES TO BE FOLLOWED BY
STOCKHOLDERS DESIRING TO EXERCISE ANY AVAILABLE DISSENTERS' RIGHTS. THE
PRESERVATION AND EXERCISE OF DISSENTERS' RIGHTS REQUIRE STRICT ADHERENCE TO THE
APPLICABLE PROVISIONS OF SECTION 13 OF CALIFORNIA LAW, A COMPLETE COPY OF WHICH
IS ATTACHED HERETO AS SCHEDULE II.
 
    Notwithstanding anything in the Merger Agreement to the contrary, if demands
for payment are filed (within the meaning of California Law) with respect to
five percent or more of the outstanding Shares, Shares outstanding immediately
prior to the Effective Time and held by a holder who has not voted such Shares
in favor of the Merger or consented thereto in writing and who has demanded
appraisal for such Shares in accordance with California Law will not be
converted into a right to receive the Offer Price unless such holder fails to
perfect or withdraws or otherwise loses his, her or its right to appraisal under
California Law. If, after the Effective Time, such holder fails to perfect or
withdraws (with the consent of the Company to the extent such consent is
required by applicable law) or loses his, her or its right to appraisal under
California Law, such holder's Shares will be treated as if they had been
converted as of the Effective Time into a right to receive the Offer Price
without interest thereon.
 
REPRESENTATIONS AND WARRANTIES
 
    The Merger Agreement contains various representations and warranties of the
Company, including representations by the Company as to (i) organization,
qualification and similar corporate matters of the Company and its subsidiaries,
(ii) capitalization of the Company and its subsidiaries, (iii) the
authorization, execution, delivery, performance and enforceability of the Merger
Agreement, (iv) the non-contravention of the Merger Agreement and related
transactions with any provision of the Articles of Incorporation or Bylaws,
material contract, order, law or regulation to which the Company or its
subsidiaries is a party or by which it is bound or obligated, (v) the filing of
required Commission reports and the absence of untrue statements of material
facts or omissions of material facts in such reports, (vi) the absence of
changes or events which have had a material adverse effect on the Company other
than the changes or events set forth in the Merger Agreement, (vii) the absence
of any untrue statement of a material fact or omission of any material fact
required to be stated in any recommendation statement of the Company's Board of
Directors, document related to the Offer or proxy or information statement or
similar materials distributed to the Company's stockholders in connection with
the Merger, (viii) the absence of payments to any intermediary other than listed
intermediaries of any finder's, professional or other fee or commission, (ix)
the absence of any vote or other approval of the holders of a class of any
Company security required to approve the Merger or to approve or adopt the
Merger Agreement except any actions required to be taken by Purchaser pursuant
to California Law other than the satisfaction of the condition described in
 
                                       46
<PAGE>
"Conditions to the Consummation of the Merger" below, (x) Wasserstein Perella's
delivery to the Special Committee, and authorization to deliver to the Company's
stockholders pursuant to California Law, its written opinion to the effect that,
as of the date of such opinion, subject to the various assumptions and
limitations set forth therein as of the date of such opinion, the cash
consideration to be received by the holders of Shares pursuant to the Offer and
the Merger is fair to such holders from a financial point of view and (xi) the
Company and its Board of Directors having taken all necessary action so that
from and after January 15, 1996 (a) Parent and its affiliates (including,
without limitation, Purchaser) have never been and will never be included in the
definition of "Acquiring Person" under the Company's Amended and Restated Rights
Agreement dated as of October 19, 1995, as amended, between the Company and the
First National Bank of Boston (the "Rights Agreement") and (b) the acquisition
of Shares (whether pursuant to the Exchange and Purchase Agreement (as defined
in "Exchange and Purchase Agreement; No Restrictions on Purchase" below), the
Merger Agreement or otherwise) by Parent and its affiliates (including, without
limitation, Purchaser) has never caused and will never cause under any
circumstances whatsoever any adverse consequence to Parent, any of its
affiliates (including, without limitation, Purchaser), or the Company pursuant
to the Rights Agreement, including, without limitation, the occurrence of a
Distribution Date (as defined in the Rights Agreement) or any adjustment to the
Purchase Price (as defined in the Rights Agreement). The Merger Agreement
provides that no representation or warranty is made by the Company as to certain
matters or conditions which were known to Parent's designees to the Board on or
prior to the date of the Merger Agreement, or as to certain other listed matters
or conditions.
 
    The Merger Agreement contains various customary representations and
warranties of Parent and Purchaser, including representations by Parent and
Purchaser as to (i) organization, qualification and similar limited liability
company or corporate matters of Parent and Purchaser, (ii) the authorization,
execution, delivery, performance and enforceability of the Merger Agreement,
(iii) the non-contravention of the Merger Agreement and related transactions
with any provision of the limited liability company agreement of Parent, the
Certificate of Incorporation or Bylaws of Purchaser, or any material contract,
order, law or regulation to which Parent or Purchaser is a party or by which it
is bound or obligated, (iv) the absence of untrue statements of material facts
or omissions of material facts in any documents related to the Offer and in
information provided to the Company in connection with the Schedule 14D-9 or
proxy or information statement or similar materials distributed to the Company's
stockholders in connection with the Merger, (v) the absence of prior activities
of Purchaser other than in connection with or as contemplated by the Merger
Agreement, (vi) the availability of all funds necessary to satisfy Purchaser's
obligations under the Merger Agreement, (vii) the absence of payments to any
intermediary other than listed intermediaries of any finder's, professional or
other fee or commission and (viii) the availability of Parent's "director and
officer" insurance coverage for the members of the Special Committee.
 
COVENANTS
 
    CONDUCT OF THE BUSINESS OF THE COMPANY.  Except with respect to certain
enumerated items, from the date of the Merger Agreement to the earlier of the
Effective Time or the date on which the Merger Agreement is terminated in
accordance with its terms, the Company and its subsidiaries will each conduct
its operations in the ordinary course of business consistent with past practice,
and the Company and its subsidiaries will, consistent with the foregoing, each
use its reasonable best efforts to preserve its business organization, to keep
available the services of its officers and employees and to maintain existing
relationships with licensors, licensees, suppliers, contractors, distributors,
customers and others having business relationships with it.
 
    Accordingly, prior to the Effective Time, except as otherwise expressly
provided in the Merger Agreement, neither the Company nor any of its
subsidiaries may, without the prior written consent of Purchaser, which consent
will not be unreasonably withheld or delayed, engage or agree to engage in an
enumerated list of transactions generally characterized as being outside the
ordinary course of business.
 
                                       47
<PAGE>
Transactions requiring Purchaser's prior approval include actions by the Company
or its subsidiaries to (i) authorize for issuance, issue, sell, deliver or agree
to commit to issue, sell or deliver any Shares, any stock of any class or any
other securities or equity equivalents (including, without limitation, stock
appreciation rights), or amend any of the terms of any such securities or
agreements outstanding as of the date of the Merger Agreement; (ii) split,
combine or reclassify any shares of its capital stock, declare, set aside or pay
any dividend or other distribution (whether in cash, stock, or property or any
combination thereof) in respect of its capital stock, or redeem, repurchase or
otherwise acquire any of its securities or any securities of its subsidiaries;
or (iii) take or agree to take any action which would violate the covenants or
any action which would cause the condition described in paragraph (d) of Section
13 not to be satisfied.
 
    REASONABLE BEST EFFORTS.  Each of the parties will use its reasonable best
efforts to take all actions and do all things reasonably necessary to consummate
and make effective the transactions contemplated by the Merger Agreement.
 
    PUBLIC ANNOUNCEMENTS.  Parent and Purchaser, on the one hand, and the
Company, on the other hand, will consult with each other before issuing any
press release or otherwise making any public statements with respect to the
transactions contemplated by the Merger Agreement.
 
    INDEMNIFICATION.  Parent will cause the Surviving Corporation to keep in
effect in its Articles of Incorporation and Bylaws the provisions with respect
to exculpation of director and officer liability and indemnification and
advancement of expenses set forth in the Articles of Incorporation and First
Amended and Restated Bylaws of the Company on the date of the Merger Agreement
to the fullest extent permitted under applicable law, which provisions will not
be amended, repealed or otherwise modified for at least six years after the
Effective Time except as required by applicable law or except to make changes
permitted by applicable law that would enlarge the exculpation or rights of
indemnification or advancement of expenses thereunder. Parent will also cause
the Surviving Corporation to honor in accordance with their terms the existing
Indemnification Agreements between the Company and its directors and executive
officers.
 
    From and after the Effective Time, Parent will guarantee the obligations of
the Surviving Corporation to perform all of its obligations under the Surviving
Corporation's Articles of Incorporation and Bylaws with respect to
indemnification and to cause the Surviving Corporation to perform all such
obligations.
 
    The Company will, to the fullest extent permitted under applicable law and
regardless of whether the Merger becomes effective, indemnify and hold harmless,
to the fullest extent permitted by applicable law, Joseph P. Sullivan and
Clayton K. Yeutter (collectively, the "Indemnified Parties") against all costs
and expenses (including attorneys' fees), judgments, fines, losses, claims,
damages, liabilities and settlement amounts paid in connection with any claim,
action, suit, proceeding or investigation, whether civil, criminal,
administrative or investigative, arising out of or pertaining to any action or
omission in such Indemnified Party's capacity as a director (including, without
limitation, as a member of the Special Committee) or fiduciary of the Company
(including, without limitation, in connection with the transactions contemplated
by the Merger Agreement) occurring on or before the Effective Time (or, if the
Merger Agreement is terminated without the Merger becoming effective, occurring
on or before the termination of the Merger Agreement), until the expiration of
the statute of limitations relating thereto (and will pay any expenses in
advance of the final disposition of such action or proceeding to each
Indemnified Party to the fullest extent permitted under applicable law, upon
receipt, in the case of the Company or the Surviving Corporation, as the case
may be, from the Indemnified Party to whom expenses are advanced of any
undertaking to repay such advances required under applicable law). If the Merger
becomes effective, Parent shall be jointly and severally responsible, to the
fullest extent permitted under applicable law (it being understood that
applicable law may permit Parent to indemnify or advance expenses to the
Indemnified Parties under circumstances in which the Company could not do so),
for the indemnification and advancement of expenses obligations provided for in
the immediately preceding sentence. If the Merger does not become effective,
Parent shall have the same responsibilities set forth in the immediately
 
                                       48
<PAGE>
preceding sentence, except that Parent shall have no responsibility for
indemnifying or advancing expenses to the Indemnified Parties with respect to
matters that do not arise out of or pertain to the work of the Special
Committee, the Merger Agreement or the transactions contemplated by the Merger
Agreement. In the event of any such claim, action, suit, proceeding or
investigation covered by this paragraph, (i) the Company, Parent or the
Surviving Corporation, as the case may be, will pay the reasonable fees and
expenses of counsel selected by the Indemnified Parties, which counsel will be
reasonably satisfactory to the Company or the Surviving Corporation, promptly
after statements therefor are received and (ii) the Company, Parent and the
Surviving Corporation will cooperate in the defense of any such matter;
provided, however, that neither the Company nor Parent nor the Surviving
Corporation will be liable for any settlement effected without its written
consent; and provided, further, that neither the Company, Parent nor the
Surviving Corporation, as the case may be, will be obligated as described in
this paragraph to pay the fees and expenses of more than one counsel (plus
appropriate local counsel) for all Indemnified Parties in any single action
except to the extent that two or more of such Indemnified Parties will have
conflicting interests in the outcome of such action, in which case additional
counsel (including local counsel) as may be required to avoid any such conflict
or likely conflict may be retained by the Indemnified Parties at the expense of
the Company, Parent or the Surviving Corporation, as the case may be; and
provided further that, in the event any claim for indemnification is asserted or
made within the period prior to the expiration of the applicable statute of
limitations, all rights to indemnification in respect of such claim will
continue until the disposition of such claim. In connection with Parent or the
Surviving Corporation making any payment or advancing any funds as described in
this paragraph, Parent or the Surviving Corporation, as the case may be, will be
entitled to require the Indemnified Party in question to use their reasonable
best efforts at the cost and expense of Parent and the Surviving Corporation, to
cause Parent or the Surviving Corporation, as the case may be, to be subrogated
to the rights of such Indemnified Party under any insurance coverage maintained
by the Surviving Corporation, Parent or any of their respective affiliates with
respect to the underlying subject matter of, and to the extent of, such payment
or advance.
 
    Parent will cause the Surviving Corporation to maintain in effect for six
years from the Effective Time, if available, the coverage provided by the
current directors' and officers' liability insurance policies maintained by the
Company (provided that the Surviving Corporation may substitute therefor
policies of at least the same coverage containing terms and conditions which are
not less favorable) with respect to matters occurring prior to the Effective
Time; provided, however, that nothing contained in this Agreement will require
the Surviving Corporation to incur any annual premium in excess of 200% of the
last annual aggregate premium paid prior to the date of this Agreement for all
current directors' and officers' liability insurance policies maintained by the
Company. In addition, Parent will cause the Indemnified Parties to receive, for
six years following the date of the Merger Agreement, the same directors and
officers insurance coverage that other present or formal independent directors
of TDCC or its subsidiaries receive.
 
    Heirs, representatives and estates of the Indemnified Parties will have the
right to enforce the indemnification obligations arising under the Merger
Agreement.
 
    NOTIFICATION OF CERTAIN MATTERS.  The Company will give prompt notice to
Parent or Purchaser, and Parent or Purchaser will give prompt notice to the
Company, as the case may be, of (i) the occurrence, or non-occurrence of any
event which would be likely to cause any condition contained in the Merger
Agreement to be unsatisfied and (ii) any failure of the Company, Parent or
Purchaser, as the case may be, to comply with or satisfy any covenant or
agreement under the Merger Agreement.
 
    EXCHANGE AND PURCHASE AGREEMENT; NO RESTRICTIONS ON PURCHASE.  The parties
agreed to amend the Exchange and Purchase Agreement to the extent necessary to
permit the execution, delivery and performance of the Merger Agreement and the
consummation of the transactions contemplated by the Merger Agreement. From and
after the date that Purchaser first makes payment with respect to validly
tendered and not withdrawn Shares pursuant to the Offer, the Exchange and
Purchase Agreement will be deemed to
 
                                       49
<PAGE>
have been canceled and terminated and no longer binding on the parties thereto
and shall be of no further force or effect; provided, however, that the
provisions of Section 6.10 of the Exchange and Purchase Agreement will remain in
full force and effect without any amendment thereto. Without limiting the
generality of the foregoing, from and after the date that Purchaser first makes
payment with respect to validly tendered and not withdrawn Shares pursuant to
the Offer, Parent, Purchaser and their affiliates will no longer be bound by the
restrictions set forth in Sections 6.12 and 6.13 of the Exchange and Purchase
Agreement and, subject to Purchaser's obligations under the Merger Agreement to
effect the Merger, Parent, Purchaser and their affiliates will be permitted to
acquire additional Shares and/or increase their percentage ownership of the
Company (whether through any tender offer, open market purchase, negotiated
transaction, merger, consolidation, reverse stock split or otherwise) without
restriction under the Exchange and Purchase Agreement.
 
    COMPLIANCE BY PURCHASER; FINANCING.  Parent will cause Purchaser to timely
perform and comply with all of its obligations under or related to the Merger
Agreement, including, without limitation, all obligations in or with respect to
the Offer.
 
    TDCC will ensure that Purchaser has sufficient funds to acquire all the
outstanding Shares in the Offer and the Merger. In the Merger Agreement, TDCC
made a representation and warranty as to the validity of TDCC's execution and
delivery of the Merger Agreement and its enforceability against TDCC.
 
    ACCESS TO INFORMATION.  From the date of the Merger Agreement to the
Effective Time, subject to any applicable legal restrictions, fiduciary duties
or applicable privileges, the Company will (and will cause its subsidiaries to)
afford to authorized representatives (including, without limitation, attorneys,
auditors and financial advisors) of Parent and Purchaser reasonable access
during normal business hours to the Company's personnel, offices and other
facilities and to all books and records of the Company and will cause its
officers and employees to furnish Parent and Purchaser and their authorized
representatives such financial and operating data and other information with
respect to the Company's business and properties as Parent and Purchaser and
their authorized representatives may from time to time reasonably request.
 
CONDITIONS TO THE CONSUMMATION OF THE MERGER
 
    The obligations of each party to the Merger Agreement to effect the Merger
under the Merger Agreement are subject to the satisfaction or, if appropriate,
waiver of the following conditions:
 
        (i) PURCHASE OF SHARES. Purchaser will have purchased all Shares validly
    tendered and not withdrawn pursuant to the Offer and Purchaser will be the
    record and beneficial owner of a sufficient number of Shares (90% of the
    outstanding Shares (assuming the transfer to Purchaser of all Shares owned
    by Parent)) to permit the Merger to be effected pursuant to California Law.
 
        (ii) NO PROHIBITION. No order, decree or ruling or other action
    restraining, enjoining or otherwise prohibiting the Merger, will have been
    issued or taken by any court or other governmental body.
 
TERMINATION
 
    The Merger Agreement provides that the Merger Agreement may be terminated
and the Offer and the Merger may be abandoned at any time prior to the Effective
Time (i) by mutual written consent of Parent and Purchaser, on the one hand, and
of the Company acting upon the direction of the Special Committee, on the other
hand, (ii) by the Company acting upon the direction of the Special Committee or
by Parent to the extent that performance is prohibited, enjoined or otherwise
materially restrained by any final, non-appealable judgment, (iii) by the
Company acting upon the direction of the Special Committee or by Parent if, due
to an occurrence or circumstance that would result in a failure to satisfy any
condition set forth in Section 13, Purchaser will have (a) failed to commence
the Offer within 60 days following the date of the Merger Agreement or (b)
terminated the Offer without having accepted any Shares for payment thereunder;
provided, that the right to terminate this Agreement under this clause (iii)
will not be
 
                                       50
<PAGE>
available to any party whose failure to fulfill any material obligation under
this Agreement has been the cause or resulted in the circumstances described in
this clause (iii), (iv) by the Company, acting upon the direction of the Special
Committee if, prior to the purchase of Shares pursuant to the Offer, Parent or
Purchaser will have failed to comply in all material respects with any of its
covenants or agreements contained in the Merger Agreement required to be
complied with prior to the date of such termination, which failure to comply has
not been cured within 20 business days following receipt by Parent or Purchaser
of written notice of such failure to comply, (v) by the Company acting upon the
direction of the Special Committee if, prior to the purchase of Shares pursuant
to the Offer, there has been (a) a breach in any material respect by Parent or
Purchaser of any representation or warranty that is not qualified as to
materiality which has the effect of making such representation or warranty not
true and correct in all material respects or (b) a breach by Parent or Purchaser
of any representation that is qualified as to materiality, in each case which
breach has not been cured within 20 business days following receipt by Parent or
Purchaser of written notice of the breach, or (vi) by either the Company acting
upon the direction of the Special Committee or by Parent if the Merger will not
have occurred on or prior to April 30, 1999; provided, that the right to
terminate the Merger Agreement under this clause will not be available to any
party whose failure to fulfill any material obligation under the Merger
Agreement has been the cause of, or resulted in, the failure of the Merger to
have occurred on or before such date.
 
    In the event of the termination and abandonment of the Merger Agreement as
described in the next previous paragraph, the Merger Agreement will become void
and have no effect, other than as described in this paragraph and in "Survival
of Representations and Warranties" below. No termination of the Merger Agreement
and nothing described in this paragraph or in "Survival of Representation and
Warranties" below will relieve any party from liability for any willful breach
of any representation or warranty contained in the Merger Agreement or any
breach of any covenant contained in the Merger Agreement occurring prior to such
termination.
 
    Subject to the description in the next previous paragraph, each party will
bear its own expenses and costs in connection with the Merger Agreement and the
transactions.
 
AMENDMENT; EXTENSION; WAIVER
 
    The Merger Agreement may be not be amended except by an instrument in
writing signed by Parent, Purchaser and the Company. Any amendment to the Merger
Agreement, any termination of the Merger Agreement by the Company, any extension
by the Company of the time for the performance of any of the obligations or
other acts of Parent or Purchaser or any waiver of any of the Company's rights
under the Merger Agreement will require the unanimous concurrence of the Special
Committee.
 
    Subject to the description in the next previous paragraph, at any time prior
to the Effective Time, the Company, on the one hand, and Parent and Purchaser,
on the other hand, may (i) extend the time for the performance of any of the
obligations or other acts of the other party, (ii) waive any inaccuracies in the
representations and warranties of the other party contained in the Merger
Agreement or in any document, certificate or writing delivered pursuant to the
Merger Agreement or (iii) waive compliance by the other party with any of the
agreements or conditions contained in the Merger Agreement. Any agreement on the
part of any party to any such extension or waiver will be valid only if set
forth in an instrument in writing signed on behalf of such party. The failure of
any party to assert any of its rights under the Merger Agreement shall not
constitute a waiver of such rights. Without limiting the rights of any other
party to the Merger Agreement, the Merger Agreement provides that the Special
Committee has the right to exercise the Company's rights and enforce the terms
of the Merger Agreement on behalf of the Company.
 
SURVIVAL OF REPRESENTATIONS AND WARRANTIES
 
    The representations and warranties made in the Merger Agreement will not
survive beyond the Effective Time or any termination of the Merger Agreement.
The covenants and agreements in the Merger
 
                                       51
<PAGE>
Agreement or the termination of the Merger Agreement will survive the Effective
Time in accordance with their terms or as contemplated by such terms.
 
GOVERNING LAW
 
    The Merger Agreement is governed by and construed in accordance with the
laws of the State of Delaware applicable to contracts executed in and to be
performed in that State, provided that matters of internal corporate law
relevant to the Company are governed by California Law.
 
CONFIDENTIALITY AGREEMENTS
 
    The following summary of the Confidentiality Agreement does not purport to
be complete and is qualified in its entirety by reference to the complete text
of the Confidentiality Agreement, which is filed as an exhibit to Schedule 14D-1
and incorporated herein by reference.
 
    On July 16, 1998, the Company (by the Special Committee), Parent, TDCC and
Wasserstein Perella entered into the Confidentiality Agreement providing for the
nondisclosure of confidential information to be provided by Parent and TDCC to
the Special Committee and its advisors. The Confidentiality Agreement provided
that the Special Committee and its attorneys and financial advisors, each agree
that the non-public, confidential, proprietary and/or privileged Parent or TDCC
information related to the Company, Parent or TDCC ("Confidential Information")
provided to the Special Committee and its attorneys and financial advisors will
be kept confidential and used only for evaluation of the proposed amendment and
transaction. Merrill Lynch has also agreed to be bound by the terms of the
Confidentiality Agreement.
 
    All Confidential Information will remain subject to the terms of the
Confidentiality Agreement for ten years.
 
    In addition to the Confidentiality Agreement, the members of the Special
Committee in their individual capacities entered into separate agreements with
TDCC and Parent to maintain the confidentiality of certain information of TDCC
and Parent.
 
11. SOURCE AND AMOUNT OF FUNDS
 
    The total amount of funds required by Purchaser and Parent to consummate the
Offer and the Merger and to pay related fees and expenses is estimated to be
approximately $377 million. Purchaser has available to it all funds necessary to
satisfy its obligations under the Merger Agreement. TDCC will ensure that
Purchaser has sufficient funds to acquire all the outstanding Shares in the
Offer and the Merger.
 
12. CERTAIN EFFECTS OF THE OFFER
 
    Following the consummation of the Offer, assuming satisfaction of the
Minimum Condition, Purchaser and Parent, collectively, will own at least 90% of
the outstanding Shares of the Company.
 
SHORT-FORM MERGER--SECTION 1110 OF CALIFORNIA LAW
 
    The Merger Agreement provides, among other things, for the making of the
Offer and further provides that, following Purchaser's purchase of Shares
pursuant to the Offer, upon the terms and subject to the conditions set forth in
the Merger Agreement, and in accordance with California Law and Delaware Law,
Purchaser will be merged with and into the Company and the Company will continue
as the Surviving Corporation.
 
    If Purchaser acquires, pursuant to the Offer, Shares which, together with
Shares owned by Parent, constitute at least 90% of the Shares then outstanding,
and Parent subsequently transfers its Shares to Purchaser, then under Section
1110 of California Law, Purchaser will be able to approve the Merger
 
                                       52
<PAGE>
Agreement and the transactions contemplated thereby, including the Merger,
without a vote of the Company's stockholders (a "short-form merger"). In such
event, Parent, Purchaser and the Company have agreed to take all necessary and
appropriate action to cause the Merger to become effective as soon as
practicable after such acquisition, without a meeting of the Company's
stockholders.
 
    Section 1110 of California Law further provides that the Merger may not be
accomplished for cash paid to the Company's stockholders if Purchaser or Parent
owns directly or indirectly more than 50% but less than 90% of the then
outstanding shares unless either all the stockholders consent or the
Commissioner of Corporations of the State of California approves, after a
hearing, the terms and conditions of the Merger and the fairness thereof.
Purchaser currently intends to effect a short-form merger if it is able to do
so.
 
    For a description of stockholder rights under California Law to dissent to
the Merger, see Section 10.
 
POSSIBLE EFFECTS OF THE OFFER ON THE MARKET FOR THE SHARES
 
    The purchase of Shares pursuant to the Offer will reduce the number of
Shares that might otherwise trade publicly and could adversely affect the
liquidity and market value of the remaining Shares held by the public. The
purchase of Shares pursuant to the Offer can also be expected to reduce the
number of holders of Shares. Purchaser cannot predict whether the reduction in
the number of Shares that might otherwise trade publicly could adversely affect
the liquidity and market value of the remaining Shares held by the public.
Purchaser cannot predict whether the reduction in the number of Shares that
might otherwise trade publicly would have an adverse or beneficial effect on the
market price for or marketability of the Shares or whether it would cause future
market prices to be greater or less than the Offer Price therefor.
 
STOCK QUOTATION
 
    Depending upon the number of Shares purchased pursuant to the Offer, the
Shares may no longer meet the listing requirements for the NASDAQ NMS, which
require that an issuer have at least 200,000 publicly held shares, held by at
least 400 stockholders or 300 stockholders of round lots, with a market value of
at least $1,000,000, and have net tangible assets of at least $1,000,000,
$2,000,000 or $4,000,000, depending on profitability levels during the issuer's
four most recent fiscal years. If these standards are not met, the Shares might
nevertheless continue to be publicly quoted in an over-the-counter market but if
the number of holders of the Shares were to fall below 300, or if the number of
publicly held Shares were to fall below 100,000 or there were not at least two
registered and active market makers for the Shares, the NASD's rules provide
that the Shares would no longer be "qualified" for NASD reporting and the NASD
would cease to provide any quotations. Shares held directly or indirectly by
directors, officers or beneficial owners of more than 10% of the Shares are not
considered as being publicly held for this purpose. According to the Company's
Form 10-K, as of October 14, 1997, there were approximately 4,694 holders of
Shares and, as of September 30, 1997, there were 31,404,483 Shares outstanding.
If, as a result of the purchase of Shares pursuant to the Offer or otherwise,
the Shares no longer meet the listing requirements for NASDAQ NMS or for any
other over-the-counter market, the market for Shares could be adversely
affected.
 
    In the event that the Shares no longer meet the requirements of the NASD for
continued inclusion in any tier of the NASDAQ, it is possible that the Shares
would continue to trade in an over-the-counter market and that price quotations
would be reported by other sources. The extent of the public market for the
Shares and the availability of such quotations would, however, depend upon the
number of holders of Shares remaining at such time, the interests in maintaining
a market in Shares on the part of securities firms, the possible termination of
registration of the Shares under the Exchange Act, as described below, and other
factors.
 
                                       53
<PAGE>
EXCHANGE ACT REGISTRATION; FILING REQUIREMENTS
 
    The Shares are currently registered under the Exchange Act. The purchase of
the Shares pursuant to the Offer may result in the Shares becoming eligible for
deregistration under the Exchange Act. Registration of the Shares may be
terminated upon application by the Company to the Commission if the Shares are
not listed on a "national securities exchange" and there are fewer than 300
record holders of Shares. Termination of registration of the Shares under the
Exchange Act would substantially reduce the information required to be furnished
by the Company to its stockholders and the Commission and would make certain
provisions of the Exchange Act, such as the short-swing profit recovery
provisions of Section 16(b) and the requirements of furnishing a proxy statement
in connection with stockholders' meetings pursuant to Section 14(a) or 14(c) and
the related requirement of an annual report, no longer applicable to the
Company. If the Shares are no longer registered under the Exchange Act, the
requirements of Rule 13e-3 under the Exchange Act with respect to "going
private" transactions would no longer be applicable to the Company. Furthermore,
the ability of "affiliates" of the Company and persons holding "restricted
securities" of the Company to dispose of such securities pursuant to Rule 144
promulgated under the Securities Act of 1933, as amended, may be impaired or,
with respect to certain persons, eliminated. If registration of the Shares under
the Exchange Act were terminated, the Shares would no longer be "margin
securities" or eligible for stock exchange listing or NASD reporting. Purchaser
believes that the purchase of the Shares pursuant to the Offer may result in the
Shares becoming eligible for deregistration under the Exchange Act, and it would
be the intention of Purchaser to cause the Company to make an application for
termination of registration of the Shares as soon as possible after successful
completion of the Offer if the Shares are then eligible for such termination.
 
    If registration of the Shares is not terminated prior to the Merger, then
the registration of the Shares under the Exchange Act and the quotation of the
Shares on the NASDAQ NMS will be terminated following the consummation of the
Merger.
 
    In addition to the possibility of deregistration under the Exchange Act,
Purchaser's purchase of the Shares pursuant to the Offer may result in the
suspension of the duty of the Company to file periodic and other reports with
the Commission. Under Section 15(d) of the Exchange Act, the duty of an issuer
of a class of securities to file certain periodic and other reports with the
Commission is automatically suspended as to any fiscal year (other than the
fiscal year in which the registration statement with respect to that class of
securities became effective), if, at the beginning of such fiscal year, the
securities are held by less than 300 persons. The suspension of the filing
requirements of the Company under the Exchange Act would substantially reduce
the information required to be provided by the Company to its stockholders and
the Commission.
 
MARGIN REGULATIONS
 
    The Shares are currently "margin securities" under the regulations of the
Board of Governors of the Federal Reserve System (the "Federal Reserve Board"),
which have the effect, among other things, of allowing brokers to extend credit
on the collateral of such Shares for the purpose of buying, carrying or trading
in securities ("Purpose Loans"). Depending upon factors such as the number of
record holders of the Shares and the number and market value of publicly held
Shares, following the purchase of Shares pursuant to the Offer, the Shares might
no longer constitute "margin securities" for purposes of the Federal Reserve
Board's margin regulations and, therefore, could no longer be used as collateral
for Purpose Loans made by brokers. In addition, if registration of the Shares
under the Exchange Act were terminated, the Shares would no longer constitute
"margin securities."
 
13.  CERTAIN CONDITIONS OF THE OFFER
 
    Notwithstanding any other provision of the Offer, the obligation of
Purchaser to accept for payment any Shares tendered pursuant to the Offer shall
be subject to (the following being referred to as the "Offer
 
                                       54
<PAGE>
Conditions") (i) the satisfaction or waiver (under the circumstances in which
such waiver is permitted under the Merger Agreement) of the Minimum Condition
and (ii) the satisfaction or waiver of the following conditions:
 
        (a) NO PROHIBITION. There shall not have been any action or proceeding
    brought by any governmental authority before any court, or any order or
    preliminary or permanent injunction entered in any action or proceeding
    before any court or governmental, administrative or regulatory authority or
    any statute, rule, regulation, legislation, interpretation, judgment or
    order proposed or sought, enacted, entered, enforced, promulgated, amended,
    issued or deemed applicable to the Offer or the Merger by any court,
    governmental, administrative or regulatory authority which could reasonably
    be expected to have the effect of: (i) making illegal or otherwise
    restraining or prohibiting or imposing material penalties or fines or
    requiring the payment of material damages in connection with the making of
    the Offer, the acceptance for payment of, payment for, or ownership of some
    of or all the Shares by Parent or Purchaser, the consummation of the Offer
    or the Merger; (ii) prohibiting or materially limiting the ownership or
    operation by the Company or by Parent of all or any material portion of the
    business or assets of the Company and any of its subsidiaries or Parent,
    taken as a whole, or compelling Parent to dispose of or hold separate all or
    any material portion of the business or assets of the Company and its
    subsidiaries, taken as a whole, as a result of the transactions contemplated
    by the Merger Agreement; (iii) imposing or confirming material limitations
    on the ability of Parent effectively to acquire or hold or to exercise full
    rights of ownership of Shares, including, without limitation, the right to
    vote any Shares on all matters properly presented to the stockholders of the
    Company, including, without limitation, the adoption and approval of the
    Merger Agreement and the Merger or the right to vote any shares of capital
    stock of any subsidiary of the Company; or (iv) requiring divestiture by
    Parent or Purchaser, directly or indirectly, of any Shares.
 
        (b) OUTSIDE EVENTS. There shall not have occurred (i) any general
    suspension of trading in, or limitation on prices for, securities on any
    securities exchange or in the over-the-counter market in the United States
    (other than a shortening of trading hours or any coordinated trading halt
    triggered solely as a result of a specified increase or decrease in a market
    index) or (ii) the declaration of a banking moratorium or any suspension of
    payments in respect of banks in the United States.
 
        (c) PERFORMANCE. The Company shall have performed in all material
    respects its material covenants and agreements under the Merger Agreement.
 
        (d) REPRESENTATIONS AND WARRANTIES TRUE. The representations and
    warranties of the Company set forth in the Merger Agreement which are
    qualified as to Material Adverse Effect (as defined in the Merger Agreement)
    shall not be true and correct when made and as of the expiration of the
    Offer, or any of the other representations and warranties of the Company set
    forth in the Merger Agreement shall not be true and correct when made and as
    of the expiration of the Offer, which failure would have a Material Adverse
    Effect or, in the case of certain enumerated representations and warranties,
    which failure would be material with respect to the transactions
    contemplated by the Merger Agreement (except, in each case, in the case of
    representations and warranties of the Company which address matters only as
    of a particular date, which need only be true and correct as aforesaid as of
    such date).
 
        (e) NO TERMINATION. The Merger Agreement shall not have been terminated
    in accordance with its terms or the Offer shall not have been amended or
    terminated with the consent of the Company, acting at the direction of the
    Special Committee.
 
    Purchaser shall not be required to accept for payment any Shares tendered
pursuant to the Offer if any of the above conditions occurs and remains in
effect, which, in the reasonable judgment of Purchaser in any such case, and
regardless of the circumstances (including any action or omission by Purchaser
other than any breach by Parent or Purchaser of the Merger Agreement, or, in the
case of (c) or (d) above, a
 
                                       55
<PAGE>
failure of such condition which Parent or Purchaser has caused to occur) giving
rise to any such condition which makes it inadvisable to proceed with such
acceptance for payment or payments for Shares.
 
    The foregoing conditions are for the sole benefit of Purchaser and may be
asserted by Purchaser regardless of the circumstances (including any action or
omission by Purchaser other than any breach by Parent or Purchaser of the Merger
Agreement, or, in the case of (c) or (d) above, a failure of such condition
which Parent or Purchaser has caused to occur) giving rise to any such condition
or may be waived by Purchaser in whole or in part at any time or from time to
time in its sole discretion. The failure by Purchaser at any time to exercise
any of the foregoing rights shall not be deemed a waiver of any such right, the
waiver of any such right with respect to particular facts or circumstances shall
not be deemed a waiver with respect to any other facts or circumstances, and
each such right shall be deemed an ongoing right that may be asserted at any
time or from time to time.
 
14. CERTAIN LEGAL MATTERS; REGULATORY APPROVALS
 
    Except as described below, Purchaser is not aware of any governmental
license or regulatory permit that appears to be material to the business of the
Company and its subsidiaries, taken as a whole, that might be adversely affected
by Purchaser's acquisition of the Company's Shares as contemplated herein or of
any approval or other action by any governmental, administrative or regulatory
authority or agency, domestic or foreign, that would be required for the
acquisition or ownership of Shares by Purchaser as contemplated herein. Should
any such approval or other action be required, Purchaser and Parent currently
contemplate that such approval or other action will be sought. Except as
otherwise expressly described in this Section 14, Purchaser does not presently
intend to delay the acceptance for payment of or payment for Shares tendered
pursuant to the Offer pending the outcome of any such matter. Purchaser is
unable to predict whether it may determine that it is required to delay the
acceptance for payment of or payment for Shares tendered pursuant to the Offer
pending the outcome of any such matter. There can be no assurance that any such
approval or other action, if needed, would be obtained or would be obtained
without substantial conditions or that the failure to obtain any such approval
or other action might not result in consequences adverse to the Company's
business or that certain parts of the Company's business might not have to be
disposed of. See Section 13 for certain conditions to the Offer.
 
15. FEES AND EXPENSES
 
    Salomon Smith Barney is acting as the Dealer Manager in connection with the
Offer and has provided certain financial advisory services in connection with
the acquisition of the Company. Parent and Purchaser have agreed to pay Salomon
Smith Barney a fee of $1.75 million upon consummation of the Offer. The Company
also has agreed to reimburse Salomon Smith Barney for certain expenses incurred
in connection with the Offer, including out-of-pocket expenses and reasonable
attorney's fees and disbursements, and to indemnify Salomon Smith Barney against
certain liabilities in connection with the Offer, including certain liabilities
under the federal securities laws.
 
    Purchaser has retained Georgeson & Company Inc. to act as the Information
Agent, and BankBoston, N.A. to act as the Depositary, in connection with the
Offer. The Information Agent may contact holders of Shares by mail, telephone,
telex, telegraph and personal interview and may request brokers, dealers and
other nominee stockholders to forward the Offer materials to beneficial owners.
Each of the Information Agent and the Depositary will receive reasonable and
customary compensation for their respective services, will be reimbursed for
certain reasonable out-of-pocket expenses and will be indemnified against
certain liabilities and expenses in connection with the Offer, including certain
liabilities under the federal securities laws.
 
                                       56
<PAGE>
    The following table sets forth the estimated expenses incurred in connection
with the Merger. These fees will be paid by Parent and its affiliates and will
not be the responsibility of the Company.
 
<TABLE>
<S>                                                               <C>
Filing fees.....................................................  $  84,437
Printing costs..................................................  $ 200,000
Legal fees......................................................  $ 600,000
Accounting fees.................................................  $       0
Solicitation expenses...........................................  $  35,000
Financial Advisory Fees.........................................  $1,750,000
                                                                  ---------
    Total.......................................................  $2,669,437
                                                                  ---------
                                                                  ---------
</TABLE>
 
    Except as set forth above, Purchaser will not pay any fees or commissions to
any broker or dealer or other person for soliciting tenders of Shares pursuant
to the Offer. Brokers, dealers, commercial banks and trust companies will, upon
request, be reimbursed by Purchaser for customary mailing and handling expenses
incurred by them in forwarding the Offer materials to their customers.
 
16. MISCELLANEOUS
 
    The Offer is being made solely by this Offer to Purchase, the related Letter
of Transmittal, the Option Election, the Stock Purchase Election and the
Restricted Stock Election and is being made to all holders of Shares, Options,
Purchase Rights and Restricted Shares. The Offer is not being made to, nor will
tenders be accepted from or on behalf of, holders of Shares, Options, Purchase
Rights and Restricted Shares of the Company residing in any jurisdiction in
which the making of the Offer or the acceptance thereof would not be in
compliance with the securities, blue sky or other laws of such jurisdiction.
However, Purchaser may, in its discretion, take such action as it may deem
necessary to make the Offer in any jurisdiction and extend the Offer to holders
of Shares, Options, Purchase Rights and Restricted Shares in such jurisdiction.
In any jurisdiction where the securities, blue sky or other laws require the
Offer to be made by a licensed broker or dealer, the Offer will be deemed to be
made on behalf of Purchaser by the Dealer Manager or one or more registered
brokers or dealers that are licensed under the laws of such jurisdiction.
 
    Parent and Purchaser have filed with the Commission the Schedule 14D-1
pursuant to Rule 14d-3 under the Exchange Act containing certain additional
information with respect to the Offer. Such Schedule and any amendments thereto,
including exhibits, may be examined and copies may be obtained from the
principal office of the Commission in the manner set forth in Section 8 (except
that they will not be available at the regional offices of the Commission).
 
    NO PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR MAKE ANY
REPRESENTATION ON BEHALF OF PURCHASER OR PARENT NOT CONTAINED IN THIS OFFER TO
PURCHASE OR IN THE LETTER OF TRANSMITTAL AND, IF GIVEN OR MADE, SUCH INFORMATION
OR REPRESENTATIONS MUST NOT BE RELIED UPON AS HAVING BEEN AUTHORIZED.
 
                                       57
<PAGE>
                                                                      SCHEDULE I
 
     INFORMATION CONCERNING THE DIRECTORS AND EXECUTIVE OFFICERS OF PARENT,
                   PURCHASER AND CERTAIN AFFILIATES OF PARENT
 
A. DIRECTORS AND EXECUTIVE OFFICERS OF PARENT
 
    The following table sets forth the name, present principal occupation or
employment and material occupation, positions, offices or employment for the
past five years of each director and executive officer of Parent. Unless
otherwise indicated below, the address of each director and officer is 9330
Zionsville Road, Indianapolis, Indiana 46268 and each such person is a citizen
of the United States.
 
<TABLE>
<CAPTION>
                                                    PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND
NAME AND BUSINESS ADDRESS                                    FIVE-YEAR EMPLOYMENT HISTORY
- ------------------------------------  ---------------------------------------------------------------------------
<S>                                   <C>
A. Charles Fischer..................  Mr. Fischer has served as Vice President-Agricultural Chemicals and Urban
                                      Pest of Parent since November 1997. Prior to assuming his current position,
                                      Mr. Fischer had been Vice President-North America of Parent since 1992.
 
John L. Hagaman.....................  Mr. Hagaman has served as President and Chief Executive Officer of Parent
                                      since the formation of Parent in October 1989. He was appointed to the
                                      Members Committee of Parent in August 1997. Mr. Hagaman served as a
                                      Director of the Company from February 1996 to March 1997 and was reelected
                                      to the Company board in March 1998. He is also a member of the Corporate
                                      Leadership Team of TDCC.
 
Nickolas D. Hein....................  Mr. Hein is Vice President-Biotechnology for Parent. Prior to assuming that
                                      role in February 1998, Mr. Hein had served as Parent's Global Vice
                                      President since 1990. Mr. Hein has been a Director of the Company since
                                      March 1997, and Chairman of the Board of Directors of the Company since May
                                      1997.
 
Louis W. Pribila....................  Mr. Pribila has served as Vice President, Secretary and General Counsel of
                                      Parent since May 1995. Mr. Pribila has been a Director of the Company since
                                      December 1996. Prior to assuming his current position at Parent, Mr.
                                      Pribila had been Assistant General Counsel of TDCC since 1989.
 
Sean S. Skinner.....................  Mr. Skinner has been Treasurer of Parent since the formation of Parent in
                                      October 1989.
 
John A. Tomke.......................  Mr. Tomke has served as Vice President-Operations for Parent since January
                                      1992.
 
Jerry E. Toomer.....................  Mr. Toomer has been Vice President-Human Resources, for Parent since June
                                      1995. Prior to that, Dr. Toomer had been Director of Human Resources for
                                      TDCC's Pacific Area organization since 1991.
 
Gary L. Whitlock....................  Mr. Whitlock has served as Vice President-Finance for Parent since February
                                      1998. In 1996, Mr. Whitlock was named Global Cost and Functional Controller
                                      for TDCC. In addition, he was the financial liaison to a major joint
                                      venture, DuPont Dow Elastomers LLC.
</TABLE>
 
                                      I-1
<PAGE>
<TABLE>
<CAPTION>
                                                    PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND
NAME AND BUSINESS ADDRESS                                    FIVE-YEAR EMPLOYMENT HISTORY
- ------------------------------------  ---------------------------------------------------------------------------
<S>                                   <C>
Joseph L. Downey....................  Mr. Downey has served as Chairman of the Members Committee of Parent since
                                      August 1997. Mr. Downey has been a Director of TDCC since 1989. Mr. Downey
                                      has served as a Senior Consultant to TDCC since 1994. Until July 1994 Mr.
                                      Downey served as a Senior Vice President of TDCC.
 
Fernand J. Kaufmann.................  Mr. Kaufmann has served on the Members Committee of Parent since August
                                      1997. Mr. Kaufmann has been a Vice President for New Businesses and
                                      Strategic Development of TDCC since 1995. Prior to 1995, Mr. Kaufmann
                                      served as Group Vice President for the Ventures, Chemicals and Plastics
                                      Business Group of TDCC. Mr. Kaufmann is a citizen of Luxembourg.
 
J. Pedro Reinhard...................  Mr. Reinhard has served on the Members Committee of Parent since August
                                      1997. Mr. Reinhard has been a Director and the Chief Financial Officer of
                                      TDCC since October 1995. Mr. Reinhard was elected Executive Vice President
                                      of TDCC in November 1996. Prior to October 1995, Mr. Reinhard served as
                                      Financial Vice President of TDCC. Mr. Reinhard is a citizen of Brazil.
 
William S. Stavropoulos.............  Mr. Stavropoulos has served on the Members Committee of Parent since August
                                      1997. Mr. Stavropoulos has been the Chief Executive Officer of TDCC since
                                      November 1995. Prior to 1995, Mr. Stavropoulos served as President and
                                      Chief Operating Officer of TDCC. Mr. Stavropoulos has been a Director since
                                      July 1990.
</TABLE>
 
                                      I-2
<PAGE>
B. DIRECTORS AND EXECUTIVE OFFICERS OF PURCHASER
 
    The following table sets forth the name, business address, present principal
occupation or employment and material occupations, positions, offices or
employment for the past five years of each director and executive officer of
Purchaser. Unless otherwise indicated below, the address of each director and
officer is 2030 Dow Center, Midland, Michigan 48674.
 
<TABLE>
<CAPTION>
                                                    PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND
NAME AND BUSINESS ADDRESS                                    FIVE-YEAR EMPLOYMENT HISTORY
- ------------------------------------  ---------------------------------------------------------------------------
<S>                                   <C>
Brian G. Taylorson..................  Mr. Taylorson is a Director and also the President of Purchaser. Mr.
                                      Taylorson has served as Corporate Director, Mergers and Acquisitions of
                                      TDCC since July 1995. Prior to that Mr. Taylorson served as Treasurer of
                                      Dow Chemical Canada Inc. Mr. Taylorson is a citizen of the United Kingdom.
 
Charles J. Hahn.....................  Mr. Hahn is a Director and also the Treasurer of Purchaser. Mr. Hahn has
                                      served as Tax Director and Assistant Secretary of TDCC since 1994. Prior to
                                      that, Mr. Hahn was a member of TDCC's Tax Department.
 
Jane M. Gootee......................  Ms. Gootee is a Director and also the Secretary of Purchaser. Ms. Gootee
                                      has served as the Manager-Financial Law for TDCC since June 1994. Prior to
                                      that Ms. Gootee served as a Senior Counsel of Dow Europe S.A.
</TABLE>
 
                                      I-3
<PAGE>
C. DIRECTORS AND EXECUTIVE OFFICERS OF CENTEN
 
    The following table sets forth the name, business address, present principal
occupation or employment and material occupations, positions, offices or
employment for the past five years of each director and executive officer of
Centen. Unless otherwise indicated below, the address of each director and
officer is 2030 Dow Center, Midland, Michigan 48674 and each such person is a
citizen of the United States.
 
<TABLE>
<CAPTION>
                                                          PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND FIVE-YEAR
NAME AND BUSINESS ADDRESS                                                    EMPLOYMENT HISTORY
- --------------------------------------------------------  --------------------------------------------------------
<S>                                                       <C>
Alfonso Escudero........................................  Mr. Escudero is a Director and also the Treasurer of
                                                          Centen. Mr. Escudero has served as Corporate Finance
                                                          Director of TDCC since November 1996. Prior to that Mr.
                                                          Escudero served as Treasurer for the Benelux/Nordic
                                                          region in Belgium. Mr. Escudero is a citizen of Spain.
 
Jane M. Gootee..........................................  Ms. Gootee is a Director and also the Secretary of
                                                          Centen. Ms. Gootee has served as the Manager-Financial
                                                          Law for TDCC since June 1994. Prior to that Ms. Gootee
                                                          served as a Senior Counsel of Dow Europe S.A.
 
Douglas F. Ward.........................................  Mr. Ward is a Director of Centen. Mr. Ward has served as
                                                          Corporate Reporting Controller of TDCC since February
                                                          1998. Prior to that Mr. Ward served as Director of
                                                          Accounting Analysis and Reporting for the Corporate
                                                          Controllers Department of TDCC since 1993.
 
Brian G. Taylorson......................................  Mr. Taylorson is a Director and also the President of
                                                          Centen. Mr. Taylorson has served as Corporate Director,
                                                          Mergers and Acquisitions of TDCC since July 1995. Prior
                                                          to that Mr. Taylorson served as Treasurer of Dow
                                                          Chemical Canada Inc. Mr. Taylorson is a citizen of the
                                                          United Kingdom.
</TABLE>
 
                                      I-4
<PAGE>
D. DIRECTORS AND EXECUTIVE OFFICERS OF ROFAN
 
    The following table sets forth the name, business address, present principal
occupation or employment and material occupations, positions, offices or
employment for the past five years of each director and executive officer of
Rofan. Unless otherwise indicated below, the address of each director and
officer is 2030 Dow Center, Midland, Michigan 48674 and each such person is a
citizen of the United States.
 
<TABLE>
<CAPTION>
                                                          PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND FIVE-YEAR
NAME AND BUSINESS ADDRESS                                                    EMPLOYMENT HISTORY
- --------------------------------------------------------  --------------------------------------------------------
<S>                                                       <C>
J. Pedro Reinhard.......................................  Mr. Reinhard is a Director and also the President of
                                                          Rofan. Mr. Reinhard has been a Director and the Chief
                                                          Financial Officer of TDCC since October 1995. Mr.
                                                          Reinhard was elected Executive Vice President of TDCC in
                                                          November 1996. Mr. Reinhard served as Financial Vice
                                                          President of TDCC from 1995-96 and as TDCC Treasurer
                                                          from 1988-96. Mr. Reinhard is a citizen of Brazil.
 
Geoffery E. Merszei.....................................  Mr. Merszei is a Director and also a Vice President of
                                                          Rofan. Mr. Merszei has served as Vice President of TDCC
                                                          since July 1996 and as Treasurer of TDCC since May 1996.
                                                          Prior to that Mr. Merszei served as Director of Finance
                                                          for Dow Europe S.A. Mr. Merszei is a citizen of Canada.
 
Brian G. Taylorson......................................  Mr. Taylorson is a Director and also a Vice President of
                                                          Rofan. Mr. Taylorson has served as Corporate Director,
                                                          Mergers and Acquisitions of TDCC since July 1995. Prior
                                                          to that Mr. Taylorson served as Treasurer of Dow
                                                          Chemical Canada Inc. Mr. Taylorson is a citizen of the
                                                          United Kingdom.
 
Jane M. Gootee..........................................  Ms. Gootee is a Director and also the Secretary of
                                                          Rofan. Ms. Gootee has served as the Manager-Financial
                                                          Law for TDCC since June 1994. Prior to that Ms. Gootee
                                                          served as a Senior Counsel of Dow Europe S.A.
</TABLE>
 
                                      I-5
<PAGE>
E. DIRECTORS AND EXECUTIVE OFFICERS OF TDCC
 
    The following table sets forth the name, business address, present principal
occupation or employment and material occupations, positions, offices or
employment for the past five years of each director and executive officer of
TDCC. Unless otherwise indicated below, the address of each director and officer
is 2030 Dow Center, Midland, Michigan 48674 and each such person is a citizen of
the United States.
 
<TABLE>
<CAPTION>
                                                          PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND FIVE-YEAR
NAME AND BUSINESS ADDRESS                                                    EMPLOYMENT HISTORY
- --------------------------------------------------------  --------------------------------------------------------
<S>                                                       <C>
Frank P. Popoff.........................................  Mr. Popoff has been the Chairman of the Board of
                                                          Directors of TDCC since December 1992 and has been a
                                                          Director since 1982. Mr. Popoff also served as Chief
                                                          Executive Officer of TDCC until November 1995. Mr.
                                                          Popoff is a Director of American Express Company, US
                                                          WEST, Inc., Chemical Financial Corporation, United
                                                          Technologies Corporation and the Michigan Molecular
                                                          Institute.
 
William S. Stavropoulos.................................  Mr. Stavropoulos has been a Director of TDCC since July
                                                          1990, Chief Executive Officer of TDCC since November
                                                          1995 and President of TDCC since 1993. Prior to 1995,
                                                          Mr. Stavropoulos served as Chief Operating Officer of
                                                          TDCC. Mr. Stavropoulos has served on the Members
                                                          Committee of Parent since August 1997. Mr. Stavropoulos
                                                          is a Director of Dow Corning Corporation, NCR
                                                          Corporation, BellSouth Corporation, Chemical Financial
                                                          Corporation, and Chemical Bank and Trust Company.
 
J. Pedro Reinhard.......................................  Mr. Reinhard has been a Director and the Chief Financial
                                                          Officer of TDCC since October 1995. Mr. Reinhard was
                                                          elected Executive Vice President of TDCC in November
                                                          1996. Mr. Reinhard served as Financial Vice President of
                                                          TDCC from 1995-1996 and as TDCC Treasurer from
                                                          1988-1996. Mr. Reinhard has served on the Members
                                                          Committee of Parent since August 1997. Mr. Reinhard is a
                                                          citizen of Brazil.
 
Arnold A. Allemang......................................  Mr. Allemang has been a Director of TDCC since July
                                                          1996. Mr. Allemang has also served as Vice President of
                                                          Operations of TDCC since August 1997. From 1993-1995,
                                                          Mr. Allemang was Vice President of Manufacturing
                                                          Operations for Dow Europe S.A. Mr. Allemang was Vice
                                                          President and Director of Manufacturing and Engineering
                                                          from 1995-1997.
 
Jacqueline K. Barton....................................  Dr. Barton has been a Director of TDCC since 1993. Dr.
                                                          Barton is the "Arthur and Marian Hanisch Memorial
                                                          Professor of Chemistry" at the California Institute of
                                                          Technology.
</TABLE>
 
                                      I-6
<PAGE>
<TABLE>
<CAPTION>
                                                          PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND FIVE-YEAR
NAME AND BUSINESS ADDRESS                                                    EMPLOYMENT HISTORY
- --------------------------------------------------------  --------------------------------------------------------
<S>                                                       <C>
David T. Buzzelli.......................................  Mr. Buzzelli has been a Director of TDCC since 1993. Mr.
                                                          Buzzelli has served as a Senior Consultant to TDCC since
                                                          July 1997. Mr. Buzzelli was Corporate Director of Public
                                                          Affairs from 1993-1997, Corporate Director of
                                                          Environment, Health and Safety from 1990-1997 and Dow
                                                          Vice President from 1990-1997. Mr. Buzzelli is also a
                                                          Director of the Dow Corning Corporation.
 
Anthony J. Carbone......................................  Mr. Carbone has been a Director of TDCC since July 1995
                                                          and has been Executive Vice President, Plastics,
                                                          Hydrocarbons and Energy of TDCC since 1996. Mr. Carbone
                                                          was Group Vice President-Global Plastics, Hydrocarbons
                                                          and Energy from 1995-1996 and Group Vice President for
                                                          Global Plastics from 1993-1995.
 
Fred P. Corson..........................................  Mr. Corson has been a Director of TDCC since 1994. Mr.
                                                          Corson has been a Senior Consultant to TDCC since April
                                                          1998. Mr. Corson served as Vice President and Director
                                                          of Research and Development of TDCC from 1990 until
                                                          March 31, 1998.
 
John C. Danforth........................................  Senator Danforth has been a Director of TDCC since
                                                          February 1996. Senator Danforth represented the State of
                                                          Missouri in the United States Senate from 1976 until his
                                                          retirement from the Senate in 1995. Mr. Danforth is a
                                                          partner with the law firm of Bryan Cave LLP. He is a
                                                          Director of General American Life Insurance Company and
                                                          Cerner Corporation.
 
Willie D. Davis.........................................  Mr. Davis has been a Director of TDCC since 1988. Mr.
                                                          Davis is owner of All-Pro Broadcasting, Inc., a Los
                                                          Angeles broadcasting company. Mr. Davis is also a
                                                          Director of Sara Lee Corporation, Alliance Bank, MGM
                                                          Grand Company, Kmart Corporation, Wicor, Inc., Johnson
                                                          Controls Inc., Rally's Hamburgers Inc. and the Strong
                                                          Funds.
 
Michael L. Dow..........................................  Mr. Dow has been a Director of TDCC since 1988. Mr. Dow
                                                          is Chairman and Chief Executive Officer of General
                                                          Aviation, Inc. Mr. Dow is also a Director of Chemical
                                                          Financial Corporation and Chemical Bank and Trust
                                                          Company. Mr. Dow is also a trustee and the Treasurer of
                                                          the Herbert H. and Grace A. Dow Foundation and a trustee
                                                          of the Michigan State University Foundation.
</TABLE>
 
                                      I-7
<PAGE>
<TABLE>
<CAPTION>
                                                          PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND FIVE-YEAR
NAME AND BUSINESS ADDRESS                                                    EMPLOYMENT HISTORY
- --------------------------------------------------------  --------------------------------------------------------
<S>                                                       <C>
Joseph L. Downey........................................  Mr. Downey has been a Director of TDCC since 1989. Mr.
                                                          Downey has served as a Senior Consultant to TDCC since
                                                          1994. Until July 1994 Mr. Downey served as a Senior Vice
                                                          President of TDCC. Mr. Downey has also served as
                                                          Chairman of the Members Committee of Parent since 1989.
                                                          Mr. Downey is a Director of Security National Bank.
 
Enrique C. Falla........................................  Mr. Falla has been a Director of TDCC since 1985. Mr.
                                                          Falla has served as a Senior Vice President to TDCC
                                                          since May 1997 and has been a Senior Consultant since
                                                          1997. Prior to that, Mr. Falla served as Executive Vice
                                                          President from 1991-1997 and Chief Financial Officer
                                                          from 1987-1995. Mr. Falla is a Director of Dow Corning
                                                          Corporation, Kmart Corporation, Guidant Corporation, and
                                                          the University of Miami.
 
Barbara Hackman Franklin................................  Ms. Franklin has served as a Director of TDCC since
                                                          1993. From 1992 to 1993, Ms. Franklin served as the U.S.
                                                          Secretary of Commerce. Ms. Franklin was a business
                                                          consultant from 1993 to 1995. Ms. Franklin has been
                                                          President and Chief Executive Officer of Barbara
                                                          Franklin Enterprises, a private consulting and
                                                          investment firm, since 1995.
 
Allan D. Gilmour........................................  Mr. Gilmour has served as a Director of TDCC since 1995.
                                                          Mr. Gilmour retired as Vice Chairman of the Ford Motor
                                                          Company in 1995. Mr. Gilmour is a Director of DTE Energy
                                                          Company, The Prudential Insurance Company of America, US
                                                          WEST, Inc. and Whirlpool Corporation.
 
Michael D. Parker.......................................  Mr. Parker has served as a Director of TDCC since July
                                                          1995. Mr. Parker has served as Executive Vice President
                                                          of TDCC since 1996. Mr. Parker has been President of Dow
                                                          North America and Group Vice President-
                                                          Chemicals and Metals of TDCC since 1995. Mr. Parker was
                                                          Dow Group Vice President from 1993-1996 and Group Vice
                                                          President-Chemicals and Hydrocarbons 1993-1995. He is
                                                          also a Director of the National Association of
                                                          Manufacturers and the National Legal Center for the
                                                          Public Interest. Mr. Parker is a citizen of the United
                                                          Kingdom.
</TABLE>
 
                                      I-8
<PAGE>
<TABLE>
<CAPTION>
                                                          PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND FIVE-YEAR
NAME AND BUSINESS ADDRESS                                                    EMPLOYMENT HISTORY
- --------------------------------------------------------  --------------------------------------------------------
<S>                                                       <C>
Harold T. Shapiro.......................................  Dr. Shapiro has served as a Director of TDCC since 1985.
                                                          Dr. Shapiro is the President of Princeton University as
                                                          well as a professor of economics and public affairs. Dr.
                                                          Shapiro is Chairman of the Board and a Trustee of the
                                                          Alfred P. Sloan Foundation. He is also a Trustee of
                                                          Educational Testing Service, the University of
                                                          Pennsylvania Medical Center and the Universities
                                                          Research Association. He also serves as a Director of
                                                          the National Bureau of Economic Research. Dr. Shapiro is
                                                          a member of the Institute of Medicine and the American
                                                          Philosophical Society and a fellow of the American
                                                          Academy of Arts and Sciences.
 
Paul G. Stern...........................................  Dr. Stern has been a Director of TDCC since 1992. Dr.
                                                          Stern is a partner and co-founder, in 1995, of Thayer
                                                          Capital Partners. From 1993-1995, Dr. Stern was a
                                                          Special Partner at Forstmann Little & Co. Dr. Stern is
                                                          also a director of LTV Corporation and Whirlpool
                                                          Corporation. Dr. Stern is Treasurer of the John F.
                                                          Kennedy Center for the Performing Arts.
 
John G. Scriven.........................................  Mr. Scriven has served as Vice President and General
                                                          Counsel since January 1994 and Secretary of TDCC since
                                                          August 1996. Mr. Scriven is a visiting professor at
                                                          McGeorge School of Law, University of the Pacific and a
                                                          guest lecturer to the Swiss Banking Institute. Mr.
                                                          Scriven is a member of the North America Board of
                                                          Advisors of the Swiss Chamber of Commerce and a member
                                                          of the board of directors of the American Arbitration
                                                          Association. Mr. Scriven is a citizen of Switzerland.
 
Lawrence J. Washington, Jr..............................  Mr. Washington has served as Vice President-
                                                          Human Resources since October 1995 and as Vice President
                                                          of Environment, Health & Safety, Human Resources and
                                                          Public Affairs for TDCC since July 1997. From 1990-1994,
                                                          Mr. Washington served as Vice President, Dow North
                                                          America and General Manager for Michigan Division.
 
Geoffery E. Merszei.....................................  Mr. Merszei has served as Vice President of TDCC since
                                                          July 1996 and as Treasurer of TDCC since May 1996. Prior
                                                          to that Mr. Merszei served as Director of Finance for
                                                          Dow Europe S.A. Mr. Merszei is a citizen of Canada.
</TABLE>
 
                                      I-9
<PAGE>
<TABLE>
<CAPTION>
                                                          PRESENT PRINCIPAL OCCUPATION OF EMPLOYMENT AND FIVE-YEAR
NAME AND BUSINESS ADDRESS                                                    EMPLOYMENT HISTORY
- --------------------------------------------------------  --------------------------------------------------------
<S>                                                       <C>
G. Michael Lynch........................................  Mr. Lynch has served as Vice President and Controller of
                                                          TDCC since February 1997. Prior to that date Mr. Lynch
                                                          was an executive with the Ford Motor Company.
 
Richard M. Gross........................................  Mr. Gross has served as Vice President and Director of
                                                          Research & Development of TDCC since April 1998. From
                                                          1995-March 1998, Mr. Gross served as Vice President and
                                                          Director of Michigan Operations and Core Research and
                                                          Development. From 1992-94, Mr. Gross served as Research
                                                          and Development Director for North American Chemicals
                                                          and Metals/Hydrocarbons Research and Development. Mr.
                                                          Gross is on the governing board of the Council for
                                                          Chemical Research and is a member of the external
                                                          advisory board for the Chemical Engineering Department
                                                          at Georgia Tech University.
</TABLE>
 
                                      I-10
<PAGE>
                                                                     SCHEDULE II
 
              CHAPTER 13 OF THE CALIFORNIA GENERAL CORPORATION LAW
 
    SECTION 1300 [SHORT FORM MERGER; PURCHASE OF SHARES AT FAIR MARKET VALUE;
"DISSENTING SHARES" AND DISSENTING SHAREHOLDER].-- (a) If the approval of the
outstanding shares (Section 152) of a corporation is required for a
reorganization under subdivisions (a) and (b) or subdivision (e) or (f) of
Section 1201, each shareholder of the corporation entitled to vote on the
transaction and each shareholder of a subsidiary corporation in a short-form
merger may, by complying with this chapter, require the corporation in which the
shareholder holds shares to purchase for cash at their fair market value the
shares owned by the shareholder which are dissenting shares as defined in
subdivision (b). The fair market value shall be determined as of the day before
the first announcement of the terms of the proposed reorganization or short-form
merger, excluding any appreciation or depreciation in consequence of the
proposed action, but adjusted for any stock split, reverse stock split, or share
dividend which becomes effective thereafter.
 
    (b) As used in this chapter, "dissenting shares" means shares which come
within all of the following descriptions:
 
        (1) Which were not immediately prior to the reorganization or short-form
    merger either (A) listed on any national securities exchange certified by
    the Commissioner of Corporations under subdivision (o) of Section 25100 or
    (B) listed on the list of OTC margin stocks issued by the Board of Governors
    of the Federal Reserve System, and the notice of meeting of shareholders to
    act upon the reorganization summarizes this section and Sections 1301, 1302,
    1303 and 1304; provided, however, that this provision does not apply to any
    shares with respect to which there exists any restriction on transfer
    imposed by the corporation or by any law or regulation; and provided,
    further, that this provision does not apply to any class of shares described
    in subparagraph (A) or (B) if demands for payment are filed with respect to
    5 percent or more of the outstanding shares of that class.
 
        (2) Which were outstanding on the date for the determination of
    shareholders entitled to vote on the reorganization and (A) were not voted
    in favor of the reorganization or, (B) if described in subparagraph (A) or
    (B) of paragraph (1) (without regard to the provisos in that paragraph),
    were voted against the reorganization, or which were held of record on the
    effective date of a short-form merger; provided, however, that subparagraph
    (A) rather than subparagraph (B) of this paragraph applies in any case where
    the approval required by Section 1201 is sought by written consent rather
    than at a meeting.
 
        (3) Which the dissenting shareholder has demanded that the corporation
    purchase at their fair market value, in accordance with Section 1301.
 
        (4) Which the dissenting shareholder has submitted for endorsement, in
    accordance with Section 1302.
 
    (c) As used in this chapter, "dissenting shareholder" means the recordholder
of dissenting shares and includes a transferee of record.
 
    SECTION 1301 [DISSENTERS' RIGHTS; DEMAND ON CORPORATION FOR PURCHASE OF
SHARES].-- (a) If, in the case of a reorganization, any shareholders of a
corporation have a right under Section 1300, subject to compliance with
paragraphs (3) and (4) of subdivision (b) thereof, to require the corporation to
purchase their shares for cash, such corporation shall mail to each such
shareholder a notice of the approval of the reorganization by its outstanding
shares (Section 152) within 10 days after the date of such approval, accompanied
by a copy of Sections 1300, 1302, 1303, 1304 and this section, a statement of
the price determined by the corporation to represent the fair market value of
the dissenting shares, and a brief description of the procedure to be followed
if the shareholder desires to exercise the shareholder's
 
                                      II-1
<PAGE>
right under such sections. The statement of price constitutes an offer by the
corporation to purchase at the price stated any dissenting shares as defined in
subdivision (b) of Section 1300, unless they lose their status as dissenting
shares under Section 1309.
 
    (b) Any shareholder who has a right to require the corporation to purchase
the shareholder's shares for cash under Section 1300, subject to compliance with
paragraphs (3) and (4) of subdivision (b) thereof, and who desires the
corporation to purchase such shares shall make written demand upon the
corporation for the purchase of such shares and payment to the shareholder in
cash of their fair market value. The demand is not effective for any purpose
unless it is received by the corporation or any transfer agent thereof (1) in
the case of shares described in clause (i) or (ii) of paragraph (1) of
subdivision (b) of Section 1300 (without regard to the provisos in that
paragraph), not later than the date of the shareholders' meeting to vote upon
the reorganization, or (2) in any other case within 30 days after the date on
which the notice of the approval by the outstanding shares pursuant to
subdivision (a) or the notice pursuant to subdivision (i) of Section 1110 was
mailed to the shareholder.
 
    (c) The demand shall state the number and class of the shares held of record
by the shareholder which the shareholder demands that the corporation purchase
and shall contain a statement of what such shareholder claims to be the fair
market value of those shares as of the day before the announcement of the
proposed reorganization or short-form merger. The statement of fair market value
constitutes an offer by the shareholder to sell the shares at such price.
 
    SECTION 1302 [DISSENTING SHARES, STAMPING OR ENDORSING].-- Within 30 days
after the date on which notice of the approval by the outstanding shares or the
notice pursuant to subdivision (i) of Section 1110 was mailed to the
shareholder, the shareholder shall submit to the corporation at its principal
office or at the office of any transfer agent thereof, (a) if the shares are
certificated securities, the shareholder's certificates representing any shares
which the shareholder demands that the corporation purchase, to be stamped or
endorsed with a statement that the shares are dissenting shares or to be
exchanged for certificates of appropriate denomination so stamped or endorsed or
(b) if the shares are uncertificated securities, written notice of the number of
shares which the shareholder demands that the corporation purchase. Upon
subsequent transfers of the dissenting shares on the books of the corporation
the new certificates, initial transaction statement, and other written
statements issued therefor shall bear a like statement, together with the name
of the original dissenting holder of the shares.
 
    SECTION 1303 [DISSENTING SHAREHOLDER ENTITLED TO AGREED PRICE WITH INTEREST;
TIME OF PAYMENT].-- (a) If the corporation and the shareholder agree that the
shares are dissenting shares and agree upon the price of the shares, the
dissenting shareholder is entitled to the agreed price with interest thereon at
the legal rate on judgments from the date of the agreement. Any agreements
fixing the fair market value of any dissenting shares as between the corporation
and the holders thereof shall be filed with the secretary of the corporation.
 
    (b) Subject to the provisions of Section 1306, payment of the fair market
value of dissenting shares shall be made within 30 days after the amount thereof
has been agreed or within 30 days after any statutory or contractual conditions
to the reorganization are satisfied, whichever is later, and in the case of
certificated securities, subject to surrender of the certificates therefor,
unless provided otherwise by agreement.
 
    SECTION 1304 [DISSENTERS' ACTIONS; JOINDER; CONSOLIDATION; APPOINTMENT OF
APPRAISERS].-- (a) If the corporation denies that the shares are dissenting
shares, or the corporation and the shareholder fail to agree upon the fair
market values of the shares, then the shareholder demanding purchase of such
shares as dissenting shares or any interested corporation, within six months
after the date on which notice of the approval by the outstanding shares
(Section 152) or notice pursuant to subdivision (i) of Section 1110 was mailed
to the shareholder, but not thereafter, may file a complaint in the superior
court of the proper county praying the court to determine whether the shares are
dissenting
 
                                      II-2
<PAGE>
shares or the fair market value of the dissenting shares or both or may
intervene in any action pending on such a complaint.
 
    (b) Two or more dissenting shareholders may join as plaintiffs or be joined
as defendants in any such action and two or more such actions may be
consolidated.
 
    (c) On the trial of the action, the court shall determine the issues. If the
status of the shares as dissenting shares is in issue, the court shall first
determine that issue. If the fair market value of the dissenting shares is in
issue, the court shall determine, or shall appoint one or more impartial
appraisers to determine, the fair market value of the shares.
 
    SECTION 1305 [APPRAISERS' DUTY AND REPORT; COURT JUDGMENT; PAYMENT; APPEAL;
COSTS OF ACTION].-- (a) If the court appoints an appraiser or appraisers, they
shall proceed forthwith to determine the fair market value per share. Within the
time fixed by the court, the appraisers, or a majority of them, shall make and
file a report in the office of the clerk of the court. Thereupon, on the motion
of any party, the report shall be submitted to the court and considered on such
evidence as the court considers relevant. If the court finds the report
reasonable, the court may confirm it.
 
    (b) If a majority of the appraisers appointed fail to make and file a report
within 10 days from the date of their appointment or within such further time as
may be allowed by the court or the report is not confirmed by the court, the
court shall determine the fair market value of the dissenting shares.
 
    (c) Subject to the provisions of Section 1306, judgment shall be rendered
against the corporation for payment of an amount equal to the fair market value
of each dissenting share multiplied by the number of dissenting shares which any
dissenting shareholder who is a party, or who has intervened, is entitled to
require the corporation to purchase, with interest thereon at the legal rate
from the date on which judgment was entered.
 
    (d) Any such judgment shall be payable forthwith with respect to
uncertificated securities and, with respect to certificated securities, only
upon the endorsement and delivery to the corporation of the certificates for the
shares described in the judgment. Any party may appeal from the judgment.
 
    (e) The costs of the action, including reasonable compensation to the
appraisers to be fixed by the court, shall be assessed or apportioned as the
court considers equitable, but, if the appraisal exceeds the price offered by
the corporation, the corporation shall pay the costs (including in the
discretion of the court attorneys' fees, fees of expert witnesses and interest
at the legal rate on judgments from the date of compliance with Sections 1300,
1301 and 1302 if the value awarded by the court for the shares is more than 125
percent of the price offered by the corporation under subdivision (a) of Section
1301).
 
    SECTION 1306 [DISSENTING SHAREHOLDERS: EFFECT OF PREVENTION OF PAYMENT OF
FAIR MARKET VALUE].-- To the extent that the provisions of Chapter 5 prevent the
payment to any holders of dissenting shares of their fair market value, they
shall become creditors of the corporation for the amount thereof together with
interest at the legal rate on judgments until the date of payment, but
subordinate to all other creditors in any liquidation proceeding, such debt to
be payable when permissible under the provisions of Chapter 5.
 
    SECTION 1307 [DISSENTING SHARES, DISPOSITION OF DIVIDENDS].-- Cash dividends
declared and paid by the corporation upon the dissenting shares after the date
of approval of the reorganization by the outstanding shares (Section 152) and
prior to payment for the shares by the corporation shall be credited against the
total amount to be paid by the corporation therefor.
 
    SECTION 1308 [DISSENTING SHARES, RIGHTS AND PRIVILEGES].-- Except as
expressly limited in this chapter, holders of dissenting shares continue to have
all the rights and privileges incident to their shares, until the fair market
value of their shares is agreed upon or determined. A dissenting shareholder may
not withdraw a demand for payment unless the corporation consents thereto.
 
                                      II-3
<PAGE>
    SECTION 1309 [DISSENTING SHARES, LOSS OF STATUS].-- Dissenting shares lose
their status as dissenting shares and the holders thereof cease to be dissenting
shareholders and cease to be entitled to require the corporation to purchase
their shares upon the happening of any of the following:
 
    (a) The corporation abandons the reorganization. Upon abandonment of the
reorganization, the corporation shall pay on demand to any dissenting
shareholder who has initiated proceedings in good faith under this chapter all
necessary expenses incurred in such proceedings and reasonable attorneys' fees.
 
    (b) The shares are transferred prior to their submission for endorsement in
accordance with Section 1302 or are surrendered for conversion into shares of
another class in accordance with the articles.
 
    (c) The dissenting shareholder and the corporation do not agree upon the
status of the shares as dissenting shares or upon the purchase price of the
shares, and neither files a complaint or intervenes in a pending action as
provided in Section 1304, within six months after the date on which notice of
the approval by the outstanding shares or notice pursuant to subdivision (i) of
Section 1110 was mailed to the shareholder.
 
    (d) The dissenting shareholder, with the consent of the corporation,
withdraws the shareholder's demand for purchase of the dissenting shares.
 
    SECTION 1310 [SUSPENSION OF CERTAIN PROCEEDINGS WHILE LITIGATION IS
PENDING].-- If litigation is instituted to test the sufficiency or regularity of
the votes of the shareholders in authorizing a reorganization, any proceedings
under Sections 1304 and 1305 shall be suspended until final determination of
such litigation.
 
    SECTION 1311 [CHAPTER INAPPLICABLE TO CERTAIN CLASSES OF SHARES].-- This
chapter, except Section 1312, does not apply to classes of shares whose terms
and provisions specifically set forth the amount to be paid in respect to such
shares in the event of a reorganization or merger.
 
    SECTION 1312 [VALIDITY OF REORGANIZATION OR SHORT-FORM MERGER, ATTACK ON;
SHAREHOLDERS' RIGHTS; BURDEN OF PROOF].-- (a) No shareholder of a corporation
who has a right under this chapter to demand payment of cash for the shares held
by the shareholder shall have any right at law or in equity to attack the
validity of the reorganization or short-form merger, or to have the
reorganization or short-form merger set aside or rescinded, except in an action
to test whether the number of shares required to authorize or approve the
reorganization have been legally voted in favor thereof; but any holder of
shares of a class whose terms and provisions specifically set forth the amount
to be paid in respect to them in the event of a reorganization or short-form
merger is entitled to payment in accordance with those terms and provisions or,
if the principal terms of the reorganization are approved pursuant to
subdivision (b) of Section 1202, is entitled to payment in accordance with the
terms and provisions of the approved reorganization.
 
    (b) If one of the parties to a reorganization or short-form merger is
directly or indirectly controlled by, or under common control with, another
party to the reorganization or short-form merger, subdivision (a) shall not
apply to any shareholder of such party who has not demanded payment of cash for
such shareholder's shares pursuant to this chapter; but if the shareholder
institutes any action to attack the validity of the reorganization or short-form
merger or to have the reorganization or short-form merger set aside or
rescinded, the shareholder shall not thereafter have any right to demand payment
of cash for the shareholder's shares pursuant to this chapter. The court in any
action attacking the validity of the reorganization or short-form merger or to
have the reorganization or short-form merger set aside or rescinded shall not
restrain or enjoin the consummation of the transaction except upon 10 days,
prior notice to the corporation and upon a determination by the court that
clearly no other remedy will adequately protect the complaining shareholder or
the class of shareholders of which such shareholder is a member.
 
                                      II-4
<PAGE>
    (c) If one of the parties to a reorganization or short-form merger is
directly or indirectly controlled by, or under common control with, another
party to the reorganization or short-form merger, in any action to attack the
validity of the reorganization or short-form merger or to have the
reorganization or short-form merger set aside or rescinded, (1) a party to a
reorganization or short-form merger which controls another party to the
reorganization or short-form merger shall have the burden of proving that the
transaction is just and reasonable as to the shareholders of the controlled
party, and (2) a person who controls two or more parties to a reorganization
shall have the burden of proving that the transaction is just and reasonable as
to the shareholders of any party so controlled.
 
                                      II-5
<PAGE>
                                                                    SCHEDULE III
 
                                 [LOGO]
 
                                                                 August 31, 1998
 
Special Committee of the Board of Directors
Mycogen Corporation
5501 Oberlin Drive
San Diego, CA 92121
Members of the Special Committee of the Board:
 
    You have asked us to advise you with respect to the fairness, from a
financial point of view, to the holders (other than The Dow Chemical Company and
its affiliates (collectively, the "Dow Group")) of shares of common stock, par
value $.001 per share (the "Shares"), of Mycogen Corporation, a California
corporation (the "Company"), of the consideration to be received by such holders
in the Transactions (as defined below) pursuant to the Agreement and Plan of
Merger, dated as of August 31, 1998, by and among the Company, Dow AgroSciences
LLC ("Parent") and AgroSciences Acquisition Inc. ("Acquisition") (the "Merger
Agreement"). The Merger Agreement provides for, among other things, a cash
tender offer (the "Tender Offer") by Acquisition to acquire all of the
outstanding Shares, other than Shares held by members of the Dow Group, at a
price of $28.00 per Share, net to the seller in cash (the "Cash Price"), and for
a subsequent merger of Acquisition with and into the Company pursuant to which
each outstanding Share (other than as provided in the Merger Agreement) will be
converted into the right to receive the Cash Price (the "Merger" and, together
with the Tender Offer, the "Transactions"). The terms and conditions of the
Transactions are set forth in more detail in the Merger Agreement.
 
    In connection with rendering our opinion, we have reviewed the financial
terms and provisions of a draft of the Merger Agreement, and for purposes
hereof, we have assumed that the financial terms and provisions of the final
form of the Merger Agreement will not differ in any material respect from the
draft provided to us. We also reviewed the Exchange and Purchase Agreement,
dated January 15, 1996, among the Company, Agrigenetics, Inc., DowElanco and
United Agriseeds, Inc. (the "Exchange Agreement"), including the Dow Group's
rights and obligations thereunder both if the Transactions are completed and not
completed. We further reviewed and analyzed certain publicly available business
and financial information relating to the Company for recent years and interim
periods to date, as well as certain internal financial and operating
information, financial forecasts, projections and analyses prepared by or on
behalf of the Company and provided to us for purposes of our analysis. We have
met with certain representatives of the Company and the Dow Group to review and
discuss such information and, among other matters, the Company's business,
financial condition, results of operations and prospects.
 
                                 [LOGO]
 
                                     III-1
<PAGE>
Special Committee of the Board of Directors
August 31, 1998
Page 2
 
    We have reviewed and considered certain financial and stock market data
relating to the Company, and we have compared that data with similar data for
certain other companies, the securities of which are publicly traded, that we
believe may be relevant or comparable in certain respects to the Company or one
or more of its businesses or assets, and we have reviewed and considered the
financial terms of certain recent acquisitions and business combination
transactions in the seed and agrobiotech industries specifically, and in other
industries generally, which we believe to be reasonably comparable to the
Transactions or otherwise relevant to our inquiry. We have also performed such
other studies, analyses and investigations and reviewed such other information
as we considered appropriate for purposes of this opinion.
 
    In our review and analysis and in formulating our opinion, we have assumed
and relied upon the accuracy and completeness of all the financial and other
information provided to or discussed with us or publicly available, including
the financial projections, forecasts, analyses and other information provided to
us, and we have not assumed any responsibility for independent verification of,
and express no opinion as to, any of such information. We also have relied upon
the reasonableness and accuracy of the unadjusted projections, forecasts,
analyses and other information furnished to us, and have assumed, with the
Special Committee's consent, that such projections, forecasts and analyses and
other information were reasonably prepared in good faith and on bases reflecting
the best currently available judgments and estimates of the Company's management
as of the date hereof and that management of the Company is unaware of any facts
that would make the projections, forecasts and other information provided to us
incomplete or misleading. We express no opinion with respect to such
projections, forecasts and analyses or the assumptions on which they are based.
We have not reviewed any of the books and records of the Company or Parent, and
although we have visited selected facilities, we were not retained to conduct,
nor have we assumed any responsibility for conducting, a physical inspection of
the properties or facilities of the Company or Parent, or for making or
obtaining an independent valuation or appraisal of the assets or liabilities of
the Company or Parent, and no such independent valuation or appraisal was
provided to us. Our opinion is necessarily based on economic and market
conditions and other circumstances as they exist and can be evaluated by us as
of the date hereof. It should be understood that, although subsequent
developments may affect this opinion, we do not have any obligation to update,
revise or reaffirm this opinion. Finally, we have assumed that the transactions
described in the Merger Agreement will be consummated on the terms set forth
therein, without material waiver or modification.
 
    In the context of our engagement, we have not been authorized to and have
not solicited alternative offers for the Company or its assets, or investigated
any other alternative transactions which may be available to the Company. We
express no opinion with respect to the Third Party Sale Value of the Company as
such term is defined in the Exchange Agreement.
 
    We are acting as financial advisor to the Special Committee of the Board of
Directors of the Company (the "Special Committee") in connection with the
proposed Transactions and will receive a fee for our services, including this
opinion, a significant portion of which is contingent upon the completion of the
proposed Transactions and the amount of consideration received by holders of the
Shares (other than the Dow Group) in the Transactions. In the ordinary course of
our business, we may actively trade the securities of the Company or members of
the Dow Group for our own account and for the accounts of customers and,
accordingly, may at any time hold a long or short position in such securities.
 
                                 [LOGO]
 
                                     III-2
<PAGE>
Special Committee of the Board of Directors
August 31, 1998
Page 3
 
    Our opinion addresses only the fairness from a financial point of view to
the holders of the Shares (other than the members of the Dow Group) of the
consideration to be paid to them pursuant to the Merger Agreement and does not
address the Special Committee's underlying business decision to recommend the
Transactions.
 
    This letter is for the benefit and use of the Special Committee in its
consideration of the Transactions, and may not be used for any other purpose or
reproduced, disseminated, quoted or referred to at any time, in any manner or
for any purpose without our prior written consent (except as otherwise provided
in the engagement letter, dated as of June 11, 1998, between the Company and
us). We have been engaged and are acting solely as an advisor to the Special
Committee and not as an advisor to or agent of any other person. This opinion
does not constitute a recommendation to any stockholder with respect to whether
such holder should tender Shares pursuant to the Tender Offer or as to how such
holder should vote or otherwise act with respect to the Merger, and should not
be relied upon by any stockholder as to any such matter.
 
    Based upon and subject to the foregoing, including the various assumptions
and limitations set forth herein it is our opinion that, as of the date hereof,
the Cash Price to be received by the holders of Shares (other than members of
the Dow Group) in the Transactions pursuant to the Merger Agreement is fair to
such holders from a financial point of view.
 
                                          Very truly yours,
 
                                                     [LOGO]
 
                                     III-3
<PAGE>
                        THE DEPOSITARY FOR THE OFFER IS:
 
                                BANKBOSTON, N.A.
 
<TABLE>
<S>                                     <C>                              <C>
               BY MAIL:                            BY HAND:               BY OVERNIGHT, CERTIFIED OR
           BankBoston, N.A.                  Securities Transfer &          EXPRESS MAIL DELIVERY:
    Attn: Corporate Reorganization         Reporting Services, Inc.            BankBoston, N.A.
            P.O. Box 8029                   c/o Boston EquiServe LP             Attn: Corporate
   Boston, Massachusetts 02266-8029            1 Exchange Plaza                 Reorganization
                                            55 Broadway, 3rd Floor             150 Royall Street
                                           New York, New York 10006       Canton, Massachusetts 02021
</TABLE>
 
<TABLE>
<S>                                 <C>
          BY FACSIMILE:               CONFIRM FACSIMILE BY TELEPHONE:
       (781) 575-2233/2232                     (800) 730-4001
 (For Eligible Institutions Only)         (For Confirmation Only)
</TABLE>
 
    Questions and requests for assistance may be directed to the Information
Agent or the Dealer Manager at their respective addresses and telephone numbers
listed below. Additional copies of this Offer to Purchase, the Letter of
Transmittal and other tender offer materials may be obtained from the
Information Agent as set forth below and will be furnished promptly at
Purchaser's expense. You may also contact the Dealer Manager or your broker,
dealer, commercial bank, trust company or other nominee for assistance
concerning the Offer.
 
                    THE INFORMATION AGENT FOR THE OFFER IS:
 
                                     [LOGO]
 
                               Wall Street Plaza
                            New York, New York 10005
                 Banks and Brokers Call Collect: (212) 440-9800
                   ALL OTHERS CALL TOLL-FREE: (800) 223-2064
 
                      THE DEALER MANAGER FOR THE OFFER IS:
 
                           SALOMON SMITH BARNEY INC.
                            Seven World Trade Center
                            New York, New York 10048

<PAGE>
                             LETTER OF TRANSMITTAL
                        TO TENDER SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
                              MYCOGEN CORPORATION
           PURSUANT TO THE OFFER TO PURCHASE DATED SEPTEMBER 4, 1998
                                       OF
                         AGROSCIENCES ACQUISITION INC.
                         A MAJORITY-OWNED SUBSIDIARY OF
                              DOW AGROSCIENCES LLC
 
                   AND A WHOLLY OWNED INDIRECT SUBSIDIARY OF
                            THE DOW CHEMICAL COMPANY
      -------------------------------------------------------------------
      THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
                                     TIME,
            ON FRIDAY, OCTOBER 2, 1998, UNLESS THE OFFER IS EXTENDED.
- --------------------------------------------------------------------------------
 
To: BankBoston, N.A., Depositary
 
<TABLE>
<S>                             <C>                                       <C>
           BY MAIL:                             BY HAND:                    BY OVERNIGHT, CERTIFIED OR EXPRESS MAIL
       BankBoston, N.A.             Securities Transfer & Reporting                        DELIVERY:
Attn: Corporate Reorganization               Services, Inc.                             BankBoston, N.A.
        P.O. Box 8029                   c/o Boston EquiServe LP                  Attn: Corporate Reorganization
    Boston, Massachusetts                   1 Exchange Plaza                           150 Royall Street
          02266-8029                     55 Broadway, 3rd Floor                   Canton, Massachusetts 02021
                                        New York, New York 10006
</TABLE>
 
<TABLE>
<S>                           <C>
       BY FACSIMILE:              CONFIRM FACSIMILE BY
    (781) 575-2233/2232                TELEPHONE:
 (For Eligible Institutions          (800) 730-4001
           Only)                 (For Confirmation Only)
</TABLE>
 
  DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET FORTH
   ABOVE OR TRANSMISSION OF INSTRUCTIONS VIA A FACSIMILE TRANSMISSION TO A
       NUMBER OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID
      DELIVERY. THE INSTRUCTIONS ACCOMPANYING THIS LETTER OF TRANSMITTAL
       SHOULD BE READ CAREFULLY BEFORE THIS LETTER OF TRANSMITTAL IS
                                   COMPLETED.
 
    This Letter of Transmittal is to be used by stockholders of Mycogen
Corporation if certificates for Shares (as defined below) are to be forwarded
herewith or, unless an Agent's Message (as defined in the Offer to Purchase) is
utilized, if delivery of Shares is to be made by book-entry transfer to the
Depositary's account at The Depository Trust Company (the "Book-Entry Transfer
Facility" or "DTC") pursuant to the book-entry transfer procedures set forth
under "The Tender Offer--3. Procedure for Tendering Shares" in the Offer to
Purchase dated September 4, 1998. Stockholders who tender Shares by book-entry
transfer are referred to herein as "Book-Entry Stockholders." Delivery of
documents to the Book-Entry Transfer Facility does not constitute delivery to
the Depositary.
 
    Stockholders who cannot deliver their Shares and all other documents
required hereby to the Depositary on or prior to the Expiration Date (as defined
in the Offer to Purchase) or who cannot complete the procedures for book-entry
transfer on a timely basis, must tender their Shares pursuant to the guaranteed
delivery procedure set forth under "The Tender Offer--3. Procedure for Tendering
Shares" in the Offer to Purchase. See Instruction 2.
<TABLE>
<CAPTION>
- ---------------
                                                DESCRIPTION OF SHARES TENDERED
                                                  (SEE INSTRUCTIONS 2 AND 4)
 ------------
                                                                NAMES(S) AND ADDRESS(ES) OF REGISTERED HOLDER(S)
                 SHARES TENDERED                        (PLEASE FILL IN, IF BLANK, EXACTLY AS NAME(S) APPEAR(S) ON SHARE
     (ATTACH ADDITIONAL LIST, IF NECESSARY)                                       CERTIFICATES)
<C>              <C>              <C>              <S>
- ---------------
 
<CAPTION>
                 TOTAL NUMBER OF
                     SHARES          NUMBER OF
  CERTIFICATE    REPRESENTED BY       SHARES
  NUMBER(S)*     CERTIFICATE(S)*    TENDERED**
<C>              <C>              <C>              <S>
- ---------------
 
- ---------------
 
- ---------------
 
- ---------------
 
- ---------------
 
- ---------------
 
- ---------------
 
- ---------------
 TOTAL SHARES
- ---------------
*   Need not be completed by stockholders tendering by book-entry transfer.
**  Unless otherwise indicated, it will be assumed that all Shares represented by any certificates delivered to the Depositary
    are being tendered. See Instruction 4.
 -------------
</TABLE>
 
<PAGE>
                    NOTE: SIGNATURES MUST BE PROVIDED BELOW
                PLEASE READ ACCOMPANYING INSTRUCTIONS CAREFULLY
 
<TABLE>
<CAPTION>
   -------------------------------------------------------------------------------------------
 
/ /  CHECK HERE IF TENDERED SHARES ARE BEING DELIVERED BY BOOK-ENTRY TRANSFER TO THE DEPOSITARY'S
     ACCOUNT AT THE BOOK-ENTRY TRANSFER FACILITY AND COMPLETE THE FOLLOWING:
<S>        <C>
 
Name of Tendering Institution:
DTC Account No.:
DTC Transaction Code No.:
/ /  CHECK HERE IF TENDERED SHARES ARE BEING DELIVERED PURSUANT TO A NOTICE OF GUARANTEED DELIVERY
     PREVIOUSLY SENT TO THE DEPOSITARY AND COMPLETE THE FOLLOWING:
 
Name(s) of Registered Stockholder(s):
Window Ticket Number (if any):
Date of Execution of Notice of Guaranteed Delivery:
Name of Institution which Guaranteed Delivery:
If delivery is by book entry transfer:
           Name of Tendering Institution:
           DTC Account No.:
           DTC Transaction Code No.:
- -------------------------------------------------------------------------------------------
</TABLE>
 
Ladies and Gentlemen:
 
    The undersigned hereby tenders to AgroSciences Acquisition Inc., a Delaware
corporation ("Purchaser") and a majority-owned subsidiary of Dow AgroSciences
LLC, the above-described shares of common stock, par value $0.001 per share
(including the associated preferred stock purchase rights) (the "Shares"), of
Mycogen Corporation, a California corporation (the "Company"), pursuant to
Purchaser's offer to purchase all of the outstanding Shares at a price of $28.00
per Share, net to the seller in cash, without interest thereon, upon the terms
and subject to the conditions set forth in the Offer to Purchase dated September
4, 1998 (the "Offer to Purchase"), receipt of which is hereby acknowledged, and
in this Letter of Transmittal (which together, as may be amended or supplemented
from time to time, constitute the "Offer").
 
    Subject to, and effective upon, acceptance for payment of the Shares
tendered herewith in accordance with the terms of the Offer, including, if the
Offer is extended or amended, the terms and conditions of any such extension or
amendment, the undersigned hereby sells, assigns and transfers to or upon the
order of Purchaser all right, title and interest in and to all the Shares that
are being tendered hereby or orders the registration of such Shares delivered by
book-entry transfer (and any and all other Shares or other securities issued or
issuable in respect thereof on or after September 4, 1998, and any or all
dividends thereon or distributions with respect thereto (collectively,
"Distributions")) and irrevocably appoints the Depositary the true and lawful
agent and attorney-in-fact of the undersigned with respect to such Shares (and
all Distributions), with full power of substitution (such power of attorney
being deemed to be an irrevocable power coupled with an interest), to (a)
deliver certificates for such Shares (and all Distributions), or transfer
ownership of such Shares (and all Distributions) on the account books maintained
by the Book-Entry Transfer Facility, together, in any such case, with all
accompanying evidences of transfer and
 
                                       2
<PAGE>
authenticity to, or upon the order of, Purchaser upon receipt by the Depositary,
as the undersigned's agent, of the purchase price, (b) present such Shares (and
all Distributions) for transfer on the books of the Company and (c) receive all
benefits and otherwise exercise all rights of beneficial ownership of such
Shares (and all Distributions), all in accordance with the terms of the Offer.
 
    The undersigned hereby irrevocably appoints Charles J. Hahn, Jane M. Gootee
and Brian G. Taylorson and each of them, the attorneys-in-fact and proxies of
the undersigned, each with full power of substitution, to exercise all voting
and other rights of the undersigned in such manner as each such attorney and
proxy or his substitute shall in his sole discretion deem proper, with respect
to all of the Shares (and all Distributions) tendered hereby which have been
accepted for payment by Purchaser prior to the time of any vote or other action
at any meeting of stockholders of the Company (whether annual or special and
whether or not an adjourned meeting), by written consent or otherwise. This
power of attorney and proxy is coupled with an interest and is irrevocable and
is granted in consideration of, and is effective upon, the acceptance for
payment of such Shares by Purchaser in accordance with the terms of the Offer.
Such acceptance for payment shall revoke, without any further action, any other
power of attorney or proxy granted by the undersigned at any time with respect
to such Shares, and no subsequent power of attorney or proxies will be given or
will be executed by the undersigned (and if given or executed, will not be
deemed to be effective). The undersigned understands that Purchaser reserves the
right to require that, in order for such Shares to be deemed validly tendered,
immediately upon Purchaser's acceptance for payment of such Shares, Purchaser is
able to exercise full voting rights with respect to such Shares and other
securities, including voting at any meeting of stockholders.
 
    The undersigned hereby represents and warrants that the undersigned has full
power and authority to tender, sell, assign and transfer the Shares and all
Distributions tendered hereby and that when the same are accepted for payment by
Purchaser, Purchaser will acquire good and marketable title and unencumbered
ownership thereto, free and clear of all liens, restrictions, charges, security
interests, and encumbrances and not subject to any adverse claims. The
undersigned will, upon request, execute and deliver any additional documents
deemed by the Depositary or Purchaser to be necessary or desirable to complete
the sale, assignment and transfer of the Shares and all Distributions tendered
hereby. In addition, the undersigned will promptly remit and transfer to the
Depositary for the account of Purchaser any and all Distributions in respect of
the Shares tendered hereby, accompanied by appropriate documentation of transfer
and, pending such remittance or appropriate assurance thereof, Purchaser shall
be entitled to all rights and privileges as owner of any such Distributions, and
may withhold the entire purchase price or deduct from the purchase price of
Shares tendered hereby, the amount or value thereof, as determined by Purchaser
in its sole discretion.
 
    All authority herein conferred or agreed to be conferred shall survive the
death or incapacity of the undersigned, and any obligation of the undersigned
hereunder shall be binding upon the heirs, personal representatives, successors
and assigns of the undersigned. Except as stated in the Offer or otherwise
required by applicable law, this tender is irrevocable.
 
    The undersigned understands that tenders of Shares pursuant to any one of
the procedures described under "The Tender Offer--3. Procedure for Tendering
Shares" in the Offer to Purchase and in the instructions hereto will constitute
a binding agreement between the undersigned and Purchaser upon the terms and
subject to the conditions of the Offer.
 
    The undersigned recognizes that, under certain circumstances set forth in
the Offer to Purchase, Purchaser may terminate or amend the Offer or may not be
required to accept for payment any of the Shares tendered herewith.
 
    Unless otherwise indicated under "Special Payment Instructions," please
issue the check for the purchase price or return any Shares not tendered or
accepted for payment in the name(s) of the undersigned. Similarly, unless
otherwise indicated under "Special Delivery Instructions," please mail the check
for the purchase price or return any Share certificates not tendered or accepted
for payment (and accompanying documents, as appropriate) to the undersigned at
the address shown below the undersigned's signature(s). In the event that both
"Special Payment Instructions" and "Special Delivery Instructions" are
completed, please issue the check for the purchase price or return any Shares
not tendered or accepted for payment in the name(s) of, and deliver said check
or return certificates to, the
 
                                       3
<PAGE>
person or persons so indicated. Stockholders tendering Shares by book-entry
transfer may request that any Shares not accepted for payment be returned by
crediting such account maintained at the Book-Entry Transfer Facility as such
stockholder may designate by making an appropriate entry under "Special Payment
Instructions." The undersigned recognizes that Purchaser has no obligation
pursuant to the "Special Payment Instructions" to transfer any Shares from the
name of the registered holder thereof if Purchaser does not accept for payment
any of such Shares.
 
                                  INSTRUCTIONS
             FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER
 
    1. GUARANTEE OF SIGNATURES.  Except as otherwise provided below, all
signatures on this Letter of Transmittal must be guaranteed by a member firm of
a registered national securities exchange, a member of the National Association
of Securities Dealers, Inc., a financial institution (including most banks,
trust companies, savings and loan associations and brokerage houses) which is a
participant in the Securities Transfer Agents Medallion Program, the New York
Stock Exchange Medallion Signature Program or the Stock Exchange Medallion
Program (an "Eligible Institution"). Signatures on this Letter of Transmittal
need not be guaranteed (a) if this Letter of Transmittal is signed by the
registered holder(s) of the Shares (which term, for purposes of this document,
shall include any participant in the Book-Entry Transfer Facility whose name
appears on a security position listing as the owner of Shares) tendered herewith
and such holder(s) have not completed the instruction entitled "Special Delivery
Instruments" or "Special Payment Instructions" on this Letter of Transmittal or
(b) if such Shares are tendered for the account of an Eligible Institution. See
Instruction 5.
 
    2. DELIVERY OF LETTER OF TRANSMITTAL AND SHARES.  This Letter of Transmittal
is to be used either if certificates are to be forwarded herewith or if Shares
are to be delivered by book-entry transfer pursuant to the procedures set forth
in "The Tender Offer--3. Procedure for Tendering Shares" of the Offer to
Purchase. Certificates for all physically delivered Shares, or a confirmation of
a book-entry transfer into the Depositary's account at the Book-Entry Transfer
Facility of all Shares delivered electronically, as well as a properly completed
and duly executed Letter of Transmittal (or facsimile thereof) (or, in the case
of a book-entry delivery, an Agent's Message) and any other documents required
by this Letter of Transmittal, must be received by the Depositary at one of its
addresses set forth on the front page of this Letter of Transmittal on or prior
to the Expiration Date. Stockholders who cannot deliver their Shares and all
other required documents to the Depositary on or prior to the Expiration Date
must tender their Shares pursuant to the guaranteed delivery procedure set forth
in "The Tender Offer--3. Procedure for Tendering Shares" of the Offer to
Purchase. Pursuant to such procedure: (a) such tender must be made by or through
an Eligible Institution, (b) a properly completed and duly executed Notice of
Guaranteed Delivery substantially in the form provided by AgroSciences
Acquisition Inc. ("Purchaser") must be received by the Depositary on or prior to
the Expiration Date and (c) the certificates for all physically delivered
Shares, or a confirmation of a book-entry transfer into the Depositary's account
at the Book-Entry Transfer Facility of all Shares delivered electronically, as
well as a properly completed and duly executed Letter of Transmittal (or
facsimile thereof) (or, in the case of a book-entry delivery, an Agent's
Message) and any other documents required by this Letter of Transmittal, must be
received by the Depositary within three NASDAQ National Market System trading
days after the date of execution of such Notice of Guaranteed Delivery, all as
provided in "The Tender Offer--3. Procedure for Tendering Shares." If Shares are
forwarded separately to the Depositary, each must be accompanied by a duly
executed Letter of Transmittal (or facsimile thereof).
 
    THE METHOD OF DELIVERING SHARES, THE LETTER OF TRANSMITTAL AND ALL OTHER
REQUIRED DOCUMENTS INCLUDING DELIVERY THROUGH THE BOOK-ENTRY TRANSFER FACILITY,
IS AT THE OPTION AND SOLE RISK OF THE TENDERING STOCKHOLDER AND THE DELIVERY
WILL BE DEEMED MADE ONLY WHEN ACTUALLY RECEIVED BY THE DEPOSITARY. IF DELIVERY
IS BY MAIL, REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS
RECOMMENDED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY
DELIVERY.
 
                                       4
<PAGE>
    No alternative, conditional or contingent tenders will be accepted. By
executing this Letter of Transmittal (or facsimile thereof), the tendering
stockholder waives any right to receive any notice of the acceptance for payment
of the Shares.
 
    3. INADEQUATE SPACE.  If the space provided herein is inadequate, the
certificate numbers or the number of Shares should be listed on a separate
schedule attached hereto and separately signed on each page thereof in the same
manner as this Letter of Transmittal is signed.
 
    4. PARTIAL TENDERS (NOT APPLICABLE TO STOCKHOLDERS WHO TENDER BY BOOK-ENTRY
TRANSFER).  If fewer than all the Shares represented by any certificate
delivered to the Depositary are to be tendered, fill in the number of Shares
which are to be tendered in the box entitled "Number of Shares Tendered." In
such case, a new certificate for the remainder of the Shares represented by the
old certificate will be sent to the person(s) signing this Letter of
Transmittal, unless otherwise provided in the appropriate box on this Letter of
Transmittal, as promptly as practicable following the expiration or termination
of the Offer. All Shares represented by certificates delivered to the Depositary
will be deemed to have been tendered unless otherwise indicated.
 
    5. SIGNATURES ON LETTER OF TRANSMITTAL; STOCK POWERS AND ENDORSEMENTS.  If
this Letter of Transmittal is signed by the registered holder(s) of the Shares
tendered hereby, the signature(s) must correspond with the name(s) as written on
the face of the certificates without alteration, enlargement or any change
whatsoever.
 
    If any of the Shares tendered hereby are held of record by two or more
persons, all such persons must sign this Letter of Transmittal.
 
    If any of the Shares tendered hereby are registered in different names on
different certificates, it will be necessary to complete, sign and submit as
many separate Letters of Transmittal as there are different registrations of
certificates.
 
    If this Letter of Transmittal is signed by the registered holder(s) of the
Shares tendered hereby, no endorsements of certificates or separate stock powers
are required unless payment of the purchase price is to be made, or Shares not
tendered or not purchased are to be returned, in the name of any person other
than the registered holder(s). Signatures on any such certificates or stock
powers must be guaranteed by an Eligible Institution.
 
    If this Letter of Transmittal is signed by a person other than the
registered holder(s) of the Shares tendered hereby, certificates must be
endorsed or accompanied by appropriate stock powers, in either case, signed
exactly as the name(s) of the registered holder(s) appear(s) on the certificates
for such Shares. Signature(s) on any such certificates or stock powers must be
guaranteed by an Eligible Institution.
 
    If this Letter of Transmittal or any certificate or stock power is signed by
a trustee, executor, administrator, guardian, attorney-in-fact, officer of a
corporation or other person acting in a fiduciary or representative capacity,
such person should so indicate when signing, and proper evidence satisfactory to
Purchaser of the authority of such person so to act must be submitted.
 
    6. STOCK TRANSFER TAXES.  Except as provided in this Instruction 6,
Purchaser will pay any stock transfer taxes with respect to the sale and
transfer of any Shares to it or its order pursuant to the Offer. If, however,
payment of the purchase price is to be made to, or Shares not tendered or not
purchased are to be returned in the name of, any person other than the
registered holder(s), or if a transfer tax is imposed for any reason other than
the sale or transfer of Shares to Purchaser pursuant to the Offer, then the
amount of any stock transfer taxes (whether imposed on the registered holder(s),
such other person or otherwise) will be deducted from the purchase price unless
satisfactory evidence of the payment of such taxes, or exemption therefrom, is
submitted herewith.
 
    EXCEPT AS PROVIDED IN THIS INSTRUCTION 6, IT WILL NOT BE NECESSARY FOR
TRANSFER TAX STAMPS TO BE AFFIXED TO THE CERTIFICATES LISTED IN THIS LETTER OF
TRANSMITTAL.
 
    7. SPECIAL PAYMENT AND DELIVERY INSTRUCTIONS.  If the check for the purchase
price of any Shares purchased is to be issued, or any Shares not tendered or not
purchased are to be returned, in the name of a person other than the person(s)
signing this Letter of Transmittal or if the check or any certificates for
 
                                       5
<PAGE>
Shares not tendered or not purchased are to be mailed to someone other than the
person(s) signing this Letter of Transmittal or to the person(s) signing this
Letter of Transmittal at an address other than that shown above, the appropriate
boxes on this Letter of Transmittal should be completed. Stockholders tendering
Shares by book-entry transfer may request that Shares not purchased be credited
to such account at the Book-Entry Transfer Facility as such stockholder may
designate under "Special Payment Instructions." If no such instructions are
given, any such Shares not purchased will be returned by crediting the account
at the Book-Entry Transfer Facility designated above.
 
    8. SUBSTITUTE FORM W-9.  Under the federal income tax laws, the Depositary
will be required to backup withhold 31% of the amount of any payments made to
certain stockholders pursuant to the Offer. In order to avoid such backup
withholding, each tendering stockholder, and, if applicable, each other payee,
must provide the Depositary with such stockholder's or payee's correct taxpayer
identification number and certify that such stockholder or payee is not subject
to such backup withholding by completing the Substitute Form W-9 set forth
below. In general, if a stockholder or payee is an individual, the taxpayer
identification number is the Social Security number of such individual. If the
Depositary is not provided with the correct taxpayer identification number, the
stockholder or payee may be subject to a $50 penalty imposed by the Internal
Revenue Service ("IRS"). Certain stockholders or payees (including, among
others, all corporations and certain foreign individuals) are not subject to
these backup withholding and reporting requirements. In order to satisfy the
Depositary that a foreign individual qualifies as an exempt recipient, such
stockholder or payee must submit a statement, signed under penalties of perjury,
attesting to that individual's exempt status. Such statements can be obtained
from the Depositary. For further information concerning backup withholding and
instructions for completing the Substitute Form W-9 (including how to obtain a
taxpayer identification number if you do not have one and how to complete the
Substitute Form W-9 if Shares are held in more than one name), consult the
enclosed GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION NUMBER ON
SUBSTITUTE FORM W-9.
 
    Failure to complete the Substitute Form W-9 will not, by itself, cause
Shares to be deemed invalidly tendered, but may require the Depositary to
withhold 31% of the amount of any payments made pursuant to the Offer. Backup
withholding is not an additional federal income tax. Rather, the federal income
tax liability of a person subject to backup withholding will be reduced by the
amount of tax withheld. If withholding results in an overpayment of taxes, a
refund may be obtained provided that the required information is furnished to
the IRS.
 
    If a tendering stockholder has not been issued a TIN and has applied for a
TIN or intends to apply for a TIN in the near future, such holder must complete
the Certificate Awaiting Taxpayer Identification Number below in order to avoid
backup withholding. Notwithstanding that the Certificate of Awaiting Taxpayer
Identification Number is completed, the Depository will withhold 31% of all
payments made prior to the time a properly certified TIN is provided to the
Depository. However, such amounts will be refunded to such holder if a TIN is
provided to the Depository within 60 days.
 
    NOTE: FAILURE TO COMPLETE AND RETURN THE SUBSTITUTE FORM W-9 MAY RESULT IN
BACKUP WITHHOLDING OF 31% OF ANY PAYMENTS MADE TO YOU PURSUANT TO THE OFFER.
PLEASE REVIEW THE ENCLOSED GUIDELINES FOR CERTIFICATION OF TAXPAYER
IDENTIFICATION NUMBER ON SUBSTITUTE FORM W-9 FOR ADDITIONAL DETAILS.
 
    9. REQUESTS FOR ASSISTANCE OR ADDITIONAL COPIES.  Requests for assistance or
additional copies of the Offer to Purchase and this Letter of Transmittal may be
obtained from the Information Agent or Dealer Manager at their respective
addresses or telephone numbers set forth below.
 
    10. MYCOGEN CORPORATION 1992 STOCK OPTION PLAN.  Holders of options (each an
"Option") to purchase Shares through the Mycogen Corporation 1992 Stock Option
Plan (which incorporates outstanding Options granted under the Mycogen
Corporation 1983 Stock Option Plan) may not use this Letter of Transmittal to
direct the exercise of Options and the tender of Shares issuable upon exercise
of such Options, but must use the separate Option Election sent or delivered to
them by the Company. See Section 3 of the Offer to Purchase.
 
                                       6
<PAGE>
    11. MYCOGEN CORPORATION 1995 EMPLOYEE STOCK PURCHASE PLAN.  Participants in
the Mycogen Corporation 1995 Employee Stock Purchase Plan (the "Stock Purchase
Plan") must use this Letter of Transmittal to direct the exercise of purchase
rights outstanding under the Stock Purchase Plan (each a "Purchase Right") and
the tender of Shares issuable upon exercise of such Purchase Rights, but must
use the separate Stock Purchase Election sent or delivered to them by the
Company. See Section 3 of the Offer to Purchase.
 
    12. MYCOGEN CORPORATION RESTRICTED STOCK ISSUANCE PLAN.  Holders of unvested
Shares ("Restricted Stock") through the Mycogen Corporation Restricted Stock
Issuance Plan MUST use this Letter of Transmittal to tender Restricted Stock,
and also MUST use the separate Restricted Stock Election sent or delivered to
them by the Company. See Section 3 of the Offer to Purchase. Completed Letters
of Transmittal relating to Restricted Stock should be returned, along with a
completed Restricted Stock Election and your Restricted Stock Certificate(s), to
Mycogen Corporation, AgroSciences Tender Offer, 5501 Oberlin Drive, San Diego,
California 92121, Attention: Cheri Manis. DO NOT return a Letter of Transmittal
relating to Restricted Stock to the Depositary.
 
    13. LOST, DESTROYED OR STOLEN CERTIFICATES.  If any certificate(s)
representing Shares has been lost, destroyed or stolen, the stockholder should
promptly notify the Depositary. Instructions will then be given to what steps
must be taken to obtain a replacement certificate(s). The Letter of Transmittal
and related documents cannot be processed until the procedures for replacing
such missing certificate(s) have been followed.
 
                                       7
<PAGE>
    Facsimile copies of the Letter of Transmittal, properly completed and duly
executed, will be accepted. The Letter of Transmittal, certificates of Shares
and any other required documents should be sent or delivered by each stockholder
of the Company or his broker, dealer, commercial bank, trust company or other
nominee to the Depositary at one of its addresses set forth below:
 
                        THE DEPOSITARY FOR THE OFFER IS:
 
                                BANKBOSTON, N.A.
 
<TABLE>
<S>                             <C>                            <C>
           BY MAIL:                       BY HAND:              BY OVERNIGHT, CERTIFIED OR
       BankBoston, N.A.             Securities Transfer &         EXPRESS MAIL DELIVERY:
Attn: Corporate Reorganization    Reporting Services, Inc.           BankBoston, N.A.
        P.O. Box 8029              c/o Boston EquiServe LP           Attn: Corporate
    Boston, Massachusetts             1 Exchange Plaza                Reorganization
          02266-8029               55 Broadway, 3rd Floor           150 Royall Street
                                  New York, New York 10006     Canton, Massachusetts 02021
</TABLE>
 
<TABLE>
<S>                           <C>
       BY FACSIMILE:              CONFIRM FACSIMILE BY
    (781) 575-2233/2232                TELEPHONE:
 (For Eligible Institutions          (800) 730-4001
           Only)                 (For Confirmation Only)
</TABLE>
 
    Questions and requests for assistance may be directed to the Information
Agent or the Dealer Manager at their respective addresses and telephone numbers
listed below. Additional copies of this Offer to Purchase, the Letter of
Transmittal and other tender offer materials may be obtained from the
Information Agent as set forth below, and will be furnished promptly at
Purchaser's expense. You may also contact your broker, dealer, commercial bank,
trust company or other nominee for assistance concerning this Offer.
 
                    THE INFORMATION AGENT FOR THE OFFER IS:
 
                                     [LOGO]
 
                               Wall Street Plaza
                            New York, New York 10005
                Call Collect (Banks and Brokers): (212) 440-9800
                   All Others Call Toll-Free: (800) 223-2064
 
                      THE DEALER MANAGER FOR THE OFFER IS:
 
                           SALOMON SMITH BARNEY INC.
                            Seven World Trade Center
                               New York, NY 10048
 
                                       8
<PAGE>
- ------------------------------------------------
 
                          SPECIAL PAYMENT INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)
 
      To be completed ONLY if the check for the purchase price of Shares
  purchased or stock certificates for Shares not tendered or not purchased are
  to be issued in the name of someone other than the undersigned.
 
  Issue check or certificates to:
 
  Name: ______________________________________________________________________
                                 (PLEASE PRINT)
 
  Address ____________________________________________________________________
  ____________________________________________________________________________
                               (INCLUDE ZIP CODE)
  ____________________________________________________________________________
                  (TAX IDENTIFICATION OR SOCIAL SECURITY NO.)
                         (COMPLETE SUBSTITUTE FORM W-9)
 
- ------------------------------------------------
- ------------------------------------------------
 
                         SPECIAL DELIVERY INSTRUCTIONS
                        (SEE INSTRUCTIONS 1, 5, 6 AND 7)
 
      To be completed ONLY if the check for the purchase price of Shares
  purchased or stock certificates for Shares not tendered or not purchased are
  to be mailed to someone other than the undersigned or to the undersigned at
  an address other than that shown below the undersigned's signature(s).
  Mail check or certificates to:
  Name _______________________________________________________________________
                                 (PLEASE PRINT)
  Address ____________________________________________________________________
  ____________________________________________________________________________
                               (INCLUDE ZIP CODE)
- -----------------------------------------------
 
- --------------------------------------------------------------------------------
 
                                   SIGN HERE
                  (PLEASE COMPLETE SUBSTITUTE FORM W-9 BELOW)
 
  X___________________________________________________________________________
 
  X___________________________________________________________________________
                            SIGNATURE(S) OF OWNER(S)
 
  Dated: _______________________________________________________________, 1998
 
  Name(s) ____________________________________________________________________
                                 (PLEASE PRINT)
  ____________________________________________________________________________
  Capacity (full title): _____________________________________________________
  Address: ___________________________________________________________________
  ____________________________________________________________________________
                               (INCLUDE ZIP CODE)
  Area Code and Telephone Number: ____________________________________________
  Tax Identification or Social Security No.: _________________________________
                                         (COMPLETE SUBSTITUTE W-9 ON REVERSE
                                     SIDE)
 
      (Must be signed by registered holder(s) exactly as name(s) appear(s) on
  stock certificate(s) or on a security position listing or by person(s)
  authorized to become registered holder(s) by certificates and documents
  transmitted herewith. If signature is by a trustee, executor, administrator,
  guardian, attorney-in-fact, officer of a corporation or other person acting
  in a fiduciary or representative capacity, please set forth full title and
  see Instruction 5.)
 
                           GUARANTEE OF SIGNATURE(S)
                           (SEE INSTRUCTIONS 1 AND 5)
 
  Name of Firm: ______________________________________________________________
 
  Authorized Signature: ______________________________________________________
 
  Name: ______________________________________________________________________
 
  Address: ___________________________________________________________________
  ____________________________________________________________________________
                               (INCLUDE ZIP CODE)
 
  Area Code and Telephone Number: ____________________________________________
 
  Dated: _______________________________________________________________, 1998
 
- --------------------------------------------------------------------------------
 
                                       9
<PAGE>
                 TO BE COMPLETED BY ALL TENDERING STOCKHOLDERS
                              (SEE INSTRUCTION 8)
 
                         PAYER'S NAME: BANKBOSTON, N.A.
 
<TABLE>
<C>                               <S>                    <C>
- -----------------------------------------------------------------------------------------
           SUBSTITUTE             Part I--PLEASE              Social Security Number
            FORM W-9              PROVIDE YOUR TIN IN      or ------------------------
   Department of the Treasury     THE BOX AT RIGHT AND    Employer Identification Number
    Internal Revenue Service      CERTIFY BY SIGNING
                                  AND DATING BELOW
- -----------------------------------------------------------------------------------------
 CERTIFICATION--Under penalty of perjury, I certify that:
 
 (1) The number shown on this form is my correct taxpayer identification number (or I am
     waiting for a number to be issued to me);
 
 (2) I am not subject to backup withholding because (a) I am exempt from backup
     withholding, or (b) I have not been notified by the Internal Revenue Service ("IRS")
     that I am subject to backup withholding as a result of a failure to report all
     interest or dividends, or (c) the IRS has notified me that I am no longer subject to
     backup withholding.
 
 CERTIFICATION INSTRUCTIONS--You must cross out item (2) above if you have been notified
 by the IRS that you are currently subject to backup withholding because of
 underreporting or dividends on your tax return. However, if after being notified by the
 IRS that you were subject to backup withholding you received another notification from
 the IRS that you are no longer subject to backup withholding, do not cross out such item
 (2).
 
 SIGNATURE: -------------------------------------------- DATE:--------------------, 1998
- -----------------------------------------------------------------------------------------
</TABLE>
 
NOTE: FAILURE TO COMPLETE AND RETURN THIS FORM MAY RESULT IN BACKUP WITHHOLDING
      OF 31% OF ANY PAYMENTS MADE TO YOU PURSUANT TO THE OFFER. PLEASE REVIEW
      THE ENCLOSED GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
      NUMBER ON SUBSTITUTE FORM W-9 FOR ADDITIONAL DETAILS.
 
YOU MUST COMPLETE THE FOLLOWING CERTIFICATE IF YOU ARE AWAITING A TAX
IDENTIFICATION NUMBER.
 
<TABLE>
<CAPTION>
- ----------------------------------------------------------------------------------------
                 CERTIFICATE OF AWAITING TAXPAYER IDENTIFICATION NUMBER
<S>                                                                                        <C>
    I certify under penalties of perjury that a taxpayer identification number has not
been issued to me, and either (1) I have mailed or delivered an application to receive a
taxpayer identification number to the appropriate Internal Revenue Service Center or
Social Security Administration Office or (2) I intend to mail or deliver an application
in the near future. I understand that if I do not provide a taxpayer identification
number by the time of payment, 31% of all reportable payments made to me will be
withheld, but that such amounts will be refunded to me if I then provide a Taxpayer
Identification Number within sixty (60) days.
SIGNATURE: ------------------------------------------- DATE: -------------------, 1998
- ----------------------------------------------------------------------------------------
</TABLE>
 
                                       10

<PAGE>
                         NOTICE OF GUARANTEED DELIVERY
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)
                        TO TENDER SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
                              MYCOGEN CORPORATION
           PURSUANT TO THE OFFER TO PURCHASE DATED SEPTEMBER 4, 1998
                                       OF
                         AGROSCIENCES ACQUISITION INC.
                         A MAJORITY-OWNED SUBSIDIARY OF
                              DOW AGROSCIENCES LLC
                   AND A WHOLLY OWNED INDIRECT SUBSIDIARY OF
                            THE DOW CHEMICAL COMPANY
 
    This Notice of Guaranteed Delivery, or one substantially equivalent to the
attached form, must be used to accept the Offer (as defined below) if (i)
certificates for shares of common stock, par value $0.001 per share (including
the associated preferred stock purchase rights) (the "Shares"), of Mycogen
Corporation and all other documents required by the Letter of Transmittal cannot
be delivered to the Depositary by the expiration of the Offer (as defined in the
Offer to Purchase) or (ii) the procedures for delivery of book-entry transfer
cannot be completed on a timely basis. This Notice of Guaranteed Delivery may be
delivered by hand or sent by facsimile transmission or mail to the Depositary.
See "The Tender Offer--3. Procedure for Tendering Shares" in the Offer to
Purchase.
 
                        THE DEPOSITARY FOR THE OFFER IS:
 
                                BANKBOSTON, N.A.
 
<TABLE>
<S>                                     <C>                              <C>
               BY MAIL:                            BY HAND:               BY OVERNIGHT, CERTIFIED OR
           BankBoston, N.A.                  Securities Transfer &          EXPRESS MAIL DELIVERY:
    Attn: Corporate Reorganization         Reporting Services, Inc.            BankBoston, N.A.
            P.O. Box 8029                   c/o Boston EquiServe LP             Attn: Corporate
   Boston, Massachusetts 02266-8029            1 Exchange Plaza                 Reorganization
                                            55 Broadway, 3rd Floor             150 Royall Street
                                           New York, New York 10006       Canton, Massachusetts 02021
</TABLE>
 
<TABLE>
<S>                                 <C>
          BY FACSIMILE:               CONFIRM FACSIMILE BY TELEPHONE:
       (781) 575-2233/2232                     (800) 730-4001
 (For Eligible Institutions Only)         (For Confirmation Only)
</TABLE>
 
    DELIVERY OF THIS NOTICE OF GUARANTEED DELIVERY TO AN ADDRESS OTHER THAN AS
SET FORTH ABOVE OR TRANSMISSION OF INSTRUCTIONS VIA A FACSIMILE TRANSMISSION TO
A NUMBER OTHER THAN AS SET FORTH ABOVE DOES NOT CONSTITUTE A VALID DELIVERY.
 
    THIS NOTICE OF GUARANTEED DELIVERY IS NOT TO BE USED TO GUARANTEE
SIGNATURES. IF A SIGNATURE ON A LETTER OF TRANSMITTAL IS REQUIRED TO BE
GUARANTEED BY AN "ELIGIBLE INSTITUTION" UNDER THE INSTRUCTIONS THERETO, SUCH
SIGNATURE GUARANTEE MUST APPEAR IN THE APPLICABLE SPACE PROVIDED IN THE
SIGNATURE BOX ON THE LETTER OF TRANSMITTAL.
<PAGE>
LADIES AND GENTLEMEN:
 
    The undersigned hereby tenders to AgroSciences Acquisition Inc.
("Purchaser"), upon the terms and subject to the conditions set forth in the
Offer to Purchase dated September 4, 1998, and the related Letter of Transmittal
(which together constitute the "Offer"), receipt of which is hereby
acknowledged, the number (indicated below) of Shares pursuant to the guaranteed
delivery procedure set forth in "The Tender Offer--3. Procedure for Tendering
Shares" of the Offer to Purchase.
 
Number of Shares being tendered hereby: __________________________________Shares
 
- ------------------------------------------------
 
  CERTIFICATE NO(S).
  (IF AVAILABLE):
  ____________________________________________________________________________
 
  IF SHARES WILL BE TENDERED BY BOOK-ENTRY TRANSFER:
 
  NAME OF TENDERING INSTITUTION:
 
  ____________________________________________________________________________
  DTC ACCOUNT NO.: ___________________________________________________________
- ------------------------------------------------
- ------------------------------------------------
 
                                   SIGN HERE:
 
  ____________________________________________________________________________
 
                                 (SIGNATURE(S))
 
   ___________________________________________________________________________
 
                  (NAMES(S) OF RECORD HOLDERS) (PLEASE PRINT)
 
   ___________________________________________________________________________
 
                                   (ADDRESS)
 
   ___________________________________________________________________________
 
                               (INCLUDE ZIP CODE)
 
   ___________________________________________________________________________
 
                        (AREA CODE AND TELEPHONE NUMBER)
- -----------------------------------------------
 
                                   GUARANTEE
                    (NOT TO BE USED FOR SIGNATURE GUARANTEE)
 
    The undersigned, a firm which is a member of a registered national
securities exchange or the National Association of Securities Dealers, Inc., or
a commercial bank or trust company having an office, branch or agency in the
United States, hereby (a) represents that the above named person(s) "own(s)" the
Shares tendered hereby within the meaning of Rule 14e-4 under the Securities
Exchange Act of 1934, as amended, (b) represents that such tender complies with
Rule 14e-4 and (c) guarantees to deliver to the Depositary the Shares tendered
hereby, together with a properly completed and duly executed Letter(s) of
Transmittal (or facsimile(s) thereof) or an Agent's Message as defined in the
Offer to Purchase in the case of a book-entry delivery, and any other required
documents, all within three NASDAQ National Market System trading days of the
date hereof.
 
- ------------------------------------------------
 
  ____________________________________________________________________________
 
                                 (NAME OF FIRM)
 
  ____________________________________________________________________________
 
                                   (ADDRESS)
 
  ____________________________________________________________________________
 
                               (INCLUDE ZIP CODE)
 
  ____________________________________________________________________________
 
                        (AREA CODE AND TELEPHONE NUMBER)
 
  DATED: ______________________________________________________________, 1998.
 
- ------------------------------------------------
- ------------------------------------------------
 
  ____________________________________________________________________________
 
                             (AUTHORIZED SIGNATURE)
 
  ____________________________________________________________________________
 
                                     (NAME)
 
  ____________________________________________________________________________
 
                                    (TITLE)
 
- -----------------------------------------------
 
                 DO NOT SEND STOCK CERTIFICATES WITH THIS FORM.
      YOUR STOCK CERTIFICATES MUST BE SENT WITH THE LETTER OF TRANSMITTAL.
 
                                       2

<PAGE>
SALOMON SMITH BARNEY INC.
SEVEN WORLD TRADE CENTER
NEW YORK, NEW YORK 10048
 
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
                              MYCOGEN CORPORATION
                                       AT
                              $28.00 NET PER SHARE
                                       BY
                         AGROSCIENCES ACQUISITION INC.
                         A MAJORITY-OWNED SUBSIDIARY OF
                              DOW AGROSCIENCES LLC
                   AND A WHOLLY OWNED INDIRECT SUBSIDIARY OF
                            THE DOW CHEMICAL COMPANY
 
       THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK
      CITY TIME, ON FRIDAY, OCTOBER 2, 1998, UNLESS THE OFFER IS EXTENDED.
 
                                                               September 4, 1998
 
To Brokers, Dealers, Commercial Banks,
Trust Companies and Other Nominees:
 
    We have been appointed by AgroSciences Acquisition Inc., a Delaware
corporation ("Purchaser") and a majority-owned subsidiary of Dow AgroSciences
LLC, a Delaware limited liability company ("Parent"), to act as Dealer Manager
in connection with Purchaser's offer to purchase all of the outstanding shares
of common stock, par value $0.001 per share (including the associated preferred
stock purchase rights) (the "Shares"), of Mycogen Corporation, at $28.00 per
Share, net to the seller in cash, upon the terms and subject to the conditions
set forth in Purchaser's Offer to Purchase dated September 4, 1998 (the "Offer
to Purchase") and the related Letter of Transmittal (which, together with any
amendments or supplements thereto, constitute the "Offer").
 
    THE OFFER IS SUBJECT TO SEVERAL CONDITIONS CONTAINED IN THE OFFER TO
PURCHASE, INCLUDING THE CONDITION THAT THERE ARE VALIDLY TENDERED AND NOT
PROPERLY WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER A NUMBER OF SHARES SUCH
THAT PURCHASER AND PARENT, COLLECTIVELY, WILL BE THE OWNERS OF SHARES
REPRESENTING AT LEAST 90% OF THE FULLY DILUTED SHARES (AS DEFINED IN THE
INTRODUCTION OF THE OFFER TO PURCHASE) (THE "MINIMUM CONDITION"); PROVIDED,
HOWEVER, PURCHASER MAY, BUT NEED NOT, WAIVE THE MINIMUM CONDITION (1) WITHOUT
THE APPROVAL OF THE SPECIAL COMMITTEE COMPRISED OF TWO MEMBERS OF THE COMPANY'S
BOARD OF DIRECTORS INDEPENDENT OF TDCC, PARENT, PURCHASER AND MANAGEMENT OF THE
COMPANY (THE "SPECIAL COMMITTEE"), IF PURCHASER AND PARENT, COLLECTIVELY, WILL
BE THE OWNERS OF SHARES REPRESENTING AT LEAST 81.07% OF THE FULLY DILUTED
SHARES, OR (2) WITH THE APPROVAL OF THE SPECIAL COMMITTEE, IF PURCHASER AND
PARENT, COLLECTIVELY, WILL BE THE OWNERS OF SHARES REPRESENTING LESS THAN 81.07%
OF THE FULLY DILUTED SHARES. THE OFFER IS ALSO SUBJECT TO OTHER TERMS AND
CONDITIONS CONTAINED IN THE OFFER TO PURCHASE. SEE "THE TENDER OFFER--13.
CERTAIN CONDITIONS OF THE OFFER" IN THE OFFER TO PURCHASE.
 
    For your information and for forwarding to your clients for whom you hold
Shares registered in your name or in the name of your nominee, we are enclosing
the following documents:
 
    1.  Offer to Purchase dated September 4, 1998;
 
    2.  Letter of Transmittal to tender Shares for your use and for the
information of your clients, together with GUIDELINES FOR CERTIFICATION OF
TAXPAYER IDENTIFICATION NUMBER ON SUBSTITUTE FORM W-9
<PAGE>
providing information relating to backup federal income tax withholding
(facsimile copies of the Letter of Transmittal may be used to tender Shares);
 
    3.  Notice of Guaranteed Delivery to be used to accept the Offer if the
certificates for the Shares being tendered and all other required documents
cannot be delivered to the Depositary by the Expiration Date as defined in the
Offer to Purchase or if procedures for book-entry transfer cannot be completed
by the Expiration Date;
 
    4.  A printed form of letter which may be sent to your clients for whose
accounts you hold Shares registered in your name or in the name of your nominee,
with space provided for obtaining such clients' instructions with regard to the
Offer;
 
    5.  A letter to Mycogen Corporation stockholders from Carlton J. Eibl,
President, and Nickolas D. Hein, Chairman of the Board, of Mycogen Corporation;
and
 
    6.  A return envelope addressed to the Depositary.
 
    YOUR PROMPT ACTION IS REQUESTED. WE URGE YOU TO CONTACT YOUR CLIENTS AS
PROMPTLY AS POSSIBLE. PLEASE NOTE THAT THE OFFER AND WITHDRAWAL RIGHTS WILL
EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON FRIDAY, OCTOBER 2, 1998, UNLESS
THE OFFER IS EXTENDED.
 
    Upon the terms and subject to the conditions of the Offer (including, if the
Offer is extended or amended, the terms and conditions of any such extension or
amendment), Purchaser will accept for payment and pay for the Shares which are
validly tendered prior to the Expiration Date and not theretofore properly
withdrawn when, as and if Purchaser gives oral or written notice to the
Depositary of Purchaser's acceptance of such Shares for payment pursuant to the
Offer. Payment for the Shares purchased pursuant to the Offer will in all cases
be made only after timely receipt by the Depositary of certificates for the
Shares or timely confirmation of a book-entry transfer of such Shares into the
Depositary's account at The Depository Trust Company, pursuant to the procedures
described in "The Tender Offer--3. Procedure for Tendering Shares" of the Offer
to Purchase, a properly completed and duly executed Letter of Transmittal (or
manually signed facsimile thereof) or an Agent's Message in connection with a
book-entry transfer, and all other documents required by the Letter of
Transmittal.
 
    If holders of Shares wish to tender, but it is impracticable for them to
forward their certificates or other required documents on or prior to the
Expiration Date or to comply with the book-entry transfer procedure on a timely
basis, a tender may be effected by following the guaranteed delivery procedures
specified in "The Tender Offer--3. Procedure for Tendering Shares" in the Offer
to Purchase.
 
    Purchaser will not pay any fees or commissions to any broker or dealer or
other person (other than to the Dealer Manager as described in the Offer to
Purchase) for soliciting tenders of the Shares pursuant to the Offer. Purchaser
will, however, upon request, reimburse brokers, dealers, commercial banks and
trust companies for reasonable and necessary costs and expenses incurred by them
in forwarding materials to their customers. Purchaser will pay all stock
transfer taxes applicable to its purchase of Shares pursuant to the Offer,
subject to Instruction 6 of the Letter of Transmittal.
 
    Any inquiries you may have with respect to the Offer should be addressed to,
and additional copies of the enclosed materials may be obtained from, the
Information Agent or the undersigned at the addresses and telephone numbers set
forth on the back cover of the Offer to Purchase and the Letter of Transmittal.
 
                                          Very truly yours,
 
                                          SALOMON SMITH BARNEY INC.
 
    NOTHING CONTAINED HEREIN OR IN THE ENCLOSED DOCUMENTS SHALL CONSTITUTE YOU
OR ANY PERSON AS AN AGENT OF PARENT, PURCHASER, THE DEALER MANAGER, THE
INFORMATION AGENT OR THE DEPOSITARY, OR AUTHORIZE YOU OR ANY OTHER PERSON TO USE
ANY DOCUMENT OR MAKE ANY STATEMENT ON BEHALF OF ANY OF THEM IN CONNECTION WITH
THE OFFER OTHER THAN THE DOCUMENTS ENCLOSED HEREWITH AND THE STATEMENTS
CONTAINED THEREIN.
 
                                       2

<PAGE>
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
                              MYCOGEN CORPORATION
                                       AT
                              $28.00 NET PER SHARE
                                       BY
                         AGROSCIENCES ACQUISITION INC.
                         A MAJORITY-OWNED SUBSIDIARY OF
                              DOW AGROSCIENCES LLC
                   AND A WHOLLY OWNED INDIRECT SUBSIDIARY OF
                            THE DOW CHEMICAL COMPANY
 
       THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK
      CITY TIME, ON FRIDAY, OCTOBER 2, 1998, UNLESS THE OFFER IS EXTENDED.
 
To Our Clients:
 
    Enclosed for your consideration are the Offer to Purchase dated September 4,
1998 (the "Offer to Purchase"), and the related Letter of Transmittal (which,
together with any amendments or supplements thereto, constitute the "Offer") in
connection with the offer by AgroSciences Acquisition Inc., a Delaware
corporation ("Purchaser") and a majority-owned subsidiary of Dow AgroSciences
LLC ("Parent"), to purchase all of the outstanding shares of common stock, par
value $0.001 per share (including the associated preferred stock purchase
rights) (the "Shares"), of Mycogen Corporation (the "Company"), at a price of
$28.00 per share, net to the seller in cash, without interest thereon, upon the
terms and conditions set forth in the Offer. We are the holder of record of the
Shares held for your account. A tender of such Shares can be made only by us as
the holder of record and pursuant to your instructions. THE LETTER OF
TRANSMITTAL IS FURNISHED TO YOU FOR YOUR INFORMATION ONLY AND CANNOT BE USED BY
YOU TO TENDER SHARES HELD BY US FOR YOUR ACCOUNT.
 
    THE SPECIAL COMMITTEE COMPRISED OF TWO MEMBERS OF THE COMPANY'S BOARD OF
DIRECTORS INDEPENDENT OF TDCC, PARENT, PURCHASER AND MANAGEMENT OF THE COMPANY
(THE "SPECIAL COMMITTEE"), UNANIMOUSLY RECOMMENDED TO THE COMPANY'S BOARD OF
DIRECTORS THAT IT APPROVE THE OFFER. THE COMPANY'S ENTIRE BOARD OF DIRECTORS
ALSO REVIEWED THE OFFER AND, AFTER RECEIPT OF THE RECOMMENDATION OF THE SPECIAL
COMMITTEE, CONCLUDED THAT THE OFFER IS IN THE BEST INTERESTS OF THE COMPANY AND
ITS STOCKHOLDERS (OTHER THAN TDCC OR ITS AFFILIATES). ACCORDINGLY, THE COMPANY'S
BOARD OF DIRECTORS UNANIMOUSLY HAS APPROVED THE OFFER AND RECOMMENDS THAT
STOCKHOLDERS OF THE COMPANY ACCEPT THE OFFER AND TENDER THEIR SHARES.
 
    We request instructions as to whether you wish us to tender any or all of
the Shares held by us for your account, upon the terms and subject to the
conditions set forth in the Offer.
 
    PLEASE NOTE CAREFULLY THE FOLLOWING:
 
    1.  The tender price is $28.00 per Share, net to the seller in cash, without
interest thereon, upon the terms and subject to the conditions set forth in the
Offer.
<PAGE>
    2.  The Offer and withdrawal rights expire at 12:00 Midnight, New York City
time, on Friday, October 2, 1998, unless the Offer is extended (the "Expiration
Date").
 
    3.  The Offer is being made for all of the Shares.
 
    4.  THE OFFER IS CONDITIONED UPON, AMONG OTHER THINGS, THERE BEING VALIDLY
TENDERED AND NOT PROPERLY WITHDRAWN PRIOR TO THE EXPIRATION OF THE OFFER A
NUMBER OF SHARES OF THE COMPANY SUCH THAT, UPON PURCHASE OF SUCH SHARES BY
PURCHASER, PURCHASER AND PARENT, COLLECTIVELY, WILL BE THE OWNERS OF SHARES
REPRESENTING AT LEAST 90% OF THE FULLY DILUTED SHARES (AS DEFINED IN THE
INTRODUCTION TO THE OFFER TO PURCHASE) (THE "MINIMUM CONDITION"); PROVIDED,
HOWEVER, PURCHASER MAY, BUT NEED NOT, WAIVE THE MINIMUM CONDITION (1) WITHOUT
THE APPROVAL OF THE SPECIAL COMMITTEE IF PURCHASER AND PARENT, COLLECTIVELY,
WILL BE THE OWNERS OF SHARES REPRESENTING AT LEAST 81.07% OF THE FULLY DILUTED
SHARES, OR (2) WITH THE APPROVAL OF THE SPECIAL COMMITTEE, IF PURCHASER AND
PARENT, COLLECTIVELY, WILL BE THE OWNERS OF SHARES REPRESENTING LESS THAN 81.07%
OF THE FULLY DILUTED SHARES. THE OFFER IS ALSO SUBJECT TO OTHER TERMS AND
CONDITIONS CONTAINED IN THE OFFER TO PURCHASE. SEE THE INTRODUCTION AND SECTIONS
1 AND 13 THEREOF.
 
    5.  Any brokerage fees, commissions or stock transfer taxes applicable to
the sale of the Shares to Purchaser pursuant to the Offer will be paid by such
Purchaser, except as otherwise provided in Instruction 6 of the Letter of
Transmittal.
 
    If you wish to have us tender any or all of your Shares, please so instruct
us by completing, executing, detaching and returning to us the instruction form
set forth below. An envelope to return your instructions to us is enclosed. If
you authorize tender of your Shares, all such Shares will be tendered unless
otherwise specified on the instruction form set forth below.
 
    YOUR INSTRUCTIONS SHOULD BE FORWARDED TO US IN AMPLE TIME TO PERMIT US TO
SUBMIT A TENDER ON YOUR BEHALF BY THE EXPIRATION OF THE OFFER. THE OFFER, AND
WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY TIME, ON FRIDAY,
OCTOBER 2, 1998, UNLESS PURCHASER EXTENDS THE OFFER.
 
    The Offer is not being made to, nor will tenders be accepted from or on
behalf of, holders of the Shares in any jurisdiction in which the making of the
Offer or acceptance thereof would not be in compliance with the laws of such
jurisdiction. In those jurisdictions the laws of which require that the Offer be
made by a licensed broker or dealer, the Offer shall be deemed to be made on
behalf of Purchaser by Salomon Smith Barney Inc., or one or more registered
brokers or dealers licensed under the laws of such jurisdiction.
 
                                       2
<PAGE>
                          INSTRUCTIONS WITH RESPECT TO
                           OFFER TO PURCHASE FOR CASH
                     ALL OUTSTANDING SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
                              MYCOGEN CORPORATION
 
    The undersigned acknowledge(s) receipt of your letter and the enclosed Offer
to Purchase dated September 4, 1998, and the related Letter of Transmittal
(which collectively constitute the "Offer") in connection with the offer by
AgroSciences Acquisition Inc., a Delaware corporation and a majority-owned
subsidiary of Dow AgroSciences LLC, to purchase all of the outstanding shares of
common stock, par value $0.001 per share (including the associated preferred
stock purchase rights) (the "Shares"), of Mycogen Corporation.
 
    This will instruct you to tender the number of Shares indicated below held
by you for the account of the undersigned, upon the terms and subject to the
conditions set forth in the Offer to Purchase and the related Letter of
Transmittal.
 
Number(1) of Shares to be Tendered: _____________________________________ Shares
 
Account Number: ____________________________________
 
Dated: _____________________, 1998
                                   SIGN HERE
 
Signature(s): __________________________________________________________________
 
Print Name(s): _________________________________________________________________
 
Print Address(es): _____________________________________________________________
 
Area Code and Telephone Number: ________________________________________________
 
Taxpayer ID No. or Social Security No.: ________________________________________
 
(1) Unless otherwise indicated, it will be assumed that all Shares held by us
    for your account are to be tendered.

<PAGE>
                                OPTION ELECTION
            TO EXERCISE OPTIONS AND TO TENDER SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
 
                              MYCOGEN CORPORATION
           PURSUANT TO THE OFFER TO PURCHASE DATED SEPTEMBER 4, 1998
                                       OF
                         AGROSCIENCES ACQUISITION INC.
                         A MAJORITY-OWNED SUBSIDIARY OF
                              DOW AGROSCIENCES LLC
                   AND A WHOLLY OWNED INDIRECT SUBSIDIARY OF
                            THE DOW CHEMICAL COMPANY
 
- ----------------------------------------------------------------
 
                          SIGNATURE REQUIRED ON PAGE 4
  ----------------------------------------------------------------------------
 
Dear Option Holder:
 
    AgroSciences Acquisition Inc. ("Purchaser"), a majority-owned subsidiary of
Dow AgroSciences LLC ("Parent") and a wholly owned indirect subsidiary of The
Dow Chemical Company ("TDCC"), has made an offer to purchase all of the
outstanding shares of common stock, par value $0.001 per share (including the
associated preferred stock purchase rights) (the "Shares"), of Mycogen
Corporation (the "Company"), at a purchase price of $28.00 per Share, net to the
seller in cash. The enclosed Offer to Purchase dated September 4, 1998 (the
"Offer to Purchase"), and the related Letter of Transmittal enclosed with this
Option Election (which, together with the Offer to Purchase, constitute the
"Offer"), describe the Offer in greater detail.
 
    As a holder of options ("Options") to purchase Shares under the Mycogen
Corporation 1992 Stock Option Plan (which incorporates outstanding Options
granted under the Mycogen Corporation 1983 Stock Option Plan) (the "1992 Plan"),
you may submit to the Company this Option Election exercising all of your
outstanding Options (whether or not the Option was previously exercisable) and
instructing the Company to tender each of the Shares issuable under all such
Options (the "Option Shares") in the Offer, as set forth below under
"Instructions"; provided, that any exercise of an Option must be in accordance
with the terms of the 1992 Plan.
 
    By signing below, you hereby agree that, immediately prior to the purchase
of Shares by Purchaser in the Offer, and contingent upon such purchase, you will
be deemed to have fully exercised each Option held by you and to have tendered
each of the Option Shares to Purchaser pursuant to the Offer. By signing below,
you also agree that the exercise price per Option Share (the "Exercise Price")
will be deemed to be paid with the proceeds of an interest free advance from the
Company (the "Advance"). The Advance will be deemed to be repaid in full on your
behalf by Purchaser from a portion of the consideration due to you for such
Shares in the Offer. After such repayment, you will be entitled to receive from
Purchaser with respect to each Option Share purchased by Purchaser pursuant to
the Offer an amount equal to the difference between (a) the Exercise Price and
(b) the price per Share paid by Purchaser pursuant to the Offer.
 
    By signing below, you acknowledge that you have been advised that (1)
Options for which a valid Option Election has been executed and delivered to the
Company that are not already vested will become vested immediately prior to the
expiration of the Offer (but contingent upon the purchase by Purchaser of Shares
pursuant to the Offer), (2) the Company and Parent will make it possible for
Option Shares issuable upon exercise of the Options covered by Option Elections
above to be tendered in the Offer and (3) upon the purchase of Option Shares
pursuant to this Option Election, you will have no further rights under such
Option.
 
    TO ASSURE THAT YOUR OPTION ELECTION CAN BE PROCESSED ON TIME, PLEASE EXECUTE
THIS OPTION ELECTION AND DELIVER IT TO THE COMPANY ACCORDING TO THE INSTRUCTIONS
SET FORTH BELOW, BEFORE 5:00 P.M., SAN DIEGO, CALIFORNIA TIME, ON WEDNESDAY,
SEPTEMBER 30, 1998, UNLESS THE OFFER IS EXTENDED.
 
    The Offer is being made in connection with an Agreement and Plan of Merger
(the "Merger Agreement") dated as of August 31, 1998, among the Company,
Purchaser, Parent and, for the limited purpose set forth in the Merger
Agreement, TDCC. If you decide not to execute this Option Election and return it
to the Company and, thereby, not exercise your Options and tender your Option
Shares under the Offer, then your Options will become exercisable immediately
prior to the Effective Time of the Merger (as defined in the Offer to Purchase)
(contingent upon the purchase by Purchaser of Shares pursuant to the Offer) and
the Company intends on treating your Options as terminated and no longer
outstanding as of the Effective Time of the Merger; provided, however, that the
Company will make arrangements so that if you consent to the termination of your
Options (either before the Effective Time of the Merger or within a reasonable
time thereafter), then you will be entitled to receive in respect of your
Options an amount in cash equal to $28.00 less the exercise price per Share
under each of your Options multiplied by the number of Option Shares.
 
    If you require additional information concerning the terms and conditions of
the Offer, please call Georgeson & Company Inc., the Information Agent, at (800)
223-2064. If you require additional information
<PAGE>
concerning the procedure to tender Option Shares or the completion of this
Option Election, please call Cheri Manis of the Company's Investor Relations
Department at (800) 745-7475.
 
    BEFORE COMPLETING THIS FORM, PLEASE READ CAREFULLY THE ACCOMPANYING OFFER TO
PURCHASE AND ALL OTHER ENCLOSED MATERIALS.
 
    THE SPECIAL COMMITTEE COMPRISED OF TWO MEMBERS OF THE COMPANY'S BOARD OF
DIRECTORS INDEPENDENT OF TDCC, PARENT AND PURCHASER (THE "SPECIAL COMMITTEE"),
UNANIMOUSLY RECOMMENDED TO THE COMPANY'S BOARD OF DIRECTORS THAT IT APPROVE THE
OFFER. THE COMPANY'S ENTIRE BOARD OF DIRECTORS ALSO REVIEWED THE OFFER AND,
AFTER RECEIPT OF THE RECOMMENDATION OF THE SPECIAL COMMITTEE, CONCLUDED THAT THE
OFFER IS IN THE BEST INTERESTS OF THE COMPANY AND ITS STOCKHOLDERS (OTHER THAN
TDCC OR ITS AFFILIATES). ACCORDINGLY, THE COMPANY'S BOARD OF DIRECTORS
UNANIMOUSLY HAS APPROVED THE OFFER AND RECOMMENDS THAT STOCKHOLDERS OF THE
COMPANY ACCEPT THE OFFER AND TENDER THEIR SHARES.
                            ------------------------
 
                                  INSTRUCTIONS
 
    Carefully complete this Option Election below. To assure that your Option
Election can be processed on time, please be sure to sign and date the form and
return this Option Election to Mycogen Corporation, AgroSciences Tender Offer,
5501 Oberlin Drive, San Diego, California 92121, Attention: Cheri Manis, not
later than 5:00 p.m., San Diego, California time, on Wednesday, September 30,
1998, unless the Offer is extended.
 
    The Company reserves the absolute right to waive any defect or irregularity
in the exercise of any Option or the tender of any Shares. No exercise of
Options and tender of Option Shares will be deemed to be properly made until all
defects or irregularities have been cured or waived. None of the Company, the
Dealer Manager, the Depositary, the Information Agent or any other person is or
will be obligated to give notice of any defects or irregularities in tenders of
exercises of Options and Option Shares, and none of them will incur any
liability for failure to give any such notice.
 
    THE METHOD OF DELIVERY OF THIS DOCUMENT IS AT THE ELECTION AND RISK OF THE
TENDERING HOLDER OF OPTIONS. NO FACSIMILE TRANSMISSIONS OF THE OPTION ELECTION
WILL BE ACCEPTED. IF DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN RECEIPT
REQUESTED IS RECOMMENDED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO
ASSURE DELIVERY BY 5:00 P.M., SAN DIEGO, CALIFORNIA TIME, ON WEDNESDAY,
SEPTEMBER 30, 1998.
 
                                       2
<PAGE>
OPTION EXERCISE
 
    If you want to exercise your Options and tender your Option Shares in the
Offer, follow the instructions below.
 
    THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
TIME, ON FRIDAY, OCTOBER 2, 1998, UNLESS PURCHASER EXTENDS THE OFFER. EXCEPT AS
SET FORTH HEREIN, IF YOU WANT TO PARTICIPATE IN THE OFFER, YOU MUST COMPLETE AND
RETURN THE ENCLOSED OPTION ELECTION AS SET FORTH IN INSTRUCTION (2) BELOW PRIOR
TO THE EXPIRATION OF THE OFFER.
 
    To properly complete your Option Election, you need to do the following:
 
    (1) Complete, date and sign the Option Election on page 4.
 
    (2) Return this Option Election to Mycogen Corporation, AgroSciences Tender
Offer, 5501 Oberlin Drive, San Diego, California 92121, Attention: Cheri Manis,
not later than 5:00 p.m., San Diego, California time, on Wednesday, September
30, 1998, unless the Offer is extended. Option Elections received after the
expiration of the Offer will not be honored. NO FACSIMILE TRANSMITTALS OF THE
OPTION ELECTION WILL BE ACCEPTED.
 
WITHDRAWAL
 
    If completely and properly submitted, your direction to exercise Options and
tender the related Shares will be deemed irrevocable upon receipt by the Company
unless withdrawn prior to the Expiration of the Offer, unless extended. In order
to make an effective withdrawal, you must submit a new Option Election which may
be obtained by calling Cheri Manis of the Company's Investor Relations
Department at (800) 745-7475 (or use a photocopy of an Option Election). Your
new Option Election must be signed and dated on page 4. You must also write
"WITHDRAW" in the space beneath the signature block on page 4. Upon receipt of a
new, signed, dated and properly completed Option Election, your previous
direction will be deemed canceled. You may be deemed to re-exercise your Options
and be deemed to re-tender your Option Shares by obtaining another Option
Election from Cheri Manis (or use a photocopy of an Option Election) and
repeating the previous instructions for directing exercises and tenders as set
forth above.
 
FURTHER INFORMATION
 
    If you require additional information concerning the terms and conditions of
the Offer, please call Georgeson & Company Inc., the Information Agent, at (800)
223-2064. If you require additional information concerning the procedure to
tender Shares receivable upon exercise of your Options or the completion of this
Option Election, please call Cheri Manis of the Company's Investor Relations
Department at (800) 745-7475.
 
                                       3
<PAGE>
- --------------------------------------------------------------------------------
 
                                   SIGNATURE
                                   (REQUIRED)
 
      The undersigned acknowledges receipt of the Offer to Purchase, dated
  September 4, 1998, from Purchaser and Parent and represents that the
  undersigned has carefully read such documents. The undersigned hereby
  instructs the Company, subject to the terms and conditions set forth in this
  Option Election and the Offer to Purchase, to carry out the instructions
  contained in this form.
 
      The Company is hereby authorized to exercise all Options of which the
  undersigned is a holder and to tender the undersigned's Option Shares.
 
      The undersigned understands that withholding taxes, at the minimum rate
  or the rate specified in Form B tax election previously filed with the
  Company, will be withheld from any proceeds received by the undersigned
  (unless the undersigned has submitted with this form, or pursuant to
  subsequent notification from the Company, a check in an amount sufficient to
  cover such amount). The undersigned further agrees that, if such proceeds
  are insufficient to cover applicable withholding taxes, Option Shares will
  not be credited to his or her account until he or she has, upon request of
  the Company, forwarded to the Company a check in an amount sufficient to
  cover such taxes. In lieu of withholding at such rates, the undersigned
  instructs the Company to withhold taxes at the following rates (which may
  not be less than the minimum federal, state or local tax rates applicable to
  you, nor in excess of such proceeds):
             Federal:________%;  State:________%;  Local:________%.
 
      THE METHOD OF DELIVERY OF THIS DOCUMENT IS AT THE ELECTION AND RISK OF
  THE UNDERSIGNED.
 
  Signature:________________________              Date:_______________________
  Name:_______________________  Social Security Number:_______________________
                  (PLEASE PRINT)
 
  Address:____________________________________________________________________
          (STREET ADDRESS, INCLUDING APARTMENT NUMBER -- PLEASE PRINT)
 
   __________________________________________________________________________
   (CITY)                          (STATE)                         (ZIP CODE)
 
   --------------------------------------------------------------------------
 
                                       4

<PAGE>
                            STOCK PURCHASE ELECTION
        TO EXERCISE PURCHASE RIGHTS AND TO TENDER SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
 
                              MYCOGEN CORPORATION
           PURSUANT TO THE OFFER TO PURCHASE DATED SEPTEMBER 4, 1998
                                       OF
                         AGROSCIENCES ACQUISITION, INC.
                         A MAJORITY-OWNED SUBSIDIARY OF
                              DOW AGROSCIENCES LLC
                   AND A WHOLLY-OWNED INDIRECT SUBSIDIARY OF
                            THE DOW CHEMICAL COMPANY
 
- ----------------------------------------------------------------
 
                          SIGNATURE REQUIRED ON PAGE 4
  ----------------------------------------------------------------------------
 
Dear Purchase Rights Holder:
 
    AgroSciences Acquisition Inc. ("Purchaser"), a majority-owned subsidiary of
Dow AgroSciences LLC ("Parent") and a wholly owned indirect subsidiary of The
Dow Chemical Company ("TDCC"), has made an offer to purchase all of the
outstanding shares of common stock, par value $0.001 per share (including the
associated preferred stock purchase rights) (the "Shares"), of Mycogen
Corporation (the "Company"), at a purchase price of $28.00 per Share, net to the
seller in cash. The enclosed Offer to Purchase dated September 4, 1998 (the
"Offer to Purchase"), and the related Letter of Transmittal enclosed with this
Stock Purchase Election (which, together with the Offer to Purchase, constitute
the "Offer"), describe the Offer in greater detail.
 
    As a holder of purchase rights ("Purchase Rights") to purchase Shares under
the Mycogen Corporation 1995 Employee Stock Purchase Plan (the "Stock Purchase
Plan"), you may submit to the Company this Stock Purchase Election exercising
all of your Purchase Rights (calculated assuming your payroll deductions had
continued at the same level through November 30, 1998) and the Company will
tender each of the Shares issuable under all such Purchase Rights (the "Stock
Purchase Shares") in the Offer, as set forth below under "Instructions";
provided that any exercise of Purchase Rights must be in accordance with the
terms of the Stock Purchase Plan.
 
    By signing below, you hereby agree that, immediately prior to the purchase
of Shares by Purchaser in the Offer, and contingent upon such purchase, you will
be deemed to have fully exercised your Purchase Rights and to have tendered each
of the Stock Purchase Shares to Purchaser pursuant to the Offer. By signing
below, you also agree that the amount of payroll deductions accumulated in your
account under the Stock Purchase Plan will be used to exercise the Purchase
Rights and that the difference between the entire purchase price for the Stock
Purchase Shares and the amount of the accumulated payroll deductions shall be
deemed to be paid with the proceeds of an interest free advance from the Company
(the "Advance"). The Advance will be deemed to be repaid in full on your behalf
by Purchaser from a portion of the consideration due to you for such Stock
Purchase Shares in the Offer. After such repayment, you will be entitled to
receive from Purchaser the balance of such consideration with respect to each
Stock Purchase Share purchased by Purchaser pursuant to the Offer.
 
    By signing below, you acknowledge that you have been advised that (1) the
Company and Parent will make it possible for Stock Purchase Shares issuable upon
exercise of Purchase Rights covered by Stock Purchase Elections above to be
deemed tendered in the Offer, and (2) upon the purchase of Stock Purchase Shares
pursuant to this Stock Purchase Election, you will have no further rights under
such Purchase Rights.
 
    TO ASSURE THAT YOUR STOCK PURCHASE ELECTION CAN BE PROCESSED ON TIME, PLEASE
EXECUTE THIS STOCK PURCHASE ELECTION AND DELIVER IT TO THE COMPANY ACCORDING TO
THE INSTRUCTIONS SET FORTH BELOW, BEFORE 5:00 P.M., SAN DIEGO, CALIFORNIA TIME,
ON WEDNESDAY, SEPTEMBER 30, 1998, UNLESS THE OFFER IS EXTENDED.
 
    The Offer is being made in connection with an Agreement and Plan of Merger
(the "Merger Agreement") dated as of August 31, 1998, among the Company,
Purchaser, Parent and, for the limited purpose set forth in the Merger
Agreement, TDCC. If you decide not to execute this Stock Purchase Election and
return it to the Company and, thereby, not exercise your Purchase Rights and
tender your Stock Purchase Shares under the Offer, then, contingent upon the
purchase by Purchaser of Shares pursuant to the Offer, the Company intends to
treat your Purchase Rights as terminated and no longer outstanding as of the
Effective Time of the Merger (as defined in the Offer to Purchase) and your
payroll deductions will be returned to you; provided, however, that the Company
will make arrangements so that if you consent to the termination of your
Purchase Rights (either before the Effective Time of the Merger, or within a
reasonable time thereafter), then you will be entitled to receive in respect of
your Purchase Rights an amount in cash equal to the net amount you would have
received if you had executed the Stock Purchase Election.
 
    If you require additional information concerning the terms and conditions of
the Offer, please call Georgeson & Company Inc., the Information Agent, at (800)
223-2064. If you require additional information
<PAGE>
concerning the procedure to tender Stock Purchase Shares or the completion of
this Stock Purchase Election, please call Cheri Manis of the Company's Investor
Relations Department at (800) 745-7475.
 
    BEFORE COMPLETING THIS FORM, PLEASE READ CAREFULLY THE ACCOMPANYING OFFER TO
PURCHASE AND ALL OTHER ENCLOSED MATERIALS.
 
    THE SPECIAL COMMITTEE COMPRISED OF TWO MEMBERS OF THE COMPANY'S BOARD OF
DIRECTORS INDEPENDENT OF TDCC, PARENT AND PURCHASER (THE "SPECIAL COMMITTEE"),
UNANIMOUSLY RECOMMENDED TO THE COMPANY'S BOARD OF DIRECTORS THAT IT APPROVE THE
OFFER. THE COMPANY'S ENTIRE BOARD OF DIRECTORS ALSO REVIEWED THE OFFER AND,
AFTER RECEIPT OF THE RECOMMENDATION OF THE SPECIAL COMMITTEE, CONCLUDED THAT THE
OFFER IS IN THE BEST INTERESTS OF THE COMPANY AND ITS STOCKHOLDERS (OTHER THAN
TDCC OR ITS AFFILIATES). ACCORDINGLY, THE COMPANY'S BOARD OF DIRECTORS
UNANIMOUSLY HAS APPROVED THE OFFER AND RECOMMENDS THAT STOCKHOLDERS OF THE
COMPANY ACCEPT THE OFFER AND TENDER THEIR SHARES.
                            ------------------------
 
                                  INSTRUCTIONS
 
    Carefully complete this Stock Purchase Election below. To assure that your
Stock Purchase Election can be processed on time, please be sure to sign and
date the form and return this Stock Purchase Election to Mycogen Corporation,
AgroSciences Tender Offer, 5501 Oberlin Drive, San Diego, California 92121,
Attention: Cheri Manis, not later than 5:00 p.m., San Diego, California time, on
Wednesday, September 30, 1998, unless the Offer is extended.
 
    The Company reserves the absolute right to waive any defect or irregularity
in the exercise of any Purchase Rights or the tender of any Stock Purchase
Shares. No exercise of Purchase Rights and tender of Stock Purchase Shares will
be deemed to be properly made until all defects or irregularities have been
cured or waived. None of the Company, the Dealer Manager, the Depositary, the
Information Agent or any other person is or will be obligated to give notice of
any defects or irregularities in tenders of exercises of Purchase Rights and
Stock Purchase Shares, and none of them will incur any liability for failure to
give any such notice.
 
    THE METHOD OF DELIVERY OF THIS DOCUMENT IS AT THE ELECTION AND RISK OF THE
TENDERING HOLDER OF PURCHASE RIGHTS. NO FACSIMILE TRANSMISSIONS OF THE STOCK
PURCHASE ELECTION WILL BE ACCEPTED. IF DELIVERY IS BY MAIL, REGISTERED MAIL WITH
RETURN RECEIPT REQUESTED IS RECOMMENDED. IN ALL CASES, SUFFICIENT TIME SHOULD BE
ALLOWED TO ASSURE DELIVERY.
 
                                       2
<PAGE>
STOCK PURCHASE EXERCISE
 
    If you want to exercise your Purchase Rights and tender your Stock Purchase
Shares in the Offer, follow the instructions below.
 
    THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
TIME, ON FRIDAY, OCTOBER 2, 1998, UNLESS PURCHASER EXTENDS THE OFFER. EXCEPT AS
SET FORTH HEREIN, IF YOU WANT TO PARTICIPATE IN THE OFFER, YOU MUST COMPLETE AND
RETURN THE ENCLOSED STOCK PURCHASE ELECTION AS SET FORTH IN INSTRUCTION (2)
BELOW PRIOR TO THE EXPIRATION OF THE OFFER.
 
    To properly complete your Stock Purchase Election, you need to do the
following:
 
    (1) Complete, date and sign the Stock Purchase Election on page 4.
 
    (2) Return this Stock Purchase Election to Mycogen Corporation, AgroSciences
Tender Offer, 5501 Oberlin Drive, San Diego, California 92121, Attention: Cheri
Manis, not later than 5:00 p.m., San Diego, California time, on Wednesday,
September 30, 1998, unless the Offer is extended. Stock Purchase Elections
received after the expiration of the Offer will not be honored. NO FACSIMILE
TRANSMITTALS OF THE STOCK PURCHASE ELECTION WILL BE ACCEPTED.
 
WITHDRAWAL
 
    If completely and properly submitted, your direction to exercise Purchase
Rights and tender the related Stock Purchase Shares will be deemed irrevocable
upon receipt by the Company unless withdrawn prior to the expiration of the
Offer, unless the Offer is extended. In order to make an effective withdrawal,
you must submit a new Stock Purchase Election which may be obtained by calling
Cheri Manis of the Company's Investor Relations Department at (800) 745-7475 (or
use a photocopy of a Stock Purchase Election). Your new Stock Purchase Election
must be signed and dated on page 4. You must also write "WITHDRAW" in the space
beneath the signature block on page 4. Upon receipt of a new, signed, dated and
properly completed Stock Purchase Election, your previous direction will be
deemed canceled. You may be deemed to re-exercise your Purchase Rights and be
deemed to re-tender your Stock Purchase Shares by obtaining another Stock
Purchase Election from Cheri Manis (or use a photocopy of a Stock Purchase
Election) and repeating the previous instructions for directing exercises and
tenders as set forth above.
 
FURTHER INFORMATION
 
    If you require additional information concerning the terms and conditions of
the Offer, please call Georgeson & Company Inc., the Information Agent, at (800)
223-2064. If you require additional information concerning the procedure to
tender Stock Purchase Shares receivable upon exercise of your Purchase Rights or
the completion of this Stock Purchase Election, please call Cheri Manis of the
Company's Investor Relations Department at (800) 745-7475.
 
                                       3
<PAGE>
- --------------------------------------------------------------------------------
 
                                   SIGNATURE
                                   (REQUIRED)
 
      The undersigned acknowledges receipt of the Offer to Purchase, dated
  September 4, 1998, from Purchaser and Parent and represents that the
  undersigned has carefully read such documents. The undersigned hereby
  instructs the Company, subject to the terms and conditions set forth in this
  Stock Purchase Election and the Offer to Purchase, to carry out the
  instructions contained in this form.
 
      The Company is hereby authorized to exercise all Purchase Rights of
  which the undersigned is a holder and to tender the undersigned's Stock
  Purchase Shares.
 
      The undersigned understands that withholding taxes, at the minimum rate
  or the rate specified in Form B tax election previously filed with the
  Company, will be withheld from any proceeds received by the undersigned
  (unless the undersigned has submitted with this form, or pursuant to
  subsequent notification from the Company, a check in an amount sufficient to
  cover such amount). The undersigned further agrees that, if such proceeds
  are insufficient to cover applicable withholding taxes, Stock Purchase
  Shares will not be credited to his or her account until he or she has, upon
  request of the Company, forwarded to the Company a check in an amount
  sufficient to cover such taxes. In lieu of withholding at such rates, the
  undersigned instructs the Company to withhold taxes at the following rates
  (which may not be less than the minimum federal, state or local tax rates
  applicable to you, nor in excess of such proceeds):
             Federal________%;  State:________%;  Local:________%.
 
      THE METHOD OF DELIVERY OF THIS DOCUMENT IS AT THE ELECTION AND RISK OF
  THE UNDERSIGNED.
 
  Signature:________________________              Date:_______________________
  Name:_______________________  Social Security Number:_______________________
                  (PLEASE PRINT)
 
  Address:____________________________________________________________________
          (STREET ADDRESS, INCLUDING APARTMENT NUMBER -- PLEASE PRINT)
 
   __________________________________________________________________________
   (CITY)                          (STATE)                         (ZIP CODE)
 
   --------------------------------------------------------------------------
 
                                       4

<PAGE>
                           RESTRICTED STOCK ELECTION
                        TO TENDER SHARES OF COMMON STOCK
           (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)
                                       OF
 
                              MYCOGEN CORPORATION
           PURSUANT TO THE OFFER TO PURCHASE DATED SEPTEMBER 4, 1998
                                       OF
                         AGROSCIENCES ACQUISITION INC.
                         A MAJORITY-OWNED SUBSIDIARY OF
                              DOW AGROSCIENCES LLC
                   AND A WHOLLY OWNED INDIRECT SUBSIDIARY OF
                            THE DOW CHEMICAL COMPANY
 
- --------------------------------------------------------------------------------
 
                          SIGNATURE REQUIRED ON PAGE 4
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
                   YOU MUST ALSO COMPLETE, SIGN AND RETURN TO
                    THE COMPANY A LETTER OF TRANSMITTAL AND
                      YOUR RESTRICTED STOCK CERTIFICATE(S)
- --------------------------------------------------------------------------------
 
Dear Restricted Stock Holder:
 
    AgroSciences Acquisition Inc. ("Purchaser"), a majority-owned subsidiary of
Dow AgroSciences LLC ("Parent") and a wholly owned indirect subsidiary of The
Dow Chemical Company ("TDCC"), has made an offer to purchase all of the
outstanding shares of common stock, par value $0.001 per share (including the
associated preferred stock purchase rights) (the "Shares"), of Mycogen
Corporation (the "Company"), at a purchase price of $28.00 per Share, net to the
seller in cash. The enclosed Offer to Purchase dated September 4, 1998 (the
"Offer to Purchase"), and the related Letter of Transmittal enclosed with this
Restricted Stock Election (which, together with the Offer to Purchase,
constitute the "Offer"), describe the Offer in greater detail.
 
    As a holder of Shares under the Mycogen Corporation Restricted Stock
Issuance Plan (the "Restricted Stock Plan") that are not vested under the
Restricted Stock Plan ("Restricted Shares"), you may submit to the Company (i)
this Restricted Stock Election instructing the Company to tender each of the
Restricted Shares in the Offer, (ii) a Letter of Transmittal, as set forth below
under "Instructions" and (iii) your Restricted Stock Certificate(s).
 
    By signing below, you hereby agree that, immediately prior to the purchase
of Shares by Purchaser in the Offer, and contingent upon such purchase, you will
be deemed to have tendered each of your Restricted Shares (regardless of the
fact that the Restricted Shares were not previously vested) to Purchaser
pursuant to the Offer. You will be entitled to receive from Purchaser with
respect to each Restricted Share purchased by Purchaser pursuant to the Offer an
amount equal to the price per Share paid by Purchaser pursuant to the Offer.
 
    By signing below, you acknowledge that you have been advised that (1)
Restricted Shares for which a valid Restricted Stock Election and a Letter of
Transmittal have been executed and delivered to the Company will become vested
immediately prior to the expiration of the Offer (but contingent upon the
purchase by Purchaser of Shares pursuant to the Offer), (2) the Company and
Parent will make it possible for Restricted Shares covered by Restricted Stock
Elections above to be tendered in the Offer, and (3) upon the purchase of
Restricted Shares pursuant to this Restricted Stock Election, you will have no
further rights under your Restricted Shares.
 
    TO ASSURE THAT YOUR RESTRICTED STOCK ELECTION CAN BE PROCESSED ON TIME,
PLEASE EXECUTE THIS RESTRICTED STOCK ELECTION AND A LETTER OF TRANSMITTAL AND
DELIVER THEM ALONG WITH YOUR RESTRICTED STOCK CERTIFICATE(S) TO THE COMPANY
ACCORDING TO THE INSTRUCTIONS SET FORTH BELOW, BEFORE 5:00 P.M., SAN DIEGO,
CALIFORNIA TIME, ON WEDNESDAY, SEPTEMBER 30, 1998, UNLESS THE OFFER IS EXTENDED.
 
    The Offer is being made in connection with an Agreement and Plan of Merger
(the "Merger Agreement") dated as of August 31, 1998, among the Company,
Purchaser, Parent and, for the limited purpose set forth in the Merger
Agreement, TDCC. If you decide not to execute this Restricted Stock Election and
a Letter of Transmittal and return them to the Company and, thereby, not tender
your Restricted Shares under the Offer, then, contingent on the purchase by
Purchaser of Shares pursuant to the Offer, your Restricted Shares will become
fully vested immediately prior to the Effective Time of the Merger (as defined
in the Offer to Purchase).
 
    If you require additional information concerning the terms and conditions of
the Offer, please call Georgeson & Company Inc., the Information Agent, at (800)
223-2064. If you require additional information
<PAGE>
concerning the procedure to tender Restricted Shares or the completion of this
Restricted Stock Election, please call Cheri Manis of the Company's Investor
Relations Department at (800) 745-7475.
 
    BEFORE COMPLETING THIS FORM, PLEASE READ CAREFULLY THE ACCOMPANYING OFFER TO
PURCHASE AND ALL OTHER ENCLOSED MATERIALS.
 
    THE SPECIAL COMMITTEE COMPRISED OF TWO MEMBERS OF THE COMPANY'S BOARD OF
DIRECTORS INDEPENDENT OF TDCC, PARENT AND PURCHASER (THE "SPECIAL COMMITTEE"),
UNANIMOUSLY RECOMMENDED TO THE COMPANY'S BOARD OF DIRECTORS THAT IT APPROVE THE
OFFER. THE COMPANY'S ENTIRE BOARD OF DIRECTORS ALSO REVIEWED THE OFFER AND,
AFTER RECEIPT OF THE RECOMMENDATION OF THE SPECIAL COMMITTEE, CONCLUDED THAT THE
OFFER IS IN THE BEST INTERESTS OF THE COMPANY AND ITS STOCKHOLDERS (OTHER THAN
TDCC OR ITS AFFILIATES). ACCORDINGLY, THE COMPANY'S BOARD OF DIRECTORS
UNANIMOUSLY HAS APPROVED THE OFFER AND RECOMMENDS THAT STOCKHOLDERS OF THE
COMPANY ACCEPT THE OFFER AND TENDER THEIR SHARES.
                            ------------------------
 
                                  INSTRUCTIONS
 
    Carefully complete this Restricted Stock Election below. To assure that your
Restricted Stock Election can be processed on time, please be sure to sign and
date the form and return this Restricted Stock Election along with a completed
Letter of Transmittal to Mycogen Corporation, AgroSciences Tender Offer, 5501
Oberlin Drive, San Diego, California 92121, Attention: Cheri Manis, not later
than 5:00 p.m., San Diego, California time, on Wednesday, September 30, 1998,
unless the Offer is extended.
 
    The Company reserves the absolute right to waive any defect or irregularity
in the tender of any Restricted Shares. No tender of Restricted Shares will be
deemed to be properly made until all defects or irregularities have been cured
or waived. None of the Company, the Dealer Manager, the Depositary, the
Information Agent or any other person is or will be obligated to give notice of
any defects or irregularities in tenders of Restricted Shares, and none of them
will incur any liability for failure to give any such notice.
 
    THE METHOD OF DELIVERY OF THIS DOCUMENT IS AT THE ELECTION AND RISK OF THE
TENDERING HOLDER OF RESTRICTED SHARES. NO FACSIMILE TRANSMISSIONS OF THE OPTION
ELECTION WILL BE ACCEPTED. IF DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN
RECEIPT REQUESTED, PROPERLY INSURED, IS RECOMMENDED. IN ALL CASES, SUFFICIENT
TIME SHOULD BE ALLOWED TO ASSURE DELIVERY BY 5:00 P.M., SAN DIEGO, CALIFORNIA
TIME, ON WEDNESDAY, SEPTEMBER 30, 1998, UNLESS THE OFFER IS EXTENDED.
 
TENDER OF RESTRICTED SHARES
 
    If you want to tender your Restricted Shares in the Offer, follow the
instructions below.
 
    THE OFFER AND WITHDRAWAL RIGHTS EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY
TIME, ON FRIDAY, OCTOBER 2, 1998, UNLESS PURCHASER EXTENDS THE OFFER. EXCEPT AS
SET FORTH HEREIN, IF YOU WANT TO PARTICIPATE IN THE OFFER, YOU MUST COMPLETE AND
RETURN THE ENCLOSED RESTRICTED STOCK ELECTION, THE LETTER OF TRANSMITTAL AND
YOUR RESTRICTED STOCK CERTIFICATE(S) AS SET FORTH IN INSTRUCTION (3) BELOW PRIOR
TO THE EXPIRATION OF THE OFFER.
 
                                       2
<PAGE>
    To properly complete your Restricted Stock Election, you need to do the
following:
 
    (1) Complete, date and sign the Restricted Stock Election on page 4.
 
    (2) Complete, date and sign a Letter of Transmittal respecting the
Restricted Shares.
 
    (3) Return this Restricted Stock Election, the Letter of Transmittal and
your Restricted Stock Certificate(s) to Mycogen Corporation, AgroSciences Tender
Offer, 5501 Oberlin Drive, San Diego, California 92121, Attention: Cheri Manis,
not later than 5:00 p.m., San Diego, California time, on Wednesday, September
30, 1998, unless the Offer is extended. Restricted Stock Elections received
after the expiration of the Offer will not be honored. NO FACSIMILE TRANSMITTALS
OF THE RESTRICTED STOCK ELECTION OR THE LETTER OF TRANSMITTAL WILL BE ACCEPTED.
 
WITHDRAWAL
 
    If completely and properly submitted, your direction to tender your
Restricted Shares and Letter of Transmittal will be deemed irrevocable upon
receipt by the Company unless withdrawn prior to the Expiration of the Offer,
unless extended. In order to make an effective withdrawal, you must submit a new
Restricted Stock Election which may be obtained by calling Cheri Manis of the
Company's Investor Relations Department at (800) 745-7475 (or use a photocopy of
a Restricted Stock Election). Your new Restricted Stock Election must be signed
and dated on page 4. You must also write "WITHDRAW" in the space beneath the
signature block on page 4. Upon receipt of a new, signed, dated and properly
completed Restricted Stock Election, your previous direction will be deemed
canceled. You may be deemed to re-tender your Restricted Shares by obtaining
another Restricted Stock Election and Letter of Transmittal from Cheri Manis (or
use a photocopy of a Restricted Stock Election and Letter of Transmittal) and
repeating the previous instructions for directing exercises and tenders as set
forth above.
 
FURTHER INFORMATION
 
    If you require additional information concerning the terms and conditions of
the Offer, please call Georgeson & Company Inc., the Information Agent, at (800)
223-2064. If you require additional information concerning the procedure to
tender your Restricted Shares or the completion of this Restricted Stock
Election and Letter of Transmittal, please call Cheri Manis of the Company's
Investor Relations Department at (800) 745-7475.
 
                                       3
<PAGE>
- --------------------------------------------------------------------------------
 
                                   SIGNATURE
                                   (REQUIRED)
 
      The undersigned acknowledges receipt of the Offer to Purchase, dated
  September 4, 1998, from Purchaser and Parent and represents that the
  undersigned has carefully read such documents. The undersigned hereby
  instructs the Company, subject to the terms and conditions set forth in this
  Restricted Stock Election and the Offer to Purchase, to carry out the
  instructions contained in this form.
 
      The Company is hereby authorized to tender the undersigned's Restricted
  Shares by delivering the completed Letter of Transmittal and your Restricted
  Stock Certificate(s) to the Depositary.
 
      The undersigned understands that withholding taxes, at the minimum rate
  or the rate specified in Form B tax election previously filed with the
  Company, will be withheld from any proceeds received by the undersigned
  (unless the undersigned has submitted with this form, or pursuant to
  subsequent notification from the Company, a check in an amount sufficient to
  cover such amount). The undersigned further agrees that, if such proceeds
  are insufficient to cover applicable withholding taxes, Restricted Shares
  will not be treated as vested for his or her account until he or she has,
  upon request of the Company, forwarded to the Company a check in an amount
  sufficient to cover such taxes. In lieu of withholding at such rates, the
  undersigned instructs the Company to withhold taxes at the following rates
  (which may not be less than the minimum federal, state or local tax rates
  applicable to you, nor in excess of such proceeds):
             Federal:________%;  State:________%;  Local:________%.
 
      THE METHOD OF DELIVERY OF THIS DOCUMENT IS AT THE ELECTION AND RISK OF
  THE UNDERSIGNED.
 
  Signature:________________________              Date:_______________________
  Name:_______________________  Social Security Number:_______________________
                  (PLEASE PRINT)
 
  Address:____________________________________________________________________
          (STREET ADDRESS, INCLUDING APARTMENT NUMBER -- PLEASE PRINT)
 
   __________________________________________________________________________
   (CITY)                          (STATE)                         (ZIP CODE)
 
- --------------------------------------------------------------------------------
 
                                       4

<PAGE>
            GUIDELINES FOR CERTIFICATION OF TAXPAYER IDENTIFICATION
                         NUMBER ON SUBSTITUTE FORM W-9
 
    GUIDELINES FOR DETERMINING THE PROPER IDENTIFICATION NUMBER TO GIVE THE
PAYER.--Social Security numbers have nine digits separated by two hyphens: i.e.,
000-00-0000. Employer identification numbers have nine digits separated by only
one hyphen: i.e., 00-0000000. The table below will help determine the number to
give the payer.
 
<TABLE>
<CAPTION>
FOR THIS TYPE OF ACCOUNT:                                         GIVE THE SOCIAL SECURITY NUMBER OF--
- ----------------------------------------------------------------  -----------------------------------------------------
<S>        <C>                                                    <C>
1.         An individual's account                                The individual
 
2.         Two or more individuals (joint account)                The actual owner of the account or, if combined
                                                                  funds, any one of the individuals(1)
 
3.         Husband and wife (joint account)                       The actual owner of the account or, if joint funds,
                                                                  either person(1)
 
4.         Custodian account of a minor (Uniform Gift to Minors   The minor(2)
           Act)
 
5.         Adult and minor (joint account)                        The adult or, if the minor is the only contributor,
                                                                  the minor(1)
 
6.         Account in the name of guardian or committee for a     The ward, minor or incompetent person(3)
           designated ward, minor or incompetent person
 
7.         a. The usual revocable savings trust account (grantor  The grantor-trustee(1)
           is also trustee)
           b. So-called trust account that is not a legal or      The actual owner(1)
           valid trust under State law
 
8.         Sole proprietorship                                    The owner(4)
 
9.         A valid trust, estate or pension trust                 The legal entity (Do not furnish the number of the
                                                                  personal representative or trustee unless the legal
                                                                  entity itself is not designated in the account
                                                                  title)(5)
 
10.        Corporate account                                      The corporation
 
11.        Religious, charitable or educational organization      The organization
           account
 
12.        Partnership account held in the name of the business   The partnership
 
13.        Association, club or other tax-exempt organization     The organization
 
14.        A broker or registered nominee                         The broker or nominee
 
15.        Account with the Department of Agriculture in the      The public entity
           name of a public entity (such as a state or local
           government, school district or prison) that receives
           agriculture program payments
</TABLE>
 
- ------------------------
 
(1) List first and circle the name of the person whose number you furnish.
 
(2) Circle the minor's name and furnish the minor's social security number.
 
(3) Circle the ward's, minor's or incompetent person's name and furnish such
    person's social security number.
 
(4) You must show your individual name, but you may also enter your business or
    "doing business as" name. You may use either your social security number or
    your employer identification number.
 
(5) List first and circle the name of the legal trust, estate or pension trust.
 
NOTE: If no name is circled when there is more than one name, the number will be
      considered to be that of the first name listed.
<PAGE>
OBTAINING A NUMBER
 
    If you don't have a taxpayer identification number or you do not know your
number, obtain Form SS-5, Application for a Social Security Number Card, or Form
SS-4, Application for Employer Identification Number, at the local office of the
Social Security Administration or the Internal Revenue Service and apply for a
number.
 
PAYEES EXEMPT FROM BACKUP WITHHOLDING
 
    Payees specifically exempted from backup withholding on ALL payments include
the following:
 
    - A corporation.
 
    - A financial institution.
 
    - An organization exempt from tax under section 501(a), of the Internal
      Revenue Code of 1986, as amended (the "Code"), or an individual retirement
      plan.
 
    - The United States or any agency or instrumentality thereof.
 
    - A State, the District of Columbia, a possession of the United States or
      any subdivision or instrumentality thereof.
 
    - A foreign government, a political subdivision of a foreign government or
      any agency or instrumentality thereof.
 
    - An international organization or any agency or instrumentality thereof.
 
    - A registered dealer in securities or commodities registered in the United
      States or a possession of the United States.
 
    - A real estate investment trust.
 
    - A common trust fund operated by a bank under section 584(a) of the Code.
 
    - An exempt charitable remainder trust, or a non-exempt trust described in
      section 4947(a)(1) of the Code.
 
    - An entity registered at all times under the Investment Company Act of
      1940.
 
    - A foreign central bank of issue.
 
PAYMENTS NOT GENERALLY SUBJECT TO BACKUP WITHHOLDING
 
    Payments of dividends and patronage dividends not generally subject to
backup withholding include the following:
 
    - Payments to nonresident aliens subject to withholding under section 1441
      of the Code.
 
    - Payments to partnerships not engaged in a trade or business in the United
      States and which have at least one nonresident partner.
 
    - Payments of patronage dividends where the amount received is not paid in
      money.
 
    - Payments made by certain foreign organizations.
 
    - Section 404(k) payments made by an ESOP.
 
    Payments of interest not generally subject to backup withholding include the
following:
 
    - Payments of interest on obligations issued by individuals. Note: A Payee
      may be subject to backup withholding if this interest is $600 or more and
      is paid in the course of the payer's trade or business and such payee has
      not provided its correct taxpayer identification number to the payer.
 
    - Payments of tax-exempt interest (including exempt-interest dividends under
      section 852 of the Code).
 
    - Payments described in section 6049(b)(5) of the Code to nonresident
      aliens.
 
    - Payments on tax-free covenant bonds under section 1451 of the Code.
 
    - Payments made by certain foreign organizations.
 
    - Mortgage interest paid to you.
 
EXEMPT PAYEES DESCRIBED ABOVE MUST STILL COMPLETE THE SUBSTITUTE FORM W-9 TO
AVOID POSSIBLE ERRONEOUS BACKUP WITHHOLDING. FILE SUBSTITUTE FORM W-9 WITH THE
PAYER, FURNISH YOUR TAXPAYER IDENTIFICATION NUMBER, WRITE "EXEMPT" ON THE FACE
OF THE FORM, AND RETURN IT TO THE PAYER. IF THE PAYMENTS ARE INTEREST, DIVIDENDS
OR PATRONAGE DIVIDENDS, ALSO SIGN AND DATE THE FORM.
 
    Certain payments other than interest, dividends and patronage dividends,
that are not subject to information reporting are also not subject to backup
withholding. For details, see the regulations under sections 6041, 6041A(a),
6045 and 6050A of the Code.
 
    PRIVACY ACT NOTICE.--Section 6109 of the Code requires most recipients of
dividends, interest or other payments to give taxpayer identification numbers to
payers who must report the payments to the IRS. The IRS uses the numbers for
identification purposes. Payers must be given the numbers whether or not
recipients are required to file tax returns. Payers must generally withhold 31%
of taxable interest, dividends, and certain other payments to a payee who does
not furnish a taxpayer identification number to a payer. Certain penalties may
also apply.
 
PENALTIES
 
(1) PENALTY FOR FAILURE TO FURNISH TAXPAYER IDENTIFICATION NUMBER. If you fail
    to furnish your taxpayer identification number to a payer, you are subject
    to a penalty of $50 for each such failure unless your failure is due to
    reasonable cause and not to willful neglect.
 
(2) CIVIL PENALTY FOR FALSE INFORMATION WITH RESPECT TO WITHHOLDING. If you make
    a false statement with no reasonable basis that results in no imposition of
    backup withholding, you are subject to a penalty of $500.
 
(3) CRIMINAL PENALTY FOR FALSIFYING INFORMATION. Falsifying certifications or
    affirmations may subject you to criminal penalties including fines and/or
    imprisonment.
 
(4) FAILURE TO REPORT CERTAIN DIVIDEND AND INTEREST PAYMENTS. If you fail to
    include any portion of an includable payment for interest, dividends or
    patronage dividends in gross income and such failure is due to negligence, a
    penalty of 20% is imposed on any portion of an underpayment attributable to
    that failure.
 
FOR ADDITIONAL INFORMATION, CONTACT YOUR TAX CONSULTANT OR THE INTERNAL REVENUE
SERVICE.

<PAGE>

THIS ANNOUNCEMENT IS NEITHER AN OFFER TO PURCHASE NOR A SOLICITATION OF AN 
OFFER TO SELL SHARES. THE OFFER IS MADE SOLELY BY THE OFFER TO PURCHASE DATED 
SEPTEMBER 4, 1998 AND THE RELATED LETTER OF TRANSMITTAL, AND IS BEING MADE TO 
ALL HOLDERS OF SHARES, EXCEPT IN ANY JURISDICTION WHERE THE MAKING OF SUCH 
WOULD BE ILLEGAL. THE PURCHASER IS NOT AWARE OF ANY STATE IN WHICH THE MAKING 
OF THE OFFER IS PROHIBITED BY ADMINISTRATIVE OR JUDICIAL ACTION PURSUANT TO A 
STATE STATUTE. IF THE PURCHASER BECOMES AWARE OF ANY STATE WHERE THE MAKING 
OF THE OFFER IS SO PROHIBITED, THE PURCHASER WILL MAKE A GOOD FAITH EFFORT TO 
COMPLY WITH ANY SUCH STATUTE OR SEEK TO HAVE SUCH STATUTE DECLARED 
INAPPLICABLE TO THE OFFER. IF, AFTER SUCH GOOD FAITH EFFORT, THE PURCHASER 
CANNOT COMPLY WITH ANY APPLICABLE STATUTE, THE OFFER WILL NOT BE MADE TO (NOR 
WILL TENDERS BE ACCEPTED FROM OR ON BEHALF OF) HOLDERS OF SHARES IN SUCH 
STATE. IN ANY JURISDICTIONS, THE SECURITIES LAWS OR BLUE SKY LAWS OF WHICH 
REQUIRE THE OFFER TO BE MADE BY A LICENSED BROKER OR DEALER, THE OFFER SHALL 
BE DEEMED TO BE MADE ON BEHALF OF THE PURCHASER, IF AT ALL, BY SALOMON SMITH 
BARNEY INC. OR ONE OR MORE REGISTERED BROKERS OR DEALERS LICENSED  UNDER THE 
LAWS OF SUCH JURISDICTION.

                   NOTICE OF OFFER TO PURCHASE FOR CASH
                  ALL OUTSTANDING SHARES OF COMMON STOCK
        (INCLUDING THE ASSOCIATED PREFERRED STOCK PURCHASE RIGHTS)

                                  OF

                          MYCOGEN CORPORATION
                                  AT
                           $28.00 NET PER SHARE
                                  BY
                        AGROSCIENCES ACQUISITION INC.
                       A MAJORITY-OWNED SUBSIDIARY OF
                          DOW AGROSCIENCES LLC
                   AND A WHOLLY-OWNED INDIRECT SUBSIDIARY
                         OF THE DOW CHEMICAL COMPANY

AgroSciences Acquisition Inc., a Delaware corporation (the "Purchaser") which 
is a majority-owned subsidiary of Dow AgroSciences LLC, a Delaware limited 
liability company ("Parent") and a wholly-owned indirect subsidiary of The 
Dow Chemical Company, a Delaware corporation ("TDCC"), is offering to 
purchase any and all shares of common stock, $0.001 par value per share 
(including the associated preferred stock purchase rights) (the "Shares"), of 
Mycogen Corporation, a California corporation (the "Company"), at $28.00 per 
Share (the "Offer Price"), net to the seller in cash, without interest 
thereon, upon the terms and subject to the conditions set forth in the Offer 
to Purchase dated September 4, 1998 (the "Offer to Purchase") and in the 
related Letter of Transmittal (which, together, constitute the "Offer").

- -------------------------------------------------------------------------------
THE OFFER AND WITHDRAWAL RIGHTS WILL EXPIRE AT 12:00 MIDNIGHT, NEW YORK CITY 
TIME, ON FRIDAY, OCTOBER 2, 1998 (THE "EXPIRATION DATE"), UNLESS THE OFFER IS 
EXTENDED.
- -------------------------------------------------------------------------------
      The Offer is conditioned upon, among other things, there being validly 
tendered and not properly withdrawn prior to the expiration of the Offer a 
number of Shares such that, upon purchase of such Shares by Purchaser, 
Purchaser and Parent, collectively, will be the owners of Shares representing 
at least 90% of the Fully Diluted Shares (as defined below) (the "Minimum 
Condition"). Purchaser may waive the Minimum Condition if the Special 
Committee consents or if, following the consummation of the Offer, Purchaser 
and Parent, collectively, would be the owners of Shares representing at least 
81.07% of the Fully Diluted Shares. Parent and Purchaser would collectively 
own at least this percentage of Fully Diluted Shares only if Purchaser 
purchased at least a majority of the Fully Diluted Shares which Parent does 
not already own and therefore could be purchased by Purchaser pursuant to the 
Offer. "Fully Diluted Shares" as of a particular date means the issued and 
outstanding Shares as of such date, plus the Shares that would be issued if 
all options to purchase Shares under the Company's option plan (whether or 
not vested) outstanding as of that date were exercised and all Shares that 
would be issued if all eligible persons executed and delivered valid Stock 
Purchase Elections (as defined in Section 10 of the Offer to Purchase) under 
the Company's Stock Purchase Plan to the Company. Certain other conditions to 
the Offer are described in "The Tender Offer--13. Certain Conditions of the 
Offer" in the Offer to Purchase.

      The Offer is being made in connection with an Agreement and Plan of 
Merger (the "Merger Agreement") dated as of August 31, 1998, among the 
Company, Purchaser, Parent and, for the limited purpose set forth therein, 
TDCC.  The Merger Agreement provides that, among other things, as soon as 
practicable after the purchase of Shares pursuant to the Offer, if Purchaser 
and Parent collectively own at least 90% of the outstanding Shares and if the 
other conditions set forth in the Merger Agreement are satisfied, in 
accordance with the California General Corporation Law ("California Law") and 
the Delaware General Corporation Law, Parent will cause Purchaser to become 
the beneficial and record owner of all Shares 

<PAGE>

then owned of record by Parent, Purchaser will be merged with and into the 
Company (the "Merger") and the Company will be the surviving corporation.  As 
a result of the Merger, the Company will become a wholly-owned indirect 
subsidiary of TDCC and, other than Shares held by Parent, Purchaser or the 
Company or by stockholders who shall have demanded and perfected appraisal 
rights under California Law, will be canceled and converted into the right to 
receive an amount in cash equal to the Offer Price.  If, after Purchaser 
purchases Shares pursuant to the Offer, Purchaser and Parent do not 
collectively own at least 90% of the outstanding Shares, Purchaser will be 
unable to effect the Merger under California Law and Purchaser will not be 
obligated to do so pursuant to the Merger Agreement.

      A Special Committee of the Company's directors independent of TDCC, 
Parent, Purchaser or the Company's management (the "Special Committee"), 
unanimously recommended to the Company's Board of Directors that it enter 
into the Merger Agreement and approve the Offer. The Company's Board of 
Directors unanimously has approved the Offer and recommends that stockholders 
of the Company accept the Offer and tender their Shares. See "Recommendation 
of the Company's Board of Directors" in the Offer to Purchase.

      For purposes of the Offer, the Purchaser will be deemed to have 
accepted for payment, and thereby purchased, Shares validly tendered and not 
validly withdrawn, as, if and when the Purchaser gives oral or written notice 
to BankBoston, N.A. (the "Depositary") of the Purchaser's acceptance of such 
Shares for payment pursuant to the Offer. In all cases, upon the terms and 
subject to the conditions of the Offer, payment for Shares purchased pursuant 
to the Offer will be made by deposit of the purchase price therefor with the 
Depositary, which will act as agent for tendering stockholders for the 
purpose of receiving payments from the Purchaser and transmitting such 
payments to validly tendering stockholders. Under no circumstances will 
interest on the purchase price for Shares be paid by the Purchaser by reason 
of any delay in making such payment. In all cases (except as provided in the 
Offer to Purchase), payment for Shares accepted for payment pursuant to the 
Offer will be made only after timely receipt by the Depositary of (a) 
certificates for such Shares ("Share Certificates") or timely confirmation of 
the book-entry transfer of such Shares into the Depositary's account at The 
Depository Trust Company (the "Book-Entry Transfer Facility"), pursuant to 
the procedures set forth in "The Tender Offer--Section 3. Procedures for 
Tendering Shares" in the Offer to Purchase, (b) the Letter of Transmittal (or 
facsimile thereof) properly completed and duly executed with any required 
signature guarantees (or, alternatively, an Agent's Message as set forth in 
the Offer to Purchase) and (c) any other documents required by the Letter of 
Transmittal.

      The term "Expiration Date" means 12:00 Midnight, New York City time, on 
Friday, October 2, 1998, unless and until the Purchaser shall have extended 
the period of time for which the Offer is open in which event the term 
"Expiration Date" shall mean the latest time and date at which the Offer, as 
so extended by the Purchaser, shall expire. The Purchaser expressly reserves 
the right, under the circumstances described in the Offer to Purchase, to 
extend the period during which the Offer is open by giving oral or written 
notice of such extension to the Depositary, followed as promptly as 
practicable by public announcement no later than 9:00 A.M., New York City 
time, on the next business day after the previously scheduled Expiration 
Date. During any such extension, all Shares previously tendered and not 
withdrawn will remain subject to the Offer, subject to the right of tendering 
shareholders to withdraw such stockholder's Shares.

      The Purchaser's acceptance for payment of Shares tendered pursuant to 
any one of the procedures described in the Offer to Purchase and in the 
Letter of Transmittal will constitute a binding agreement between the 
tendering stockholder and the Purchaser upon the terms and subject to the 
conditions of the Offer. Except as otherwise provided in "The Tender 
Offer--Section 4. Withdrawal Rights; Statutory Rights" in the Offer to 
Purchase, tenders of Shares made pursuant to the Offer are irrevocable. 
Shares tendered pursuant to the Offer may be withdrawn at any time on or 
prior to the Expiration Date and, unless theretofore accepted for payment as 
provided herein, may also be withdrawn after November 2, 1998. For a 
withdrawal to be effective, a written or facsimile transmission notice of 
withdrawal must be timely received by the Depositary at one of its addresses 
set forth on the back cover of the Offer to Purchase. Any such notice of 
withdrawal must specify the name of the person who tendered the Shares to be 
withdrawn, the number of shares to be withdrawn and if Share Certificates 
have been tendered, the name of the registered holder of the Shares as set 
forth in the Share Certificate, if different from that of the person who 
tendered such Shares. If Share Certificates have been delivered or otherwise 
identified to the Depositary, then prior to the physical release of such 
certificates, the tendering shareholder must submit the serial numbers shown 
on the particular certificates evidencing the Shares to be withdrawn and the 
signature on the notice of withdrawal must be guaranteed by an Eligible 
Institution (as defined in the Offer to Purchase), except in the case of 
Shares tendered for the account of an Eligible Institution. If Shares have 
been tendered pursuant to the procedures for book-entry transfer as set forth 
in "The Tender Offer--Section 3. Procedure for Tendering Shares" in the Offer 
to Purchase, the notice of withdrawal must specify the name and number of the 
account at the appropriate Book-Entry Transfer Facility to be credited with 
the withdrawn Shares, in which case a notice of withdrawal will be effective 
if a written or facsimile transmission notice of withdrawal is timely 
received by the Depositary at one of its addresses set forth on the back 
cover of the Offer to Purchase. Withdrawals of Shares may not be rescinded. 
Any Shares properly withdrawn will be deemed not validly tendered for 
purposes of the Offer, but may be retendered at any subsequent time prior to 
the Expiration Date by following any of the procedures described in "The 
Tender Offer--Section 3. Procedure for Tendering Shares" in the Offer to 
Purchase. All questions as to the form and validity (including time of 
receipt) of any notices of withdrawal will be determined by the Purchaser, in 
its sole discretion, whose determination will be final and binding.

      The information required to be disclosed by Rule 14d-6(e)(1) of the 
General Rules and Regulations under the Securities Exchange Act of 1934, as 
amended, is contained in the Offer to Purchase and is incorporated herein by 
reference.

      The Company has provided the Company's stockholder list and security 
position listings to the Purchaser for the purpose of disseminating the Offer 
to stockholders. The Offer to Purchase and the related Letter of Transmittal 
and, if required, other relevant materials will be mailed to stockholders 
whose names appear on the Company's stockholder list and will be furnished 
for subsequent transmittal to beneficial owners of Shares, to brokers, 
dealers, commercial banks, trust companies and similar persons whose names, 
or the names of whose nominees, appear on the shareholder list or, if 
applicable, who are listed as participants in a clearing agency's security 
listing.

                                      -2-
<PAGE>

      Stockholders are urged to read the Offer to Purchase and the related 
Letter oF Transmittal carefully before deciding whether to tender their 
Shares.

      Questions and requests for assistance may be directed to the 
Information Agent or the Dealer Manager at the addresses and telephone 
numbers set forth below. Requests for copies of the Offer to Purchase and the 
related Letter of Transmittal and other tender Offer materials may be 
directed to the Information Agent, the Dealer Manager or brokers, dealers, 
commercial banks and trust companies and such materials will be furnished 
promptly at the Purchaser's expense. The Purchaser will not pay any fees or 
commissions to brokers, dealers, or other persons (other than the Information 
Agent and the Dealer Manager) for soliciting tenders of Shares pursuant to 
the Offer.
                                    
                 THE INFORMATION AGENT FOR THE OFFER IS:
                                    
                                GEORGESON
                             & COMPANY INC.

                         --------------------- 


                            Wall Street Plaza
                         New York, New York 10005

                BANKS AND BROKERS CALL COLLECT (212) 440-9800
                  ALL OTHERS CALL TOLL FREE (800) 223-2064


                   THE DEALER MANAGER FOR THE OFFER IS:

                        SALOMON SMITH BARNEY INC.
                                    
                        Seven World Trade Center
                        New York, New York 10048

September 4, 1998

                                   -3-

<PAGE>


MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA 92101
Telephone:  619/231-1058

ABBEY, GARDY & SQUITIERI, LLP
MARK C. GARDY
JAMES S. NOTIS
212 East 39th Street
New York, NY 10016
Telephone:  212/889-3700

Attorneys for Plaintiff

                   SUPERIOR COURT OF THE STATE OF CALIFORNIA
                             COUNTY OF SAN DIEGO

LESLIE SUSSER, On Behalf of Himself   )  Case No.
and All Others Similarly Situated,    )
                                      )  CLASS ACTION
                    Plaintiff,        )
                                      )  COMPLAINT BASED UPON UNFAIR
     vs.                              )  BUSINESS PRACTICES, SELF
                                      )  DEALING AND BREACH OF
MYCOGEN CORPORATION, J. PEDRO         )  FIDUCIARY DUTY
REINHARD, CARLTON J. EIBL, JOHN L.    )
HAGAMAN, JOSEPH P. SULLIVAN, ROY M.   )
BARBEE, GEORGE KHACHATOURIANS,        )
NICKOLAS D. HEIN, G. WILLIAM          )
TOLBERT, LOUIS W. PRIBILA, DOW        )
CHEMICAL COMPANY and DOES 1-25,       )
inclusive,                            )
                                      )
                    Defendants.       )  Plaintiff Demands A
                                      )  Trial By Jury
- ------------------------------------- )  -------------------


<PAGE>

     Plaintiff. by his name attorneys, alleges upon information and belief, 
except as to PARA4 which plaintiff alleges upon knowledge, as follows:

                          JURISDICTION AND VENUE

     1. This Court has jurisdiction over all causes of action asserted herein 
pursuant to the California Constitution, Article XL, Section 10, because this 
case is a cause not given by statute to other trial courts.

     2. This court has jurisdiction over Mycogen because this defendant is a 
California corporation with its principal place of business at 5501 Oberlin 
Drive, San Diego, California.

     3. Venue is proper in this Court because the conduct at issue took place 
and had an effect in this County and defendants made misrepresentations which 
had an effect in this County.

                                  PARTIES

     4. Plaintiff Leslie Susser is a stockholder of defendant Mycogen 
Corporation ("Mycogen" or the "Company").

     5. Defendant Mycogen is a corporation duly organized and existing under 
the laws of the state of California, with its principal offices located at 
5501 Oberlin Drive, San Diego, California 92121. Mycogen develops, 
manufactures and markets biopesticides as alternatives to chemical pesticides 
to control a variety of insects, weeds and parasitic worms. As of April 7, 
1998, there were over 36 million shares of Mycogen common stock outstanding.

     6. Defendant Dow Chemical Company ("Dow") is a corporation duly 
organized and existing under the laws of the State of Delaware with its 
principal offices located at 2030 Dow Center, Midland,



                                  1
<PAGE>

Michigan 48674.  Dow is the fifth largest chemical company in the world, with 
annual sales of more than $20 billion.  Dow manufactures and supplies 
chemicals, plastics, energy, agricultural products, consumer goods and 
environmental services.  Through its wholly-owned subsidiary, Dow 
Agrosciences, LLC ("Dow Agrosciences"), Dow owns or controls shares 
representing approximately 69 percent of the outstanding common stock of 
Mycogen.

     7.  Defendant J. Pedro Reinhard is a Director of Mycogen and the Chief 
Financial Officer and Executive Vice President of Dow Agrosciences.

     8.  Defendant Charles J. Eibl is the President of Mycogen and a member 
of its Board of Directors.

     9.  Defendant John L. Hagaman is a Director of Mycogen and the President 
of Dow Agrosciences.

     10.  Defendant Joseph P. Sullivan is a Director of Mycogen.

     11.  Defendant Roy M. Barbee is a Director of Mycogen.

     12.  Defendant George Khachatourians is a Director of Mycogen.

     13.  Defendant Nickolas D. Hein is a Chairman of Mycogen's Board of 
Directors and a Vice President of "Global Growth" for Dow Agrosciences.

     14.  Defendant G. William Tolbert is a Director of Mycogen and a "Global 
Business Development Director" for Dow Agrosciences.

     15.  Defendant Louis W. Pribila is a Director of Mycogen and the 
Secretary, General Counsel and Vice President of Dow Agrosciences.

     16.  The Defendants named in PARAs 7 through 15 are sometimes 
collectively referred to herein as the "Individual Defendants."



                                      2
<PAGE>


     17.  The true names and capacities of defendants sued herein under 
California Code of Civil Procedure Section 474 as Does 1 through 25, 
inclusive, are presently not known to plaintiff, who therefore sues these 
defendants by such fictitious names.  Plaintiff will seek to amend this 
Complaint and include these Doe defendants' true names and capacities when 
they are ascertained.  Each of the fictitiously named defendants is 
responsible in some manner for the conduct alleged herein and for the 
injuries suffered by the Class.

     18.  The Individual Defendants as officers and/or directors of Mycogen 
have a fiduciary relationship and responsibility to plaintiff and the other 
common public stockholders of Mycogen and owe to plaintiff the other class 
members the highest obligations of good faith, loyalty, fair dealing, due care
and candor.

                         CLASS ACTION ALLEGATIONS

     19.  Plaintiff brings this action pursuant to Section 382 of the 
California Code of Civil Procedure on his own behalf and as a class action on 
behalf of all common stockholders of Mycogen, or their successors in 
interest, who are being and will be harmed by defendants' actions described 
below (the "Class").  Excluded from the Class are defendants herein and any 
person, firm, trust, corporation, or other entity related to or affiliated 
with any of the defendants.

     20.  This action is properly maintainable as a class action because:

          (a)  The Class is so numerous that joinder of all members is 
impracticable.  There are hundreds of Mycogen stockholders of record who are 
located throughout the United States; 


                                  3
            
<PAGE>


          (b)  There are questions of law and fact which are common to the 
Class, including:  whether the defendants have engaged or are continuing to 
act in a manner calculated to benefit themselves at the expense of Mycogen's 
minority stockholders;  and whether plaintiff and the other members of the 
Class would be irreparably damaged if the defendants are not enjoined in the 
manner described below;

          (c)  The defendants have acted or refused to act on grounds 
generally applicable to the Class, thereby making appropriate final 
injunctive relief with respect to the Class as a whole;

          (d)  Plaintiff is committed to prosecuting this action and has 
retained competent counsel experienced in litigation of this nature.  The 
claims of plaintiff are typical of the claims of the other members of the 
Class and plaintiff has the same interests as the other members of the Class. 
Accordingly, plaintiff is an adequate representative of the Class and will 
fairly and adequately protect the interests of the Class; and

          (e)  Plaintiff anticipates that there will be no difficulty in the 
management of this litigation as a class action.

     21.  For the reasons stated herein, a class action is superior to other 
available methods for the fair and efficient adjudication of this controversy.

                           CLAIM FOR RELIEF

     22.  Mycogen is a California corporation that develops, manufactures and 
markets biopesticides as alternatives to chemical pesticides to control a 
variety of insects, weeds and parasitic worms.  The Company's products are 
based on natural agents that are 

                                 4


<PAGE>

compatible with the environment and are developed through genetic engineering 
technology and innovative formulations.
  
     23. Dow currently owns or controls approximately 69 percent of the 
outstanding common stock of Mycogen. Under the terms of a prior agreement 
with Mycogen (the "Agreement"), Dow cannot acquire the remaining shares of 
Mycogen before February 1999.

     24. After the close of trading on April 30, 1998, it was reported that 
Dow, through Dow Argosciences, requested an amendment to the Agreement to 
permit it to begin discussions regarding the acquisition of the remaining 
shares of Mycogen common stock it does not already own for $20.50 per share 
in cash.

     25. As set forth above, Mycogen has 9 board members whose loyalties are,
at best, divided in the instant transaction and cannot be expected to act 
in the best interest of Mycogen's minority stockholders.

     26. The purpose of the proposed acquisition is to enable Dow to acquire 
the shares of Mycogen it does not already own, as well as Mycogen's valuable 
assets, for Dow's own benefit at the expense of Mycogen's minority 
stockholders.

     27. The proposed acquisition comes at a time when Mycogen has performed 
well and Dow expects it will continue to perform well because it is already 
well positioned to do so.

     28. Dow has timed this transaction to capture Mycogen's future potential 
and use it to its own ends without paying an adequate or fair price for the 
Company's remaining shares.

     29. Amidst this backdrop of positive and improving financial position 
and increased prospects for growth, Dow announced its desire to acquire the 
remaining shares of Mycogen for $20.50 cash



                                  5
<PAGE>

per share. The offer made by Dow represents no premium over the current price 
of Mycogen common stock. In fact, prior to Dow's announcement on April 30, 
1998, the price of Mycogen common stock closed at $20.625 per share -- higher 
than the price offered by Dow in the proposed acquisition.

     30. The Individual Defendants and Dow are in a position of control and 
power over Mycogen's stockholders and have access to internal financial 
information about Mycogen, its true value, expected increase in true value 
and the benefits to Dow of 100 percent ownership of Mycogen to which 
plaintiff and the Class members are not privy. Defendants are using their 
positions of power and control to benefit Dow in this transaction, to the 
detriment of the Mycogen common stockholders.

     31. In proposing the aquisition, Dow and the Individual Defendants have 
committed or threatened to commit the following acts to the detriment and 
disadvantage of Mycogen minority stockholders:

         (a) They have undervalued Mycogen's common stock by ignoring the full
value of its assets and future prospects. The proposed acquisition 
consideration does not reflect the value of Mycogen's valuable assets; and

         (b) They timed the announcement of the proposed buyout to place an 
artificial lid on the market price of Mycogen's common stock to justify a 
price that is unfair to Mycogen's minority stockholders.
 
     32. The Individual Defendants have clear and material conflicts of 
interest and are acting to better the interests of Dow and themselves at the 
expense of Mycogen's minority stockholders.



                                  6
<PAGE>

     33.  In light of the foregoing, the Individual Defendants must, as their 
fiduciary obligations require:

     -    undertake an appropriate evaluation of Mycogen's worth as an 
          acquisition candidate;

     -    act independently so that the interests of Mycogen's minority 
          stockholders will be protected, including but not limited to the 
          retention of independent advisors and the appointment of a Special 
          Committee of some or all of the members of the Mycogen's board to 
          consider the Dow offer and negotiate with Dow on behalf of 
          Mycogen's minority stockholders;

     -    adequately ensure that no conflicts of interest exist between 
          defendants' own interests and their fiduciary obligation to 
          maximize stockholder value or, if such conflicts exist, to ensure 
          that all conflicts be resolved in the best interests of Mycogen's 
          minority stockholders; and

     -    if an acquisition transaction is to go forward, require that it be 
          approved by a majority of Mycogen's minority stockholders.

     34.  As a result of the defendants' failure to take such steps to date, 
plaintiff and the other members of the Class have been and will be damaged in 
that they have not and will not receive their proportionate share of the 
value of the Company's assets and business, and have been and will be 
prevented from obtaining a fair price for their common stock.

     35.  Defendants, in failing to disclose the material non-public 
information in their possession as to the value of Mycogen's assets, the full 
extent of the future earnings potential of Mycogen and its expected increase 
in profitability, are engaging in self-dealing, are not acting in good faith 
toward plaintiff and the other members of the Class, and have breached and 
are breaching their fiduciary duties to the member of the Class.

     36.  As a result of the defendants' unlawful actions, plaintiff and the 
other members of the Class will be irreparably


                                       7 

<PAGE>

harmed in that they will not receive their fair portion of the value of 
Mycogen's assets and business and will be prevented from obtaining the real 
value of their equity ownership of the Company.  Unless the proposed 
acquisition is enjoined by the Court, defendants will continue to breach 
their fiduciary duties owed to plaintiff and the members of the Class, will 
not engage in arm's-length negotiations on the acquisition terms, and will 
not supply to Mycogen's minority stockholders sufficient information to 
enable them to cast informed votes on the proposed acquisition and may 
consummate the proposed acquisition, all to the irreparable harm of the 
members of the Class.

     37.  Plaintiff and other members of the Class have no adequate remedy at 
law.
                             PRAYER FOR RELIEF

     WHEREFORE, plaintiff prays for judgment and relief as follows:

     1.  Ordering that this action may be maintained as a class action and 
certifying plaintiff as the Class representative;

     2.  Declaring that defendants have breached their fiduciary and other 
duties to plaintiff and other members of the Class;

     3.  Entering an order requiring defendants to take the steps set forth 
hereinabove;

     4.  Preliminarily and permanently enjoining the defendants and their 
counsel, agents, employees and all persons acting under, in concert with, or 
for them, from proceeding with, consummating or closing the proposed 
transaction;

     5.  In the event the proposed acquisition is consummated, rescinding it 
and setting it aside;


                                      8
<PAGE>

     6.  Awarding compensatory damages against defendants individually and 
severally in an amount to be determined at trial, together with prejudgment 
interest at the maximum rate allowable by law;

     7.  Awarding costs and disbursements, including plaintiff's counsel's 
fees and experts' fees; and

     8.  Granting such other and further relief as to the Court may seem 
just and proper.

DATED:  May 1, 1998                  MILBERG WEISS BERSHAD
                                      HYNES & LERACH LLP
                                     WILLIAM S. LERACH
                                     ALAN SCHULMAN
                                     DARREN J. ROBBINS


                                         /s/ Alan Schulman
                                     -----------------------------------
                                             ALAN SCHULMAN

                                     600 West Broadway, Suite 1800
                                     San Diego, CA 92101
                                     Telephone: 619/231-1058

                                     ABBEY, GARDY & SQUITIERI, LLP
                                     MARK C. GARDY
                                     JAMES S. NOTIS
                                     212 East 39th Street
                                     New York, NY 10016
                                     Telephone: 212/889-3700

                                     Attorneys for Plaintiff



                                      9 

<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA 92101
Telephone:  619/231-1058

ABBEY, GARDY & SQUITIERI, LLP
MARK C. GARDY
JAMES S. NOTIS
212 East 39th Street
New York, NY 10016
Telephone:  212/889-3700

Attorneys for Plaintiff

                   SUPERIOR COURT OF THE STATE OF CALIFORNIA
                             COUNTY OF SAN DIEGO

<TABLE>

<S>                                   <C>

LESLIE SUSSER, On Behalf of Himself   )  Case No. 720255
and All Others Similarly Situated,    )
                                      )  CLASS ACTION
                    Plaintiff,        )
                                      )  JURY DEMAND
     vs.                              )
                                      )
MYCOGEN CORPORATION, J. PEDRO         )
REINHARD, CARLTON J. EIBL, JOHN L.    )
HAGAMAN, JOSEPH P. SULLIVAN, ROY M.   )
BARBEE, GEORGE KHACHATOURIANS,        )
NICKOLAS D. HEIN, G. WILLIAM          )
TOLBERT, LOUIS W. PRIBILA, DOW        )
CHEMICAL COMPANY and DOES 1-25,       )
inclusive.                            )
                                      )
                    Defendants.       )
                                      )
- ------------------------------------- )

</TABLE>

<PAGE>

     Plaintiff demands a trial by jury.

DATED:  May 1, 1998                  MILBERG WEISS BERSHAD
                                      HYNES & LERACH LLP
                                     WILLIAM S. LERACH
                                     ALAN SCHULMAN
                                     DARREN J. ROBBINS


                                         /s/ Alan Schulman
                                     -----------------------------------
                                             ALAN SCHULMAN

                                     600 West Broadway, Suite 1800
                                     San Diego, CA 92101
                                     Telephone: 619/231-1058

                                     ABBEY, GARDY & SQUITIERI, LLP
                                     MARK C. GARDY
                                     JAMES S. NOTIS
                                     212 East 39th Street
                                     New York, NY 10016
                                     Telephone: 212/889-3700

                                     Attorneys for Plaintiff


                                       1


<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LEARCH (68581)
ALAN SCHULMAN (128661)
DAREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA 92101
Telephone:  619/231-1058

WECHSLER HARWOOD HALEBIAN
  & FEFFER LLP
SAMUEL K. ROSEN
488 Madison Avenue
8th Floor
New York, NY 10022
Telephone: 212/935-7400

Attorneys for Plaintiff

                   SUPERIOR COURT OF THE STATE OF CALIFORNIA
                             COUNTY OF SAN DIEGO

HARBOR FINANCE PARTNERS,              )  Case No. 720256
Individually and On Behalf of All     )
Others Similarly Situated,            )  CLASS ACTION
                    Plaintiff,        )
                                      )  COMPLAINT
     vs.                              )
                                      )
MYCOGEN CORPORATION, CARLTON J.       )
EIBL, JOHN L. HAGAMAN, NICKOLAS D.    )
HEIN, LOUIS W. PRIBILA, WILLIAM C.    )
SCHMIDT, G. WILLIAM TOLBERT, DOW      )
AGROSCIENCES and DOES 1-25,           )
inclusive,                            )
                                      )
                    Defendants.       )  Plaintiff Demands A
                                      )  Trial By Jury
- ------------------------------------- )  -------------------


<PAGE>

     Plaintiff, by its attorneys, for its class action complaint against 
defendants, makes the following allegations upon information and belief, 
except as to Paragraph 5, which is alleged upon knowledge.  Plaintiff's 
information and belief is based on, inter alia, investigation conducted by 
its attorneys, including review of documents filed with the Securities and 
Exchange Commission, articles in the financial news media, press releases, 
and other publicly available information.

                        JURISDICTION AND VENUE

     1.  This Court has jurisdiction over all causes of action asserted 
herein pursuant to the California Constitution, Article XL, Section 10, 
because this case is a cause not given by statute to other trial courts.

     2.  This Court has jurisdiction over Mycogen because this defendant is a 
California corporation with its principal place of business at 5501 Oberlin 
Drive, San Diego, California.

    3.  Venue is proper in this Court because the conduct at issue took place 
and had an effect in this County and defendants made misrepresentations which 
had an effect in this County.

    4.  Plaintiff brings this action individually and as a class action on 
behalf of all persons, other than defendants and persons or entities related 
to them, who own the common stock of Mycogen Corp. ("Mycogen" or the "Company") 
and thus are similarly situated (the "Class"), for injunctive and other 
relief.  Plaintiff seeks injunctive relief herein to, inter alia, enjoin the 
implementation of an inherently unfair transaction ("the Offer") whereby 
Mycogen's majority shareholder, Dow AgroSciences, formerly known as Dow 
Elanco ("DowAgro") -- which owns approximately 69% of the


                                     1
<PAGE>

outstanding common stock of Mycogen and controls the operations of the 
Company -- will acquire all of the remaining shares of the Company that it 
does not already own for a grossly inadequate price. Alternatively, in the 
event that the proposed transaction is implemented, plaintiff seeks to 
recover damages caused by the breach of fiduciary duties owned by defendants.

                            PARTIES

     5.  Plaintiff Harbor Finance is a Colorado partnership, and at all 
relevant times has been the owner of Mycogen common stock.

     6.  Defendant Mycogen is a California corporation that maintains its 
principal place of business at 5501 Oberlin Drive, San Diego, California. 
Mycogen's shares trade on the NASDAQ National Market System. Mycogen is a 
diversified agribusiness and biotechnology company that develops and markets 
seed for improved crop varieties and provides crop protection products.

     7.  Defendant DowAgro, an Indiana partnership, is a subsidiary of the 
Dow Chemical Company and presently owns or controls approximately 69% of 
Mycogen's outstanding stock.

     8.  Defendant Carlton J. Eibl ("Eibl") is and has been a director of the 
Company since January 1998. He is the Company's President.

     9.  Defendants John L. Hagaman, Nickolas D. Hein, Louis W. Pribila, 
William C. Schmidt, and G. William Tolbert are, and have at all relevant 
times, been directors of Mycogen. Each is, and has at all relevant times, 
been an officer of DowAgro.

     10. The true names and capacitates of defendants sued herein under 
California Code of Civil Procedure Section 474 as Does 1 through 25, 
inclusive, are presently not known to plaintiff, who therefore sues


                                    2 

<PAGE>

these defendants by such fictitious names. Plaintiff will seek to amend this 
Complaint and include these Doe defendants' true names and capacities when 
they are ascertained. Each of the fictitiously named defendants is 
responsible in some manner for the conduct alleged herein and for the 
injuries suffered by the Class.

     11.  By reason of its dominant position as the majority stockholder of 
Mycogen and its ability to control the business and corporate affairs of 
Mycogen at all relevant times, DowAgro owed and owes Mycogen stockholders 
fiduciary duties of fairness and trust, and was and is obligated to refrain 
from using its dominant position over Mycogen to enrich itself at the expense 
of other stockholders.

     12.  The individual director defendant, by reason of their corporate 
directorship and/or executive positions, stand in a fiduciary position 
relative to the Company's shareholders, which fiduciary relationship, at all 
times relevant herein, required the defendants to exercise their best 
judgment, and to act in a prudent manner and in the best interests of the 
Company's shareholders. A director is not permitted to act in his/her own 
self-interest to the detriment of the shareholders.

     13.  Each defendant herein is sued individually as a conspirator and 
aider and abettor, as well as in his/her capacity as an officer and/or 
director of the Company, and the liability of each arises from the fact that 
he or she has engaged in all or part of the unlawful acts, plans, schemes, or 
transactions complained of herein.


                                      3
<PAGE>

                          CLASS ACTION ALLEGATIONS

     14.  Plaintiff brings this action individually on its own behalf and as a
class action, pursuant to Section 382 of the California Civil Code of Civil 
Procedure on behalf of all stockholders of the Company (except the defendants 
herein and any person, firm, trust, corporation, or other entity related to 
or affiliated with any of the defendants) and their successors in interest, 
who are or will be threatened with injury arising from defendants' actions 
as more fully described herein (the "Class").

     15.  This action is properly maintainable as a class action.

     16.  The Class is so numerous that joinder of all members is 
impracticable. There are thousands of shareholders who hold the approximately 
31,000,000 shares of Mycogen common stock outstanding. The disposition of 
their claims in a class action will be of benefit to the parties and the 
Court. The record holders of Mycogen securities can be easily determined from 
the stock transfer journals maintained by Mycogen or its agents.

     17.  A class action is superior to other methods for the fair and 
efficient adjudication of the claims herein asserted, and no unusual 
difficulties are likely to be encountered in the management of this action as 
a class action. The likelihood of individual class members prosecuting 
separate claims is remote.

     18.  There is a well-defined community of interest in the questions of 
law and fact involved affecting the members of the Class. Among the questions 
of law and fact which are common to the Class, which predominate over 
questions affecting any individual class member are, inter alia, the 
following:


                                       4
<PAGE>

          (a)  whether defendants have engaged in conduct constituting unfair 
dealing by failing to maximize shareholder value through an adequate auction 
or market check process;

          (b)  whether the proposed buy-out is grossly unfair to the public 
stockholders of Mycogen;

          (c)  whether defendants have failed to disclose all material facts 
relating to the buy-out proposal including the potential and expected 
positive future financial benefits which they expect to derive from Mycogen;

          (d)  whether defendants have engaged and are continuing to engage in 
a plan and scheme to eliminate the public stockholders of Mycogen through 
fraudulent, deceptive, and coercive means and devices;

          (e)  whether defendants willfully and wrongfully failed or refused to 
obtain or attempt to obtain a purchaser for the assets of Mycogen at a price 
higher than the buy-out proposal;

          (f)  whether plaintiff and the other members of the Class would be 
irreparably damaged were the transaction complained of herein consummated;

          (g)  whether defendants have breached or aided and abetted the breach
of the fiduciary and other common law duties owed by them to plaintiff and the 
members of the Class;  and

          (h)  whether defendants are pursuing a scheme and course of business 
designed to eliminate the public stockholders of Mycogen in violation of the 
laws of the State of California.

     19.  Plaintiff is a member of the Class and is committed to prosecuting 
this action.  Plaintiff has retained competent counsel experienced in 
litigation of this nature.  The claims of the


                                      5

<PAGE>


plaintiff are typical of the claims of other members of the Class, and 
plaintiff has the same interests as the other members of the Class. Plaintiff 
does not have interests antagonistic to or in conflict with those it seeks to 
represent. Plaintiff is an adequate representative of the Class.

     20. The likelihood of individual class members prosecuting separate 
individual actions is remote due to the relatively small loss suffered by 
each Class member as compared to the burden and expense of prosecuting 
litigation of this nature and magnitude. Absent a class action, the 
defendants are likely to avoid liability for their wrongdoing, and Class 
members are unlikely to obtain redress for their wrongs alleged herein. 
There are no difficulties likely to be encountered in the management of the 
Class claims. This Court is an appropriate forum for this dispute.

                         SUBSTANTIVE ALLEGATIONS

     21. By the acts, transactions, and courses of conduct alleged herein, 
defendants, individually and as part of a common plan and scheme and/or 
aiding and abetting one another in total disregard of their fiduciary duties, 
are attempting to deceive plaintiff and the Class and deprive them unfairly 
of their investment in Mycogen.

     22. On April 30, 1998, Dow Chemical announced it wanted to amend an 
agreement (the "Agreement") dated January 15, 1996, pursuant to which DowAgro 
had already acquired 69% of Mycogen's shares of common stock. Under the terms 
of the Agreement, DowAgro cannot acquire all the remaining stock of Mycogen 
until February 1999. The amendment Dow Chemical seeks is the right to acquire 
the balance of Mycogen's shares now. The proposed transaction would provide 
Mycogen shareholders $20.50 cash, per share, exactly the




                                  6
<PAGE>

price at which Mycogen closed on the NASDAQ before the proposal was announced 
thus giving them no premium for their shares.

     23.  DowAgro is taking advantage of its majority stock ownership 
position in Mycogen by imposing the inadequate Offer on Mycogen's public 
stockholders. The Offer is being made at a time when, based upon DowAgro's 
inside knowledge and dominance and control of Mycogen, DowAgro can acquire 
the balance of Mycogen's shares at prices lower than it expects to pay in 
February 1999.

     24.  Under the terms of the Agreement, the remaining shares of Mycogen 
can only be bought  by DowAgro (then Dow Elanco) under the following terms:

      DowElanco may increase its beneficial ownership of Common Stock above 
      79.9% of the total outstanding shares only pursuant to a tender offer, 
      merger or similar transaction (but not a sale of assets) for all of the 
      outstanding shares of Common Stock that offers each holder of Common 
      Stock other than DowElanco the opportunity to dispose of some or all of 
      their Common Stock at the value that an unaffiliated third party would 
      be expected to pay in an arms' -length transaction negotiated by a 
      willing seller and a willing buyer for all of Mycogen's then 
      outstanding shares of Common Stock and not taking into account the 
      potentially controlling position of DowElanco (a "Buyout Transaction").

     25.  DowAgro announced the Offer during the period when the Agreement   
precludes its acquisition of the remainder of Mycogen's publicly traded 
shares of Mycogen because DowAgro believes that the price of Mycogen's shares 
will increase prior to February 1999 and wishes to acquire those shares at a 
lower price than it believes it will have to pay on that date.

     26.  Because of its position of dominance and control of Mycogen, 
DowAgro has announced the Offer at this time so that it can cap the price of 
Mycogen at no more than the approximate amount of the Offer, thereby limiting 
the price it will have to pay for


                                    7

<PAGE>

the balance of Mycogen's stock. By announcing the Offer now, DowAgro has 
locked in the offer price and avoided having to make a higher offer were 
Mycogen's stock, unaffected by the Offer, to rise between now and February 
1999.

     27. Besides being the largest stockholder of Mycogen, DowAgro has 5 of 
the 6 members on Mycogen's Board. Thus, DowAgro seeks, through its 
hand-picked Board for Mycogen, to acquire Mycogen's business, growth, and cash 
flow and squeeze out Mycogen's public stockholders at a price which is wholly 
inadequate.

     28. Even in light of what had been publicly disclosed about Mycogen's 
present business and future prospects, the Offer is grossly unfair, 
inadequate, and provides value to Mycogen's shareholders substantially below 
the fair or inherent value of the Company. The intrinsic value of the equity 
of Mycogen is materially greater than the consideration contemplated by the 
Offer price, taking into account Mycogen's pharmaceutical business, asset 
value, liquidation value, its expected growth, and its revenues and cash flow.

     29. The Offer is wrong, unfair, harmful to Mycogen's public 
stockholders, wholly inadequate, and will deny Class members their right to 
share proportionately in the true value of Mycogen's valuable assets, 
profitable business, and future growth in profits and earnings, while 
usurping the same for the benefit of defendants.

     30. The Offer is not the result of arm's-length negotiations but was 
fixed arbitrarily by DowAgro, which dominates and controls Mycogen, as part 
of its unlawful plan and scheme to obtain 100%



                                     8
<PAGE>

ownership of Mycogen at the lowest possible price and to usurp for itself 
Mycogen's profitable business.

     31.  Defendants have violated fiduciary and other common law duties owed 
to plaintiff and the other members of the Class in that it is using its 
dominant control position over Mycogen to enrich itself at the expense of 
Mycogen's other stockholders.

     32.  As a result of defendants' actions, plaintiff and the Class have 
been and will be damaged by breaches of fiduciary duty and, therefore, 
plaintiff and the Class will not receive the fair value of Mycogen's assets 
and businesses.

     33.  Unless enjoined by this Court, defendants will continue to breach 
their fiduciary duties owed to plaintiff and the Class, and will succeed in 
their plan to exclude plaintiff and the Class from the fair proportionate 
share of Mycogen's valuable assets and businesses, all to the irreparable 
harm of the Class.

     34.  Plaintiff and the Class have no adequate remedy of law.

                                    PRAYER FOR RELIEF

          WHEREFORE, plaintiff prays for judgment and relief as follows:

     1.   declaring that this lawsuit is properly maintainable as a class 
action and certifying plaintiff as representative of the Class;

     2.   declaring that the defendants and each of them have committed or 
aided and abetted a gross abuse of trust and have breached their fiduciary 
duties to plaintiff and the other members of the Class;

     3.  declaring the transaction to be a nullity;


                                     9

<PAGE>

     4.  preliminarily and permanently enjoining defendants and their counsel, 
agents, employees, and all persons acting under, in concert with, or for 
them, from proceeding with, consummating or closing the transaction;

     5.  in the event the transaction is consummated, rescinding it and 
setting it aside;

     6.  ordering defendants, jointly and severally, to account to plaintiff 
and the Class for all profits realized and to be realized by them as a result 
of the transaction complained of and, pending such accounting, to hold such 
profits in a constructive trust for the benefit of plaintiff and other 
members of the Class;

     7.  ordering defendants to permit a stockholders' committee comprising of 
class members and the representatives only to ensure a fair procedure, 
adequate procedural safe-guards, and independent input by plaintiff and the 
Class in connection with any transaction for the public shares of Mycogen;

     8.  awarding compensatory damages against defendants, jointly and 
severally, in an amount to be determined at trial, together with prejudgment 
interest at the maximum rate allowable by law;

     9.  awarding plaintiff and the Class their costs and disbursements and 
reasonable allowances for plaintiff's counsel and experts' fees and expenses; 
and



                                     10

<PAGE>


     10. granting such other and further relief as may be just and proper.

DATED:  May 1, 1998                  MILBERG WEISS BERSHAD
                                      HYNES & LERACH LLP
                                     WILLIAM S. LERACH
                                     ALAN SCHULMAN
                                     DARREN J. ROBBINS




                                     /S/ Alan Schulman
                                     -----------------------------------
                                             ALAN SCHULMAN

                                     600 West Broadway, Suite 1800
                                     San Diego, CA 92101
                                     Telephone: 619/231-1058

                                     WECHSLER HARWOOD HALEBIAN
                                      & FEFFER LLP
                                     SAMUEL K. ROSEN
                                     488 Madison Avenue
                                     8th Floor
                                     New York, NY 10022
                                     Telephone: 212/935-7400

                                     Attorneys for Plaintiff






                                     11
<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA 92101
Telephone:  619/231-1058

WECHSLER HARWOOD HALEBIAN
 & FEFFER LLP
SAMUEL K. ROSEN
488 Madison Avenue
8th Floor
New York, NY 10022
Telephone:  212/935-7400

Attorneys for Plaintiff

                   SUPERIOR COURT OF THE STATE OF CALIFORNIA
                             COUNTY OF SAN DIEGO

<TABLE>
<CAPTION>

<S>                                      <C>
HARBOR FINANCE PARTNERS,              )  Case No. 720256
Individually and On Behalf of All     )
Others Similarly Situated,            )  CLASS ACTION
                                      )
                    Plaintiff,        )
                                      )  JURY DEMAND
     vs.                              )
                                      )
MYCOGEN CORPORATION, CARLTON J.       )
EIBL, JOHN L. HAGAMAN, NICKOLAS D.    )
HEIN, LOUIS W. PRIBILA, WILLIAM C.    )
SCHMIDT, G. WILLIAM TOLBERT, DOW      )
AGROSCIENCES and DOES 1-25,           )
inclusive.                            )
                                      )
                    Defendants.       )
                                      )
- ------------------------------------- )




</TABLE>

<PAGE>


     Plaintiff demands a trial by jury.

DATED:  May 1, 1998                  MILBERG WEISS BERSHAD
                                      HYNES & LERACH LLP
                                     WILLIAM S. LERACH
                                     ALAN SCHULMAN
                                     DARREN J. ROBBINS




                                     /S/ Alan Schulman
                                     -----------------------------------
                                             ALAN SCHULMAN

                                     600 West Broadway, Suite 1800
                                     San Diego, CA 92101
                                     Telephone: 619/231-1058

                                     WECHSLER HARWOOD HALEBIAN
                                      & FEFFER LLP
                                     SAMUEL K. ROSEN
                                     488 Madison Avenue
                                     8th Floor
                                     New York, NY 10022
                                     Telephone: 212/935-7400

                                     Attorneys for Plaintiff



                                  2


<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA 92101
Telephone:  619/231-1058

BERNSTEIN LIEBHARD & LIFSHITZ
STANLEY D. BERNSTEIN
274 Madison Avenue
New York, NY 10016
Telephone:  212/779-1414

Attorneys for Plaintiff

                   SUPERIOR COURT OF THE STATE OF CALIFORNIA

                             COUNTY OF SAN DIEGO


ELLIS INVESTMENTS, LTD., On Behalf    )  Case No. 720257
of Itself and All Others Similarly    )
Situated,                             )  CLASS ACTION
                    Plaintiff,        )
                                      )  COMPLAINT FOR BREACHES OF
     vs.                              )  FIDUCIARY DUTIES
                                      )
CARLTON J. EIBL, PERRY J. GEHRING,    )
NICKOLAS D. HEIN, LOUIS W. PRIBILA,   )
WILLIAM C. SCHMIDT, G. WILLIAM        )
TOLBERT, MYCOGEN CORP., DOW           )
AGROSCIENCES LLC and DOES 1-25,       )
inclusive                             )
                                      )
                    Defendants.       )  Plaintiff Demands A
                                      )  Trial By Jury
- ------------------------------------- )  -------------------

<PAGE>

     Plaintiff, by its attorneys, for its complaint against defendants, 
alleges upon information and belief, except for paragraph 4 hereof, which is 
alleged upon knowledge, as follows:

 
                               JURISDICTION AND VENUE

     1.   This Court has jurisdiction over all causes of action asserted 
herein pursuant to the California Constitution, Article XL, Section 10, 
because this case is a cause not given by statute to other trial courts.

     2.   This Court has jurisdiction over Mycogen because this defendant is 
a California corporation with its principal place of business at 5501 
Oberlin Drive, San Diego, California.

     3.   Venue is proper in this Court because the conduct at issue took 
place and had an effect in this County and defendants made misrepresentations 
which had an effect in this County.

     4.   This Court has jurisdiction over all causes of action asserted 
herein pursuant to the California Constitution, Article XL, Section 10, 
because this case is a cause not given by statute to other trial courts.

     5.   This Court has jurisdiction over Mycogen because this defendant is 
a California corporation with its principal place of business at 5501 Oberlin 
Drive, San Diego, California.

     6.   Venue is proper in this Court because the conduct at issue took 
place and had an effect in this County and defendants made misrepresentations 
which had an effect in this County.


                                     PARTIES

     7.   Plaintiff Ellis Investments, Ltd. has been the owner of the common 
stock of the Mycogen Corp. ("Mycogen" or the "Company")


                                       1
<PAGE>

since prior to the transaction herein complained of and continuously to date.

     8.  Defendant Mycogen is a corporation duly organized and existing under 
the laws of the State of California and maintains its principal executive 
offices at 5501 Oberlin Drive, San Diego, California. The Company is a 
diversified agribusiness and biotechnology company that develops and markets 
seed for improved crop varieties and provides crop protection products and 
services.

     9.  Defendant Dow AgroSciences LLC ("Dow AG") is a wholly owned 
subsidiary of the Dow Chemical Company which maintains its principal offices 
at 2030 Dow Center, Midland, Michigan. Dow AG owns or controls approximately 
69% of Mycogen.

     10.  Defendant Nickolas D. Hein is Chairman of the Board of Directors of 
Mycogen.

     11.  Defendant Carlton J. Eibl is President and a Director of Mycogen.

     12.  Defendant Perry J. Gehring is a Director of Mycogen and a Vice 
President of Dow AG.

     13.  Defendant Louis W. Pribila is a Director of Mycogen and a Vice 
President and General Counsel of Dow AG.

     14.  Defendant William C. Schmidt is a Director of Mycogen and Vice 
President and Chief Financial Officer of Dow AG.

     15.  Defendant G. William Tolbert is a Director of Mycogen and a 
Director of Dow AG.

     16.  The Individual Defendants named in paragraphs 7 through 12 are 
controlled by Dow AG and are in a fiduciary relationship with plaintiff and 
the other public stockholders of Mycogen and owe them the highest obligations 
of good faith and fair dealing.

                                      2 

     
<PAGE>

     17. The true names and capacitates of defendants sued herein under 
California Code of Civil Procedure  Section 474 as Does 1 through 25, 
inclusive, are presently not known to plaintiff, who therefore sues these 
defendants by such fictitious names. Plaintiff will seek to amend this 
Complaint and include these Doe defendants' true names and capacities when 
they are ascertained. Each of the fictitiously named defendants is 
responsible in some manner for the conduct alleged herein and for the 
injuries suffered by the Class.

     18. Each defendant herein is sued individually as a conspirator and aider 
and abbetor, as well as in his capacity as an officer and/or director of the 
Company (in the case of the Individual Defendants), or as a control person, 
and the liability of each arises from the fact that he or it has engaged in 
all or part of the unlawful acts, plans, schemes, or transactions complained 
of herein.

                                 CLASS ACTION ALLEGATIONS
                                 ------------------------

     19. Plaintiff brings this action on its own behalf and as a class 
action, pursuant to Section 382 of the California Code of Civil Procedure, on 
behalf of all common stockholders of the Company (except the defendants 
herein and any person, firm, trust, corporation or other entity related to or 
affiliated with any of the defendants) and their successors in interest, who
are or will be threatened with injury arising from defendants' actions as 
more fully described herein (the "Class").

     20. This action is properly maintainable as a class action.

     21. The Class is so numerous that joinder of all members is 
impracticable. As of November 25,1997, there were in excess of 


                                        3

<PAGE>

31.4 million shares of Mycogen common stock outstanding, of which 
approximately 31% were held by persons not affiliated with Dow AG.

     22.   There are questions of law and fact which are common to the Class 
and which predominate over questions affecting any individual Class member. 
The common questions include, inter alia, the following: (a) whether 
defendants have breached their fiduciary and other common law duties owed by 
them to plaintiff and the members of the Class; (b) whether defendants are 
pursing a scheme or course of conduct designed to eliminate the public 
securities holders of Mycogen in violation of the laws of the State of 
California in order to enrich Dow AG at the expense and to the detriment of 
the public shareholders of Mycogen; (c) whether the proposed transaction, 
hereinafter described, constitutes a breach of the duty of fair dealing with 
respect to the plaintiff and the other members of the Class; and (d) whether 
the Class is entitled to injunctive relief or damages as a result of the 
wrongful conduct committed by defendants.

     23.   Plaintiff is committed to prosecuting this action and has retained 
competent counsel experienced in litigation of this nature. The claims of the 
plaintiff are typical of the claims of other members of the Class, and 
plaintiff has the same interests as  the other members the Class. Plaintiff 
will fairly and adequately represent the Class. A class action is superior to 
any other type of adjudication of this controversy.

     24.   Defendants have acted in a manner which affects plaintiff and all 
members of the Class, thereby making appropriate injunctive relief and/or 
corresponding declaratory relief with respect to the Class as a whole.



                                  4
<PAGE>

     25.   The prosecution of separate actions by individual members of the 
Class would create a risk of inconsistent or varying adjudications with 
respect to individual members of the Class, which would establish 
incompatible standards of conduct for defendants, or adjudications with 
respect to individual members of the Class which would, as a practical matter, 
be dispositive of the interests of other members or substantially impair or 
impede their ability to protect their interests.

                            SUBSTANTIVE ALLEGATIONS

     26.  In February 1996, Dow AG (at the time known as Dow AG LLC) purchased 
37% of Mycogen's common stock from the Lubrizol Corporation, and in a 
simultaneous transaction, Mycogen issued Dow AG 9% of its common stock in 
return for cash and Dow AG's seed businesses. As part of this transaction, 
Dow AG entered into an agreement (the "1996 Agreement") whereby it was 
prohibited from acquiring all of the shares of Mycogen prior to February 1999.

     27.   On April 30, 1998, Dow, through a press release, announced that, 
through Dow AG, it had requested an amendment to the 1996 Agreement to permit 
Dow AG to acquire the shares of Mycogen that it does not already own. If the 
amendment to the 1996 Agreement is approved, Dow AG will offer to purchase 
the shares held by Mycogen's minority shareholders for $20.50 per share.

     28.   The press release indicated that Dow's request to amend the 1996 
Agreement would have to be approved by "Mycogen's board of directors and the 
independent directors." Given Dow's stranglehold over the Company, none of 
the directors can be considered "independent," and they cannot be expected to 
vigorously protect the rights and interests of Mycogen's public shareholders.


                                      5
<PAGE>

     Accordingly, the approval of the amendment is a foregone conclusion.

     29.  The price of $20.50 per share to be paid to the Class members is 
unconscionable, unfair and grossly inadequate consideration because, among 
other things: (a) the intrinsic value of the stock of Mycogen is materially 
in excess of $20.50 per share, giving due consideration to the possibilities 
of growth and profitability of Mycogen in light of its business, earnings and 
earnings power, present and future; (b) the $20.50 per share price is 
inadequate and offers no premium to the public stockholders of Mycogen in 
light of the fact that Mycogen shares closed at $20.50 on April 30, 1998, 
prior to the announcement by Dow; and (c) the $20.50 per share price is not 
the result of arm's-length negotiations but was fixed arbitrarily by Dow AG 
to "cap" the market price of Mycogen stock. As part of a plan for Dow AG to 
obtain complete ownership of Mycogen's assets and business at the lowest 
possible price.

     30.  The proposed bid serves no legitimate business purpose of Mycogen 
but rather is an attempt by defendants to unfairly benefit Dow AG from the 
transaction at the expense of Mycogen's public stockholders. The proposed 
plan will, for a grossly inadequate consideration, deny plaintiff and the 
other members of the Class their right to share proportionately in the future 
success of Mycogen and its valuable assets, while permitting Dow AG to reap 
huge benefits from the transaction.

     31.  By reason of the foregoing acts, practices and course of conduct, 
Dow AG has breached and will breach its duty as

                                      6

<PAGE>

controlling stockholder of Mycogen by engaging in improper overreaching in 
attempting to carry out the proposed transaction.

     32.   By reason of the foregoing, the Individual Defendants will violate 
their fiduciary duties to Mycogen and the minority stockholders of Mycogen in 
the event that they fail to oppose the bid on the terms presently proposed.

     33.   Plaintiff and the Class have suffered and will continue to suffer 
irreparable damage unless defendants are enjoined from breaching their 
fiduciary duties and from carrying out the aforesaid plan and scheme.

     34.   Plaintiff and the other members of the Class have no adequate 
remedy at law.


                               PRAYER FOR RELIEF

     WHEREFORE, plaintiff demands judgment against the defendants jointly and 
severally, as follows:

     1.   declaring this action to be a class action and certifying 
plaintiff as Class representative;

     2.   enjoining, preliminarily and permanently, Dow AG's offer for 
acquisition of the Mycogen stock owned by plaintiff and the other members of 
the Class under the terms presently proposed;

     3.   to the extent, if any, that the transaction or transactions 
complained of are consummated prior to the entry of this Court's final 
judgment, rescinding such transaction or transactions, and granting, inter 
alia, rescissory damages;

     4.   directing that defendants pay to plaintiff and the other members of 
the Class all damages caused to them and account for all profits and any 
special benefits obtained as a result of their unlawful conduct;


                                       7
<PAGE>


     5.  awarding the plaintiff the costs and disbursements of this action, 
including a reasonable allowance for the fees and expenses of plaintiff's 
attorneys and experts; and

     6.  granting plaintiff and the other members of the Class such other and 
further relief as may be just and proper.

DATED:  May 1, 1998                  MILBERG WEISS BERSHAD
                                      HYNES & LERACH LLP
                                     WILLIAM S. LERACH
                                     ALAN SCHULMAN
                                     DARREN J. ROBBINS




                                     /S/ Alan Schulman
                                     -----------------------------------
                                             ALAN SCHULMAN

                                     600 West Broadway, Suite 1800
                                     San Diego, CA 92101
                                     Telephone: 619/231-1058

                                     BERNSTEIN LIEBHARD & LIFSHITZ
                                     STANLEY D. BERNSTEIN
                                     274 Madison Avenue
                                     New York, NY 10016
                                     Telephone: 212/779-1414

                                     Attorneys for Plaintiff



                                      8

<PAGE>

2MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DAREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA 92101
Telephone:  619/231-1058

BERNSTEIN LIEBHARD & LIFSHITZ
STANLEY D. BERNSTEIN
274 Madison Avenue
New Yor, NY 10016
Telephone: 212/779-1414

Attorneys for Plaintiff

                   SUPERIOR COURT OF THE STATE OF CALIFORNIA
                             COUNTY OF SAN DIEGO

ELLIS INVESTMENTS, LTD., On behalf    )  Case No.
of Itself and All Others Similarly    )
Situated,                             )  CLASS ACTION
                    Plaintiff,        )
                                      )
     vs.                              )  JURY DEMAND
                                      )
CARLTON H. EIBL, PERRY J. GEHRING,    )
NICKOLAS D. HEIN, LOUIS W. PRIBILA,   )
WILLIAM C. SCHMIDT, G. WILLIAM        )
TOLBERT, MYCOGEN CORP., and DOW       )
AGROSCIENCES LLC, and DOES 1-25,      )
inclusive                             )
                                      )
                    Defendants.       )
                                      )
- ------------------------------------- )


<PAGE>


     Plaintiff demands a trial by jury.

DATED:  May 1, 1998                  MILBERG WEISS BERSHAD
                                      HYNES & LERACH LLP
                                     WILLIAM S. LERACH
                                     ALAN SCHULMAN
                                     DARREN J. ROBBINS




                                     /S/ Alan Schulman
                                     -----------------------------------
                                             ALAN SCHULMAN

                                     600 West Broadway, Suite 1800
                                     San Diego, CA 92101
                                     Telephone: 619/231-1058

                                     BERNSTEIN LIEHARD & LIFSHITZ
                                     STANLEY D. BERNSTEIN
                                     274 Madison Avenue
                                     New York, NY 10016
                                     Telephone: 212/779-1414

                                     Attorneys for Plaintiff




                                   1



<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA  92101
Telephone:  619/231-1058

WOLF POPPER LLP
ROBERT M. KORNREICH
PAUL O. PARADIS
845 Third Avenue
New York, NY  10022
Telephone:  212/759-4600

Attorneys for Plaintiff

                    SUPERIOR COURT OF THE STATE OF CALIFORNIA

                               COUNTY OF SAN DIEGO

RICHARD A. KOLB, INDIVIDUAL                 )  Case No. 720388
RETIREMENT ACCOUNT, On Behalf of            )
Himself and All Others Similarly            )  CLASS ACTION
Situated,                                   )  ------------
                                            )
                    Plaintiff,              )
                                            )
     vs.                                    )
                                            )  JURY DEMAND
MYCOGEN CORPORATION, J. PEDRO               )
REINHARD, CARLTON J. EIBL, JOHN L.          )
HAGAMAN, JOSEPH P. SULLIVAN, ROY M.         )
BARBEE, GEORGE KHACHATOURIANS,              )
NICKOLAS D. HEIN, G. WILLIAM                )
TOLBERT, LOUIS W. PRIBILA, DOW              )
CHEMICAL COMPANY and DOES 1-25,             )
inclusive,                                  )
                                            )
                    Defendants.             )
                                            )
- ------------------------------------------- )

<PAGE>

     Plaintiff demands a trial by jury.

DATED:  May 5, 1998
                                             MILBERG WEISS BERSHAD         
                                               HYNES & LERACH LLP          
                                             WILLIAM S. LERACH
                                             ALAN SCHULMAN
                                             DARREN J. ROBBINS

                                                 /s/ William S. Lerach
                                             ------------------------------
                                                   WILLIAM S. LERACH

                                             600 West Broadway, Suite 1800 
                                             San Diego, CA  92101          
                                             Telephone:  619/231-1058      
                                                                           
                                             WOLF POPPER LLP               
                                             ROBERT M. KORNREICH           
                                             PAUL O. PARADIS               
                                             845 Third Avenue              
                                             New York, NY  10022           
                                             Telephone:  212/759-4600      
                                                                           
                                             Attorneys for Plaintiff       

                                     - 1 -
<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA  92101
Telephone:  619/231-1058

WOLF POPPER LLP
ROBERT M. KORNREICH
PAUL O. PARADIS
845 Third Avenue
New York, NY  10022
Telephone:  212/759-4600

Attorneys for Plaintiff

                    SUPERIOR COURT OF THE STATE OF CALIFORNIA

                               COUNTY OF SAN DIEGO

RICHARD A. KOLB, INDIVIDUAL                 )  Case No. 720388
RETIREMENT ACCOUNT, On Behalf of            )
Himself and All Others Similarly            )  CLASS ACTION
Situated,                                   )  ------------
                                            )
                    Plaintiff,              )  COMPLAINT BASED UPON UNFAIR
                                            )  BUSINESS PRACTICES, SELF
     vs.                                    )  DEALING AND BREACH OF
                                            )  FIDUCIARY DUTY
MYCOGEN CORPORATION, J. PEDRO               )
REINHARD, CARLTON J. EIBL, JOHN L.          )
HAGAMAN, JOSEPH P. SULLIVAN, ROY M.         )
BARBEE, GEORGE KHACHATOURIANS,              )
NICKOLAS D. HEIN, G. WILLIAM                )
TOLBERT, LOUIS W. PRIBILA, DOW              )
CHEMICAL COMPANY and DOES 1-25,             )
inclusive,                                  )
                                            )
                    Defendants.             )  Plaintiff Demands A
                                            )  Trial By Jury
- ------------------------------------------- )  --------------------

<PAGE>

     Plaintiff, by his attorneys, alleges upon information and belief, except 
as to PARA 4 which plaintiff alleges upon knowledge, as follows:

                             JURISDICTION AND VENUE

     1.   This court has jurisdiction over all causes of action asserted 
herein pursuant to the California Constitution, Article XL, Section 10, 
because this case is a cause not given by statute to other trial courts.

     2.   This Court has jurisdiction over Mycogen Corporation because this 
defendant is a California corporation with its principal place of business at 
5501 Oberlin Drive, San Diego, California.

     3.   Venue is proper in this Court because the conduct at issue took 
place and had an effect in this County and defendants made misrepresentations 
which had an effect in this County.

                                    PARTIES

     4.   Plaintiff Richard A. Kolb Individual Retirement Account is a 
stockholder of defendant Mycogen Corporation ("Mycogen" or the "Company").

     5.   Defendant Mycogen is a corporation duly organized and existing 
under the laws of the State of California, with its principal offices located 
at 5501 Oberlin Drive, San Diego, California 92121. Mycogen develops, 
manufacturers and markets biopesticides as alternatives to chemical 
pesticides to control a variety of insects, weeds and parasitic worms. As of 
April 7, 1998, there were over 36 million shares of Mycogen common stock 
outstanding.

                                     - 1 -
<PAGE>

     6.   Defendant Dow Chemical Company ("Dow") is a corporation duly 
organized and existing under the laws of the State of Delaware with its 
principal offices located at 2030 Dow Center, Midland, Michigan 48674. Dow is 
the fifth largest chemical company in the world, with annual sales of more 
than $20 billion. Dow manufactures and supplies chemicals, plastics, energy, 
agricultural products, consumer goods and environmental services. Through its 
wholly-owned subsidiary, Dow Agrosciences, LLC ("Dow Agrosciences"), Dow owns 
or controls shares representing approximately 69 percent of the outstanding 
common stock of Mycogen.

     7.   Defendant J. Pedro Reinhard is a Director of Mycogen and the Chief 
Financial Officer and Executive Vice President of Dow Agrosciences.

     8.   Defendant Carlton J. Eibl is the President of Mycogen and a member 
of its Board of Directors.

     9.   Defendant John L. Hagaman is a Director of Mycogen and the 
President of Dow Agrosciences.

     10.  Defendant Joseph P. Sullivan is a Director of Mycogen.

     11.  Defendant Roy M. Barbee is a Director of Mycogen.

     12.  Defendant George Khacharourians is a Director of Mycogen.

     13.  Defendant Nickolas D. Hein is the Chairman of Mycogen's Board of 
Directors and a Vice President of "Global Growth" for Dow Agrosciences.

     14.  Defendant G. William Tolbert is a Director of Mycogen and a "Global 
Business Development Director" for Dow Agrosciences.

                                     - 2 -
<PAGE>

     15.  Defendant Louis W. Pribila is a Director of Mycogen and the 
Secretary, General Counsel and a Vice President of Dow Agrosciences.

     16.  The defendants named in PARA 7 through 15 are sometimes 
collectively referred to herein as the "Individual Defendants."

     17.  The true names and capacities of defendants sued herein under 
California Code of Civil Procedures Section 474 as Does 1 through 25, 
inclusive, are presently not known to plaintiff, who therefore sues these 
defendants by such fictitious names. Plaintiff will seek to amend this 
Complaint and include these Doe Defendants' true names and capacities when 
they are ascertained. Each of the fictitiously named defendants is 
responsible in some manner for the conduct alleged herein and for the injuries 
suffered by the Class.

     18.  The Individual Defendants as officers and/or directors of Mycogen 
have a fiduciary relationship and responsibility to plaintiff and the other 
common public stockholders of Mycogen and owe to plaintiff and the other class 
members the highest obligations of good faith, loyalty, fair dealing, due 
care and candor.

                            CLASS ACTION ALLEGATIONS

     19.  Plaintiff brings this action pursuant to Section 382 of the 
California Code of Civil Procedure on his own behalf and as a class action on 
behalf of all common stockholders of Mycogen, or their successors in 
interest, who are being and will be harmed by defendants' actions described 
below (the "Class"). Excluded from the Class are defendants herein and any 
person, firm, trust, corporation, or other entity related to or affiliated 
with any defendants.

                                     - 3 -

<PAGE>

     20.  This action is properly maintainable as a class action because:

          (a)  The Class is so numerous that joinder of all members is 
impracticable. There are hundreds of Mycogen stockholders of record who are 
located throughout the United States;

          (b)  There are questions of law and fact which are common to the 
Class, including: whether the defendants have engaged or are continuing to 
act in a manner calculated to benefit themselves at the expense of Mycogen's 
minority stockbrokers; and whether plaintiff and other members of the Class 
would be irreparably damaged if the defendants are not enjoined in the manner 
described below;

          (c)  The defendants have acted or refuse to act on grounds 
generally applicable to the Class thereby making appropriate final injunctive 
relief with respect to the Class as a whole;

          (d)  Plaintiff is committed to prosecuting this action and has 
retained competent counsel experienced in litigation of this nature. The 
claims of plaintiff are typical of the claims of the other members of the 
Class and plaintiff has the same interest as the other members of the Class. 
Accordingly, plaintiff is an adequate representative of the Class and will 
fairly and adequately protect the interests of the Class; and

          (e)  Plaintiff anticipates that there will be no difficulty in the 
management of this litigation as a class action.

     21.  For the reasons stated herein, a class action is superior to other 
available methods for the fair and efficient adjudication of this controversy.


                                    - 4 -
<PAGE>

                               CLAIM FOR RELIEF

     22.  Mycogen is a California corporation that develops, manufactures and 
markets biopesticides as alternatives to chemical pesticides to control a 
variety of insects, weeds and parasitic worms. The Company's products are 
based on natural agents that are compatible with the environment and are 
developed through genetic engineering technology and innovative formulations.

     23.  Dow currently owns or controls approximately 69 percent of the 
outstanding common stock of Mycogen. Under the terms of a prior stand still 
agreement with Mycogen (the "Agreement"), Dow cannot acquire the remaining 
shares of Mycogen prior to February 1999.

     24.  After the close of trading on April 30, 1998, it was reported that 
Dow is seeking to amend the Agreement to permit it, acting through Dow 
Agrosciences, to begin discussions regarding the acquisition of the remaining 
shares of Mycogen common stock Dow does not already own for $20.50 per share 
in cash.

     25.  The majority of the nine board members identified above are in 
irrevocable positions of conflict and cannot be expected to act in the best 
interest of Mycogen's minority stockholders in connection with this proposed 
transaction. They alone have the authority to vote to allow the amendment to 
the Agreement that is being sought by Dow and to thereby deprive Mycogen's 
minority shareholders of the true value of their Mycogen shares.

     26.  The sole purpose of the proposed acquisition is to enable Dow to 
acquire the shares of Mycogen it does not already own, as well as Mycogen's 
valuable assets, for Dow's own benefit at the expense of Mycogen's minority 
stockholders.


                                    - 5 -
<PAGE>

     27.  The proposed acquisition comes at a time when Mycogen has performed 
well and Dow expects it will continue to perform well because it is already 
positioned to do so.

     28.  Dow has timed this transaction to capture Mycogen's future 
potential and is seeking to appropriate Mycogen's assets for itself without 
paying an adequate or fair price for the Company's remaining shares.

     29.  Amidst a backdrop of an improving financial position and increased 
prospects for growth, Dow announced its desire to acquire the remaining 
shares of Mycogen for $20.50 cash per share. The offer made by Dow represents 
no premium over the current price of Mycogen common stock. In fact, prior to 
Dow's announcement on April 30, 1998, the price of Mycogen common stock 
closed at $20.625 per share -- higher than the price offered by Dow in the 
proposed acquisition.

     30.  The Individual Defendants and Dow are in a position of control and 
power over Mycogen's stockholders and have access to internal financial 
information about Mycogen, its true value, expected increase in true value, 
and the benefits to Dow of 100 percent ownership of Mycogen, to which 
plaintiff and the Class members are not privy. Defendants are using their 
positions of power and control to benefit Dow in this transaction, to the 
detriment of Mycogen's minority common stockholders.

     31.  In proposing the acquisition, Dow and the Individual Defendants 
have committed or threatened to commit the following acts to the detriment 
and disadvantage of Mycogen minority stockholders:


                                   - 6 -

<PAGE>

          (a)  They have undervalued Mycogen's common stock by ignoring the 
full value of its assets and future prospects. The proposed acquisition 
consideration does not reflect the value of Mycogen's valuable assets; and

          (b)  They timed the announcement of the proposed buyout in order to 
artificially depress the market price of Mycogen's common stock to justify a 
price that is unfair to Mycogen's minority stockholders.

     32.  The Individual Defendants have clear and material conflicts of 
interest and are acting to better the interests of Dow and themselves at the 
expense of Mycogen's minority stockholders.

     33.  In light of the foregoing, the Individual Defendants must, as their 
fiduciary obligations require:

          *    undertake an appropriate evaluation of Mycogen's worth as an 
               acquisition candidate;

          *    act independently so that the interests of Mycogen's minority 
               stockholders will be protected, including, but not limited to, 
               the retention of independent advisors and the appointment of a 
               Special Committee of some or all of the members of Mycogen's 
               board to consider the Dow offer and negotiate with Dow on 
               behalf of Mycogen's minority stockholders;

          *    adequately ensure that no conflicts of interest exist between 
               defendants' own interests and their fiduciary obligation to 
               maximize stockholder value or, if such conflicts exist, to 
               ensure that all

                                      - 7 -
<PAGE>

               conflicts be resolved in the best interests of Mycogen's 
               minority stockholders; and

          *    if an acquisition transaction is to go forward, require that 
               it be approved by a majority of Mycogen's minority 
               stockholders.

     34.  As a result of the defendants' failure to take such steps to date, 
plaintiff and the other members of the Class have been and will be damaged in 
that they have not and will not receive their proportionate share of the 
value of the Company's assets and business, and have been and will be 
prevented from obtaining a fair price for their common stock.

     35.  Defendants, in failing to disclose the material non-public 
information in their possession as to the value of Mycogen's assets, the full 
extent of the future earnings potential of Mycogen and its expected increase 
in profitability, are engaging in self-dealing, are not acting in good faith 
toward plaintiff and the other members of the Class, and have breached and 
are breaching their fiduciary duties to the members of the Class.

     36.  As a result of the defendants' unlawful actions, plaintiff and the 
other members of the Class will be irreparably harmed in that they will not 
receive their fair portion of the value of Mycogen's assets and business and 
will be prevented from obtaining the real value of their equity ownership of 
the Company. Unless the proposed acquisition is enjoined by the Court, 
defendants will continue to breach their fiduciary duties owed to plaintiff 
and the members of the Class, will not engage in arm's-length negotiations on 
the acquisition terms, and will not supply to Mycogen's minority 
stockholders sufficient information to enable

                                      - 8 -
<PAGE>

them to cast informed votes on the proposed acquisition and may consummate 
the proposed acquisition, all to the irreparable harm of the members of the 
Class.

     37.  Plaintiff and the other members of the Class have no adequate 
remedy at law.

                              PRAYER FOR RELIEF

     WHEREFORE, plaintiff prays for judgment and relief as follows:

     1.   Ordering that this action may be maintained as a class action and 
certifying plaintiff as the Class representative;

     2.   Declaring that defendants have breached their fiduciary and other 
duties to plaintiff and the other members of the Class;

     3.   Entering an order requiring defendants to take the steps set forth 
herein;

     4.   Preliminarily and permanently enjoining the defendants and their 
counsel, agents, employees and all persons acting under, in concert with, or 
for them, from proceeding with, consummating or closing the proposed 
transaction;

     5.   In the event the proposed acquisition is consummated, rescinding it 
and setting it aside;

     6.   Awarding compensatory damages against defendants individually and 
severally in an amount to be determined at trial, together with prejudgment 
interest at the maximum rate allowable by law;

     7.   Awarding costs and disbursements, including plaintiff's counsel's 
fees and experts' fees; and

                                      - 9 -
<PAGE>

     8.   Granting such other and further relief as the Court may deem just 
and proper.

DATED: May 5, 1998
                                             MILBERG WEISS BERSHAD
                                               HYNES & LERACH LLP
                                             WILLIAM S. LERACH
                                             ALAN SCHULMAN
                                             DARREN J. ROBBINS

                                                  /s/ William S. Lerach
                                             --------------------------------
                                                     WILLIAM S. LERACH

                                             600 West Broadway, Suite 1800
                                             San Diego, CA 92101
                                             Telephone: 619/231-1058

                                             WOLF POPPER LLP
                                             ROBERT M. KORNREICH
                                             PAUL O. PARADIS
                                             845 Third Avenue
                                             New York, NY 10022
                                             Telephone: 212/759-4600

                                             Attorneys for Plaintiff

                                      - 10 -





<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA  92101
Telephone:  619/231-1058

WOLF POPPER LLP
ROBERT M. KORNREICH
PAUL O. PARADIS
845 Third Avenue
New York, NY  10022
Telephone:  212/759-4600                   LAW OFFICES OF JAMES V.
                                             BASHIAN, P.C.
BERMAN, DeVALERIO & PEASE                  JAMES V. BASHIAN
GLEN DeVALERIO                             500 Fifth Avenue
One Liberty Square                         Suite 2700
Boston, MA  02109                          New York, NY  10110
Telephone:  617/542-8300                   Telephone:  212/921-4110

Attorneys for Plaintiff

                    SUPERIOR COURT OF THE STATE OF CALIFORNIA

                               COUNTY OF SAN DIEGO

JEANETTE ANDERSON, On Behalf of             )  Case No. 720391
Herself and All Others Similarly            )  
Situated,                                   )  CLASS ACTION 
                                            )  ------------ 
                    Plaintiff,              )
                                            )
     vs.                                    )
                                            )  JURY DEMAND
MYCOGEN CORPORATION, J. PEDRO               )
REINHARD, CARLTON J. EIBL, JOHN L.          )
HAGAMAN, JOSEPH P. SULLIVAN, ROY M.         )
BARBEE, GEORGE KHACHATOURIANS,              )
NICKOLAS D. HEIN, G. WILLIAM                )
TOLBERT, LOUIS W. PRIBILA, DOW              )
CHEMICAL COMPANY and DOES 1-25,             )
inclusive,                                  )
                                            )
                    Defendants.             )
                                            )
- ------------------------------------------- )

<PAGE>

     Plaintiff demands a trial by jury.

DATED:  May 5, 1998
                                             MILBERG WEISS BERSHAD         
                                               HYNES & LERACH LLP          
                                             WILLIAM S. LERACH
                                             ALAN SCHULMAN
                                             DARREN J. ROBBINS

                                                 /s/ William S. Lerach
                                             ------------------------------
                                                   WILLIAM S. LERACH

                                             600 West Broadway, Suite 1800 
                                             San Diego, CA  92101          
                                             Telephone:  619/231-1058      
                                                                           
                                             WOLF POPPER LLP               
                                             ROBERT M. KORNREICH           
                                             PAUL O. PARADIS               
                                             845 Third Avenue              
                                             New York, NY  10022           
                                             Telephone:  212/759-4600      

                                             BERMAN, DeVALERIO & PEASE  
                                             GLEN DeVALERIO             
                                             One Liberty Square
                                             Boston, MA  02109
                                             Telephone:  617/542-8300   

                                             LAW OFFICES OF JAMES V.  
                                               BASHIAN, P.C.          
                                             JAMES V. BASHIAN         
                                             500 Fifth Avenue         
                                             Suite 2700               
                                             New York, NY  10110      
                                             Telephone:  212/921-4110 

                                             Attorneys for Plaintiff

                                     - 1 -
<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA  92101
Telephone:  619/231-1058

WOLF POPPER LLP
ROBERT M. KORNREICH
PAUL O. PARADIS
845 Third Avenue
New York, NY  10022
Telephone:  212/759-4600                   LAW OFFICES OF JAMES V.
                                             BASHIAN, P.C.
BERMAN, DeVALERIO & PEASE                  JAMES V. BASHIAN
GLEN DeVALERIO                             500 Fifth Avenue
One Liberty Square                         Suite 2700
Boston, MA  02109                          New York, NY  10110
Telephone:  617/542-8300                   Telephone:  212/921-4110

Attorneys for Plaintiff

                    SUPERIOR COURT OF THE STATE OF CALIFORNIA

                               COUNTY OF SAN DIEGO

JEANETTE ANDERSON, On Behalf of             )  Case No. 720391
Herself and All Others Similarly            )  
Situated,                                   )  CLASS ACTION 
                                            )  ------------ 
                    Plaintiff,              )
                                            )  COMPLAINT BASED UPON UNFAIR
     vs.                                    )  BUSINESS PRACTICES, SELF
                                            )  DEALING AND BREACH OF
MYCOGEN CORPORATION, J. PEDRO               )  FIDUCIARY DUTY
REINHARD, CARLTON J. EIBL, JOHN L.          )
HAGAMAN, JOSEPH P. SULLIVAN, ROY M.         )
BARBEE, GEORGE KHACHATOURIANS,              )
NICKOLAS D. HEIN, G. WILLIAM                )
TOLBERT, LOUIS W. PRIBILA, DOW              )
CHEMICAL COMPANY and DOES 1-25,             )
inclusive,                                  )
                                            )
                    Defendants.             )  Plaintiff Demands A
                                            )  Trial By Jury
- ------------------------------------------- )  --------------------


<PAGE>

     Plaintiff, by her attorneys, alleges upon information and belief, except 
as to PARA 4 which plaintiff alleges upon knowledge, as follows:

                             JURISDICTION AND VENUE

     1.   This court has jurisdiction over all causes of action asserted 
herein pursuant to the California Constitution, Article XL, Section 10, 
because this case is a cause not given by statute to other trial courts.

     2.   This Court has jurisdiction over Mycogen Corporation because this 
defendant is a California corporation with its principal place of business at 
5501 Oberlin Drive, San Diego, California.

     3.   Venue is proper in this Court because the conduct at issue took 
place and had an effect in this County and defendants made misrepresentations 
which had an effect in this County.

                                    PARTIES

     4.   Plaintiff Jeanette Anderson is a stockholder of defendant Mycogen 
Corporation ("Mycogen" or the "Company").

     5.   Defendant Mycogen is a corporation duly organized and existing 
under the laws of the State of California, with its principal offices located 
at 5501 Oberlin Drive, San Diego, California 92121. Mycogen develops, 
manufacturers and markets biopesticides as alternatives to chemical 
pesticides to control a variety of insects, weeds and parasitic worms. As of 
April 7, 1998, there were over 36 million shares of Mycogen common stock 
outstanding.

     6.   Defendant Dow Chemical Company ("Dow") is a corporation duly 
organized and existing under the laws of the State of Delaware

                                     - 1 -
<PAGE>

with its principal offices located at 2030 Dow Center, Midland, Michigan 
48674. Dow is the fifth largest chemical company in the world, with annual 
sales of more than $20 billion. Dow manufactures and supplies chemicals, 
plastics, energy, agricultural products, consumer goods and environmental 
services. Through its wholly-owned subsidiary, Dow Agrosciences, LLC ("Dow 
Agrosciences"), Dow owns or controls shares representing approximately 69 
percent of the outstanding common stock of Mycogen.

     7.   Defendant J. Pedro Reinhard is a Director of Mycogen and the Chief 
Financial Officer and Executive Vice President of Dow Agrosciences.

     8.   Defendant Carlton J. Eibl is the President of Mycogen and a member 
of its Board of Directors.

     9.   Defendant John L. Hagaman is a Director of Mycogen and the 
President of Dow Agrosciences.

     10.  Defendant Joseph P. Sullivan is a Director of Mycogen.

     11.  Defendant Roy M. Barbee is a Director of Mycogen.

     12.  Defendant George Khacharourians is a Director of Mycogen.

     13.  Defendant Nickolas D. Hein is the Chairman of Mycogen's Board of 
Directors and a Vice President of "Global Growth" for Dow Agrosciences.

     14.  Defendant G. William Tolbert is a Director of Mycogen and a "Global 
Business Development Director" for Dow Agrosciences.

     15.  Defendant Louis W. Pribila is a Director of Mycogen and the 
Secretary, General Counsel and a Vice President of Dow Agrosciences.

                                     - 2 -
<PAGE>

     16.  The defendants named in PARA 7 through 15 are sometimes 
collectively referred to herein as the "Individual Defendants."

     17.  The true names and capacities of defendants sued herein under 
California Code of Civil Procedures Section 474 as Does 1 through 25, 
inclusive, are presently not known to plaintiff, who therefore sues these 
defendants by such fictitious names. Plaintiff will seek to amend this 
Complaint and include these Doe Defendants' true names and capacities when 
they are ascertained. Each of the fictitiously named defendants is 
responsible in some manner for the conduct alleged herein and for the injuries 
suffered by the Class.

     18.  The Individual Defendants as officers and/or directors of Mycogen 
have a fiduciary relationship and responsibility to plaintiff and the other 
common public stockholders of Mycogen and owe to plaintiff and the other class 
members the highest obligations of good faith, loyalty, fair dealing, due 
care and candor.

                            CLASS ACTION ALLEGATIONS

     19.  Plaintiff brings this action pursuant to Section 382 of the 
California Code of Civil Procedure on her own behalf and as a class action on 
behalf of all common stockholders of Mycogen, or their successors in 
interest, who are being and will be harmed by defendants' actions described 
below (the "Class"). Excluded from the Class are defendants herein and any 
person, firm, trust, corporation, or other entity related to or affiliated 
with any defendants.

     20.  This action is properly maintainable as a class action because:

                                     - 3 -

<PAGE>

          (a)  The Class is so numerous that joinder of all members is 
impracticable. There are hundreds of Mycogen stockholders of record who are 
located throughout the United States;

          (b)  There are questions of law and fact which are common to the 
Class, including: whether the defendants have engaged or are continuing to 
act in a manner calculated to benefit themselves at the expense of Mycogen's 
minority stockbrokers; and whether plaintiff and other members of the Class 
would be irreparably damaged if the defendants are not enjoined in the manner 
described below;

          (c)  The defendants have acted or refuse to act on grounds 
generally applicable to the Class thereby making appropriate final injunctive 
relief with respect to the Class as a whole;

          (d)  Plaintiff is committed to prosecuting this action and has 
retained competent counsel experienced in litigation of this nature. The 
claims of plaintiff are typical of the claims of the other members of the 
Class and plaintiff has the same interest as the other members of the Class. 
Accordingly, plaintiff is an adequate representative of the Class and will 
fairly and adequately protect the interests of the Class; and

          (e)  Plaintiff anticipates that there will be no difficulty in the 
management of this litigation as a class action.

     21.  For the reasons stated herein, a class action is superior to other 
available methods for the fair and efficient adjudication of this controversy.


                                    - 4 -
<PAGE>

                               CLAIM FOR RELIEF

     22.  Mycogen is a California corporation that develops, manufactures and 
markets biopesticides as alternatives to chemical pesticides to control a 
variety of insects, weeds and parasitic worms. The Company's products are 
based on natural agents that are compatible with the environment and are 
developed through genetic engineering technology and innovative formulations.

     23.  Dow currently owns or controls approximately 69 percent of the 
outstanding common stock of Mycogen. Under the terms of a prior stand still 
agreement with Mycogen (the "Agreement"), Dow cannot acquire the remaining 
shares of Mycogen prior to February 1999.

     24.  After the close of trading on April 30, 1998, it was reported that 
Dow is seeking to amend the Agreement to permit it, acting through Dow 
Agrosciences, to begin discussions regarding the acquisition of the remaining 
shares of Mycogen common stock Dow does not already own for $20.50 per share 
in cash.

     25.  The majority of the nine board members identified above are in 
irrevocable positions of conflict and cannot be expected to act in the best 
interest of Mycogen's minority stockholders in connection with this proposed 
transaction. They alone have the authority to vote to allow the amendment to 
the Agreement that is being sought by Dow and to thereby deprive Mycogen's 
minority shareholders of the true value of their Mycogen shares.

     26.  The sole purpose of the proposed acquisition is to enable Dow to 
acquire the shares of Mycogen it does not already own, as well as Mycogen's 
valuable assets, for Dow's own benefit at the expense of Mycogen's minority 
stockholders.


                                    - 5 -
<PAGE>

     27.  The proposed acquisition comes at a time when Mycogen has performed 
well and Dow expects it will continue to perform well because it is already 
positioned to do so.

     28.  Dow has timed this transaction to capture Mycogen's future 
potential and is seeking to appropriate Mycogen's assets for itself without 
paying an adequate or fair price for the Company's remaining shares.

     29.  Amidst a backdrop of an improving financial position and increased 
prospects for growth, Dow announced its desire to acquire the remaining 
shares of Mycogen for $20.50 cash per share. The offer made by Dow represents 
no premium over the current price of Mycogen common stock. In fact, prior to 
Dow's announcement on April 30, 1998, the price of Mycogen common stock 
closed at $20.625 per share -- higher than the price offered by Dow in the 
proposed acquisition.

     30.  The Individual Defendants and Dow are in a position of control and 
power over Mycogen's stockholders and have access to internal financial 
information about Mycogen, its true value, expected increase in true value, 
and the benefits to Dow of 100 percent ownership of Mycogen, to which 
plaintiff and the Class members are not privy. Defendants are using their 
positions of power and control to benefit Dow in this transaction, to the 
detriment of Mycogen's minority common stockholders.

     31.  In proposing the acquisition, Dow and the Individual Defendants 
have committed or threatened to commit the following acts to the detriment 
and disadvantage of Mycogen minority stockholders:


                                   - 6 -

<PAGE>

          (a)  They have undervalued Mycogen's common stock by ignoring the 
full value of its assets and future prospects. The proposed acquisition 
consideration does not reflect the value of Mycogen's valuable assets; and

          (b)  They timed the announcement of the proposed buyout in order to 
artificially depress the market price of Mycogen's common stock to justify a 
price that is unfair to Mycogen's minority stockholders.

     32.  The Individual Defendants have clear and material conflicts of 
interest and are acting to better the interests of Dow and themselves at the 
expense of Mycogen's minority stockholders.

     33.  In light of the foregoing, the Individual Defendants must, as their 
fiduciary obligations require:

          *    undertake an appropriate evaluation of Mycogen's worth as an 
               acquisition candidate;

          *    act independently so that the interests of Mycogen's minority 
               stockholders will be protected, including, but not limited to, 
               the retention of independent advisors and the appointment of a 
               Special Committee of some or all of the members of Mycogen's 
               board to consider the Dow offer and negotiate with Dow on 
               behalf of Mycogen's minority stockholders;

          *    adequately ensure that no conflicts of interest exist between 
               defendants' own interests and their fiduciary obligation to 
               maximize stockholder value or, if such conflicts exist, to 
               ensure that all

                                      - 7 -
<PAGE>

               conflicts be resolved in the best interests of Mycogen's 
               minority stockholders; and

          *    if an acquisition transaction is to go forward, require that 
               it be approved by a majority of Mycogen's minority 
               stockholders.

     34.  As a result of the defendants' failure to take such steps to date, 
plaintiff and the other members of the Class have been and will be damaged in 
that they have not and will not receive their proportionate share of the 
value of the Company's assets and business, and have been and will be 
prevented from obtaining a fair price for their common stock.

     35.  Defendants, in failing to disclose the material non-public 
information in their possession as to the value of Mycogen's assets, the full 
extent of the future earnings potential of Mycogen and its expected increase 
in profitability, are engaging in self-dealing, are not acting in good faith 
toward plaintiff and the other members of the Class, and have breached and 
are breaching their fiduciary duties to the members of the Class.

     36.  As a result of the defendants' unlawful actions, plaintiff and the 
other members of the Class will be irreparably harmed in that they will not 
receive their fair portion of the value of Mycogen's assets and business and 
will be prevented from obtaining the real value of their equity ownership of 
the Company. Unless the proposed acquisition is enjoined by the Court, 
defendants will continue to breach their fiduciary duties owed to plaintiff 
and the members of the Class, will not engage in arm's-length negotiations on 
the acquisition terms, and will not supply to Mycogen's minority 
stockholders sufficient information to enable

                                      - 8 -
<PAGE>

them to cast informed votes on the proposed acquisition and may consummate 
the proposed acquisition, all to the irreparable harm of the members of the 
Class.

     37.  Plaintiff and the other members of the Class have no adequate 
remedy at law.

                              PRAYER FOR RELIEF

     WHEREFORE, plaintiff prays for judgment and relief as follows:

     1.   Ordering that this action may be maintained as a class action and 
certifying plaintiff as the Class representative;

     2.   Declaring that defendants have breached their fiduciary and other 
duties to plaintiff and the other members of the Class;

     3.   Entering an order requiring defendants to take the steps set forth 
herein;

     4.   Preliminarily and permanently enjoining the defendants and their 
counsel, agents, employees and all persons acting under, in concert with, or 
for them, from proceeding with, consummating or closing the proposed 
transaction;

     5.   In the event the proposed acquisition is consummated, rescinding it 
and setting it aside;

     6.   Awarding compensatory damages against defendants individually and 
severally in an amount to be determined at trial, together with prejudgment 
interest at the maximum rate allowable by law;

     7.   Awarding costs and disbursements, including plaintiff's counsel's 
fees and experts' fees; and

                                      - 9 -
<PAGE>

     8.   Granting such other and further relief as the Court may deem just 
and proper.

DATED: May 5, 1998
                                             MILBERG WEISS BERSHAD
                                               HYNES & LERACH LLP
                                             WILLIAM S. LERACH
                                             ALAN SCHULMAN
                                             DARREN J. ROBBINS

                                                  /s/ William S. Lerach
                                             --------------------------------
                                                     WILLIAM S. LERACH

                                             600 West Broadway, Suite 1800
                                             San Diego, CA 92101
                                             Telephone: 619/231-1058

                                             WOLF POPPER LLP
                                             ROBERT M. KORNREICH
                                             PAUL O. PARADIS
                                             845 Third Avenue
                                             New York, NY 10022
                                             Telephone: 212/759-4600

                                             BERMAN, DeVALERIO & PEASE
                                             GLEN DeVALERIO
                                             One Liberty Square
                                             Boston, MA 02109
                                             Telephone: 617/542-8300

                                             LAW OFFICES OF JAMES V.
                                               BASHIAN, P.C.
                                             JAMES V. BASHIAN
                                             500 Fifth Avenue
                                             Suite 2700
                                             New York, NY 10110
                                             Telephone: 212/921-4110

                                             Attorneys for Plaintiff

                                      - 10 -





<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA  92101
Telephone:  619-231-1058

KAPLAN, KILSHEIMER & FOX LLP
ROBERT N. KAPLAN
CHRISTINE M. COMAS
685 Third Avenue, 26th Fl.
New York, NY  10017
Telephone:  212-687-1980    

Attorneys for Plaintiff

[Additional Counsel On Signature Page]

                    SUPERIOR COURT OF THE STATE OF CALIFORNIA

                               COUNTY OF SAN DIEGO

JEAN BOETTCHER, On Behalf of                )  Case No. 720530
Herself and All Others Similarly            )  
Situated,                                   )  CLASS ACTION 
                                            )  ------------ 
v.                                          )
                                            )
MYCOGEN CORPORATION, J. PEDRO               )
REINHARD, CARLTON J. EIBL, JOHN L.          )
HAGAMAN, JOSEPH P. SULLIVAN, ROY M.         )
BARBEE, GEORGE KHACHATOURIANS,              )  JURY DEMAND
NICKOLAS D. HEIN, G. WILLIAM                )
TOLBERT, LOUIS W. PRIBILA, DOW              )
CHEMICAL COMPANY and DOES 1-25,             )
inclusive,                                  )
                                            )
                    Defendants.             )
                                            )
- ------------------------------------------- )


<PAGE>

     Plaintiff demands a trial by jury.

DATED:  May 8, 1998
                                             MILBERG WEISS BERSHAD         
                                               HYNES & LERACH LLP          
                                             WILLIAM S. LERACH
                                             ALAN SCHULMAN
                                             DARREN J. ROBBINS

                                                 /s/ William S. Lerach
                                             ------------------------------
                                                   WILLIAM S. LERACH

                                             600 West Broadway, Suite 1800 
                                             San Diego, CA  92101          
                                             Telephone:  619/231-1058      

                                             KAPLAN, KILSHEIMER & FOX LLP 
                                             ROBERT N. KAPLAN             
                                             CHRISTINE M. COMAS           
                                             685 Third Avenue, 26th Floor 
                                             New York, NY  10017          
                                             Telephone:  212-687-1980     

                                             WOLF POPPER LLP               
                                             ROBERT M. KORNREICH           
                                             PAUL O. PARADIS               
                                             845 Third Avenue              
                                             New York, NY  10022           
                                             Telephone:  212/759-4600      
                                                                           
                                             Attorneys for Plaintiff       

                                     - 1 -
<PAGE>

MILBERG WEISS BERSHAD
  HYNES & LERACH LLP
WILLIAM S. LERACH (68581)
ALAN SCHULMAN (128661)
DARREN J. ROBBINS (168593)
600 West Broadway, Suite 1800
San Diego, CA  92101
Telephone:  619-231-1058

KAPLAN, KILSHEIMER & FOX LLP
ROBERT N. KAPLAN
CHRISTINE M. COMAS
685 Third Avenue, 26th Fl.
New York, NY  10017
Telephone:  212-687-1980    

Attorneys for Plaintiff

[Additional Counsel On Signature Page]

                    SUPERIOR COURT OF THE STATE OF CALIFORNIA

                               COUNTY OF SAN DIEGO

JEAN BOETTCHER, On Behalf of                )  Case No. 720530
Herself and All Others Similarly            )  
Situated,                                   )  CLASS ACTION 
                                            )  ------------ 
v.                                          )  
                                            )  
MYCOGEN CORPORATION, J. PEDRO               )  COMPLAINT BASED UPON UNFAIR 
REINHARD, CARLTON J. EIBL, JOHN L.          )  BUSINESS PRACTICES, SELF    
HAGAMAN, JOSEPH P. SULLIVAN, ROY M.         )  DEALING AND BREACH OF       
BARBEE, GEORGE KHACHATOURIANS,              )  FIDUCIARY DUTY              
NICKOLAS D. HEIN, G. WILLIAM                )
TOLBERT, LOUIS W. PRIBILA, DOW              )
CHEMICAL COMPANY and DOES 1-25,             )
inclusive,                                  )
                                            )
                    Defendants.             )  Plaintiff Demands A
                                            )  Trial By Jury
- ------------------------------------------- )  --------------------


<PAGE>

     Plaintiff, by her attorneys, alleges upon information and belief, except 
as to PARA 4 which plaintiff alleges upon knowledge, as follows:

                             JURISDICTION AND VENUE

     1.   This Court has jurisdiction over all causes of action asserted 
herein pursuant to the California Constitution, Article XL, Section 10, 
because this case is a cause not given by statute to other trial courts.

     2.   This Court has jurisdiction over Mycogen Corporation ("Mycogen" or 
the "Company") because this defendant is a California corporation with its 
principal place of business at 5501 Oberlin Drive, San Diego, California.

     3.   Venue is proper in this Court because the conduct at issue took 
place and had an effect in this County and defendants made misrepresentations 
and omissions which had an effect in this County.

                                    PARTIES

     4.   Plaintiff Jean Boettcher is a stockholder of defendant Mycogen.

     5.   Defendant Mycogen is a corporation duly organized and existing 
under the laws of the State of California, with its principal offices located 
at 5501 Oberlin Drive, San Diego, California 92121. Mycogen develops, 
manufacturers and markets biopesticides as alternatives to chemical 
pesticides to control a variety of insects, weeds and parasitic worms. As of 
April 7, 1998, there were over 36 million shares of Mycogen common stock 
outstanding.

                                     - 1 -
<PAGE>

     6.   Defendant Dow Chemical Company ("Dow") is a corporation duly 
organized and existing under the laws of the State of Delaware with its 
principal offices located at 2030 Dow Center, Midland, Michigan 48674. Dow is 
the fifth largest chemical company in the world, with annual sales of more 
than $20 billion. Dow manufactures and supplies chemicals, plastics, energy, 
agricultural products, consumer goods and environmental services. Through its 
wholly-owned subsidiary, Dow Agrosciences, LLC ("Dow Agrosciences"), Dow owns 
or controls shares representing approximately 69 percent of the outstanding 
common stock of Mycogen.

     7.   Defendant J. Pedro Reinhard is a Director of Mycogen and the Chief 
Financial Officer and Executive Vice President of Dow Agrosciences.

     8.   Defendant Carlton J. Eibl is the President of Mycogen and a member 
of its Board of Directors.

     9.   Defendant John L. Hagaman is a Director of Mycogen and the 
President of Dow Agrosciences.

     10.  Defendant Joseph P. Sullivan is a Director of Mycogen.

     11.  Defendant Roy M. Barbee is a Director of Mycogen.

     12.  Defendant George Khacharourians is a Director of Mycogen.

     13.  Defendant Nickolas D. Hein is the Chairman of Mycogen's Board of 
Directors and a Vice President of "Global Growth" for Dow Agrosciences.

     14.  Defendant G. William Tolbert is a Director of Mycogen and a "Global 
Business Development Director" for Dow Agrosciences.

                                     - 2 -
<PAGE>

     15.  Defendant Louis W. Pribila is a Director of Mycogen and the 
Secretary, General Counsel and a Vice President of Dow Agrosciences.

     16.  The defendants named in PARA 7 through 15 are sometimes 
collectively referred to herein as the "Individual Defendants."

     17.  The true names and capacities of defendants sued herein under 
California Code of Civil Procedures Section 474 as Does 1 through 25, 
inclusive, are presently not known to plaintiff, who therefore sues these 
defendants by such fictitious names. Plaintiff will seek to amend this 
Complaint and include these Doe Defendants' true names and capacities when 
they are ascertained. Each of the fictitiously named defendants is 
responsible in some manner for the conduct alleged herein and for the injuries 
suffered by the Class.

     18.  The Individual Defendants as officers and/or directors of Mycogen 
have a fiduciary relationship and responsibility to plaintiff and the other 
common public stockholders of Mycogen and owe to plaintiff and the other class 
members the highest obligations of good faith, loyalty, fair dealing, due 
care and candor.

                            CLASS ACTION ALLEGATIONS

     19.  Plaintiff brings this action pursuant to Section 382 of the 
California Code of Civil Procedure on her own behalf and as a class action on 
behalf of all common stockholders of Mycogen, or their successors in 
interest, who are being and will be harmed by defendants' actions described 
below (the "Class"). Excluded from the Class are defendants herein and any 
person, firm, trust, corporation, or other entity related to or affiliated 
with any defendants.

                                     - 3 -

<PAGE>

     20.  This action is properly maintainable as a class action because:

          (a)  The Class is so numerous that joinder of all members is 
impracticable. There are hundreds of Mycogen stockholders of record who are 
located throughout the United States;

          (b)  There are questions of law and fact which are common to the 
Class, including: whether the defendants have engaged or are continuing to 
act in a manner calculated to benefit themselves at the expense of Mycogen's 
minority stockholders; and whether plaintiff and other members of the Class 
would be irreparably damaged if the defendants are not enjoined in the manner 
described below;

          (c)  The defendants have acted or refuse to act on grounds 
generally applicable to the Class thereby making appropriate final injunctive 
relief with respect to the Class as a whole;

          (d)  Plaintiff is committed to prosecuting this action and has 
retained competent counsel experienced in litigation of this nature. The 
claims of plaintiff are typical of the claims of the other members of the 
Class and plaintiff has the same interest as the other members of the Class. 
Accordingly, plaintiff is an adequate representative of the Class and will 
fairly and adequately protect the interests of the Class; and

          (e)  Plaintiff anticipates that there will be no difficulty in the 
management of this litigation as a class action.

     21.  For the reasons stated herein, a class action is superior to other 
available methods for the fair and efficient adjudication of this controversy.


                                    - 4 -
<PAGE>

                               CLAIM FOR RELIEF

     22.  Mycogen is a California corporation that develops, manufactures and 
markets biopesticides as alternatives to chemical pesticides to control a 
variety of insects, weeds and parasitic worms. The Company's products are 
based on natural agents that are compatible with the environment and are 
developed through genetic engineering technology and innovative formulations.

     23.  Dow currently owns or controls approximately 69 percent of the 
outstanding common stock of Mycogen. Under the terms of a prior stand still 
agreement with Mycogen (the "Agreement"), Dow cannot acquire the remaining 
shares of Mycogen prior to February 1999.

     24.  After the close of trading on April 30, 1998, it was reported that 
Dow is seeking to amend the Agreement to permit it, acting through Dow 
Agrosciences, to begin discussions regarding the acquisition of the remaining 
shares of Mycogen common stock Dow does not already own for $20.50 per share 
in cash.

     25.  The majority of the nine board members identified in paragraphs 7 
through 15 are in irrevocable positions of conflict and cannot be expected to 
act in the best interest of Mycogen's minority stockholders in connection with 
this proposed transaction. They alone have the authority to vote to allow the 
amendment to the Agreement that is being sought by Dow and to thereby deprive 
Mycogen's minority shareholders of the true value of their Mycogen shares.

     26.  The sole purpose of the proposed transaction is to enable Dow to 
acquire the shares of Mycogen it does not already own, as 


                                    - 5 -
<PAGE>


well as Mycogen's valuable assets, for Dow's own benefit at the expense of 
Mycogen's minority stockholders.

     27.  The proposed transaction comes at a time when Mycogen has performed 
well and Dow expects it will continue to perform well because it is already 
positioned to do so.

     28.  Dow has timed this transaction to capture Mycogen's future 
potential and is seeking to appropriate Mycogen's assets for itself without 
paying an adequate or fair price for the Company's remaining shares.

     29.  Amidst a backdrop of an improving financial position and increased 
prospects for growth, Dow announced its desire to acquire the remaining 
shares of Mycogen for $20.50 cash per share. The offer made by Dow represents 
no premium over the current price of Mycogen common stock. In fact, prior to 
Dow's announcement on April 30, 1998, the price of Mycogen common stock 
closed at $20.625 per share -- higher than the price offered by Dow in the 
proposed acquisition.

     30.  The Individual Defendants and Dow are in a position of control and 
power over Mycogen's stockholders and have access to internal financial 
information about Mycogen, its true value, its expected increase in true value, 
and the benefits to Dow of 100 percent ownership of Mycogen, to which 
plaintiff and the Class members are not privy. Defendants are using their 
positions of power and control to benefit Dow in this transaction to the 
detriment of Mycogen's minority common stockholders.

     31.  In proposing the acquisition, Dow and the Individual Defendants 
have committed or threatened to commit the following


                                   - 6 -

<PAGE>

acts to the detriment and disadvantage of Mycogen minority stockholders:

          a.  They have undervalued Mycogen's common stock by ignoring the 
full value of its assets and future prospects. The proposed acquisition 
consideration does not reflect the true value of Mycogen's valuable assets; 
and

          b.  They have timed the announcement of the proposed buyout in order
to artificially depress the market price of Mycogen's common stock to justify 
a price that is unfair to Mycogen's minority stockholders.

     32.  The Individual Defendants have clear and material conflicts of 
interest and are acting to better the interests of Dow and themselves at the 
expense of Mycogen's minority stockholders.

     33.  In light of the foregoing, the Individual Defendants must, as their 
fiduciary obligations require:

     -    undertake an appropriate evaluation of Mycogen's worth as an 
          acquisition candidate;

     -    act independently so that the interests of Mycogen's minority 
          stockholders will be protected, including, but not limited to, the 
          retention of independent advisors and the appointment of a Special 
          Committee of some or all of the members of Mycogen's board to 
          consider the Dow offer and negotiate with Dow on behalf of Mycogen's 
          minority stockholders;

     -    adequately ensure that no conflicts of interest exist between 
          defendants' own interests and their fiduciary obligation to maximize
          stockholder value or, if such conflicts exist, to ensure that all 
          conflicts be resolved

                                      -7-
<PAGE>

          in the best interests of Mycogen's minority stockholders; and

     -    if an acquisition transaction is to go forward, require that it be 
          approved by a majority of Mycogen's minority stockholders.

     34.  As a result of the defendants' failure to take such steps to date, 
plaintiff and the other members of the Class have been and will be damaged in 
that they have not and will not receive their proportionate share of the value 
of the Company's assets and business, and have been and will be prevented 
from obtaining a fair price for their common stock.

     35.  Defendants, in failing to disclose the material non-public 
information in their possession as to the value of Mycogen's assets, the full 
extent of the future earnings potential of Mycogen and its expected increase 
in profitability, are engaging in self-dealing, are not acting in good faith 
toward plaintiff and the other members of the Class, and have breached and 
continue to breach their fiduciary duties to the members of the Class.

     36.  As a result of the defendants' unlawful actions, plaintiff and the 
other members of the Class will be irreparably harmed in that they will not 
receive their fair portion of the value of Mycogen's assets and business and 
will be prevented from obtaining the real value of their equity ownership of 
the Company. Unless the proposed acquisition is enjoined by the Court, 
defendants will continue to breach their fiduciary duties owed to plaintiff 
and the members of the Class, will not engage in arm's-length negotiations on 
the acquisition terms, and will not supply to Mycogen's minority stockholders 
sufficient information to enable

                                      -8-
<PAGE>

them to cast informed votes on the proposed acquisition and may consummate 
the proposed acquisition, all to the irreparable harm of the members of the 
Class.

     37.  Plaintiff and the other members of the Class have no adequate 
remedy at law.
                                       
                              PRAYER FOR RELIEF

     WHEREFORE, plaintiff prays for judgment and relief as follows:

     1.  Ordering that this action may be maintained as a class action and 
certifying plaintiff as the Class representative;

     2.  Declaring that defendants have breached their fiduciary and other 
duties to plaintiff and the other members of the Class;

     3.  Entering an order requiring defendants to take the steps set forth 
herein;

     4.  Preliminary and permanently enjoining the defendants and their 
counsel, agents, employees and all persons acting under, in concert with, or 
for them, from proceeding with, consummating or closing the proposed 
transaction;

     5.  In the event the proposed acquisition is consummated, rescinding it 
and setting it aside;

     6.  Awarding compensatory damages against defendants individually and 
severally in an amount to be determined at trial, together with prejudgment 
interest at the maximum rate allowable by law;

     7.  Awarding costs and disbursements, including plaintiff's counsel's 
fees and experts' fees; and

                                      -9-
<PAGE>

     8.  Granting such other and further relief as the Court may deem just 
and proper.

DATED:  May 8, 1998

                                       MILBERG WEISS BERSHAD
                                         HYNES & LERACH LLP
                                       WILLIAM S. LERACH
                                       ALAN SCHULMAN
                                       DARREN J. ROBBINS

                                       /s/ William S. Lerach
                                       --------------------------------
                                       WILLIAM S. LERACH


                                       600 West Broadway, Suite 1800
                                       San Diego, CA 92101
                                       Telephone:  619/231-1058

                                       KAPLAN, KILSHEIMER & FOX, LLP
                                       ROBERT N. KAPLAN
                                       CHRISTINE M. COMAS
                                       685 Third Avenue, 26th Floor
                                       New York, NY 10017
                                       Telephone:  212/687-1980

                                       WOLF POPPER LLP
                                       ROBERT M. KORNREICH
                                       PAUL O. PARADIS
                                       845 Third Avenue
                                       New York, NY 10022
                                       Telephone:  212/759-4600

                                       Attorneys for Plaintiff



                                     -10-




<PAGE>

KEVIN J. YOURMAN (147159)
VAHN ALEXANDER (167373)
WEISS & YOURMAN
10940 Wilshire Blvd.
24th Floor
Los Angeles, California 90024
Tel: (310) 208-2800

Attorneys for Plaintiff


                        SUPERIOR COURT OF THE STATE OF CALIFORNIA

                              FOR THE COUNTY OF SAN DIEGO


PETER VERRONE on Behalf of Himself and all Others )  CASE NO. 720700
Similarly Situated,                               )
                                                  )  (VIA FACSIMILE)
     Plaintiff,                                   )
                                                  )  CLASS ACTION
                                                  )  ------------ 
          v.                                      )
                                                  )
MYCOGEN CORPORATION, DOW                          )  COMPLAINT FOR BREACH
AGROSCIENCES LLC, NICHOLAS D. HEIN,               )  OF FIDUCIARY DUTIES AND
CARLTON J. EIBL, THOMAS J. CABLE, JERRY D.        )  INJUNCTIVE RELIEF
CAULDER, PERRY J. GEHRING, LOUIS W.               )
PRIBILA, DAVID H, RAMMLER, WILLIAM C.             )  
SCHMIDT, G. WILLIAM TOLBERT, W. WAYNE             )  JURY TRIAL DEMAND
WITHERS and DOES 1-25, inclusive                  )
                                                  )
     Defendants.                                  )
                                                  )
- -------------------------------------------------

<PAGE>

KEVIN J. YOURMAN (147159)
VAHN ALEXANDER (167373)
WEISS & YOURMAN
10940 Wilshire Blvd.
24th Floor
Los Angeles, California 90024
Tel: (310) 208-2800

Attorneys for Plaintiff


                        SUPERIOR COURT OF THE STATE OF CALIFORNIA

                              FOR THE COUNTY OF SAN DIEGO


PETER VERRONE on Behalf of Himself and all Others )  CASE NO:
Similarly Situated,                               )
                                                  )  (VIA FACSIMILE)
     Plaintiff,                                   )
                                                  )  CLASS ACTION
                                                  )  ------------ 
          v.                                      )
                                                  )
                                                  )
MYCOGEN CORPORATION, DOW                          )  COMPLAINT FOR BREACH
AGROSCIENCES LLC, NICHOLAS D. HEIN                )  OF FIDUCIARY DUTIES AND
CARLTON J. EIBL, THOMAS J. CABLE, JERRY D.        )  INJUNCTIVE RELIEF
CAULDER, PERRY J. GEHRING, LOUIS W.               )
PRIBILA, DAVID H, RAMMLER, WILLIAM C.             )  
SCHMIDT, G. WILLIAM TOLBERT, W. WAYNE             )  JURY TRIAL DEMAND
WITHERS and DOES 1-25, inclusive                  )
                                                  )
     Defendants.                                  )
                                                  )
- -------------------------------------------------

<PAGE>

     Plaintiff, by his undersigned attorneys, for his complaint against 
defendants, alleges upon knowledge as to himself and his own acts, and upon 
information and belief, as to all other matters, as follows:

     1.   Plaintiff brings this action individually and as a class action on 
behalf of all persons, other than defendants, who own the common stock of 
Mycogen Corporation ("Mycogen" or the "Company") and who are similarly 
situated ("the Class"), to enjoin the consummation of the proposed acquisition 
of the remaining shares of Mycogen by Dow AgroSciences LLC ("Dow") for a 
purchase price of $20.50 per share or $232 million (the "proposed 
transaction"). Alternatively, in the event that the proposed transaction is 
consummated, plaintiff seeks to recover damages caused by the breach of 
fiduciary duties of care, candor and loyalty, described herein, owed by all 
defendants. The proposed transaction and the acts of defendants constitute a 
breach of defendants' fiduciary duties to plaintiff and the Class to take all 
necessary and appropriate steps to obtain the maximum value realizable for 
the shareholders of Mycogen.

                                    PARTIES

     2.   Plaintiff Peter Verrone is, and has been since the announcement of 
the proposed transaction described herein, the owner of shares of common 
stock of Mycogen.

     3.   Defendant Mycogen is a California corporation headquartered at 5501 
Oberlin Drive, San Diego, California, 92121. The Company is publicly traded 
on the NASDAQ market exchange under the ticker symbol "MYCO" and currently 
has over 36,100,000 shares of common stock outstanding. Mycogen is a 
diversified agribusiness and biotechnology company that develops and markets 
seeds and value-added traits for genetically-enhanced crops and provides crop 
protection products and services. Mycogen's majority owner is Dow, a 
wholly-owned subsidiary of The Dow Chemical Company of Midland, Michigan.

     4.   Defendant Dow (formerly DowElanco) is a wholly owned subsidiary of 
the Dow Chemical Company and maintains its principal offices at 9330 
Zionsville Road, Indianapolis, Indiana, 46268. Dow owns approximately 69% of 
Mycogen. Dow employs more than 3,000 people in 26 countries and has worldwide 
sales of more than $2 billion. The company discovers, develops,

                                       2

<PAGE>

manufactures and markets a wide range of agricultural and specialty products 
for farm, home and industrial use.

     5.   Defendant Nicholas D. Hein ("Hein") is, and at all relevant times 
has been, Chairman of the Board of the Company. Defendant Hein is also Vice 
President of Biotechnology of Dow.

     6.   Defendant Carlton J. Eibl ("Eibl") is, and at relevant times has 
been, President and Chief Executive Officer of the Company.

     7.   Defendant Thomas J. Cable ("Cable") is, and at all relevant times 
has been, a Director of the Company.

     8.   Defendant Jerry D. Caulder ("Caulder") is, and at all relevant 
times has been, a Director of the Company.

     9.   Defendant Perry J. Gehring ("Gehring") is, and at all relevant 
times has been, a Director of the Company. Defendant Gehring is also Vice 
President of Research and Development of Dow.

     10.  Defendant Louis W. Pribila ("Pribila") is, and at all relevant 
times has been, a Director of the Company. Defendant Pribila is also Vice 
President, Secretary and General Counsel of Dow.

     11.  Defendant David H. Rammler ("Rammler") is, and at all relevant 
times has been, a Director of the Company.

     12.  Defendant William C. Schmidt ("Schmidt") is, and at all relevant 
times has been, a Director of the Company. Defendant Schmidt is also Vice 
President and Chief Financial Officer of Dow.

     13.  Defendant G. William Tolbert ("Tolbert") is, and at all relevant 
times has been, a Director of the Company. Defendant Tolbert is also a 
Director of Dow.

     14.  Defendant W. Wayne Withers ("Withers") is, and at all relevant 
times has been, a Director of the Company.

     15.  The true names and capacities of defendants used herein under 
California Code of Civil Procedure Section 474 as Does 1 through 25, 
inclusive, are presently not known to plaintiff, who therefore sues these 
defendants by such fictitious names. Plaintiff will seek to amend this 
Complaint and include these Doe defendants' true names and capacities when 
they are ascertained. Each of the fictitiously named


                                       3


<PAGE>

defendants is responsible in some manner for the conduct alleged herein and 
for the injuries suffered by the Class.

     16.  Defendants Hein, Eibl, Cable, Caulder, Gehring, Pribila, Rammler, 
Schmidt, Tolbert and Withers (collectively the "Individual Defendants"), by 
reason of their corporate directorship and/or executive positions, stand in 
a fiduciary position relative to Mycogen's shareholders, which fiduciary 
relationship, at all times relevant herein, required the Individual 
Defendants to exercise their best judgment and to act in a prudent manner and 
in the best interests of Mycogen's shareholders. A director is not permitted 
to act in his/her own self-interest to the detriment of the shareholders.

     17.  Defendant Dow, as a majority shareholder of the Company, also stands
in a fiduciary position relative to Mycogen's shareholders, which fiduciary 
relationship, at all times relevant herein, required Dow to exercise its best 
judgment and to act in a prudent manner and in the best interests of 
Mycogen's shareholders. A majority shareholder is not permitted to act in its 
own self-interest to the detriment of the shareholders.

     18.  Each defendant herein is sued individually as a conspirator and 
aider and abettor, as well as in such defendant's capacity as an officer 
and/or director or majority shareholder of Mycogen, and the liability of each 
arises from the fact that he, she, or it has engaged in all or part of the 
unlawful acts, plans, schemes, or transactions complained of herein.
                                       
                             JURISDICTION AND VENUE

     19.  This Court has proper jurisdiction over this action pursuant to 
SECTION 410.10 of the California Code of Civil Procedure. The violations of 
law complained of herein occurred in this county. Furthermore, the amounts in 
controversy exceed the jurisdictional minimum of this Court.

     20.  Venue is proper in the Superior Court of the County of San Diego 
pursuant to California Code of Civil Procedure SECTIONS 395 and 395.5.
                                       
                           CLASS ACTION ALLEGATIONS

     21.  Plaintiff brings this action individually on his own behalf and as 
a class action, on behalf of all stockholders of Mycogen (except defendants 
herein, and any person, firm, trust, corporation, or other entity related to 
or affiliated with any of the defendants) and their successors in interest, 
who are

                                       4
<PAGE>

or will be threatened with injury arising from defendants' actions as more 
fully described herein (the "Class").

     22.  This action is properly maintained as a class action.

     23.  The class is so numerous that joinder of all members is 
impracticable. As of May 1998, there were over 36,100,000 shares of Mycogen 
common stock outstanding. The disposition of their claims in a class action 
will be of benefit to the parties and the Court. The record holders of 
Mycogen's common stock can be easily determined from the stock transfer 
journals maintained by Mycogen or its agents.

     24.  A class action is superior to other methods for the fair and 
efficient adjudication of the claims herein asserted, and no unusual 
difficulties are likely to be encountered in the management of this action as 
a class action.

     25.  There is a well-defined community of interests in the questions of 
law and fact involved affecting the members of the Class. Among the questions 
of law and fact which are common to the Class, which predominate over 
questions affecting any individual class member are, INTER ALIA, the 
following:

          a.  whether the proposed transaction is grossly unfair to the 
public stockholders of Mycogen,

          b.  whether defendants have failed to disclose all material facts 
relating to the proposal including the potential positive future financial 
benefits which they expect to derive from Mycogen;

          c.  whether defendants willfully and wrongfully failed or refused 
to obtain or attempt to obtain a purchaser for the assets of Mycogen at a 
higher price than the Dow proposal;

          d.  whether plaintiff and the other members of the Class would be 
irreparably damaged were the proposed transaction complained of herein 
consummated;

          e.  whether defendants have breached or aided and abetted the 
breach of fiduciary and other common law duties owned by them to plaintiff 
and the members of the Class; and 

          f.  whether plaintiff and the members of the Class have been 
damaged and what is the proper measure of damages.

                                       5
<PAGE>

     26.  Plaintiff is a member of the Class and is committed to prosecuting 
this action and has retained competent counsel experienced in litigation of 
this nature. Plaintiff's claims are typical of the claims of the other 
members of the Class and plaintiff has the same interests as the other 
members of the Class. Plaintiff does not have interests antagonistic to or in 
conflict with those she seeks to represent. Plaintiff is an adequate 
representative of the Class.

     27.  The likelihood of individual class members prosecuting separate 
individual actions is remote due to the relatively small loss suffered by 
each Class member as compared to the burden and expense of prosecuting 
litigation of this nature and magnitude. Absent a class action, the 
defendants are likely to avoid liability for their wrongdoing, and Class 
members are unlikely to obtain redress for their wrongs alleged herein. This 
Court is an appropriate forum for this dispute.
                                       
                          SUBSTANTIVE ALLEGATIONS

     28.  Mycogen was founded in 1983 by chemical engineer Andrew Barnes, 
biochemist David Edwards, and defendant Rammler. The goal was to use genetic 
engineering techniques to create alternatives to chemical pesticides. Mycogen 
went public in 1987 and acquired control of seed company Agrigenetics from 
The Lubrizol Corporation ("Lubrizol") in 1992. That year it also took a 
controlling interest in Lubrizol. One of the keys to Mycogen's rapid growth 
was its discovery of a protein-delivery system, a gelatin capsule that 
protects the Bt toxin from ultraviolet rays and plant acidity.

     29.  The San Diego-based company develops technology-based seed and 
biopesticide products that control agricultural pests and improve crop 
yields. Using its proprietary "Bacillus thuringiensis" (Bt) biotoxin gene 
technology, Mycogen has developed pesticides that can target specific pests. 
Its Mycogen Seeds division develops genetically enhanced pest-resistant 
planting seeds. Mycogen Crop Protection develops fungicides, herbicides, and 
insecticides, while its Soilserv subsidiary provides specialized 
crop-protection services. Mycogen also conducts research with other 
companies, including seed giant Pioneer Hi-Bred.

     30.  In February 1996, Dow purchased 37% of Mycogen's common stock from 
Lubrizol, and in a simultaneous transaction, Mycogen issued Dow 9% of its 
common stock in return for cash and Dow seed businesses. As part of this 
transaction, Dow entered into an agreement (the "1996 Agreement") whereby it 
was prohibited from acquiring all of the shares of Mycogen prior to February 
1999.

                                       6
<PAGE>

     31.  Nevertheless, since 1996, Dow has substantially increased its 
interest in Mycogen. For example, as recently as November 12, 1997, 
defendants issued a press release over the PR NEWSWIRE entitled MYCOGEN BOARD 
APPROVES $75 MILLION PRIVATE PLACEMENT WITH DOW/ELANCO. The release stated in 
pertinent part:

     The Board of Directors of Mycogen Corporation (Nasdaq: MYCO) today 
     approved private placement of up to $75 million in newly issued shares of 
     Mycogen common stock with the company's majority owner, DowElanco.

                                     *****

     As of October 31, 997, DowElanco, a wholly owned subsidiary of The Dow 
     Chemical Company (NYSE: DOW), owned 18.1 million shares, or approximately 
     57.5 percent of Mycogen's 31.4 million outstanding common shares.

     32.  This private placement boosted Dow's stake in Mycogen from 57.5% to 
63%. Shortly thereafter, Dow increased its interest in Mycogen once more. On 
or about March 17, 1998, defendant Dow issued the following press release 
over the PR NEWSWIRE entitled DOW AGROSCIENCES PURCHASES ADDITIONAL MYCOGEN 
SHARES. The release stated:

     Dow AgroSciences today announced it has purchased $40.1 million of 
     additional equity in Mycogen Corporation from Pioneer Hi-Bred 
     International, Inc. The acquisition totals two (2) million shares of 
     Mycogen common stock at $20.059 per share.

     "DOW AGROSCIENCES IS PLEASED TO ADVANCE ITS INTEREST AND OWNERSHIP OF 
     MYCOGEN," SAID NICK HEIN, VICE PRESIDENT OF BIOTECHNOLOGY AT DOW 
     AGROSCIENCES AND CHAIRMAN OF MYCOGEN'S BOARD OF DIRECTORS. "WE'VE STATED 
     BEFORE OUR BELIEF IN MYCOGEN'S LONG-TERM VALUE AND THAT WE WOULD CONTINUE 
     FROM TIME TO TIME TO ENHANCE OUR INVESTMENT IN IT. We are doubly pleased 
     that this change in ownership will in no way affect the joint research 
     and product development collaboration formed by Mycogen and Pioneer in 
     1995."

     THE ADDITIONAL INVESTMENT IN MYCOGEN INCREASES DOW AGROSCIENCES' TOTAL 
     OWNERSHIP FROM 63 PERCENT TO 69 PERCENT OF MYCOGEN'S OUTSTANDING COMMON 
     SHARES.

     33.  In response to Dow's acquisition of additional shares of Mycogen, 
THE DES MOINES REGISTER reported the following on or about March 18, 1998:

     WITH A MAJORITY INTEREST IN MYCOGEN EVEN BEFORE THE PURCHASE FROM 
     PIONEER, DOW ALREADY HAD A STRONG INFLUENCE ON THE COMPANY, ANALYSTS 
     SAID. THE ADDITIONAL SHARES WILL STRENGTHEN ITS GRIP, THEY SAID. "The 
     expectation is it's going to own 100 percent of Mycogen at some point, so 
     you have to get shares wherever you can," said George Dahlman, an analyst 
     with Piper Jaffray in Minneapolis.

     34.  Then, on or about April 30, 1998, defendants issued the following 
press release over the PR NEWSWIRE entitled DOW REQUESTS AMENDMENT TO 
AGREEMENT WITH MYCOGEN. The release noted:

                                       7
<PAGE>

     The Dow Chemical Company (NYSE:DOW), through its wholly owned subsidiary 
     Dow AgroSciences LLC, announced today that it has requested an amendment 
     to a 1996 agreement with Mycogen Corporation (Nasdaq: MYCO). The 
     amendment would allow Dow AgroSciences to begin discussions regarding 
     the acquisition of the remaining shares of Mycogen that it does not 
     already own. Dow AgroSciences currently owns approximately 69 percent of 
     Mycogen's outstanding shares.

     THE TERMS OF DOW AGROSCIENCES' 1996 AGREEMENT WITH MYCOGEN CURRENTLY 
     STATE THAT DOW AGROSCIENCES CANNOT ACQUIRE THE REMAINING SHARES OF 
     MYCOGEN BEFORE FEBRUARY 1999. IF MYCOGEN'S BOARD OF DIRECTORS AND THE 
     INDEPENDENT DIRECTORS AGREE TO AMEND THE AGREEMENT, DOW AGROSCIENCES IS 
     PREPARED TO BEGIN DISCUSSIONS IMMEDIATELY REGARDING A TRANSACTION IN 
     WHICH MYCOGEN'S MINORITY SHAREHOLDERS WOULD RECEIVE $20.50 IN CASH PER 
     SHARE. Under the terms of the proposed amendment, any transaction would 
     be subject to the prior approval of Mycogen's board of directors and the 
     independent directors.

     35.  The following day, THE NEW YORK TIMES released an article 
regarding the proposed transaction which stated:

     The Dow Chemical Company said yesterday that it would seek talks to 
     acquire the remaining shares of the Mycogen Corporation that it does not 
     already own for $20.50 a share in cash. Dow AgroSciences LLC currently 
     owns about 69 percent of Mycogen's outstanding shares. DOW AGROSCIENCES' 
     OFFER OF $20.50 IN CASH WAS EQUAL TO YESTERDAY'S CLOSING PRICE FOR THE 
     SHARES OF MYCOGEN, WHICH IS BASED IN SAN DIEGO. MYCOGEN'S MINORITY 
     SHAREHOLDERS OWN 11.3 MILLION SHARES OF THE BIOTECHNOLOGY AND 
     GENETICALLY ENGINEERED CROPS COMPANY, MAKING THE PROPOSED TRANSACTION 
     WORTH $231.7 MILLION.

     36.  In light of Dow's stranglehold over the Company, and its Board of 
Directors, Dow's request to amend the 1996 Agreement is a foregone 
conclusion. None of the directors can be considered "independent" and they 
cannot be expected to vigorously protect the rights and interests of 
Mycogen's public shareholders. Defendants' intention to pursue the above 
proposed transaction, a transaction which offers no premium whatsoever for 
Mycogen's shareholders, is in breach of their fiduciary duties of care, 
candor, and loyalty owed to the Company's stockholders to take all necessary 
steps to ensure that Mycogen's minority shareholders will receive the maximum 
value realizable for their shares in any extraordinary transaction involving 
the Company.

     37.  The $20.50 per share price is not the result of arm's-length 
negotiations but was unilaterally set by Dow so that it could obtain complete 
ownership of Mycogen's assets and business at the lowest possible price. The 
intrinsic value of the equity of the Company is materially greater than the 
consideration proposed, taking into account, INTER ALIA, Mycogen's asset 
value, liquidation value, expected growth, full extent of its future earnings 
potential, expected increase in profitability, strength of its business, its 
revenues, cash flow, and earnings power.

                                       8

<PAGE>

     38.  The defendants willingness to entertain the proposed transaction 
requires them to take all reasonable steps to assure the maximization of 
stockholder value, including the implementation of a bidding mechanism to 
foster a fair auction of those shares not held by Dow to the highest bidder or 
the exploration of strategic alternatives which will return greater or 
equivalent short-term value to the plaintiff and the Class.

     39.  Defendants, knowing all of the above, have failed to take the 
necessary and appropriate steps to obtain the maximum value realizable for 
the public shareholders of Mycogen.

     40.  There is no indication that defendants have taken any steps to 
ensure that the interests of Mycogen's minority shareholders, in maximizing 
the value of their holdings, are being protected from Dow's control. 
Defendants have not conducted an auction for those Mycogen shares not held by 
Dow, solicited other offers, or otherwise sought out other potential 
purchasers. Nor have defendants explored strategic alternatives which will 
obtain the highest possible price for Mycogen's stockholders or return 
greater or equivalent value to the plaintiff and the class.

     41.  Further, if defendants accept Dow's proposal without seeking out 
other purchasers, defendants have inhibited the chances of receiving competing 
offers. If the proposed transaction is consummated, Mycogen's shareholders 
will be deprived of the opportunity for substantial gains which the Company 
may have realized.

     42.  By reason of all of the foregoing, defendants herein have willfully 
participated in unfair dealing toward plaintiff and the other members of the 
Class and have engaged in and substantially assisted and aided and abetted 
each other in breach of the fiduciary duties owed by them to the Class.

     43.  Defendants have violated fiduciary and other common law duties owed 
to the plaintiff and the other members of the Class in that they have not and 
are not exercising independent business judgment, and have acted and are 
acting to the detriment of the Class.

     44.  As a result of the actions of defendants, plaintiff and the Class 
have been and will be damaged in that they are not receiving the fair value 
of their Mycogen shares.

     45.  Unless enjoined by this Court, defendants will continue to breach 
their fiduciary duties owed to plaintiff and the Class and will succeed in 
excluding the Class from its fair proportionate share of Mycogen's assets and 
businesses, all to the irreparable harm of the Class.

                                       9

<PAGE>

     46.  Plaintiff and the Class have no adequate remedy of law.

                            FIRST CAUSE OF ACTION
                           AGAINST ALL DEFENDANTS
         FOR BREACH OF FIDUCIARY DUTIES OF CARE, CANDOR, AND LOYALTY
         ----------------------------------------------------------- 

     47.  Plaintiff hereby incorporates by reference paragraphs 1 through 46 
above as though fully set forth herein.

     48.  By virtue of plaintiff's purchase of Mycogen's common stock, and 
the defendants' positions as directors and/or officers and majority 
shareholder of the Company, and because plaintiff reposed trust and 
confidence in them, the defendants owed to plaintiff fiduciary duties of 
care, candor and loyalty of the highest good faith, integrity and fair 
dealing.

     49.  In taking and/or failing to take the actions hertofore alleged, 
defendants violated their fiduciary obligations to plaintiff.

     50.  As a proximate result of defendants' aforesaid conduct, plaintiff 
was damaged by injury to his property, lost profits, loss of future income, 
and other general and specific damages.

     WHEREFORE, plaintiff prays for judgement and relief as follows:

          (1)  declaring that this lawsuit is properly maintainable as a 
class action and certifying plaintiff as representative of the Class;
 
          (2)  declaring that the defendants and each of them have committed 
or aided and abetted in a breach of their fiduciary duties to plaintiff and 
the other members of the Class;

          (3)  declaring the proposed transaction to be a nullity;

          (4)  preliminary and permanently enjoining defendants and all 
persons acting under, in concert with, or for them, from proceeding with, 
consummating or closing the proposed transaction;

          (5)  in the event the proposed transaction is consummated 
rescinding it and setting it aside;

          (6)  ordering defendants, jointly and severally, to account to 
plaintiff and the Class for all profits realized and to be realized by them  
as a result of the proposed transaction complained of and, pending such 
accounting, to hold such profits in a constructive trust for the benefit of 
plaintiff and other members of the Class;

                                      10

<PAGE>

          (7)  ordering defendants to permit a stockholders' committee 
comprised of class members and their representatives only to ensure a fair 
procedure, adequate procedural safeguards, and independent input by 
plaintiff and the Class in connection with any proposed transaction for the 
shares of Mycogen;

          (8)  awarding compensatory damages against defendants, jointly and 
severally, in the amount to be determined at trial, together with prejudgment 
interest at the maximum rate allowable by law;

          (9)  awarding plaintiff and the Class their costs and disbursements 
and reasonable allowances for plaintiff's counsel and experts' fees and 
expenses; and

          (10) granting such other further relief as may be just and proper.

Dated: May 15, 1998

                                       KEVIN J. YOURMAN
                                       VAHN ALEXANDER
                                       WEISS & YOURMAN

                                       By: VAHN ALEXANDER
                                          -----------------------------------
                                           Vahn Alexander

                                       10940 Wilshire Blvd., 24th Floor
                                       Los Angeles, CA 90024
                                       (213) 208-2800

                                       Attorneys for Plaintiff



                                      11

<PAGE>

                                   JURY DEMAND

Plaintiff demands a trial by jury of all issues so triable.

Dated: May 15, 1998

                                       KEVIN J. YOURMAN
                                       VAHN ALEXANDER
                                       WEISS & YOURMAN

                                       By: VAHN ALEXANDER
                                          -----------------------------------
                                           Vahn Alexander

                                       10940 Wilshire Blvd.
                                       24th Floor
                                       Los Angeles, CA 90024
                                       (213) 208-2800

                                       Attorneys for Plaintiff





                                      12







<PAGE>

                                      

          FILED
    KENNETH E. MARTONE
Clerk of the Superior Court
     June 22, 1998
  By: J. JOHNSON, Deputy





                   SUPERIOR COURT OF THE STATE OF CALIFORNIA
                             COUNTY OF SAN DIEGO


LESLIE SUSSER, On Behalf of Himself   )  Lead Case No. 720255
and All Others Similarly Situated,    )
                                      ) CLASS ACTION
                      Plaintiff,      )
                                      ) ASSIGNED TO: Judge Herbert
      vs.                             ) B. Hoffman
                                      )
MYCOGEN CORPORATION, et al.,          ) DATE: July 16, 1998
                                      ) TIME: 3:30 p.m.
                     Defendants.      ) DEPT: 51
___________________________________   ) DATE ACTION FILED: 05/01/98

                                      
                            PRETRIAL ORDER NO. 1
              RE: (i) SETTING STATUS CONFERENCE; (ii) CONSOLIDATING
              ACTIONS; (iii) APPROVING PLAINTIFFS' ORGANIZATION OF
              COUNSEL; (iv) FILING CONSOLIDATED AMENDED COMPLAINT;
                  AND (v) FILING MOTION FOR CLASS CERTIFICATION


<PAGE>

     In furtherance of efficient case management and the interests of justice 
and after due consideration and good cause appearing therefor,

     IT IS HEREBY ORDERED as follows:

 I.  SETTING OF STATUS CONFERENCE

     A status conference in this matter is hereby set for July 16, 1998 at 
3:30 p.m. All parties through their counsel shall attend.

II.  CONSOLIDATION OF PENDING ACTIONS AND FILING OF AMENDED COMPLAINT

     1.  Pursuant to California Code of Civil Procedure Section 1048, Local 
Rule 5.4, and the general equitable powers of this Court, the following 
actions shall be consolidated in Department 51 for all pretrial purposes:

     LESLIE SUSSER v. MYCOGEN CORP., et al., Case No. 720255 (filed 
     May 1, 1998; Dept. 51) ("SUSSER");

     HARBOR FINANCE PARTNERS v. MYCOGEN CORP., et al., Case No. 720256 (filed 
     May 1, 1998; Dept. 51) ("HARBOR FINANCE");

     ELLIS INVESTMENTS, LTD v. CARLTON H. EIBL, et al., Case No. 720257 
     (filed May 1, 1998; Dept. 39) ("ELLIS INVESTMENTS");

     RICHARD A. KOLB v. MYCOGEN CORP., et al., Case No. 720388 (filed 
     May 5, 1998; Dept. 40) ("KOLB");

     JEANETTE ANDERSON v. MYCOGEN CORP., et al., Case No. 720391 (filed
     May 5, 1998; Dept. 48) ("ANDERSON");

     JEAN BOETTCHER v. MYCOGEN CORP., et al., Case No. 720530 (filed
     May 8, 1998; Dept. 38) ("BOETTCHER"); and

     PETER VERRONE v. MYCOGEN CORP., et al., Case No. 720700 (filed
     May 15, 1998; Dept. 51) ("VERRONE").

     2.  Any other actions now pending or hereinafter filed in or transferred 
to this Court which arise out of the same facts as alleged in the 
above-identified cases shall be consolidated for all pretrial purposes, if, 
as and when they are drawn to the Court's attention.

                                    - 1 -

<PAGE>

     3.  Plaintiffs will file within 60 days from the entry of this order a 
Consolidated Amended Class Action Complaint. In the Consolidated Amended 
Class Action Complaint, plaintiffs may add or drop parties and claims. The 
Consolidated Amended Class Action Complaint shall supersede the complaints 
filed in the above-described actions. Defendants need not respond to the 
complaints in the SUSSER, HARBOR FINANCE, ELLIS INVESTMENTS, KOLB, ANDERSON, 
BOETTCHER and VERRONE actions. Defendants will have 30 days from the filing 
of the Consolidated Amended Class Action Complaint to respond to that 
Complaint.

     
III. ORGANIZATION OF PLAINTIFFS' COUNSEL

     The leadership structure of plaintiffs' counsel for the conduct of this 
consolidated action shall consist of the following Co-Lead Counsel:

          Milberg Weiss Bershad
           Hynes & Lerach LLP
          600 West Broadway, Suite 1800
          San Diego, CA 92101
          Telephone: 619/231-1058
                 - and -
          One Pennsylvania Plaza
          New York, NY 10119-0165
          Telephone: 212/594-5300

          Abbey, Gardy & Squitieri, LLP
          212 East 39th Street
          New York, N.Y.
          Telephone: 212/889-3700

IV. DUTIES AND RESPONSIBILITIES OF PLAINTIFFS' COUNSEL

     Plaintiffs' Co-Lead Counsel are hereby vested with the following 
responsibilities and duties on behalf of plaintiffs and plaintiffs' counsel:

     1.  Plaintiffs' Co-Lead Counsel shall have authority to speak and make 
agreements for plaintiffs in matters regarding pretrial

                                    - 2 -

<PAGE>

procedure, settlement negotiations, trial and any post-trial or appellate 
proceedings and shall make all work assignments in such manner as to 
facilitate the orderly and efficient prosecution of this litigation and to 
avoid duplicative or unproductive effort.

     2.  Plaintiffs' Co-Lead Counsel shall be responsible for coordination of 
all activities and appearances on behalf of plaintiffs and for the 
dissemination of notices and orders of this Court. No motion, request for 
discovery, or other pretrial or post-trial proceedings shall be initiated or 
filed by any plaintiff except through plaintiffs' Co-Lead Counsel.

     3.  Plaintiffs' Co-Lead Counsel also shall be available and responsible 
for communications to and from this Court.

     4.  Plaintiffs' Co-Lead Counsel shall direct the preparation for a trial 
of this matter and delegate work responsibilities as may be required in such 
a manner as to lead to the orderly and efficient prosecution of this 
litigation and to avoid duplicative or unproductive efforts.

     5.  Plaintiffs' Co-Lead Counsel is authorized to employ consultants and 
experts.

     6.  Defendants' counsel may rely upon all agreements made with 
plaintiffs' Co-Lead Counsel and such agreements shall be binding on 
plaintiffs.

     7.  Service by defendants' counsel on plaintiffs' co-lead counsel of any 
pleading, motion or other paper required to be served shall be effective as 
service on all plaintiffs.

 V.  FILING OF PLAINTIFFS' MOTION FOR CLASS CERTIFICATION

     In light of this consolidation order and the future filing of a 
Consolidated Amended Class Action Complaint, plaintiffs shall

                                    - 3 -

<PAGE>

file their Motion for Class Certification within fifteen days after 
defendants file their latest answers to the Consolidated Amended Class Action 
Complaint.

     IT IS SO ORDERED.

DATED: JUNE 22, 1998               /s/ HERBERT B. HOFFMAN
       ---------------             --------------------------------
                                   THE HONORABLE HERBERT B. HOFFMAN
                                   SUPERIOR COURT JUDGE

SUBMITTED AND APPROVED BY:

DATED:  June 15, 1998
                                         MILBERG WEISS BERSHAD
                                          HYNES & LERACH LLP
                                         WILLIAM S. LERACH
                                         STEVEN W. PEPICH
                                         RANDALL J. BARON

                                         /S/ Steven W. Pepich
                                         ------------------------
                                             STEVEN W. PEPICH

                                         600 West Broadway, Suite 1800
                                         San Diego, CA 92101
                                         Telephone: 619/231-1058

                                         MILBERG WEISS BERSHAD
                                          HYNES & LERACH LLP
                                         STEVEN G. SCHULMAN
                                         U. SETH OTTENSOSER
                                         One Pennsylvania Plaza
                                         New York, NY 10119-0165
                                         Telephone: 212/594-5300

                                         ABBEY, GARDY & SQUITIERI, LLP
                                         MARK C. GARDY
                                         JAMES S. NOTIS
                                         212 East 39th Street
                                         New York, NY 10016
                                         Telephone: 212/889-3700

                                         WECHSLER HARWOOD HALEBIAN
                                          & FEFFER LLP
                                         SAMUEL ROSEN
                                         488 Madison Avenue
                                         8th Floor
                                         New York, NY 10022
                                         Telephone: 212/935-7400

                                       - 4 -

<PAGE>

                                         BERNSTEIN LIEBHARD & LIFSHITZ
                                         STANLEY D. BERNSTEIN
                                         274 Madison Avenue
                                         New York, NY 10016
                                         Telephone: 212/779-1414

                                         WOLF POPPER LLP
                                         ROBERT M. KORNREICH
                                         PAUL O. PARADIS
                                         845 Third Avenue
                                         New York, NY 10022
                                         Telephone: 212/759-4600

                                         BERMAN, DeVALERIO & PEASE
                                         GLEN DeVALERIO
                                         One Liberty Square
                                         Boston, MA 02109
                                         Telephone: 617/542-8300

                                         LAW OFFICES OF JAMES V.
                                          BASHIAN, P.C.
                                         JAMES V. BASHIAN
                                         500 Fifth Avenue
                                         Suite 2700
                                         New York, NY 10110
                                         Telephone: 212/921-4110

                                         KAPLAN, KILSHEIMER & FOX, LLP
                                         ROBERT N. KAPLAN
                                         CHRISTINE M. COMAS
                                         685 Third Avenue, 26th Floor
                                         New York, NY 10017
                                         Telephone: 212-687-1980

DATED: June 15, 1998
                                         WEISS & YOURMAN
                                         KEVIN YOURMAN
                                         VAHN ALEXANDER

                                         /s/ Vahn Alexander
                                         -----------------------------
                                             VAHN ALEXANDER

                                         10940 Wilshire Blvd.
                                         24th Floor
                                         Los Angeles, CA 90024
                                         Telephone: 310/208-2800

                                         Attorneys for Plaintiffs

                                         MAYER, BROWN & PLATT
                                         BENNETT W. LASKO
                                         190 South La Salle Street
                                         Chicago, IL 60603-3441


                                     - 5 -

<PAGE>

                                         Telephone: 312/782-0600
DATED: June 16, 1998
                                         MAYER, BROWN & PLATT
                                         FREDRICK S. LEVIN

                                         /s/ Fredrick S. Levin
                                         --------------------------------
                                             FREDRICK S. LEVIN

                                         350 South Grand Avenue
                                         25th Floor
                                         Los Angeles, CA 90071
                                         Telephone: 213/229-9500

                                         Attorneys for Defendants
                                         Dow Agrosciences, Dow Chemical
                                         Co., Carlton J. Eibl, John L.
                                         Hagaman, Nickolas D. Hein,
                                         Louis W. Pribila, G. William
                                         Tolbert, J. Pedro Reinhard, Roy
                                         M. Barbee, William C. Schmidt
                                         and Perry J. Gehring
DATED: June 15, 1998
                                         GRAY, CARY, WARE & FREIDENRICH
                                         ROBERT W. BROWNLIE

                                         /s/ Robert W. Brownlie
                                         ---------------------------------
                                             ROBERT W. BROWNLIE

                                         401 B Street, Suite 1700
                                         San Diego, CA 92101-4297
                                         Telephone: 619/699-2700

                                         ALTHEIMER & GRAY
                                         THEODORE J. LOW
                                         10 South Wacker Dr.
                                         Suite 4000
                                         Chicago, IL 60606
                                         Telephone: 312/715-4000

                                         Attorneys for Defendants
                                         Mycogen Corp., Joseph P.
                                         Sullivan, and George
                                         Khachatourians

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