MYCOGEN CORP
8-K, 1998-09-01
AGRICULTURAL SERVICES
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                         SECURITIES AND EXCHANGE COMMISSION

                              WASHINGTON, D.C.  02549

 

                                     FORM 8-K

                       PURSUANT TO SECTION 13 OR 15(D) OF THE
                          SECURITIES EXCHANGE ACT OF 1934


Date of Report (Date of earliest event reported):  August 31, 1998


                               MYCOGEN CORPORATION
             (Exact name of registrant as specified in its charter)


California                          0-15881               95-3802654
(State or other jurisdiction      (Commission File       (IRS Employer
of incorporation)                   Number)               Identification No.)



5501 Oberlin Drive, San Diego, California                           92121
(Address of principal executive offices)                         (Zip Code)


(619) 453-8030
(Registrant's Telephone Number)

<PAGE>
Item 5.  Other Events
         ------------

     On August 31, 1998, Mycogen Corporation, a California corporation
("Mycogen")announced that it had entered into an Agreement and Plan of Merger
dated as of August 31, 1998 with Dow AgroSciences LLC ("Parent") and
Agrosciences Acquisition, Inc. ("Acquisition") (the "Merger Agreement"). Under
the Merger Agreement, Acquisition will commence a tender offer no later than
September 4, 1998 for all of the outstanding common stock of Mycogen not owned
by Parent at $28.00 per share, net to the seller in cash. The tender offer will
be followed by a merger of Acquisition into Mycogen, with Mycogen as the
surviving entity. Holders of shares not purchased in the tender will receive
cash equal to $28.00 per share.

     On August 31, 1998, Mycogen issued a press release with respect to the
Merger Agreement and the transactions contemplated thereby.

     The Merger  Agreement  and press  release  are  attached  as Exhibits 1 and
hereto, respectively, and are incorporated herein by reference.

Item 7.  Exhibits
         --------

1.     Agreement and Plan of Merger dated as of August 31, 1998 among Mycogen
       Corporation, Dow AgroSciences LLC and Agrosciences Acquisition, Inc.

2.     Press Release dated August 31, 1998.

<PAGE>
                                    SIGNATURE

     Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.


                                                MYCOGEN CORPORATION
                                                Registrant


Dated:  September 1, 1998                       /s/ Carlton J. Eibl
                                                -------------------
                                                Carlton J. Eibl
                                                President

<PAGE>

                          AGREEMENT AND PLAN OF MERGER



                                      Among



                              MYCOGEN CORPORATION,



                              DOW AGROSCIENCES LLC


                                       and


                          AGROSCIENCES ACQUISITION INC.



                           dated as of August 31, 1998








<PAGE>



                                TABLE OF CONTENTS

                                                                            Page


ARTICLE I           THE OFFER..................................................2
    Section 1.1       The Offer................................................2
    Section 1.2       Company Action...........................................4
    Section 1.3       Options..................................................5
    Section 1.4       Employee Stock Purchase Plan.............................6
    Section 1.5       Restricted Stock.........................................7

ARTICLE II          THE MERGER.................................................8
    Section 2.1       The Merger...............................................8
    Section 2.2       Effective Time; Closing..................................8
    Section 2.3       Effects of the Merger; Subsequent Actions................9
    Section 2.4       Articles of Incorporation; Bylaws........................9
    Section 2.5       Directors................................................9
    Section 2.6       Officers.................................................9
    Section 2.7       Conversion of Securities.................................9

ARTICLE III         DISSENTING SHARES; EXCHANGE OF CERTIFICATES...............10
    Section 3.1       Dissenting Shares.......................................10
    Section 3.2       Exchange of Certificates................................11

ARTICLE IV          REPRESENTATIONS AND WARRANTIES OF THE
                    COMPANY...................................................12
    Section 4.1       Organization and Qualification; Subsidiaries............12
    Section 4.2       Capitalization..........................................13
    Section 4.3       Authority Relative to This Agreement....................13
    Section 4.4       No Conflict; Required Filings and Consents..............14
    Section 4.5       SEC Reports.............................................15
    Section 4.6       Absence of Certain Changes..............................15
    Section 4.7       Schedule 14D9; Offer Documents; Proxy Statement.........15
    Section 4.8       Finder's Fee............................................16
    Section 4.9       Stockholder Action......................................16
    Section 4.10      Fairness Opinion........................................16
    Section 4.11      Inapplicability of Rights Agreement.....................16
    Section 4.12      Information Known by Parent.............................17


                                       -i-

<PAGE>



ARTICLE V           REPRESENTATIONS AND WARRANTIES OF PARENT
                    AND ACQUISITION...........................................17
    Section 5.1       Organization............................................17
    Section 5.2       Authority Relative to this Agreement....................17
    Section 5.3       No-Conflict; Required Filings and Consents..............18
    Section 5.4       Offer Documents; Schedule 14D9; Proxy Statement.........18
    Section 5.5       Acquisition.............................................19
    Section 5.6       Financing...............................................19
    Section 5.7       Brokers.................................................19
    Section 5.8       Insurance...............................................19

ARTICLE VI          COVENANTS.................................................19
    Section 6.1       Conduct of Business of the Company......................19
    Section 6.2       Reasonable Best Efforts................... .............20
    Section 6.3       Public Announcements....................................21
    Section 6.4       Indemnification.........................................21
    Section 6.5       Notification of Certain Matters.........................23
    Section 6.6       Exchange and Purchase Agreement; No Restrictions on
                      Purchase................................................23
    Section 6.7       Compliance by Acquisition...............................24
    Section 6.8       Financing...............................................24
    Section 6.9       Access to and Retention of Information..................24

ARTICLE VII         CONDITIONS TO CONSUMMATION OF THE MERGER..................24
    Section 7.1     Conditions to Each Party's Obligations to Effect the
                    Merger....................................................24

ARTICLE VIII        TERMINATION; EXPENSES; AMENDMENT; WAIVER..................25
    Section 8.1       Termination.............................................25
    Section 8.2       Effect of Termination...................................26
    Section 8.3       Fees and Expenses.......................................26
    Section 8.4       Amendment...............................................26
    Section 8.5       Extension; Waiver.......................................26

ARTICLE IX          MISCELLANEOUS.............................................27
    Section 9.1       Nonsurvival of Representations and Warranties...........27
    Section 9.2       Entire Agreement; Assignment............................27
    Section 9.3       Notices.................................................27
    Section 9.4       Governing Law; Jurisdiction and Venue; Waiver of Jury
                      Trial...................................................28
    Section 9.5       Parties in Interest.....................................29
    Section 9.6       Specific Performance....................................29
    Section 9.7       Severability............................................29

                                      -ii-

<PAGE>



    Section 9.8       Descriptive Headings....................................29
    Section 9.9       Certain Definitions.....................................30
    Section 9.10      Counterparts............................................31




                                      -iii-

<PAGE>



                                     ANNEXES

Annex A - Offer Conditions
Annex B - Press Release
Annex C - Option Election
Annex D - Stock Purchase Election
Annex E - Restricted Stock Election


                                      -iv-

<PAGE>



                          AGREEMENT AND PLAN OF MERGER

         This  AGREEMENT  AND PLAN OF  MERGER  (this  "Agreement"),  dated as of
August 31, 1998, is among Mycogen  Corporation,  a California  corporation  (the
"Company"),   Dow  AgroSciences   LLC,  a  Delaware  limited  liability  company
("Parent"),    AgroSciences    Acquisition   Inc.,   a   Delaware    corporation
("Acquisition"),  and,  solely for the limited  purpose set forth in Section 6.8
below, The Dow Chemical Company, a Delaware corporation ("TDCC").

         WHEREAS,  Parent is the holder of  24,766,157  shares of the  Company's
common stock, $.001 par value per share (including, unless the context otherwise
requires,  the  associated  preferred  stock  purchase  rights  under the Rights
Agreement (as defined below)) ("Common Stock"), representing approximately 68.3%
of the shares of Common Stock ("Shares") outstanding; and

         WHEREAS, Acquisition is a majority-owned subsidiary of Parent and an
indirect wholly owned subsidiary of TDCC; and

         WHEREAS, Parent has proposed that Parent acquire all of the remaining
issued and outstanding Shares; and

         WHEREAS,  it is proposed that Acquisition  shall make a tender offer to
acquire all outstanding  Shares for a cash amount of $28 per Share (such amount,
or any greater  amount per Share paid pursuant to the tender offer,  is referred
to as the "Per Share  Amount") net to the seller in cash in accordance  with the
terms  and  subject  to the  conditions  provided  for in  this  Agreement  (the
"Offer"); and

         WHEREAS,  the Special Committee of independent  directors (the "Special
Committee") of the Board of Directors of the Company (the "Board"), at a meeting
duly called and held on August 31, 1998, has  unanimously  recommended  that the
Board approve and authorize  the Offer,  the Merger (as defined  below) and this
Agreement; and

         WHEREAS,  the Board,  at a meeting  duly  called and held on August 31,
1998, has (A) determined that this Agreement and the  transactions  contemplated
by this Agreement (the  "Transactions") are fair to and in the best interests of
the  stockholders  of the  Company  (other  than  TDCC or its  affiliates),  (B)
approved and adopted this  Agreement and the  Transactions,  including the Offer
and the merger between  Acquisition and the Company  contemplated by Section 2.1
hereof (the "Merger") in accordance with the California General Corporation

                                                -1-

<PAGE>



Law ("California Law") and the Delaware General Corporation Law ("Delaware Law")
and upon the terms and subject to the  conditions  set forth in this  Agreement,
and (C) resolved to recommend  that the  stockholders  of the Company accept the
Offer,  tender  their  Shares  thereunder  to  Acquisition  and,  if required by
applicable law, approve and adopt this Agreement and the Merger; and

         WHEREAS,  Wasserstein Perella & Co., Inc.  ("Wasserstein  Perella") has
delivered to the Special Committee,  for its consideration,  and for delivery to
the  stockholders of the Company pursuant to Section 1203 of California Law, its
written  opinion that,  subject to the various  assumptions  and limitations set
forth  thereon  as of the date of such  opinion,  the cash  consideration  to be
received in the Offer and the Merger by the  stockholders  of the Company  other
than TDCC or its affiliates is fair to such  stockholders from a financial point
of view; and

         WHEREAS,  the members committee of Parent and the board of directors of
Acquisition  have each (A) determined  that this Agreement and the  Transactions
are fair to and in the best interests of the  stockholders  of the Company,  and
(B) approved and adopted this Agreement and approved the Transactions, including
the Merger,  in  accordance  with Delaware Law and  California  Law and upon the
terms and subject to the conditions set forth in this Agreement.

         NOW,  THEREFORE,  in  consideration  of the  foregoing  and the  mutual
covenants  and  agreements  contained  in this  Agreement,  and  intending to be
legally bound, the Company, Parent and Acquisition agree as follows;


                                    ARTICLE I

                                    THE OFFER

         Section 1.1 The Offer.  (a) Provided that this Agreement shall not have
been terminated in accordance with Section 8.1, as promptly as practicable,  but
in no event later than the fifth business day following the public  announcement
of  the  terms  of  this  Agreement,   Acquisition  shall  commence  the  Offer.
Acquisition  shall,  and Parent shall cause  Acquisition 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,  Acquisition
shall,  subject to  applicable  law, pay for such  Shares.  The Per Share Amount
payable in the Offer shall be paid net to the seller in cash, upon the terms and
subject to the  conditions  of the Offer.  Acquisition  shall not,  without  the
consent

                                                -2-

<PAGE>



of the Special Committee, accept for payment any Shares tendered pursuant to the
Offer  unless a number  of  Shares  shall  have been  validly  tendered  and not
withdrawn  prior to the expiration of the Offer such that, upon purchase of such
Shares by Acquisition, Acquisition and Parent, collectively, would be the owners
of Shares  representing  at least 81.07% of the Fully Diluted Shares (as defined
on Section  9.9) (the  "First  Minimum  Condition").  In  addition  to the First
Minimum  Condition,  the obligation of Acquisition to accept for payment and pay
for  Shares  tendered  pursuant  to the  Offer  shall  be  subject  only  to the
satisfaction  or waiver of the conditions (i) that a number of Shares shall have
been validly  tendered and not  withdrawn  prior to the  expiration  date of the
Offer such that,  upon purchase of such Shares by  Acquisition,  Acquisition and
Parent, collectively, would be the owners of Shares representing at least 90% of
the Fully  Diluted  Shares as of the  expiration  date of the Offer (the "Second
Minimum Condition") and (ii) that are set forth in Annex A to this Agreement. It
is agreed that the Second Minimum  Condition and the other  conditions set forth
in  Annex A are for the sole  benefit  of  Acquisition  and may be  asserted  by
Acquisition  regardless  of the  circumstances  unless  the  failure of any such
condition was caused by any breach by Parent or Acquisition  of this  Agreement.
Acquisition  expressly  reserves the right in its sole  discretion to waive,  in
whole  or in  part,  at any  time  or from  time to  time,  any  such  condition
(including,  without limitation, the Second Minimum Condition, but not including
the First Minimum  Condition) or to increase the cash price per Share payable in
the  Offer;  provided  that no change may be made that  decreases  the Per Share
Amount 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 those set forth in Annex A. If
requested  to do so by  Parent  or  Acquisition,  the  Company  (acting  at  the
direction of the Special  Committee)  may, in the sole discretion of the Special
Committee,  waive the First Minimum  Condition and  Acquisition  may  thereafter
accept for payment any and all Shares validly  tendered and not withdrawn  prior
to the  expiration of the Offer  whether or not the First  Minimum  Condition is
satisfied.

                  (b) The initial expiration date of the Offer shall be midnight
on the 20th  business day  following  commencement  of the Offer.  The foregoing
notwithstanding, Acquisition may, without the consent of the Company, extend the
Offer (i) for any period  required by any rule,  regulation,  interpretation  or
position of the  Securities  and  Exchange  Commission  (the "SEC") 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 Annex A have
not been satisfied or waived,  until such time as all of such  conditions  shall
have been  satisfied or waived,  or (iii) in the event all of the  conditions to
the Offer shall have been  satisfied  or waived,  other than the Second  Minimum
Condition,

                                                -3-

<PAGE>



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 Annex A shall have
been satisfied or waived.  If at any scheduled  expiration date of the Offer the
Second Minimum Condition shall not have been satisfied,  then, at the request of
the Company  (acting at the  direction of the Special  Committee,  which request
shall subsequently be confirmed in writing), Acquisition shall, and Parent shall
cause  Acquisition to, extend the Offer for a period or periods  aggregating not
more than 40 business days,  subject to the right of  Acquisition  and Parent to
terminate  this  Agreement  pursuant  to Section  8.1.  In  addition,  if at any
scheduled  expiration  date of the Offer, a condition set forth in paragraph (c)
or (d) of Annex A hereto  shall  not have  been  satisfied  but all of the other
conditions  set forth in  paragraphs  (a) - (e) of Annex A shall  then have been
satisfied,  then, at the request of the Company  (acting at the direction of the
Special Committee, which request shall subsequently be confirmed in writing) and
so long as the  Company  is using its  reasonable  best  efforts  to cause  such
conditions  to become  satisfied,  Acquisition  shall,  and Parent  shall  cause
Acquisition  to,  extend the Offer for up to an  additional  20  business  days,
subject to the right of  Acquisition  and  Parent to  terminate  this  Agreement
pursuant  to  Section  8.1.  Subject to the right of  Acquisition  and Parent to
terminate  this  Agreement  pursuant  to  Section  8.1,  Acquisition  shall  not
terminate or withdraw the Offer prior to any  scheduled  expiration  date of the
Offer,  including as extended pursuant to this Section 1.1;  provided,  however,
that Acquisition may, at its option,  terminate and withdraw the Offer if, after
such  extensions  required to be made under this Section  1.1(b),  the Offer has
expired in accordance with its terms.

                  (c) As soon as practicable on the date of  commencement of the
Offer,  Parent and  Acquisition  shall  file with the  Securities  and  Exchange
Commission  (the  "Commission")  (i) a Tender Offer Statement on Schedule 14D- 1
with respect to the Offer which will contain the offer to purchase,  the form of
the related letter of transmittal and related summary  advertisement  and (ii) a
Rule  13E-3  Transaction  Statement  with  respect  to the  Offer  and the other
transactions  contemplated  hereby (the Schedule 14D-1,  the Schedule 13E-3, the
offer to purchase and such other  documents,  together with any  supplements  or
amendments thereto, the "Offer Documents").  Parent, Acquisition and the Company
each agrees  promptly to correct any  information  provided by it for use in the
Offer Documents if and to the extent that any such information shall have become
false or  misleading  in any material  respect and Parent and  Acquisition  each
further  agrees to take all steps  necessary to cause the Offer  Documents as so
corrected to be filed with the Commission and to be  disseminated  to holders of
Shares,  in each  case  as and to the  extent  required  by  applicable  federal
securities  laws.  The  Special  Committee  and its  counsel  shall  be  given a
reasonable opportunity to review and comment on the Offer Documents prior to

                                                -4-

<PAGE>



their  filing  with the  Commission  and shall be  provided  with any written or
verbal  comments  Parent,  Acquisition  and their  counsel may receive  from the
Commission  or its staff with  respect  to the Offer  Documents  promptly  after
receipt of such comments.

         Section 1.2 Company  Action.  (a) The  Company  hereby  approves of and
consents to the Offer and represents  that the Board,  acting upon the unanimous
recommendation  of the Special  Committee,  at a meeting duly called and held on
August 31, 1998,  has  unanimously  (i)  determined  that this Agreement and the
Transactions  are fair to and in the best interests of the  stockholders  of the
Company  (other than TDCC or its  affiliates),  (ii)  approved  and adopted this
Agreement and approved the Transactions, including the Merger and the Offer, and
(iii)  resolved to recommend  that the  stockholders  of the Company  accept the
Offer,  tender  their  Shares  thereunder  to  Acquisition  and,  if required by
applicable law,  approve and adopt this Agreement and the Merger;  provided that
such  recommendation  may be  withdrawn,  modified  or amended to the extent the
Special  Committee  determines  that the failure to do so would be  inconsistent
with the fiduciary duties of the Special Committee to the Company's stockholders
under applicable law (as determined by the Special Committee in good faith after
consultation with independent  counsel).  Except as may be inconsistent with the
fiduciary duties of the Special Committee under applicable law (as determined by
the  Special  Committee  in  good  faith  after  consultation  with  independent
counsel),  the Company hereby  consents to the inclusion in the Offer  Documents
and the Proxy Statement (as defined in Section 4.7 below) of the recommendations
of the Board described in this Section 1.2(a).

                  (b) As soon as practicable on the date of  commencement of the
Offer, the Company shall file with the Commission a  Solicitation/Recommendation
Statement  on  Schedule  14D-9  (together  with any  amendments  or  supplements
thereto,  the  "Schedule  14D-9")  and  shall  mail  the  Schedule  14D-9 to the
stockholders of the Company  promptly after the  commencement of the Offer.  The
Schedule  14D-9  shall,  except to the extent  inconsistent  with the  fiduciary
duties of the Board  under  applicable  law (as  determined  in good faith after
consultation with independent counsel), at all times contain the determinations,
approvals and recommendations  described in Section 1.2(a). Parent,  Acquisition
and the Company each agrees promptly to correct any  information  provided by it
for use in the  Schedule  14D-9 if and to the extent  that any such  information
shall have become false or  misleading  in any material  respect and the Company
further  agrees to take all steps  necessary to cause the  Schedule  14D-9 as so
corrected to be filed with the Commission and to be  disseminated  to holders of
Shares,  in each  case  as and to the  extent  required  by  applicable  federal
securities laws. Parent, Acquisition and their

                                                -5-

<PAGE>



counsel  shall be given a  reasonable  opportunity  to review and comment on the
Schedule  14D-9  prior to its filing with the  Commission  and shall be provided
with any written or verbal comments the Company and its counsel may receive from
the  Commission or its staff with respect to the Schedule  14D-9  promptly after
receipt of such comments.

                  (c) In  connection  with the Offer,  the Company will, or will
cause its transfer agent to, promptly  furnish  Acquisition with mailing labels,
security position listings and any available listing or computer file containing
the names and  addresses  of the record  holders  and  non-objecting  beneficial
owners of the Shares and of Options (as  defined in Section  9.9) as of a recent
date  and  shall  furnish  Acquisition  with  such  additional  information  and
assistance  (including,  without  limitation,  updated  lists  of  stockholders,
mailing  labels and lists of securities  positions) as Acquisition or its agents
may reasonably  request in communicating  the Offer to the record and beneficial
holders of Shares. Subject to the requirements of applicable law, and except for
such steps as are  necessary to  disseminate  the Offer  Documents and any other
documents necessary to consummate the Merger, Acquisition and its affiliates and
associates  shall  hold in  confidence  the  information  contained  in any such
labels,  listings and files,  will use such  information only in connection with
the Offer and the  Merger,  and, if this  Agreement  shall be  terminated,  will
deliver to the Company all copies of such information  received from the Company
pursuant to this Agreement.

         Section  1.3  Options.  (a)  If  the  conditions  in  Article  VII  are
satisfied,  the  Company  shall use its best  efforts to cause all  Options  (as
defined in Section 9.9) 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 arrangements shall 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)  shall be entitled to
receive  in  respect  of such  Option an amount in cash  equal to (x) the Merger
Consideration  (as defined  below) 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 shall,  if
necessary,  be deemed to include the Board amending the Mycogen Corporation 1992
Stock Option Plan (which  incorporates  outstanding  options  granted  under the
Mycogen  Corporation  1983 Stock  Option Plan) (the "1992 Plan") to provide that
the term "Corporate Transaction" shall be deemed to include the Merger.

                  (b) As soon  as  practicable  after  the  commencement  of the
Offer, the Company shall use its reasonable best efforts to cause each holder of

                                                -6-

<PAGE>



Options  (whether  or not  such  Options  are  vested  as of the  date  of  this
Agreement) to execute and deliver to the Company, prior to the expiration of the
Offer, an agreement  substantially in the form of Annex C (an "Option Election")
under which such holder would agree,  contingent  upon the purchase of Shares by
Acquisition 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  Acquisition  shall
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  Acquisition  pursuant to the Offer,  the Company
shall make  available to each holder of Options the funds  necessary to exercise
such  Options,  and Parent shall  advance  such funds to the Company.  The funds
advanced to any Option holders in accordance  with the preceding  sentence shall
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
shall be retained by  Acquisition  as  repayment  of the amount  advanced to the
Company by Parent.  The Company  represents that the Plan  Administrator  of the
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 Acquisition  pursuant
to the Offer.  The parties to this  Agreement  consent to the action of the Plan
Administrator of the 1992 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 Shares
issuable upon the exercise of Options  resulting from the execution and delivery
of valid Option Elections to be tendered in the Offer.

                  (c)  Notwithstanding the foregoing,  if Acquisition  purchases
Shares pursuant to the Offer,  the Company  immediately  shall purchase  Options
granted to Clayton  Yeutter  for an amount  equal to the product of (i) 7500 and
(ii) the difference between the Per Share Amount and $23.9380. The Company shall
take all action  required to make such purchase  comply with Rule 16b-3(e) under
the Securities Exchange Act of 1934, as amended.

         Section 1.4 Employee Stock Purchase Plan. (a) The Company shall use its
best efforts to effectuate the  provisions of Section  1.4(b) below,  to provide
for  termination  of the Mycogen  Corporation  1995 Employee Stock Purchase Plan
(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  Acquisition  of Shares  pursuant  to the Offer,  any  payroll
deductions accumulated under the Stock Purchase Plan and not used

                                                -7-

<PAGE>



to  purchase  Shares  under  the  Stock  Purchase  Plan for  tender in the Offer
pursuant to Section  1.4(b)  shall be returned to the  applicable  participants;
provided,  however,  that  arrangements  shall be made so that  each  holder  of
Purchase  Rights as described in Section 1.4(b) who consents to the  termination
of all of such holder's  Purchase  Rights  (either  before the Effective Time or
within a reasonable time  thereafter)  shall be entitled to receive an amount in
cash equal to the net amount such holder of Purchase  Rights would have received
pursuant to Section 1.4(b) if such holder had made a Stock Purchase Election.

                  (b) As soon  as  practicable  after  the  commencement  of the
Offer,  the  Company  shall  use its  reasonable  best  efforts  to  cause  each
individual  who has purchase  rights  outstanding  under the Stock Purchase Plan
("Purchase  Rights")  to  execute  and  deliver  to the  Company,  prior  to the
expiration of the Offer,  an agreement  substantially  in the form of Annex D (a
"Stock Purchase Election") under which such holder would agree,  contingent upon
the  purchase  of  Shares  by  Acquisition  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   Acquisition   shall  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 Acquisition  pursuant to the Offer,  the Company shall 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 shall  advance
such funds to the Company.  The funds advanced to any holder of Purchase  Rights
in  accordance  with the  preceding  sentence  shall be deducted from the amount
payable to such holder of Purchase Rights  pursuant to the Offer,  and the Stock
Purchase Election and the Offer shall so provide. The funds so deducted shall be
retained by  Acquisition  as repayment of the amount  advanced to the Company by
Parent.  The  parties  to this  Agreement  will use their  best  efforts to take
whatever steps are necessary to make it possible for

                                                -8-

<PAGE>



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.

         Section 1.5  Restricted  Stock.  The Company  represents  that the Plan
Administrator  of the Mycogen  Corporation  Restricted  Stock Issuance Plan (the
"Restricted  Stock Plan") has taken action to provide that each  unvested  Share
("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 Acquisition pursuant to the Offer.
The parties to this 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 shall 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  substantially  in the form of Annex E (a
"Restricted  Stock  Election")  under which such holder would agree,  contingent
upon the  purchase of Shares by  Acquisition  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  of this
Section  1.5) to be tendered in the Offer.  Immediately  prior to the  Effective
Time, if the  conditions to Article VII are  satisfied,  the Company shall 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.


                                   ARTICLE II

                                   THE MERGER

         Section 2.1 The Merger.  At the Effective  Time (as defined below) upon
the terms and subject to the conditions of this Agreement and in accordance with
California Law and Delaware Law,  Acquisition  shall be merged with and into the
Company,  whereupon the separate corporate  existence of Acquisition shall cease
and the Company shall  continue as the  surviving  corporation  (the  "Surviving
Corporation").


                                                -9-

<PAGE>



         Section 2.2 Effective  Time;  Closing.  (a) At the Designated  Time (as
defined below) the parties will (i) file a certificate of ownership  pursuant to
Section  1110 of  California  Law 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 shall  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").  Prior to such filings, a closing shall be held at the offices of Mayer,
Brown & Platt, 190 South LaSalle Street, Chicago,  Illinois 60603, or such other
place as the parties shall agree, for the purpose of confirming the satisfaction
or waiver of the conditions set forth in Article VII.

                  (b)  Immediately  following the  satisfaction or waiver of all
conditions  set forth in Article  VII below  (assuming  the  transfer  of all of
Parent's Shares to  Acquisition),  Parent shall cause  Acquisition 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").

         Section  2.3  Effects of the  Merger;  Subsequent  Actions.  (a) At the
Effective  Time,  the Merger shall have the effects set forth in California  Law
and Delaware Law. Without limiting the generality of the foregoing,  and subject
thereto, at the Effective Time, all the properties,  rights, privileges,  powers
and  franchises  of the  Company  and  Acquisition  shall vest in the  Surviving
Corporation,   and  all  debts,  liabilities  and  duties  of  the  Company  and
Acquisition  shall  become the debts,  liabilities  and duties of the  Surviving
Corporation.

                  (b) If, at any time after the  Effective  Time,  the Surviving
Corporation  shall  consider  or be  advised  that  any  deeds,  bills  of sale,
assignments,  assurances  or any  other  actions  or  things  are  necessary  or
desirable to vest,  perfect or confirm of record or  otherwise in the  Surviving
Corporation  its right,  title or  interest  in, to or under any of the  rights,
properties or assets of either of the Company or  Acquisition  acquired or to be
acquired by the Surviving Corporation as a result of, or in connection with, the
Merger, or otherwise to carry out this Agreement,  the officers and directors of
the Surviving  Corporation  shall be  authorized to execute and deliver,  in the
name and on behalf of either of the  Company  or  Acquisition,  all such  deeds,
bills of sale, assignments and assurances and to take and do, in the name and on
behalf of each of such  corporations  or  otherwise,  all such other actions and
things as may be necessary or desirable to vest, perfect or confirm of record or
otherwise

                                                -10-

<PAGE>



any and all right,  title and interest in, to and under such rights,  properties
or assets of the Surviving Corporation or otherwise to carry out this Agreement.

         Section 2.4  Articles of  Incorporation;  Bylaws.  (a) The  Articles of
Incorporation of the Company in effect  immediately  prior to the Effective Time
shall be the  Articles  of  Incorporation  of the  Surviving  Corporation  until
amended in accordance with applicable law.

                  (b) The First  Amended and  Restated  Bylaws of the Company in
effect at the Effective  Time shall be the Bylaws of the  Surviving  Corporation
until amended in accordance with applicable law.

         Section 2.5  Directors.  The directors of  Acquisition at the Effective
Time shall 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.

         Section 2.6  Officers.  The  officers  of the Company at the  Effective
Time, and any additional  individuals designated by Parent, shall 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.

         Section 2.7 Conversion of Securities.  At the Effective Time, by virtue
of the Merger and without any action on the part of Parent,  Acquisition (except
as required by Section 1110 of California Law), the Company or the holder of any
of the following securities:

                  (a) Each Share issued and outstanding immediately prior to the
Effective  Time (other than Shares to be canceled  pursuant to Section 2.7(b) of
this  Agreement and  Dissenting  Shares (as defined in Section  3.1)),  shall 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 Per Share Amount (the "Merger Consideration").

                  (b) Each Share issued and outstanding immediately prior to the
Effective  Time and owned by Parent or  Acquisition  or any  direct or  indirect
wholly  owned  subsidiary  of  Parent  or  Acquisition,  or which is held in the
treasury  of the  Company  or by any of the  Company's  subsidiaries,  shall  be
canceled  and  retired  and no payment of any  consideration  shall be made with
respect thereto.


                                                -11-

<PAGE>



                  (c) Each share of common stock,  par value $0.01 per share, of
Acquisition issued and outstanding immediately prior to the Effective Time shall
be converted into and become one validly  issued,  fully paid and  nonassessable
share of common stock, par value $0.001 per share, of the Surviving Corporation.


                                   ARTICLE III

                   DISSENTING SHARES; EXCHANGE OF CERTIFICATES

         Section  3.1  Dissenting  Shares.   Notwithstanding  anything  in  this
Agreement to the contrary,  if demands for payment are filed (within the meaning
of Section 1300(b)(1) 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  ("Dissenting  Shares") shall not be converted
into a right to receive the Merger  Consideration  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  shall be  treated  as if they had been
converted  as of  the  Effective  Time  into  a  right  to  receive  the  Merger
Consideration  without  interest  thereon.  The Company shall give Parent prompt
notice of any demands  received by the Company  for  appraisal  of Shares,  and,
prior to the Effective  Time,  Parent shall have the right to participate in all
negotiations  and  proceedings  with  respect  to  such  demands.  Prior  to the
Effective  Time, the Company shall not, except with the prior written consent of
Parent,  voluntarily  make any  payment  with  respect to, or settle or offer to
settle, any such demands.

         Section 3.2 Exchange of Certificates.  (a) Prior to the Effective Time,
a bank or trust company reasonably acceptable to the Company shall be designated
by Parent (the "Paying  Agent") to act as agent in connection with the Merger to
receive and pay the Merger Consideration to which holders of Shares shall become
entitled  pursuant to Section  2.7(a).  Promptly  after the Effective  Time, the
Surviving  Corporation shall cause to be mailed to each record holder, as of the
Effective  Time, of a certificate or  certificates  (the  "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 appropriate Merger Consideration  therefor.  Subject to Section
3.2(c),

                                                -12-

<PAGE>



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 Paying Agent shall deliver to the
holder of such Certificate the Merger Consideration  multiplied by the number of
Shares formerly  represented by such Certificate in exchange therefor,  and such
Certificate  shall  forthwith be canceled.  Until so surrendered  and exchanged,
each such Certificate (other than Certificates representing Dissenting Shares or
Shares held by Parent,  Acquisition  or the  Company,  or any direct or indirect
subsidiary  thereof) shall represent solely the right to receive the appropriate
Merger  Consideration.  No  interest  shall  be paid  or  accrue  on the  Merger
Consideration.  If the Merger  Consideration  (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,  it
shall be a condition to such exchange that the Certificate so surrendered  shall
be properly  endorsed or  otherwise  be in proper form for transfer and that the
person  requesting  such exchange  shall pay to the Paying Agent any transfer or
other taxes required by reason of the payment of the Merger  Consideration  to a
person other than the registered holder of the Certificate surrendered, or shall
establish to the satisfaction of the Paying Agent that such tax has been paid or
is not applicable.

                  (b) When and as needed,  Parent or Acquisition  shall deposit,
or cause to be deposited,  in trust with the Paying Agent the appropriate Merger
Consideration to which holders of Shares shall be entitled at the Effective Time
pursuant to Section 2.7(a) of this Agreement. The funds held by the Paying Agent
pursuant to this  Section  3.2 shall not be used for any purpose  other than the
payment of the Merger Consideration pursuant to this Agreement.

                  (c) Promptly  following the date which is six months after the
Effective  Time,  Parent will cause the Paying Agent to deliver to the Surviving
Corporation   all  cash  and  documents  in  its  possession   relating  to  the
transactions  described in this  Agreement,  and the Paying Agent's duties shall
terminate.  Thereafter,  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 appropriate Merger Consideration, without any interest thereon.

                  (d) After the Effective  Time,  there shall 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 Paying  Agent,  such  Certificates  shall be
canceled and exchanged for the Merger Consideration, as provided in this Article
III, subject to applicable law in the case of Dissenting Shares.

                                                -13-

<PAGE>




                                   ARTICLE IV

                  REPRESENTATIONS AND WARRANTIES OF THE COMPANY

         The Company hereby represents and warrants to Parent and Acquisition as
follows:

         Section 4.1 Organization and Qualification; Subsidiaries. (a) Except as
set forth in Section 4.1 of the  Disclosure  Letter  delivered by the Company to
Parent concurrently with the execution hereof (the "Disclosure  Letter") each of
the  Company and its  subsidiaries  is a  corporation  duly  organized,  validly
existing  and in  good  standing  under  the  laws  of the  jurisdiction  of its
incorporation  and has all  requisite  corporate  power  and  authority  and all
necessary governmental approvals to own, lease and operate its properties and to
carry on its business as now being conducted,  except where the failure to be so
organized,  existing  and in good  standing or to have such power and  authority
would not, individually or in the aggregate,  have a Material Adverse Effect (as
defined in Section 9.9).

                  (b) Each of the Company and its subsidiaries is duly qualified
or licensed and in good standing to do business in each jurisdiction  (including
any foreign  country) in which the property  owned,  leased or operated by it or
the nature of the business conducted by it makes such qualification or licensing
necessary,  except where the failure to be so duly  qualified or licensed and in
good  standing  would not,  individually  or in the  aggregate,  have a Material
Adverse Effect.

                  (c) The  Company  has  heretofore  made  available  to  Parent
complete and correct copies of the Company's Articles of Incorporation and First
Amended and Restated Bylaws and the equivalent  organizational documents of each
of its  subsidiaries,  each as  amended  to the  date of  this  Agreement.  Such
Articles of Incorporation, Bylaws and equivalent organizational documents are in
full force and effect and no other organizational documents are applicable to or
binding upon the Company or its subsidiaries. The Company is not in violation of
any of the  provisions  of its Articles of  Incorporation  or First  Amended and
Restated  Bylaws and no  subsidiary of the Company is in violation of any of the
provisions of such subsidiary's equivalent  organizational  documents except, in
each case, for such violations that would not, individually or in the aggregate,
have a Material Adverse Effect.

                  (d) The Company has heretofore  furnished to Parent a complete
and correct list of all entities in which the Company owns, directly or

                                                -14-

<PAGE>



indirectly,  any equity or voting  interest  which is material  to the  Company,
which list sets forth the amount of capital  stock of or other equity  interests
in such entities, directly or indirectly.

         Section 4.2 Capitalization. The authorized capital stock of the Company
consists of 45,000,000 shares as follows:(i)  40,000,000 Shares, of which, as of
August 31, 1998,  36,275,538 Shares were issued and outstanding;  (ii) 4,996,060
shares of undesignated preferred stock, par value $0.001 per share, of which, as
of August 31, 1998 no shares were issued and outstanding; and (iii) 3,940 shares
of Senior Redeemable  Convertible Preferred Stock, Series A, par value $.001 per
share,  of which,  as of August 31, 1998 no shares were issued and  outstanding.
All outstanding shares of capital stock of the Company have been validly issued,
and are fully  paid,  nonassessable  and except  pursuant  to the  Exchange  and
Purchase  Agreement (as defined below),  free of preemptive rights. As of August
31, 1998,  Options to purchase an aggregate of 3,568,635 Shares were outstanding
and the weighted  average exercise price of such Options was $13.6174 per Share.
None of these  Options are  Incentive  Stock  Options under federal tax law. All
Options  were  issued  under  the  Company  Option  Plan  or  are  deemed  to be
outstanding  under the Company Option Plan pursuant to Article One, Section I.C.
thereof.  Except as set forth  above,  and except as a result of the exercise of
Options  outstanding as of August 31, 1998,  there are outstanding (i) no shares
of capital stock or other voting  securities of the Company,  (ii) no securities
of the Company  convertible  into or exchangeable for shares of capital stock or
voting  securities  of the Company,  (iii)  except  pursuant to the Exchange and
Purchase  Agreement,  the Stock  Purchase  Plan and the Rights Plan, no options,
subscriptions,  warrants,  stock appreciation  rights,  convertible  securities,
calls or other  rights to acquire  from the Company,  and no  obligation  of the
Company to issue,  deliver  or sell any  capital  stock,  voting  securities  or
securities  convertible  into  or  exchangeable  for  capital  stock  or  voting
securities of the Company, and (iv) except pursuant to the Exchange and Purchase
Agreement, no equity equivalents,  interests in the ownership or earnings of the
Company or other similar rights (collectively,  "Company Securities"). There are
no  outstanding  obligations  of the  Company  or any  of  its  subsidiaries  to
repurchase,  redeem or otherwise acquire any Company  Securities.  Except as set
forth in Section 4.2 of the Disclosure Letter, each of the outstanding shares of
capital stock of each of the Company's subsidiaries is duly authorized,  validly
issued,  fully paid and nonassessable and is directly or indirectly owned by the
Company,  free and clear of all  security  interests,  liens,  claims,  pledges,
charges,  voting  agreements  or other  encumbrances  of any  nature  whatsoever
(collectively,  "Liens"). There are no existing options, calls or commitments of
any  character  relating  to the  issued  or  unissued  capital  stock  or other
securities of any subsidiary of the Company.


                                                -15-

<PAGE>



         Section 4.3 Authority  Relative to This Agreement.  The Company has all
necessary  corporate  power and authority to execute and deliver this Agreement,
to  perform  its  obligations   under  this  Agreement  and  to  consummate  the
Transactions.  The execution, delivery and performance of this Agreement and the
consummation of the  Transactions  have been duly and validly  authorized by the
Board and the Special  Committee and no other corporate  proceedings on the part
of the Company are necessary to authorize  this  Agreement or to consummate  the
Transactions  (other than, with respect to the Merger,  any actions  required of
Acquisition  and  its  board  of  directors  if and to the  extent  required  by
applicable law and the filing of the appropriate merger documents as required by
California  Law and  Delaware  Law).  This  Agreement  has been duly and validly
executed and delivered by the Company and constitutes a legal, valid and binding
agreement of the Company  enforceable against the Company in accordance with its
terms,  except to the  extent  that  enforcement  thereof  may be limited by (a)
bankruptcy,  insolvency,  reorganization,  moratorium,  fraudulent conveyance or
similar  laws,  now or  hereafter  in  effect,  relating  to  creditors'  rights
generally  and  (b)  general   principles  of  equity   (regardless  of  whether
enforceability is considered in a proceeding at law or in equity).

         Section 4.4 No-Conflict;  Required Filings and Consents.  (a) Except as
set forth in Section 4.4 of the Disclosure  Letter the  execution,  delivery and
performance  by the  Company  of  this  Agreement  and the  consummation  of the
Transactions  (including  the  Merger)  do not and  will not (i)  contravene  or
conflict with the Articles of Incorporation or First Amended and Restated Bylaws
of  the  Company  or  the  equivalent  organizational  documents  of  any of its
subsidiaries;  (ii)  assuming that all  consents,  authorizations  and approvals
contemplated  by  subsection  (b)  below  have  been  obtained  and all  filings
described  therein have been made,  contravene  or conflict with or constitute a
violation of any provision of any law, regulation,  judgment,  injunction, order
or decree binding upon or applicable to the Company,  any of its subsidiaries or
any of their respective properties; (iii) conflict with, or result in the breach
or  termination of any provision of or constitute a default (with or without the
giving of notice or the lapse of time or both) under,  or give rise to any right
of termination,  cancellation, or loss or impairment of any benefit to which the
Company  or any of its  subsidiaries  is  entitled  under any  provision  of any
agreement,  contract,  license or other instrument binding upon the Company, any
of  its  subsidiaries  or any of  their  respective  properties,  or  allow  the
acceleration  of the performance of, any obligation of the Company or any of its
subsidiaries  under any  indenture,  mortgage,  deed of trust,  lease,  license,
contract,  instrument  or other  agreement  to which the  Company  or any of its
subsidiaries  is a party or by which the Company or any of its  subsidiaries  or
any of their respective assets or properties is subject or bound; or (iv) result
in the creation or  imposition of any Lien on any asset of the Company or any of
its

                                                -16-

<PAGE>



subsidiaries,  except in the case of clauses  (ii),  (iii) and (iv) for any such
contraventions,   conflicts,  violations,   breaches,  terminations,   defaults,
cancellations,  losses,  impairments,  accelerations  and Liens  which would not
individually or in the aggregate have a Material Adverse Effect.

                  (b) The execution,  delivery and performance by the Company of
this Agreement and the consummation of the  Transactions  (including the Merger)
by the  Company  require  no action by or in  respect  of, or filing  with,  any
governmental  body, agency,  official or authority (either domestic,  foreign or
supranational)  other than (i) the filing of the California Filing in accordance
with  California  Law; (ii) the filing of the Delaware Filing in accordance with
Delaware  Law;  (iii)  compliance  with  any  applicable   requirements  of  the
Securities  Exchange  Act of 1934,  as amended  (the  "Exchange  Act") and state
securities,  takeover and Blue Sky laws; and (iv) such actions or filings which,
if not  taken or made,  would  not,  individually  or in the  aggregate,  have a
Material Adverse Effect.

                  (c) All actions required to be taken by the Company, the Board
or the Special  Committee under the Exchange and Purchase  Agreement dated as of
January  15,  1996  among the  Company,  Agrigenetics,  Inc.,  Parent and United
Agriseeds,  Inc., as amended by the amendment  thereto dated as of July 22, 1998
(as so amended,  the "Exchange and Purchase Agreement") to permit the execution,
delivery  and  performance  of  this  Agreement  and  the  consummation  of  the
Transactions have been taken.

         Section 4.5 SEC  Reports.  The Company  has filed all  required  forms,
reports and documents with the Commission  since August 31, 1996  (collectively,
the "SEC  Reports"),  each of which has complied in all material  respects  with
applicable  requirements  of  the  Securities  Act  of  1933,  as  amended  (the
"Securities  Act"), and the Exchange Act. As of their respective  dates, none of
the SEC Reports,  including,  without  limitation,  any financial  statements or
schedules included therein, contained any untrue statement of a material fact or
omitted to state a material fact  required to be stated  therein or necessary in
order to make the statements  therein, in light of the circumstances under which
they were made, not misleading.  The audited  consolidated  financial statements
and unaudited  consolidated interim financial statements of the Company included
in the SEC Reports fairly present, in all material respects,  in conformity with
generally accepted  accounting  principles applied on a consistent basis (except
as may be  indicated in the notes  thereto or, in the case of interim  financial
statements,  as permitted by Form 10-Q under the Exchange Act), the consolidated
financial  position of the Company and its  consolidated  subsidiaries as of the
dates thereof and their consolidated results of operations and cash

                                                -17-

<PAGE>



flows for the periods then ended (subject to normal recurring audit and year-end
adjustments in the case of any unaudited interim financial statements).

         Section 4.6 Absence of Certain Changes.  Since May 31, 1998,  except as
set forth in Section 4.6 of the Disclosure  Letter or as specifically  disclosed
to the  Board on or prior to the date of this  Agreement  or in the SEC  Reports
filed  prior to the date of this  Agreement  and except for  matters  arising in
connection with or as a result of this Agreement, the transactions  contemplated
hereby or the work of the Special  Committee,  there has not been any condition,
change or event that has resulted in or would  reasonably  be expected to result
in a Material Adverse Effect.

         Section 4.7 Schedule 14D-9; Offer Documents;  Proxy Statement.  Neither
the Schedule 14D-9, nor any of the information provided by the Company and/or by
its auditors, legal counsel, financial advisors or other consultants or advisors
specifically  for use in the Offer Documents  shall, on the respective dates the
Schedule 14D-9, the Offer Documents or any supplements or amendments thereto are
filed with the Commission or on the date first  published,  sent or given to the
Company's  stockholders,  as the case may be, contain any untrue  statement of a
material fact or omit to state any material  fact required to be stated  therein
or  necessary  in  order  to  make  the  statements  therein,  in  light  of the
circumstances  under  which  they  were  made,  not  misleading.  Any  proxy  or
information   statement  or  similar  materials  distributed  to  the  Company's
stockholders  in  connection  with  the  Merger,  including  any  amendments  or
supplements thereto (the "Proxy  Statement"),  shall not, at the time filed with
the  Commission,  at the time mailed to the  Company's  stockholders,  or at the
Effective Time, contain any untrue statement of a material fact or omit to state
any material  fact  required to be stated  therein or necessary in order to make
the statements therein, in light of the circumstances under which they are made,
not   misleading.   Notwithstanding   the   foregoing,   the  Company  makes  no
representation  or warranty with respect to any information  provided by Parent,
Acquisition and/or by their auditors, legal counsel, financial advisors or other
consultants or advisors  specifically for use in the Schedule 14D-9 or the Proxy
Statement.  The Schedule 14D-9 and the Proxy Statement will comply as to form in
all material  respects with the provisions of the Exchange Act and the rules and
regulations thereunder.

         Section 4.8 Finder's Fee. No broker, finder, investment banker or other
intermediary  (other  than  Wasserstein  Perella  and  Merrill  Lynch  & Co.) is
entitled  to  any  brokerage,  finder's  financial  advisory  or  other  fee  or
commission in connection with the Transactions  based upon  arrangements made by
and on  behalf  of the  Company  or  the  Special  Committee.  The  Company  has
heretofore  furnished to Parent a complete  and correct  copy of all  agreements
between the

                                                -18-

<PAGE>



Company and Wasserstein Perella and between the Company and Merrill Lynch
& Co. pursuant to which Wasserstein Perella and Merrill Lynch & Co. would
be entitled to any payment relating to the Transactions.

         Section 4.9  Stockholder  Action.  Assuming the  condition set forth in
Section  7.1(a) below is satisfied,  no vote or other approval of the holders of
any class of any  Company  Securities  is  required  to approve the Merger or to
approve  or adopt this  Agreement  except any  actions  required  to be taken by
Acquisition pursuant to Section 1110 of California Law.

         Section 4.10 Fairness Opinion. Wasserstein Perella has delivered to the
Special   Committee,   and  has  authorized  it  to  deliver  to  the  Company's
stockholders  pursuant to Section 1203 of California Law, Wasserstein  Perella's
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 (other
than TDCC or its  affiliates)  pursuant  to the Offer and the  Merger is fair to
such holders from a financial  point of view. The Company has been authorized by
Wasserstein  Perella to permit the  inclusion of such  fairness  opinion and any
other reports,  opinions or appraisals (within the meaning of Item 9 of Schedule
13E-3 under the Exchange Act) of Wasserstein Perella related to the Transactions
in the Offer Documents,  the Schedule 14D-9 and the Proxy Statement, as required
by California Law or the rules and regulations of the SEC.

         Section 4.11 Inapplicability of Rights Agreement. Based on the terms of
the Exchange and Purchase  Agreement and the certified  resolutions of the Board
included in Section 4.11 of the Disclosure  Letter (which  resolutions  have not
been  rescinded),  the Company and the Board have heretofore taken all necessary
action so that from and after  January  15,  1996 (a) Parent and its  affiliates
(including,  without limitation,  Acquisition) 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, this Agreement or otherwise) by Parent and its affiliates (including,
without limitation, Acquisition) has never caused and will never cause under any
circumstances   whatsoever  any  adverse  consequence  to  Parent,  any  of  its
affiliates (including, without limitation, Acquisition), 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).


                                                -19-

<PAGE>



         Section 4.12 Information Known by Parent. No representation or warranty
is  made by the  Company  as to any  matter  or  condition  which  (a) J.  Pedro
Reinhard,  Nickolas D. Hein, Louis W. Pribila,  William C. Schmidt or G. William
Tolbert (each a "Parent  Designee")  had actual  knowledge of on or prior to the
date of this  Agreement  (i)  through a  written  disclosure  which  the  Parent
Designee received,  (ii) through a written or oral disclosure made by Carlton J.
Eibl, or (iii) through any means if any such Parent Designee freely acknowledges
a clear  recollection of such actual  knowledge,  (b) existed on or prior to the
date of this  Agreement and relates to pending patent  litigation  involving the
Company or (c) was discussed at any meeting of the Board on or prior to the date
of this  Agreement or any committee of the Board on or prior to the date of this
Agreement at which any Parent Designee was present.


                                    ARTICLE V

           REPRESENTATIONS AND WARRANTIES OF PARENT AND ACQUISITION

         Each of Parent and  Acquisition  represents and warrants to the Company
as follows:

         Section 5.1  Organization.  Parent is a limited  liability  company and
Acquisition  is a  corporation  duly  organized,  validly  existing  and in good
standing  under the laws of the  State of  Delaware  and each has all  requisite
power and authority to own, lease and operate its properties and to carry on its
business as now being  conducted,  except where the failure to be so  organized,
existing  and in good  standing  or to have such power and  authority  would not
reasonably  be likely to prevent or  materially  delay the  consummation  of the
Offer or the Merger.

         Section 5.2 Authority  Relative to this  Agreement.  Each of Parent and
Acquisition  has all  necessary  power and  authority to execute and deliver and
perform its obligations under this Agreement and to consummate the Transactions.
The execution,  delivery and performance of this Agreement and the  consummation
of the  Transactions  have been duly and  validly  authorized  by the members of
Parent,  by the members  committee of Parent, by the shareholders of Acquisition
and by the board of directors of  Acquisition,  and no other  proceedings on the
part of Parent or  Acquisition  are necessary to authorize  this Agreement or to
consummate the  Transactions.  This Agreement has been duly and validly executed
and delivered by each of Parent and Acquisition  and constitutes a legal,  valid
and binding agreement of each of Parent and

                                                -20-

<PAGE>



Acquisition,  enforceable  against each of Parent and  Acquisition in accordance
with its terms.

         Section  5.3  No-Conflict;  Required  Filings  and  Consents.  (a)  The
execution,  delivery and performance by Parent and Acquisition of this Agreement
and the consummation of the Transactions  (including the Merger) do not and will
not (i) contravene or conflict with the limited  liability  company agreement of
Parent or the  Certificate  of  Incorporation  or Bylaws  of  Acquisition;  (ii)
assuming  that  all  consents,  authorizations  and  approvals  contemplated  by
subsection (b) below have been obtained and all filings  described  therein have
been  made,  contravene  or  conflict  with or  constitute  a  violation  of any
provision of any law, regulation,  judgment, injunction, order or decree binding
upon  or  applicable  to  Parent  or  Acquisition  or  any of  their  respective
properties;  (iii)  conflict with, or result in the breach or termination of any
provision of or  constitute  a default  (with or without the giving of notice or
the lapse of time or both)  under,  or give  rise to any  right of  termination,
cancellation,  or loss of any benefit to which Parent or Acquisition is entitled
under any  provision of any  agreement,  contract,  license or other  instrument
binding upon Parent, Acquisition or any of their respective properties, or allow
the  acceleration of the performance of, any obligation of Parent or Acquisition
under  any  indenture,  mortgage,  deed  of  trust,  lease,  license,  contract,
instrument or other  agreement to which Parent or  Acquisition  is a party or by
which Parent or Acquisition or any of their  respective  assets or properties is
subject or bound;  or (iv) result in the creation or  imposition  of any Lien on
any asset of Parent or  Acquisition,  except in the case of clauses (ii),  (iii)
and  (iv)  for  any  such  contraventions,   conflicts,   violations,  breaches,
terminations,  defaults,  cancellations,  losses, accelerations and Liens which,
individually  or in the aggregate,  would not reasonably be likely to prevent or
materially delay the consummation of the Offer or the Merger.

                  (b) The  execution,  delivery  and  performance  by Parent and
Acquisition  of  this  Agreement  and  the   consummation  of  the  Transactions
(including  the  Merger)  by Parent and  Acquisition  require no action by or in
respect of, or filing with, any governmental body, agency, official or authority
(whether  domestic,  foreign or supranational)  other than (i) the filing of the
California  Filing in  accordance  with  California  Law; (ii) the filing of the
Delaware  Filing in  accordance  with Delaware Law;  (iii)  compliance  with any
applicable  requirements of the Exchange Act and state securities,  takeover and
Blue Sky laws;  and (iv) such  actions or filings  which,  if not taken or made,
would not, individually or in the aggregate, reasonably be likely to prevent the
consummation of the Offer or the Merger.


                                                -21-

<PAGE>



         Section 5.4 Offer Documents;  Schedule 14D-9; Proxy Statement.  Neither
the  Offer  Documents,  nor  any  of  the  information  provided  by  Parent  or
Acquisition and/or by their auditors, legal counsel, financial advisors or other
consultants or advisors specifically for use in the Schedule 14D-9 shall, on the
respective dates the Offer  Documents,  the Schedule 14D-9 or any supplements or
amendments thereto are filed with the Commission or on the date first published,
sent or given to the  Company's  stockholders,  as the case may be,  contain any
untrue  statement of a material fact or omit to state any material fact required
to be stated  therein or necessary in order to make the statements  therein,  in
light  of  the  circumstances  under  which  they  were  made,  not  misleading.
Notwithstanding  the  foregoing,   neither  Parent  nor  Acquisition  makes  any
representation  or  warranty  with  respect to any  information  provided by the
Company  and/or by its  auditors,  legal  counsel,  financial  advisors or other
consultants or advisors specifically for use in the Offer Documents. None of the
information  provided  by  Parent  or  Acquisition  and/or  by  their  auditors,
attorneys,  financial advisors or other consultants or advisors specifically for
use in the Proxy Statement shall, at the time filed with the Commission,  at the
time mailed to the Company's stockholders, or at the Effective Time, contain any
untrue  statement of a material fact or omit to state any material fact required
to be stated  therein or necessary in order to make the statements  therein,  in
light of the circumstances under which they are made, not misleading.  The Offer
Documents will comply as to form in all material respects with the provisions of
the Exchange Act and the rules and regulations thereunder.

         Section  5.5  Acquisition.   Since  the  date  of  its   incorporation,
Acquisition  has not engaged in any activities  other than in connection with or
as  contemplated by this Agreement or in connection with arranging any financing
required  to  consummate  the  Transactions.  The  outstanding  common  stock of
Acquisition  is owned 69% by Parent  and 31% by Centen Ag Inc.,  a  wholly-owned
subsidiary of TDCC.

         Section  5.6  Financing.  Acquisition  has  available  to it all  funds
necessary to satisfy its obligations  under this Agreement,  including,  without
limitation, the obligation to pay the Per Share Amount pursuant to the Offer and
the Merger Consideration  pursuant to the Merger and to pay all related fees and
expenses in connection with the Offer and the Merger.

         Section 5.7 Brokers.  Except for Salomon Smith Barney,  whose fees will
be paid by  Parent,  there is no  investment  banker,  broker,  finder  or other
intermediary  who might be entitled to any fee or commission from the Company or
any of its subsidiaries  upon  consummation of the transactions  contemplated by
this Agreement.


                                                -22-

<PAGE>



         Section 5.8 Insurance. As of the date of this Agreement, the members of
the Special  Committee  are  secondarily  insured  under  "director and officer"
insurance  coverage  generally  provided to  individuals  who serve on boards of
directors of TDCC or its subsidiaries.


                                   ARTICLE VI

                                    COVENANTS

         Section 6.1 Conduct of Business of the Company.  Except as set forth in
Section  6.1  of the  Disclosure  Letter  and  except  for  matters  arising  in
connection with or as a result of this Agreement,  the  Transactions or the work
of the Special  Committee,  during the period from the date of this Agreement to
the  earlier  of the  Effective  Time or the date on  which  this  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, subject to the foregoing,  the Company and its subsidiaries
will each use its  reasonable  best  efforts to  preserve  intact  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  significant  business
relationships  with it. Without  limiting the  generality of the foregoing,  and
except as otherwise expressly provided in this Agreement, prior to the Effective
Time  neither the Company nor any of its  subsidiaries  will,  without the prior
written consent of Acquisition:

                  (a) authorize for issuance,  issue,  sell, deliver or agree to
commit to issue,  sell or deliver  (whether  through the issuance or granting of
options, warrants, commitments,  subscriptions, rights to purchase or otherwise)
any  Shares,  any stock of any other  class or any  other  securities  or equity
equivalents (including,  without limitation,  stock appreciation rights), except
as required by  agreements  in effect  prior to the date of this  Agreement,  or
amend any of the terms of any such  securities or agreements  outstanding  as of
the date of this Agreement; or

                   (b) 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


                                                -23-

<PAGE>



                  (c) take, or agree in writing or otherwise to take, any of the
actions  described  above in Section  6.1 or any action  which  would  cause the
condition set forth in paragraph (d) of Annex A not to be satisfied.

         Section  6.2  Reasonable  Best  Efforts.   Subject  to  the  terms  and
conditions of this Agreement  (including,  without limitation,  Section 1.2(a)),
each of the parties agrees to use its reasonable  best efforts to take, or cause
to be taken, all actions,  and to do, or cause to be done, all things reasonably
necessary,  proper  or  advisable  under  applicable  laws  and  regulations  to
consummate and make effective the  Transactions in accordance with the terms and
conditions of this Agreement.  Without limiting the generality of the foregoing,
Parent,  Acquisition and the Company shall cooperate with one another (i) in the
preparation and filing of the Offer  Documents,  the Schedule  14D-9,  the Proxy
Statement and any required filings under the laws referred to in Sections 4.4(b)
and 5.3(b);  (ii) in  determining  whether action by or in respect of, or filing
with, any governmental body,  agency,  official or authority (either domestic or
foreign) is required, proper or advisable or any actions,  consents,  waivers or
approvals  are  required  to be  obtained  from  parties  to any  contracts,  in
connection  with the  Transactions;  and (iii) in  seeking to obtain in a timely
manner any such actions, consents and waivers and to make any such filings.

         Section 6.3 Public  Announcements.  Parent and Acquisition,  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,  except  as  may  be  required  by  applicable  law or by
applicable rules of any securities  exchange or inter-dealer  quotation  system.
The initial joint announcement of the Transactions shall be in the form attached
as Annex B.

         Section  6.4  Indemnification.  (a) Parent  shall  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 this Agreement to the fullest extent  permitted  under  applicable law, which
provisions shall 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 shall
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.


                                                -24-

<PAGE>



                  (b) From and after the Effective Time, Parent hereby agrees to
guarantee  the  obligations  of the  Surviving  Corporation  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.

                  (c) The Company shall,  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 under 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)  occurring on or before the Effective  Time (or, if this Agreement
is terminated without the Merger becoming effective,  occurring on or before the
termination  of  this  Agreement),  until  the  expiration  of  the  statute  of
limitations relating thereto (and shall 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 first sentence of this Section 6.4(c).
If  the  Merger  does  not  become   effective,   Parent  shall  have  the  same
responsibilities  set forth in the  immediately  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,   this  Agreement  or  the
Transactions.   In  the  event  of  any  claim,  action,  suit,   proceeding  or
investigation  covered by this Section  6.4(c),  (i) the Company,  Parent or the
Surviving  Corporation,  as the case may be, shall pay the  reasonable  fees and
expenses of counsel selected by the Indemnified Parties,  which counsel shall 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  shall  cooperate  in the  defense  of any  such  matter;
provided, however, that neither the Company nor

                                                -25-

<PAGE>



Parent nor the Surviving Corporation shall 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,  shall be obligated
pursuant to this  Section  6.4(c) 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
shall 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
shall continue until the disposition of such claim. In connection with Parent or
the Surviving  Corporation making any payment or advancing any funds pursuant to
this Section 6.4(c),  Parent or the Surviving  Corporation,  as the case may be,
shall 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.

                  (d) Parent shall 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 shall 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, which the Company represents and warrants to
be $63,000 (the "Current Premium"). If such premiums for such insurance would at
any time exceed  200% of the Current  Premium,  then the  Surviving  Corporation
shall cause to be  maintained  policies of  insurance  which,  in the  Surviving
Corporation's good faith  determination,  provide the maximum coverage available
at an annual premium equal to 200% of the Current Premium.  In addition,  Parent
shall cause the Indemnified Parties to receive, for six years following the date
of this Agreement, the same directors and officers

                                                -26-

<PAGE>



insurance coverage that other present or former independent directors of TDCC or
its subsidiaries receive.

                  (e)  In  the  event  Parent,  the  Company  or  the  Surviving
Corporation or any of their  respective  successors or assigns (i)  consolidates
with or  merges  into any  other  person  and  shall  not be the  continuing  or
surviving  corporation  or  entity  of  such  consolidation  or  merger  or (ii)
transfers all or  substantially  all of its properties and assets to any person,
then,  and in each  such  case,  proper  provision  shall  be  made so that  the
successors and assigns of Parent, the Company or the Surviving  Corporation,  as
the case may be, shall assume the obligations set forth in this Section 6.4.

                  (f) Heirs,  representatives  and  estates  of the  Indemnified
Parties  shall  have the right to enforce  the  obligations  arising  under this
Section 6.4.

         Section 6.5  Notification  of Certain  Matters.  The Company shall give
prompt notice to Parent or  Acquisition,  and Parent or  Acquisition  shall give
prompt  notice to the  Company,  as the case may be, of (i) the  occurrence,  or
non-occurrence,  of any event the respective occurrence,  or non-occurrence,  of
which would be likely to cause any condition  contained in this  Agreement to be
unsatisfied and (ii) any failure of the Company,  Parent or Acquisition,  as the
case may be, to comply with or satisfy any  covenant or agreement to be complied
with under this Agreement; provided, that the delivery of any notice pursuant to
this  Section 6.5 shall not limit or  otherwise  affect any  remedies  available
under this Agreement to the party receiving such notice.

         Section  6.6  Exchange  and  Purchase  Agreement;  No  Restrictions  on
Purchase.  The parties agree that the Exchange and Purchase  Agreement is hereby
amended  to  the  extent  necessary  to  permit  the  execution,   delivery  and
performance of this Agreement and the consummation of the Transactions. From and
after the date that  Acquisition  first makes  payment  with  respect to validly
tendered  and not  withdrawn  Shares  pursuant to the Offer,  the  Exchange  and
Purchase  Agreement  shall be deemed to 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  shall  remain in full  force and  effect  without  any
amendment  thereto.  Without limiting the generality of the foregoing,  from and
after the date that  Acquisition  first makes  payment  with  respect to validly
tendered and not withdrawn Shares pursuant to the Offer, Parent, Acquisition and
their  affiliates  shall 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
Acquisition's obligations under this Agreement to effect the Merger, Parent,

                                                -27-

<PAGE>



Acquisition and their affiliates shall be permitted to acquire additional Shares
and/or  increase its 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.

         Section 6.7 Compliance by Acquisition.  Parent shall cause  Acquisition
to timely  perform  and comply with all of its  obligations  under or related to
this  Agreement,  including,  without  limitation,  all  obligations  in or with
respect to the Offer.

         Section  6.8  Financing.   TDCC  shall  ensure  that   Acquisition  has
sufficient  funds to  acquire  all the  outstanding  Shares in the Offer and the
Merger.  TDCC has all  necessary  power and authority to execute and deliver and
perform its obligations  under this Agreement.  This Agreement has been duly and
validly  executed  and  delivered  by TDCC and  constitutes  a legal,  valid and
binding  agreement  of TDCC,  enforceable  against TDCC in  accordance  with its
terms.

         Section 6.9 Access to and  Retention of  Information.  From the date of
this  Agreement  to  the  Effective  Time,   subject  to  any  applicable  legal
restrictions,  fiduciary duties or applicable privileges, the Company shall (and
shall  cause  its   subsidiaries   to)  afford  to  authorized   representatives
(including,  without limitation,  attorneys, auditors and financial advisors) of
Parent and  Acquisition  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 shall cause its officers and employees to furnish  Parent and
Acquisition and their  authorized  representatives  such financial and operating
data and other information with respect to the Company's business and properties
as Parent and Acquisition and their authorized  representatives may from time to
time reasonably request. In addition, from and after the date of this Agreement,
the  Company  shall  (and  shall use its  reasonable  best  efforts to cause its
officers and  employees to) retain  copies of all  information  furnished by the
Company to the Special Committee from the inception of the Special Committee.


                                   ARTICLE VII

                    CONDITIONS TO CONSUMMATION OF THE MERGER

         Section 7.1       Conditions to Each Party's Obligations to Effect the
Merger.  The respective obligations of each party to this Agreement to effect


                                                -28-

<PAGE>



the Merger are subject to the satisfaction or, if appropriate,  waiver by each
party in its  sole  discretion  at or  prior to the  Effective  Time of the
following conditions:

                  (a)  Acquisition  shall  have  purchased  all  Shares  validly
tendered and not withdrawn  pursuant to the Offer and  Acquisition  shall be the
record  and  beneficial  owner of a  sufficient  number of Shares to permit  the
Merger to be effected pursuant to Section 1110 of California Law; and

                  (b) there  shall not be in effect any order,  decree or ruling
or other action  restraining,  enjoining or  otherwise  prohibiting  the Merger,
which  order,  decree,  ruling or action  shall have been issued or taken by any
court of competent  jurisdiction  or other  governmental  body located or having
jurisdiction within the United States or any country or economic region in which
the  Company  or any of its  subsidiaries  or Parent  or any of its  affiliates,
directly or indirectly, has material assets or operations.


                                  ARTICLE VIII

                    TERMINATION; EXPENSES; AMENDMENT; WAIVER

         Section 8.1       Termination.  This Agreement may be terminated and
the Merger may be abandoned at any time prior to the Effective Time,
notwithstanding approval thereof by the stockholders of the Company:

                  (a) by mutual written  consent of Parent and  Acquisition,  on
the one hand,  and of the  Company  acting  upon the  direction  of the  Special
Committee, on the other hand;

                  (b) by the Company  acting upon the  direction  of the Special
Committee  or by  Parent  if  any  court  of  competent  jurisdiction  or  other
governmental body located or having jurisdiction within the United States or any
country or economic  region in which the Company or any of its  subsidiaries  or
Parent or any of its subsidiaries,  directly or indirectly,  has material assets
or operations,  shall have issued an order,  decree or ruling or taken any other
action restraining,  enjoining or otherwise  prohibiting the Offer or the Merger
and such order,  decree,  ruling or other  action  shall have  become  final and
nonappealable;  provided,  however,  that each of the parties  hereto shall have
used  reasonable  best  efforts to prevent the entry of any such order,  decree,
ruling or other  action and to appeal as promptly  as  possible  any such order,
decree, ruling of other action that may be entered.


                                                -29-

<PAGE>



                  (c) 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 Annex A hereto,
Acquisition shall have (i) failed to commence the Offer within 60 days following
the date of this Agreement or (ii)  terminated the Offer without having accepted
any Shares for payment  thereunder;  provided,  that the right to terminate this
Agreement  under this  Section  8.1(c) shall not be 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 Section 8.1(c);

                  (d) by the Company,  acting upon the  direction of the Special
Committee if, prior to the purchase of Shares  pursuant to the Offer,  Parent or
Acquisition shall have failed to comply in all material respects with any of its
covenants or agreements contained in this 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  Acquisition  of
written notice of such failure to comply;

                  (e) 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 (i) a breach  in any  material  respect  by Parent  or  Acquisition  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  (ii)  a  breach  by  Parent  or   Acquisition   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
Acquisition of written notice of the breach; or

                  (f) by either the  Company  acting upon the  direction  of the
Special Committee or by Parent if the Merger shall not have occurred on or prior
to April 30, 1999;  provided that the right to terminate  this  Agreement  under
this Section 8.1(f) shall not be available to any party whose failure to fulfill
any material  obligation  under this Agreement has been the case of, or resulted
in, the failure of the Merger to have occurred on or before such date.

         Section 8.2 Effect of Termination.  In the event of the termination and
abandonment  of this  Agreement  pursuant to Section 8.1, this  Agreement  shall
forthwith  become  void and have no effect,  other than the  provisions  of this
Section 8.2,  Section 8.3 and Section 9.1. No  termination of this Agreement and
nothing  contained in this Section 8.2 or in Section 9.1 shall relieve any party
from  liability  for  any  willful  breach  of any  representation  or  warranty
contained  in this  Agreement  or any breach of any  covenant  contained in this
Agreement occurring prior to such termination.

                                                -30-

<PAGE>



         Section 8.3 Fees and Expenses. Subject to Section 8.2 above, each party
shall bear its own expenses and costs in connection  with this Agreement and the
Transactions.

         Section 8.4  Amendment.  This Agreement may be not be amended except by
an  instrument in writing  signed by Parent,  Acquisition  and the Company.  Any
amendment to this  Agreement,  any termination of this 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  Acquisition or any waiver of any of the
Company's rights under this Agreement will require the unanimous  concurrence of
the Special Committee.

         Section 8.5  Extension;  Waiver.  Subject to the  provisions of Section
8.4, at any time prior to the Effective Time, the Company,  on the one hand, and
Parent  and  Acquisition,  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 this Agreement or in any document, certificate or writing delivered
pursuant to this  Agreement,  or (iii) waive  compliance by the other party with
any of the agreements or conditions  contained in this Agreement.  Any agreement
on the part of any party to any such  extension or waiver shall 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 this Agreement  shall not
constitute a waiver of such rights.


                                   ARTICLE IX

                                  MISCELLANEOUS

         Section  9.1  Nonsurvival  of  Representations   and  Warranties.   The
representations  and warranties  made in this Agreement shall not survive beyond
the Effective Time or any termination of this Agreement pursuant to Section 8.1.
The covenants and agreements in this Agreement  shall survive the Effective Time
or the termination of this Agreement  pursuant to Section 8.1 in accordance with
their terms or as contemplated by such terms.

         Section  9.2  Entire  Agreement;  Assignment.  This  Agreement  and the
Exchange and Purchase  Agreement (as amended by this  Agreement)  (i) constitute
the entire  agreement  among the parties with  respect to the subject  matter of
this Agreement and supersede all other prior agreements and understandings, both
written and oral,  among the parties with respect to the subject  matter of this
Agreement and (ii) shall not be assigned by operation of

                                                -31-

<PAGE>



law  or  otherwise;   provided  that  Acquisition  may  assign  its  rights  and
obligations  in whole or in part to Parent or any  affiliate  of Parent,  but no
such  assignment  shall  relieve  Acquisition  of  its  obligations  under  this
Agreement if such assignee does not perform such obligations.

         Section 9.3 Notices. All notices,  requests,  claims, demands and other
communications  under this Agreement shall be in writing and shall be given (and
shall be deemed to have been duly given upon receipt) by delivery in person,  by
facsimile,  by recognized  overnight  courier or by registered or certified mail
(postage prepaid, return receipt requested), to the other party as follows:

         if to Parent, Acquisition or, following the Effective Time, the
Surviving Corporation:

                  AgroSciences Acquisition Inc.
                  2030 Dow Center
                  Midland, Michigan 48674
                  Fax: 517-636-0861
                  Attention: Secretary

         and

                  Dow AgroSciences LLC
                  9330 Zionsville Road
                  Indianapolis, Indiana 46268
                  Fax: 317-337-6954
                  Attention: General Counsel

         with a copy (which shall not constitute notice to any party) to:

                  Mayer, Brown & Platt
                  190 South LaSalle Street
                  Chicago, Illinois  60603-3441
                  Fax:  312-701-7711
                  Attention:  Scott J. Davis


                                                -32-

<PAGE>


         if to the Company:

                  Mycogen Corporation
                  c/o Joseph Sullivan
                  175 East Delaware, Apt. 6805
                  Chicago, Illinois 60611
                  Fax: 312-642-3143

         with a copy (which shall not constitute notice to any party) to:

                  Altheimer & Gray
                  10 South Wacker Drive
                  Suite 4000
                  Chicago, Illinois 60606
                  Fax: 312-715-4800
                  Attention: Norman M. Gold
                             Peter H. Lieberman

or to such  other  address  as the  person  to whom  notice  is  given  may have
previously furnished to the other in writing in the manner set forth above.

         Section  9.4  Governing  Law;  Jurisdiction  and Venue;  Waiver of Jury
Trial.  This Agreement shall be 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 (it being understood that matters of internal  corporate
law  relevant  to the  Company  are  governed  by  California  Law).  Each party
irrevocably and unconditionally  consents and submits to the jurisdiction of the
courts of the State of Delaware and of the United  States of America  located in
the State of Delaware for any actions,  suits or  proceedings  arising out of or
relating to this Agreement and the Transactions, and further agrees that service
of any process, summons, notice or document by U.S. registered or certified mail
to the party at the address specified in Section 9.2, shall be effective service
of process for any action,  suit or proceeding brought against such party in any
such  court.  Each  party  hereby  irrevocably  and  unconditionally  waives any
objection to the laying of venue of any action,  suit or proceeding  arising out
of this  Agreement  or the  Transactions  in the courts of the State of Delaware
located  in  Wilmington,  Delaware  or the United  States of America  located in
Wilmington,  Delaware, and hereby further irrevocably and unconditionally waives
and agrees not to plead or claim in any such court that any such action, suit or
proceeding brought in any such court has been brought in an inconvenient  forum.
Each party hereby expressly waives any right to a trial by jury in any action or
proceeding  to enforce or defend any rights under this  Agreement,  or under any
amendment, instrument, document or agreement

                                                -33-

<PAGE>



delivered or which may in the future be delivered  pursuant  hereto,  and agrees
that any such action or proceeding  shall be tried before a court and not before
a jury.

         Section 9.5 Parties in Interest.  Except for Section  6.4,  which shall
inure to the benefit of the persons identified therein,  this Agreement shall be
binding  upon and inure  solely to the benefit of each party and its  successors
and permitted  assigns,  and nothing in this Agreement,  express or implied,  is
intended  to or shall  confer  upon any other  person any  rights,  benefits  or
remedies of any nature whatsoever under or by reason of this Agreement.  Without
limiting the rights of any other party to this Agreement,  the Special Committee
shall have the right to exercise the  Company's  rights and enforce the terms of
this Agreement on behalf of the Company.

         Section 9.6 Specific  Performance.  The parties agree that  irreparable
damage  would  occur  in the  event  any  provision  of this  Agreement  was not
performed in accordance with its terms and that the parties shall be entitled to
specific  performance of the terms of this  Agreement,  in addition to any other
remedy at law or in equity.

         Section 9.7  Severability.  The provisions of this  Agreement  shall be
deemed severable and the invalidity or  unenforceability  of any provision shall
not affect the  validity  and  enforceability  of the other  provisions  of this
Agreement. If any provision of this Agreement, or the application thereof to any
person  or  entity or any  circumstance,  is  invalid  or  unenforceable,  (a) a
suitable and equitable provision shall be substituted therefor in order to carry
out,  so far as may be valid and  enforceable,  the intent  and  purpose of such
invalid and unenforceable  provision and (b) the remainder of this Agreement and
the  application of such provision to other persons,  entities or  circumstances
shall not be affected by such  invalidity  or  unenforceability,  nor shall such
invalidity or  unenforceability  affect the validity or  enforceability  of such
provision, or the application thereof, in any other jurisdiction.

         Section 9.8  Descriptive  Headings.  The  descriptive  headings in this
Agreement are inserted for convenience of reference only and are not intended to
be part of or to affect the meaning or interpretation of this Agreement.


                                                -34-

<PAGE>



         Section 9.9       Certain Definitions.  For purposes of this Agreement,
the term:

         "affiliate"  of a person  means a person that  directly or  indirectly,
through one or more  intermediaries,  controls,  is  controlled  by, or is under
common control with, the first mentioned person;

         "associate"  of a person means a corporation or  organization  of which
such  person is an  officer  or  partner  or is,  directly  or  indirectly,  the
beneficial owner of 10 percent or more of any class of equity  securities or any
person who is a director  or  officer  of such  person or any of its  parents or
subsidiaries;

         "business day" has the meaning set forth in Rule 14d-1(e) under the
Exchange Act.

         "control"  (including  the  terms  "controlled  by" and  "under  common
control  with") means the  possession,  directly or  indirectly or as trustee or
executor,  of the  power to  direct or cause  the  direction  of the  management
policies of a person,  whether  through the  ownership  of stock,  as trustee or
executor, by contract or credit arrangement or otherwise;

         "Fully  Diluted  Shares" as of a  particular  date means the issued and
outstanding  Shares (including Shares of Restricted Stock) as of such date, plus
the  Shares  that  would  be  issued  if all  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  valid Stock
Purchase  Elections to the Company.  For purposes of determining  whether either
the First Minimum Condition or the Second Minimum Condition is satisfied, Shares
issuable upon the exercise of an Option shall be deemed issued and  outstanding,
and such  Option  shall be  deemed  no  longer  outstanding,  if a valid  Option
Election  with  respect to such Option has been  executed  (and not revoked) and
delivered to the Company.

         "Material  Adverse  Effect"  means a  material  adverse  effect  on the
business,  results of operations  or financial  condition of the Company and its
subsidiaries, taken as a whole.

         "Options" means stock options under the 1992 Plan.

         "person" means an individual,  corporation,  partnership,  association,
trust, unincorporated organization, other entity or group (within the meaning of
Section 13(d)(3) of the Exchange Act); and


                                                -35-

<PAGE>



         "subsidiary"  or  "subsidiaries"  of any person means any  corporation,
limited liability company,  partnership,  joint venture or other legal entity of
which  such  person  (either  alone  or  through  or  together  with  any  other
subsidiary),  owns, directly or indirectly,  more than 50% of the stock or other
equity  interests  the  holder of which is  generally  entitled  to vote for the
election of the board of directors or other governing body of such  corporation,
partnership, joint venture or other legal entity.

         Section 9.10      Counterparts.  This Agreement may be executed in two
or more counterparts, each of which shall be deemed to be an original, but all
of which shall constitute one and the same agreement.


                                                -36-

<PAGE>



         IN WITNESS WHEREOF, each of the parties has caused this Agreement to be
executed by its duly authorized representative.



                                       MYCOGEN CORPORATION


                                       By:______________________
                                       Name:
                                       Title:


                                       DOW AGROSCIENCES LLC


                                       By:______________________
                                       Name:
                                       Title:


                                       AGROSCIENCES ACQUISITION INC.


                                       By:______________________
                                       Name:
                                       Title:


                                       Solely for the limited purpose set forth
                                       in Section 6.8 above,

                                       THE DOW CHEMICAL COMPANY

                                       By:______________________
                                       Name:
                                       Title:


                                                -37-

<PAGE>



                                                                         ANNEX A


                                OFFER CONDITIONS

         The capitalized  terms used in this Annex A have the meanings set forth
in the attached Agreement, except that the term "Merger Agreement" refers to the
attached Agreement.

         Notwithstanding any other provision of the Offer, Acquisition shall not
be required to accept for payment any Shares tendered pursuant to the Offer, and
may postpone the acceptance for payment of any Shares  tendered  pursuant to the
Offer, if (i) the Second Minimum  Condition  shall not have been  satisfied,  or
(ii) at any time on or after  September 4, 1998 and prior to the  acceptance for
payment of Shares, any of the following conditions occurs and remains in effect:

                  (a) there shall 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 agency,  located or
having  jurisdiction  within the United  States or any other country or economic
region in which the Company or any of its  subsidiaries  or Parent or any of its
subsidiaries,  directly or indirectly, has material assets or operations, or any
statute, rule,  regulation,  legislation,  judgment or order, enacted,  entered,
enforced, promulgated,  amended, issued or deemed applicable to the Offer or the
Merger by any court,  governmental,  administrative  or regulatory  authority or
agency  located or having  jurisdiction  within  the United  States or any other
country or economic  region in which the Company or any of its  subsidiaries  or
Parent or any of its subsidiaries,  directly or indirectly,  has material assets
or  operations,  which has the  effect  of: (i)  making  illegal,  or  otherwise
directly or indirectly 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,
directly or indirectly,  of some of or all the Shares by Parent or  Acquisition,
the  consummation  of the Offer or the Merger;  (ii)  prohibiting  or materially
limiting  the direct or indirect  ownership  or  operation  by the Company or by
Parent of all or any  material  portion of the business or assets of the Company
and its subsidiaries,  taken as a whole as currently constituted,  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
currently  constituted,  as a result  of the  transactions  contemplated  by the
Merger  Agreement;  (iii)  imposing or confirming  material  limitations  on the
ability of Parent  effectively  directly or  indirectly 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 or the right to vote any


<PAGE>



shares of capital stock of any subsidiary of the Company; or (iv) requiring
divestiture by Parent or Acquisition, directly or indirectly, of any Shares; or

                  (b) there shall 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; or

                  (c) the  Company  shall have  breached or failed to perform in
any material  respect any of its  material  covenants  or  agreements  under the
Merger Agreement; or

                  (d) any of the  representations  and warranties of the Company
set forth in the Merger  Agreement  which is  qualified  as to Material  Adverse
Effect 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 the  representations  and  warranties  contained  in Sections
4.1(c) (other than the last sentence thereof),  4.1(d), 4.2, 4.3, 4.7, 4.8, 4.9,
4.10 or 4.11 of the Merger  Agreement,  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); or

                  (e)  the  Merger  Agreement  shall  have  been  terminated  in
accordance  with its terms or the Offer  shall  have  been  terminated  with the
consent of the Company, acting at the direction of the Special Committee; which,
in the  reasonable  judgment of  Acquisition in any such case, and regardless of
the  circumstances  (including any action or omission by Acquisition  other than
any breach by Parent or Acquisition  of the Merger  Agreement or, in the case of
(c) or (d) above,  a failure of such condition  which Parent or Acquisition  has
caused to occur)  giving  rise to any such  condition  makes it  inadvisable  to
proceed with such acceptance for payment or payment for Shares.

                  The  foregoing  conditions  are for the sole benefit of Parent
and  Acquisition   and  may  be  asserted  by  Acquisition   regardless  of  the
circumstances  (including any action or omission by  Acquisition  other than any
breach by Parent or Acquisition  of the Merger  Agreement or, in the case of (c)
or (d) above, a failure of such condition which Parent or Acquisition has caused
to occur) giving rise to any such condition or may be waived by Acquisition in


<PAGE>



whole or in part at any time or from  time to time in its sole  discretion.  The
failure by Acquisition 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.




<PAGE>



                                                                         ANNEX B

FOR MORE INFORMATION CONTACT:

[Each entity's contact]

August 31, 1998


DOW To Acquire All Outstanding Mycogen Shares

Dow AgroSciences LLC, a wholly owned subsidiary of The Dow Chemical Company, and
Mycogen  Corporation  (NASDAQ:  MYCO)  today  announced  that they have signed a
definitive  agreement  for Dow  AgroSciences  to acquire all of the  outstanding
shares of Mycogen that it does not already own. Dow AgroSciences  currently owns
approximately 68% of the outstanding  shares of Mycogen.  Under the terms of the
agreement,  a subsidiary of Dow AgroSciences will make a tender offer to acquire
all of the remaining shares of Mycogen at $xx.00 per share. Following the tender
offer,  if Dow  AgroSciences  and the  subsidiary  own at least 90% of Mycogen's
shares,  the Dow  AgroSciences  subsidiary  will be merged into Mycogen and each
remaining Mycogen shareholder will receive $xx.00 per share in exchange for each
Mycogen share held.

Mycogen Corporation,  based in San Diego, Calif., 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.

Dow  AgroSciences  LLC, based in  Indianapolis,  Indiana,  is a global leader in
providing pest  management and  biotechnology  products that improve the quality
and quantity of the earth's food supply and contribute to the safety, health and
quality of life of the world's growing population. The company employs more than
3,000  people  in over 50  countries  and has  worldwide  sales of more  than $2
billion.

The Dow Chemical Company,  with headquarters in Midland,  Michigan, is the fifth
largest  chemical  company  in the  world,  with  annual  sales of more than $20
billion.  Dow manufactures and supplies  chemicals,  plastics,  and agricultural
products for customers in 164 countries, and employs approximately 43,000 people
worldwide.

                                                # # #



<PAGE>



                                                                         ANNEX C

                                 OPTION ELECTION

         The  undersigned  holder of an option or  options  (the  "Options")  to
purchase  ______________ shares (the "Option Shares") of common stock of Mycogen
Corporation (the "Company"), par value $0.001 per share ("Common Stock"), hereby
agrees  that,  immediately  prior to the  purchase of shares of Common  Stock by
AgroSciences  Acquisition Inc.  ("Acquisition")  in its pending tender offer for
any and all  outstanding  shares of Common Stock (the  "Offer"),  and contingent
upon such purchase, the undersigned shall be deemed to have fully exercised each
such Option (whether or not the Option was previously  exercisable)  and to have
tendered each of the Option  Shares to  Acquisition  pursuant to the Offer.  The
undersigned  agrees  that the  exercise  price per Option  Share (the  "Exercise
Price") shall be deemed to be paid with the proceeds of an interest free advance
from the Company (the  "Advance").  The Advance  shall be deemed to be repaid in
full  on  behalf  of  the  undersigned  by  Acquisition  from a  portion  of the
consideration  due the  undersigned  for such  Shares in the  Offer.  After such
repayment,  the undersigned  shall be entitled to receive from  Acquisition with
respect to each Option Share  purchased by Acquisition  pursuant to the Offer an
amount equal to the difference  between (a) the Exercise Price and (b) the price
per share of Common Stock paid by Acquisition pursuant to the Offer.

         The undersigned  acknowledges  that he or she has been advised that (i)
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  Acquisition  of
shares of Common Stock pursuant to the Offer),  (ii) 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 (iii)  upon the
purchase of Option  Shares  pursuant to this Option  Election,  the  undersigned
shall have no further rights under such Option.



                                   -----------------------------------
                                   Print Name:
                                   Date:



<PAGE>



                                                                         ANNEX D

                             STOCK PURCHASE ELECTION

         The undersigned holder of purchase rights ("Purchase Rights") under the
Mycogen  Corporation  Employee Stock Purchase Plan (the "Plan") to purchase ____
shares ("Stock  Purchase  Shares") of common stock of Mycogen  Corporation  (the
"Company"),  par value $0.001 per share  ("Common  Stock") [such number of Stock
Purchase Shares calculated assuming your payroll deductions had continued at the
same level  through  November 30, 1998 and the Purchase  Price under the Plan is
$20.08]  hereby  agrees  that,  immediately  prior to the  purchase of shares of
Common Stock by AgroSciences  Acquisition  Inc.  ("Acquisition")  in its pending
tender offer for any and all  outstanding  shares of Common Stock (the "Offer"),
and contingent  upon such purchase,  the Purchase Rights shall be deemed to have
been fully exercised and the  undersigned  shall be deemed to have tendered each
of the Stock Purchase Shares acquired upon such exercise to Acquisition pursuant
to the Offer.  The  undersigned  agrees  that the  amount of payroll  deductions
accumulated  in the  undersigned's  account  under  the  Plan  shall  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  will be deemed  to be paid with the  proceeds  of an  interest  free
advance  from the Company  (the  "Advance").  The Advance  shall be deemed to be
repaid in full on behalf of the undersigned by Acquisition from a portion of the
consideration  due the  undersigned  for such  Shares in the  Offer.  After such
repayment,  the  undersigned  shall be entitled to receive from  Acquisition the
balance  of such  consideration  with  respect  to  each  Stock  Purchase  Share
purchased by Acquisition  pursuant to the Offer an amount equal to the price per
share of Common Stock paid by Acquisition pursuant to the Offer.

         The undersigned  acknowledges  that he or she has been advised that (i)
the  Company  and Parent will make it  possible  for the Stock  Purchase  Shares
issuable upon exercise of the Purchase  rights to be tendered in the Offer,  and
(ii) upon  exercise  of the  Purchase  Rights  pursuant  to this Stock  Purchase
Election,  the  undersigned  shall have no  further  rights  under the  Purchase
Rights.



                                        ________________________________
                                        Print Name:


                                        ________________________________
                                        Date:


<PAGE>






                                                                         Annex E



                            RESTRICTED STOCK ELECTION


         The undersigned holder of shares ("Restricted  Shares") of common stock
of Mycogen  Corporation  (the  "Company"),  par value $0.001 per share  ("Common
Stock"), which were granted pursuant to the Mycogen Corporation Restricted Stock
Issuance  Plan (the "Plan") and which shares are not vested  hereby agrees that,
immediately  prior to the  purchase  of shares of Common  Stock by  AgroSciences
Acquisition  Inc.  ("Acquisition")  in its pending  tender offer for any and all
outstanding  shares of Common  Stock (the  "Offer"),  and  contingent  upon such
purchase,  the  undersigned  shall  be  deemed  to  have  tendered  each  of the
Restricted  Shares  (regardless of the fact that the Restricted  Shares were not
previously vested) to Acquisition pursuant to the Offer. Following expiration of
the Offer,  the undersigned  shall be entitled to receive from  Acquisition with
respect  to each  Restricted  Share an  amount  equal to the  price per share of
Common Stock paid by Acquisition pursuant to the Offer.

         The undersigned  acknowledges  that he or she has been advised that (i)
Restricted  Shares for which a valid Restricted Stock Election has been executed
and delivered to the Company will become vested  immediately prior to expiration
of the Offer (but  contingent  upon the  purchase  by  Acquisition  of shares of
Common Stock pursuant to the Offer),  (ii) that the Company and Parent will make
it possible  for the  Restricted  Shares to be tendered in the Offer,  and (iii)
upon the purchase of Restricted  Shares  pursuant to the Offer,  the undersigned
shall have no further rights under the Restricted Shares.


                                    ----------------------------------------
                                    Print Name:


                                    -----------------------------------------
                                    Date:




<PAGE>





Dow to Acquire All Outstanding Mycogen Shares

MIDLAND, Mich., Aug. 31 /PRNewswire/ -- Dow AgroSciences LLC, a wholly owned
subsidiary of The Dow Chemical Company (NYSE: DOW), and Mycogen Corporation
(Nasdaq: MYCO) today announced that they have signed a definitive agreement for
Dow AgroSciences to acquire all of the outstanding shares of Mycogen that it
does not already own.

Dow AgroSciences currently owns approximately 68 percent of the outstanding
shares of Mycogen. Under the terms of the agreement, a subsidiary of Dow
AgroSciences will make a tender offer to acquire all of the remaining shares of
Mycogen at $28.00 per share. Following the tender offer, if Dow AgroSciences and
the subsidiary own at least 90 percent of Mycogen's shares, the Dow AgroSciences
subsidiary will be merged into Mycogen and each remaining Mycogen shareholder
will receive $28.00 per share in exchange for each Mycogen share held.

Mycogen Corporation, based in San Diego, Calif., 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.

Dow AgroSciences, based in Indianapolis, Indiana, is a global leader in
providing pest management and biotechnology products that improve the quality
and quantity of the earth's food supply and contribute to the safety, health and
quality of life of the world's growing population. The company employs more than
3,000 people in over 50 countries and has worldwide sales of more than $2
billion.

The Dow Chemical Company with headquarters in Midland, Mich., is the fifth
largest chemical company in the world, with annual sales of more than $20
billion. Dow manufactures and supplies chemicals, plastics, and agricultural
products for customers in 164 countries, and employs approximately 43,000 people
worldwide.



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