MONSANTO CO
8-A12B, 1998-11-18
CHEMICALS & ALLIED PRODUCTS
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<PAGE>
 
                       SECURITIES AND EXCHANGE COMMISSION

                            WASHINGTON, D.C.  20549


                                    FORM 8-A


               FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                    PURSUANT TO SECTION 12(b) OR (g) OF THE
                        SECURITIES EXCHANGE ACT OF 1934

                                Monsanto Company
             (Exact name of registrant as specified in its charter)


        Delaware                                          43-0420020
(State of incorporation)                       (IRS Employer Identification No.)

                         800 North Lindbergh Boulevard
                           St. Louis, Missouri 63167
              (Address of principal executive offices) (Zip Code)
<TABLE> 
<S>                                       <C> 
If this form relates to the                  If this form relates to the
Registration of a class of securities        registration of a class of securities
pursuant to Section 12(b) of the             pursuant to Section 12(g) of the
Exchange Act and is effective                Exchange Act and is effective
pursuant to General Instruction              pursuant to General Instruction A.(d),
A.(c), please check the following box. [X]   please check the following box. [ ]
</TABLE> 

       Securities to be registered pursuant to Section 12(b) of the Act:

       Title of each class                        Name of each exchange on which
       to be so registered                        each class is to be registered
 ---------------------------------                ------------------------------
 Adjustable Conversion-rate Equity                    New York Stock Exchange
          Security Units

 
 
       Securities to be registered pursuant to Section 12(g) of the Act:
 
                                     NONE
                               (Title of Class)
<PAGE>
 
Item 1. DESCRIPTION OF REGISTRANT'S SECURITIES TO BE REGISTERED.

     The description of Monsanto Company (the "Company") Adjustable Conversion-
rate Equity Security Units (the "Units") to be registered hereunder is
incorporated herein by reference to the description included under the caption
"Description of Stock Purchase Contracts and Stock Purchase Units" in the
Registration Statement on Form S-3 of Monsanto Company (Registration No. 333-
51919) (as the same may be amended from time to time, and including any
Registration Statement filed pursuant to Rule 462(b) under the Securities Act of
1933, as amended, the "Registration Statement").  For purposes of such
description, any prospectus supplement relating to the Registration Statement
filed pursuant to Rule 424(b) under the Securities Act of 1933, as amended,
which purports to describe the Units shall be deemed to be incorporated herein
by reference.

Item 2. EXHIBITS.

1.   Restated Certificate of Incorporation of the Company as of October 28, 1997
     (incorporated herein by reference to 3(i) of the Company's Form 10-Q for
     the quarter ended September 30, 1997).

2.   By-Laws of the Company, as amended effective September 26, 1997 
     (incorporated herein by reference to Exhibit 3(ii) of the Company's 
     Form 10-Q for the quarter ended September 30, 1997).

3.   Rights Agreement, dated as of January 26, 1990, between Monsanto Company 
     and First Chicago Trust Company of New York (as successor to The First
     National Bank of Boston), as Rights Agent (incorporated by reference to
     Monsanto Company's Registration Statement on Form 8-A filed with the
     Securities and Exchange Commission on January 31, 1990).

4.   Form of Junior Subordinated Debt Security relating to the Registrant's 
     Junior Subordinated Deferrable Debentures (filed herewith).

5.   Form of Normal Adjustable Conversion-rate Equity Security Unit of the
     Registrant (filed herewith).

6.   Form of Stripped Adjustable Conversion-rate Equity Security Unit of the
     Registrant (filed herewith).

7.   Form of Indenture between the Registrant and the Trustee, providing for the
     issuance of subordinated debt securities in series (incorporated herein by
     reference to Exhibit 4.5 of the Registrant's Registration Statement on Form
     S-3, as amended (No. 333-51919)).

8.   Form of Master Unit Agreement between the Registrant and the Unit Agent
     (filed herewith).
<PAGE>
 
9.   Form of Call Option Agreement between Goldman, Sachs & Co. and the Unit 
     Agent (filed herewith).

10.  Form of Pledge Agreement among the Registrant, Goldman, Sachs & Co., the
     Collateral Agent and the Unit Agent (filed herewith).

                                       2
<PAGE>
 
SIGNATURE

          Pursuant to the requirements of Section 12 of the Securities Exchange
Act of 1934, the Registrant has duly caused this registration statement to be
signed on its behalf by the undersigned, thereunto duly authorized.

Dated: November 18, 1998

                              MONSANTO COMPANY


                              By: /s/ Juanita H. Hinshaw
                                  -----------------------------------
                                  Name:  Juanita H. Hinshaw
                                  Title: Vice President and Treasurer

                                       3
<PAGE>
 
                                  EXHIBIT LIST
<TABLE> 
<CAPTION> 
No.
- ---
<S>  <C> 
1.   Restated Certificate of Incorporation of the Company as of October 28, 1997
     (incorporated herein by reference to 3(i) of the Company's Form 10-Q for
     the quarter ended September 30, 1997).

2.   By-Laws of the Company, as amended effective September 26, 1997 
     (incorporated herein by reference to Exhibit 3(ii) of the Company's 
     Form 10-Q for the quarter ended September 30, 1997).

3.   Rights Agreement, dated as of January 26, 1990, between Monsanto Company 
     and First Chicago Trust Company of New York (as successor to The First
     National Bank of Boston), as Rights Agent (incorporated by reference to
     Monsanto Company's Registration Statement on Form 8-A filed with the
     Securities and Exchange Commission on January 31, 1990).

4.   Form of Junior Subordinated Debt Security relating to the Registrant's 
     Junior Subordinated Deferrable Debentures (filed herewith).

5.   Form of Normal Adjustable Conversion-rate Equity Security Unit of the
     Registrant (filed herewith).

6.   Form of Stripped Adjustable Conversion-rate Equity Security Unit of the
     Registrant (filed herewith).

7.   Form of Indenture between the Registrant and the Trustee, providing for the
     issuance of subordinated debt securities in series (incorporated herein by
     reference to Exhibit 4.5 of the Registrant's Registration Statement on Form
     S-3, as amended (No. 333-51919)).

8.   Form of Master Unit Agreement between the Registrant and the Unit Agent
     (filed herewith).

9.   Form of Call Option Agreement between Goldman, Sachs & Co. and the Unit 
     Agent (filed herewith).

10.  Form of Pledge Agreement among the Registrant, Goldman, Sachs & Co., the
     Collateral Agent and the Unit Agent (filed herewith).
</TABLE> 

                                       4

<PAGE>
 
                                                                       EXHIBIT 4


REGISTERED                                         REGISTERED

                               MONSANTO COMPANY

                       .% JUNIOR SUBORDINATED DEFERRABLE
                        DEBENTURES DUE NOVEMBER ., 2003

No.  -.                                                                  CUSIP .
                                                                  US$500,000,000

          MONSANTO COMPANY, a corporation duly organized and existing under the
laws of Delaware (herein called the "Company," which term includes any successor
corporation under the Indenture hereinafter referred to for value received,
hereby promises to pay to _________________________ as Collateral Agent (the
"Collateral Agent") or registered assigns, (i) the principal sum of Five Hundred
Million Dollars ($500,000,000) on November ., 2003, (the "Maturity Date") unless
previously repurchased as provided herein, (ii) interest (a) on said principal
sum from November ., 1998, or from the most recent interest payment date (each
such date, an "Interest Payment Date") to which interest has been paid or duly
provided for, quarterly (subject to deferral as set forth herein) in arrears on
January 15, April 15, July 15 and October 15, of each year, commencing on
January 15, 1999, initially at the rate of .% per annum (the "Initial Interest
Rate") until the Market Rate Increase Date (as hereinafter defined), and if the
Rate Increase Agent (as hereinafter defined) establishes a Market Increase Rate
(as hereinafter  defined) at such Market Increase Rate (whichever of the Initial
Interest Rate or the Market Increase Rate as may be in effect at any applicable
time being referred to herein as the "Interest Rate") thereafter until the
principal hereof shall have become due and payable, (b) at the Interest Rate on
any overdue principal and premium, if any, and (c) at the Interest Rate,
compounded quarterly on any overdue installment of interest and (iii) the Put
Price (as hereinafter defined) with respect hereto, in each case, without
duplication and to the extent that payment of such interest is enforceable under
applicable law.  The amount of interest payable on any Interest Payment Date
shall be computed on the basis of a 360-day year consisting of twelve 30-day
months.  In the event that any date on which principal of (or premium, if any),
or interest on or the Put Price with respect to this .% Junior Subordinated
Deferrable Interest Debentures due November ., 2003 (the "Debenture") is not a
Business Day, then payment payable on such date will be made on the next
succeeding day that is a Business Day (and to the extent such payment is made on
the next succeeding Business Day, without any interest or other payment in
respect of any such delay), except that, if such Business Day is in the next
succeeding calendar year, such payment shall be made on the immediately
preceding Business Day, in each case with the same force and effect as if made
on the date such payment was originally payable.
<PAGE>
 
          The interest so payable and punctually paid or duly provided for, on
any Interest Payment Date will, as provided in the Indenture, be paid to the
Person in whose name this Debenture is registered at the close of business on
the Regular Record Date for such interest payment, which shall be one Business
Day prior to the relevant Interest Payment Date unless this Debenture is
distributed and is issued in certificated form, in which case the record date
for such interest installment shall be the first day of the month in which the
relevant Interest Payment Date falls.  Except as otherwise provided in the
Indenture, any such interest not so punctually paid or duly provided for will
forthwith cease to be payable to the Holder on such Regular Record Date by
virtue of their having been such Holder as may either be paid to the Person in
whose name this Debenture is registered at the close of business on a Special
Record Date for the payment of such Defaulted Interest to be fixed by the
Trustee (as hereinafter defined), notice whereof is to be given to Holders of
Debentures not less than 10 calendar days prior to such Special Record Date, or
be paid at any time in any other lawful manner not inconsistent with the
requirements of any securities exchange on which the Debentures may be listed,
and upon such notice as may be required by such exchange, all as more fully
provided in said Indenture.  The principal of (and premium, if any) and the
interest on and the Put Price with respect to this Debenture shall be payable at
the office or agency of the Trustee in The City of New York or at the office(s)
of such Paying Agent(s)  as the Company may designate from time to time
maintained for that purpose in any coin or currency of the United States of
America that at the time of payment is legal tender for payment of public and
private debts; provided, however, that payment of interest may be made at the
               --------  -------                                             
option of the Company by check mailed to the registered Holder at such address
as shall appear in the Register or by transfer to an account maintained by the
Holder entitled thereto as specified in the Register, provided that proper
instructions have been received by the relevant record date.  Notwithstanding
the foregoing so long as the holder of this Debenture is the Trustee, the
payment of the principal of (and premium, if any) and interest on this Debenture
will be made in immediately available funds at such place and to such account as
may be designated by the Trustee.

          The interest rate paid on the Debentures is subject to increase in
accordance with the procedures set forth herein.  By 9:30 a.m. New York City
time, on the Market Rate Increase Date a nationally recognized investment
banking firm chosen by the Company (the "Rate Increase Agent") will determine
whether the then current market value of the Debentures, is at least equal to
100.25% of the Cash Equivalent of the Aggregate Call Option Consideration (as
hereinafter defined).  If the Rate Increase Agent determines that the current
aggregate market value of the Debentures is at least equal to 100.25% of the
Cash Equivalent of the Aggregate Call Option Exercise Consideration (or the
interest rate paid on the Debentures is already equal to or greater than the
Maximum Debenture Rate (as hereinafter defined)), interest on the Debentures
will continue to accrue at the Initial Interest Rate.  If the Rate Increase
Agent determines that the current aggregate market value of the Debentures is
not at least equal to 100.25% of the Cash Equivalent of the Aggregate Call
Option 
<PAGE>
 
Exercise Consideration (and the interest rate is less than the Maximum Debenture
Rate), the Rate Increase Agent will, by 9:30 a.m., New York City time, on the
Market Rate Increase Date, select an increased rate equal to the lower of (a)
the rate that the Rate Increase Agent determines is sufficient to cause the then
current aggregate market value of such Debentures to be at least equal to
100.25% of the Cash Equivalent of the Aggregate Call Option Exercise
Consideration and (b) the Maximum Debenture Rate, and the interest rate will
thereupon become that increased rate (the "Market Increase Rate"). Upon any such
increase of the Market Increase Rate, the Rate Increase Agent shall notify the
Company and the Call Option Holder (as hereinafter defined) of such increased
rate.

          "Cash Equivalent of the Aggregate Call Option Exercise Consideration"
means the cash value on the Market Rate Increase Date of a package of
consideration (the "Aggregate Call Option Exercise Consideration"), which
includes U.S. Treasury Strips, U.S. Treasury Bills or other U.S. Treasury
Securities (any of the foregoing being referred to herein as the "Treasury
Securities"), that will provide payments matching the aggregate interest due on
the Debentures through November ., 2001, assuming that (a) the Treasury
Securities included in the Aggregate Call Option Exercise Consideration are
highly liquid Treasury Securities maturing on or within 35 days prior to
November ., 2001 (any such Treasury Securities will be designated in good faith
by the holder of the call options on the Debentures (the "Call Option Holder")
in a notice delivered to the Rate Increase Agent by 8:30 a.m., New York City
time, on the Market Rate Increase Date or, if the Call Option Holder fails to so
designate such Treasury Securities, as designated in good faith by the Rate
Increase Agent, in either case in a manner intended to minimize the Cash
Equivalent of the Aggregate Call Option Exercise Consideration) and (b) such
Treasury Securities are valued based on the ask-side price thereof at 9:00 a.m.,
New York City time, on the Market Rate Increase Date (as determined on a same
day settlement basis by a reasonable and customary means selected in good faith
by the Rate Increase Agent and notified to the Call Option Holder prior thereto)
plus interest accrued thereon to such date.

          "Maximum Debenture Rate" means (a) the yield to maturity (calculated
in accordance with standard market price) corresponding to the bid-side price at
9:00 a.m., New York City time, on the Market Rate Increase Date (as determined
by a reasonable and customary means selected in good faith by the Rate Increase
Agent and notified to the Call Option Holder prior thereto) of highly liquid
Treasury Securities maturing on or around the Maturity Date as selected in good
faith by the Rate Increase Agent plus (b) . basis points.

          "Market Rate Increase Date" means November ., 2001 (or, if such day is
not a Trading Day (as hereinafter defined), the next succeeding Trading Day).

          "Trading Day" means a day on which the no par value common stock of
the Company (the "Common Stock") (a) is not suspended from trading on any
national or regional securities exchange or association or over-the-counter
market at the close of 
<PAGE>
 
business and (b) has traded at least once on the national or regional securities
exchange or association or over-the-counter market that is the primary market
for the trading of the Common Stock.

          If the Debentures are not otherwise pledged as collateral for the
Company's Units, the Debentures may be represented by one or more global
certificates registered in the name of Cede & Co. or other nominee of The
Depository Trust Company.

          The indebtedness evidenced by this Debenture is, to the extent
provided in the Indenture, subordinate and junior in right of payment to the
prior payment in full of all present and future Senior Indebtedness (as
hereinafter defined), and this Debenture is issued subject to the provisions of
the Indenture with respect thereto.  Each Holder of this Debenture by accepting
the same, (a) agrees to and shall be bound by such provisions, (b) authorizes
and directs the Trustee on his or her behalf to take such action as may be
necessary or appropriate to acknowledge or effectuate the subordination so
provided and (c) appoints the Trustee his or her attorney-in-fact for any and
all such purposes.  Each Holder hereof, by his or her acceptance hereof, hereby
waives all notice of the acceptance of the subordination provisions contained
herein and in the Indenture by each holder of Senior Indebtedness, whether now
outstanding or hereafter incurred, and waives reliance by each such holder upon
said provisions.

          "Senior Indebtedness" shall mean, with respect to the Company, and
without duplication, the principal, premium (if any) and unpaid interest on all
present and future (1) indebtedness of the Company for borrowed money, (2)
obligations of the Company evidenced by bonds, debentures, notes or similar
instruments, (3) indebtedness incurred, assumed or guaranteed by the Company in
connection with the acquisition by it or a Subsidiary of any business,
properties or assets (except purchase-money indebtedness classified as accounts
payable  under generally accepted accounting principles), (4) obligations of the
Company as lessee under leases required to be capitalized on the balance sheet
of the lessee under generally accepted accounting principles, (5) reimbursement
obligations of the Company in respect of letters of credit relating to
indebtedness or other obligations of the Company in respect of letters of credit
relating to indebtedness or other obligations of the Company that qualify as
indebtedness or obligations of the kind referred to in clauses (1) through (4)
above, and (6) obligations of the Company under direct or indirect guarantees in
respect of, and obligations (contingent or otherwise) to purchase or otherwise
acquire, or otherwise to assure a creditor against loss in respect of,
indebtedness or obligations of others of the kind referred to in clauses (1)
through (5) above, in each case unless in the instrument creating or evidencing
the indebtedness or obligation or pursuant to which the same is outstanding it
is provided that such indebtedness or obligation is not superior in right of
payment to senior debt securities.  Senior Indebtedness shall continue to be
Senior Indebtedness and be entitled to the benefits of the subordination
provisions 

                                      -4-
<PAGE>
 
irrespective of any amendment, modification or waiver of any term of such Senior
Indebtedness.

          This Debenture is one of a duly authorized issue of securities of the
Company (the "Securities") issued under an Indenture, dated as of November .,
1998, as amended or supplemented from time to time (the "Indenture"), between
the Company and _________________, as Trustee (the "Trustee"), to which
Indenture and all indentures supplemental thereto reference is hereby made for a
statement of the respective rights, limitations of rights, duties and immunities
thereunder of the Company, the Trustee and the Holders of the Debentures and of
the terms upon which the Securities are, and are to be, authenticated and
delivered.  This Debenture is one of the Securities designated on the face
hereof limited in aggregate principal amount to $500,000,000.

          Any one or more of the following described events with respect to the
Debentures constitutes an "Event of Default" (whatever the reason for such Event
of Default and whether it shall be voluntary or involuntary or be effected by
operation of law or pursuant to any judgment, decree or order of any court or
any order, rule or regulation of any administrative or governmental body):  (a)
failure for 30 days to pay any interest on the Debentures when due (subject to
the deferral of any due date in the case of an Extension Period (as hereinafter
defined)); or (b) failure to pay any principal on the Debentures when due at
maturity or (c) failure to pay the Put Price when due upon exercise of a Put
Option (as hereafter defined); or (d) failure to observe or perform any other of
the covenants contained in the Indenture for 90 days after written notice to the
Company from the Trustee or to the Company and the Trustee from the holders of
at least 25% in principal amount of the Debentures; or (e) the events of
bankruptcy, insolvency or reorganization of the Company set forth as Events of
Default under the Indenture.

          If any Event of Default, as provided for in the Indenture, with
respect to the Debentures shall occur and be continuing, the principal of the
Debentures may be declared due and payable in the manner and with the effect
provided in the Indenture.

          So long as no Event of Default has occurred and is continuing, the
Company will have the right at any time during the term of Debentures to defer
the payment of interest at any time or from time to time for a period not
extending beyond the Maturity Date (each such period of deferral, an "Extension
Period") or ending on a date other than an Interest Payment Date.  At the end of
an Extension Period, the Company must pay all interest then accrued and unpaid
(together with interest thereon accrued at a rate of .% per annum (plus, for the
period after the Market Rate Increase Date, the difference, if any, between the
Market Increase Rate and the Initial Interest Rate) compounded on each
succeeding Interest Payment Date).  During an Extension Period, interest will
continue to accrue and Holders of Debentures will be required to accrue interest
income for United States Federal income tax 

                                      -5-
<PAGE>
 
purposes prior to the receipt of cash attributable to such income except to the
extent that tax treatment changes as a matter of law.

          Prior to the expiration of any such Extension Period, the Company may
further extend such Extension Period, provided that such Extension Period,
together with all such previous and further extensions within such Extension
Periods, (i) shall not end on any date other than an Interest Payment Date and
(ii) shall not extend beyond the Maturity Date. Upon the termination of any such
Extension Period and the payment of all amounts then due on any Interest Payment
Date, the Company may elect to begin a new Extension Period, subject to the
above requirements.  No interest shall be due and payable during an Extension
Period, except at the end thereof.  The Company must give the Trustee written
notice of its election of any Extension Period (or an extension thereof) at
least five Business Days prior to the earlier of (a) the date the interest on
the Debentures would have been payable except for the election to begin or
extend such Extension Period, (b) the date the Company is required to give
notice to any securities exchange or to holders of Debentures of the Regular
Record Date or the date such interest is payable and (c) such Regular Record
Date.  The Company shall give notice of the Company's election to begin or
extend a new Extension Period to the holders of the Debentures.  There is no
limitation on the number of times that the Company may elect to begin an
Extension Period.

          The Company has agreed that it will not (a) declare or pay any
dividends or distributions on, or redeem, purchase, acquire, or make a
liquidation payment with respect to any of the Company's capital stock, (b) make
any payment of principal, interest or premium, if any, on or repay, repurchase
or redeem any debt securities of the Company that rank pari passu with or junior
in right of payment to the Debentures or (c) make any guarantee payments with
respect to any guarantee by the Company of any securities of any subsidiary of
the Company if such guarantee rank pari passu or junior in right of payment to
the Debentures (other than, in the case of clauses (a), (b) and (c), (i)
dividends or distributions in shares of, or options, warrants or rights to
subscribe for or purchase shares of, common stock of the Company, (ii) any
declaration of a dividend in connection with the implementation of a
stockholder's rights plan, or the issuance of stock under any such plan in the
future, or the redemption or repurchase of any such rights pursuant thereto,
(iii) as a result of a reclassification of the Company's capital stock solely
into shares of one or more classes or series of the Company's capital stock or
the exchange or conversion of one class or series of the Company's capital stock
for another class or series of the Company's capital stock, (iv) the purchase of
fractional interests in shares of the Company's capital stock pursuant to the
conversion or exchange provisions of such capital stock or the security being
converted or exchanged and (v) purchases of common stock in connection with the
satisfaction by the Company of its obligations under any of the Company's
benefit plans for its and its Subsidiaries' directors, officers or employees or
any of the Company's dividend reinvestment plans).

                                      -6-
<PAGE>
 
          Each Holder of Debentures will have the right (a "Put Option") to
require the Company to repurchase such Debentures, on November ., 2001 or, if
applicable, on the Early Settlement Date (as defined in the Master Unit
Agreement, dated as of November __, 1998, between the Company and First National
Bank of Chicago, as Unit Agent)  (either such date, the "Put Option Date"), for
a purchase price (the "Put Price") equal to the aggregate principal amount
thereof plus unpaid interest accrued thereon up to but not including the Put
Option Date, but only if the cash received on the exercise of such option is
used to settle the purchase contracts between the Company and First National
Bank of Chicago, as Unit Agent, secured thereby.

          The Holder of this Debenture and the Put Agent (the "Put Agent" which
initially will be ______________ and subsequently, any successor thereto), on
behalf of Holders whose Debentures have been delivered to the Put Agent for the
purpose of exercising the Put Option related to such Debentures, may exercise
the Put Option related to this Debenture by presenting and surrendering this
Debenture, at the offices of the Trustee, with the form of "Notice of Exercise
of Put Right" on the reverse side of this Debenture completed and executed as
indicated, by 10:00 a.m., New York City time, on the Put Option Date.

          In the event of the exercise of the Put Option with respect to this
Debenture in part only, a new Debenture or Debentures for the portion hereof not
repurchased will be issued in the name of the Holder upon the cancellation
hereof.

          The Indenture permits, with certain exceptions as therein provided,
the amendment thereof and the modification of the rights and obligations of the
Company and the rights of the Holders of the Securities of each Series of each
series to be affected under the Indenture at any time by the Company with the
consent of the Holders of not less than a majority in principal amount of the
outstanding Securities of each series to be affected.  The Indenture also
contains provisions permitting the Holders of specified percentages in principal
amount of the outstanding Securities of each series, on behalf of the Holders of
all Securities of such series, to waive, with respect to the Securities of such
series, compliance by the Company with certain provisions of the Indenture and
certain past defaults under the Indenture and their consequences.  Any such
consent or waiver by the Holder of this Debenture will be conclusive and binding
upon such Holder and upon all future Holders of this Debenture and of any
Debenture issued upon the registration of transfer hereof or in exchange herefor
or in lieu hereof, whether or not notation of such consent or waiver is made
upon this Debenture.

          Holders of Debentures may not enforce their rights pursuant to the
Indenture or the Debentures except as provided in the Indenture.  No reference
herein to the Indenture and no provision of this Debenture or of the Indenture
will alter or impair the obligation of the Company, which is absolute and
unconditional, to pay the principal of, and premium, if 

                                      -7-
<PAGE>
 
any, and interest on and the Put Price with respect to this Debenture at the
times, places and rates, herein prescribed.

          The Debentures of this series are issuable only in registered form,
without coupons, in minimum denominations of $1,000 and integral multiples
thereof.  As provided in the Indenture and subject to certain limitations
therein specified and to the limitations described below, if applicable,
Debentures of this series are exchangeable for Debentures of this series of like
aggregate principal amount of a different authorized denomination, as requested
by the Holder, surrendering the same.

          As provided in the Indenture and subject to certain limitations
therein specified and to the limitations described below, if applicable, the
transfer of this Debenture is registerable in the Register upon surrender of
this Debenture for registration of transfer at the office or agency of the
Company maintained for that purpose duly endorsed by, or accompanied by a
written instrument of transfer in form satisfactory to the Company and the
Registrar (which will initially be the Trustee at its principal corporate trust
office located in ______________) duly executed by the Holder hereof or his
attorney duly authorized in writing, and thereupon one or more new Debentures of
this series with like terms and conditions, of authorized denominations and for
the same aggregate principal amount, will be issued to the designated transferee
or transferees.

          Prior to due presentment of this Debenture for registration of
transfer, the Company and any agent of the Company may treat the Person in whose
name this Debenture is registered as the owner hereof for all purposes, whether
or not this Debenture is overdue and notwithstanding any notation of ownership
or other writing hereon, and none of the Company or any such agent will be
affected by notice to the contrary.

          Unless the certificate of authentication hereof has been executed by
the Trustee referred to herein, or its successor as Trustee, or its
Authenticating Agent, by manual signature or an authorized signatory, this
Debenture will not be entitled to any benefit under the Indenture or be valid or
obligatory for any purpose.

          No recourse shall be had for the repayment of the principal of or
premium, if any, or interest on or the Put Price in respect of this Debenture,
or for any claim based hereon, or otherwise in respect hereof, or based on or in
respect of the Indenture, against any incorporator, stockholder, officer or
director, past, present or future, as such, of the Company or any predecessor or
successor Person, whether by virtue of any constitution, statute or rule of law,
or by the enforcement of an assessment or penalty or otherwise, all such
liability being, by the acceptance hereof and as part of the consideration for
the issuance hereof, expressly waived and released.

                                      -8-
<PAGE>
 
          The Company agrees, and each holder of a beneficial interest in any
Debentures shall by the acquisition of such interest be deemed to have agreed,
that for United States Federal income tax purposes the Debentures are intended
to constitute indebtedness, except to the extent that the tax treatment of the
Debenture changes as a matter of law.

          The Indenture and the Debentures will be governed by and construed in
accordance with the laws of the State of New York.

          All capitalized terms used but not defined in this Debenture will have
the meanings assigned to them in the Indenture; and all references in the
Indenture to "Security" or "Securities" will be deemed to include this
Debenture.

          [The following legend is provided in accordance with Treasury
Regulation (S)1:1275-3(b):

          This Debenture was issued with original issue discount ("OID").  The
          Company will promptly, beginning no later than 10 days after the issue
          date of this Debenture, make available to a Holder upon request the
          information specified in Treasury Regulation section 1.1275-
          3(b)(1)(i).  Please send only such requests to Monsanto Company,
          _______________, Attention:  Taxation Vice President and Tax Counsel.]

                                      -9-
<PAGE>
 
          IN WITNESS WHEREOF, the Company has caused this instrument to be duly
executed under its corporate seal.

Date:  November __, 1998      MONSANTO COMPANY


                              By
                                ----------------------------------
[SEAL]
                              Attest:


                              By
                                ----------------------------------

                                      -10-
<PAGE>
 
          This is one of the Securities of the series designated therein
referred to in the within-mentioned Indenture.

Dated:  November __, 1998
                                   --------------------------
                                          as Trustee


                              By:
                                  ---------------------------------
                                           Authorized Officer

                                      -11-
<PAGE>
 
                                   ASSIGNMENT

                                 _____________


     FOR VALUE RECEIVED, the undersigned hereby sell(s), assign(s) and
transfer(s) the Debentures to:

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

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

        (Insert assignee's social security or tax identification number)


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

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

- --------------------------------------------------------------------------------
                   (Insert address and zip code of assignee)

and irrevocably appoints

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

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

- --------------------------------------------------------------------------------
                                              agent to transfer this Debenture
- ----------------------------------------------
on the books of the Company.  The agent may substitute another to act for him or
her.

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

Signature: 
          ---------------------------------------------------------------
          (Sign exactly as your name appears on the other side of this
     Debenture)

Signature Guarantee*: 
                     -----------------------------------------------------------


- -----------------------
* Signature must be guaranteed by an "eligible guarantor institution" that
is a bank, stockholder, savings and association or credit union meeting the
requirements of the [Registrar], which requirements include membership
participation in the Securities Transfer Agents Medallion Program ("STAMP") or
such other "signature guarantee program" as may be determined by the Registrar
in addition to, or in substitution for, STAMP, all in accordance with the
Securities and Exchange Act of 1934, as amended.
<PAGE>
 
                        NOTICE OF EXERCISE OF PUT RIGHT

 
          The undersigned holder of this Debenture (or the put agent on behalf
of such holder) hereby gives notice and irrevocably exercises the Put requiring
the Company to repurchase this Debenture, or the portion designated below, for
the aggregate principal amount thereof plus any unpaid interest accrued on this
Debenture pursuant to the terms and subject to the conditions of the Debenture
and the Indenture, dated as of November ., 1998 (the "Indenture") between the
Company and _____________, as trustee by 10:00 a.m., New York time, on  November
 ., 2001.  If any portion of the Debenture not to be repurchased is to be
registered in the name of  a Person other than the undersigned, the undersigned
will pay any transfer tax payable incident thereto.

Date:  _________________

Principal amount of the Debenture to be repurchased $1,000 or integral multiples
thereof: ____________________________________________

Signature:
          -------------------------------------------
(Sign exactly as your name appears on the other side of this Debenture)

Please print or type name and address, including zip code, and social security
or other identifying number

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

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

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

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


If any portion of the Debenture is to be registered in the name of and delivered
to a Person other than the holder hereof, please print or type name and address,
including zip code, and social security or other identifying number

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

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

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

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

Signature Guarantee*

- -------------------------------
* If this Notice of Exercise of Put Right is signed by any Person other
than the registered holder of this Debenture, the Signature must be guaranteed
by an "eligible guarantor institution" that is a bank, stockbroker, savings and
loan association or credit union meeting the requirements of the [Registrar],
which requirements include membership or participation in the Securities
Transfer Agents Medallion Program ("STAMP") or such other "signature guarantee
program" as may be determined by the Registrar in addition to, or in
substitution for, STAMP, all in accordance with the Securities and Exchange Act
of 1934, as amended.

<PAGE>
 
                                                                       EXHIBIT 5

THIS UNIT CERTIFICATE IS A GLOBAL UNIT CERTIFICATE WITHIN THE MEANING OF THE
MASTER UNIT AGREEMENT HEREINAFTER REFERRED TO AND IS REGISTERED IN THE NAME OF A
DEPOSITARY OR A NOMINEE THEREOF.  THIS UNIT CERTIFICATE MAY NOT BE EXCHANGED IN
WHOLE OR IN PART FOR A UNIT CERTIFICATE REGISTERED, AND NO TRANSFER OF THIS UNIT
CERTIFICATE IN WHOLE OR IN PART MAY BE REGISTERED, IN THE NAME OF ANY PERSON
OTHER THAN SUCH DEPOSITARY OR A NOMINEE THEREOF, EXCEPT IN THE LIMITED
CIRCUMSTANCES DESCRIBED IN THE MASTER UNIT AGREEMENT.


                                MONSANTO COMPANY

              .% Adjustable Conversion-rate Equity Security Units

                       (Stated Amount $. per Normal Unit)


CUSIP No. 611662305

No. .                                                             . Normal Units


          This Unit Certificate certifies that Cede & Co. is the registered
Holder of the number of Normal Units set forth above.  Each Normal Unit
represents the right to purchase Common Stock under a Purchase Contract with
Monsanto Company, a Delaware corporation (the "Company"), together with
ownership of the Junior Subordinated Deferrable Debentures (the "Debentures") or
other Pledged Securities pledged to secure the obligations referred to in (a)
and (b) below, subject to (a) the obligations owed to the Company under such
Purchase Contract, (b) for so long as any Call Options remain exercisable, the
obligations owed to the Call Option Holder under a Call Option and (c) the
pledge arrangements securing the foregoing obligations.

          Each Purchase Contract evidenced hereby is governed by a Master Unit
Agreement, dated as of November ., 1998 (the "Master Unit Agreement"), between
the Company and First National Bank of Chicago, as unit agent (herein called the
"Unit Agent"), and the terms of each Purchase Contract set forth therein.  All
terms used herein which are not defined herein and which are defined in the
Master Unit Agreement have the meanings set forth therein.  Each Call Option
evidenced hereby is governed by the Call Option Agreement.  The Pledge evidenced
hereby is governed by the Pledge 
<PAGE>
 
Agreement. Reference is hereby made to the Master Unit Agreement, the Call
Option Agreement and the Pledge Agreement, and any supplemental agreements
thereto, for a description of the respective rights, limitations of rights,
obligations, duties and immunities thereunder of the Unit Agent, the Company,
the Call Option Holder, the Collateral Agent and the Holders. The summary
contained herein is qualified in its entirety by the provisions of the Principal
Agreements, and the Principal Agreements shall govern the rights of the parties
to the extent that there is any conflict between such summary and such
provisions.

          Each Purchase Contract evidenced hereby obligates the Holder of this
Unit Certificate to purchase, and the Company to sell, on November ., 2001 (the
"Stock Purchase Date"), at a price equal to $. (the "Stated Amount"), a number
of shares of Common Stock, no par value per share, having such terms as set
forth in the Company's certificate of incorporation, as amended from time to
time ("Common Stock"), of the Company equal to the Settlement Rate, unless on or
prior to the Stock Purchase Date there shall have occurred a Termination Event.
The "Settlement Rate" is equal to (a) if the Applicable Market Value (as defined
in the Master Unit Agreement) is greater than or equal to $. (the "Threshold
Appreciation Price"), . of a share of Common Stock per Purchase Contract, (b) if
the Applicable Market Value is less than the Threshold Appreciation Price but is
greater than the Stated Amount, a fractional share of Common Stock per Purchase
Contract equal to the Stated Amount divided by the Applicable Market Value
(rounded to the nearest 1/10,000th of a share or, if there is no nearest
1/10,000th of a share, rounded downward to the nearest 1/10,000th of a share)
and (c) if the Applicable Market Amount is less than or equal to the Stated
Amount, one share of Common Stock per Purchase Contract, in each case subject to
adjustment as provided in the Master Unit Agreement.  No fractional shares of
Common Stock will be issued upon settlement of Purchase Contracts, but instead
of issuing any fractional interest the Company shall make a cash payment as
provided in the Master Unit Agreement.  The purchase price for the shares of
Common Stock to be purchased pursuant to each Purchase Contract evidenced
hereby, if not paid by 10:00 a.m., New York City time, on the Stock Purchase
Date, shall be paid by application of payments received by the Company on the
Stock Purchase Date from the Collateral Agent pursuant to the Pledge Agreement
in respect of the Pledged Securities pledged to secure such Holder's obligations
under such Purchase Contract.

          The Purchase Contracts and the obligations and rights of the Company
and the Holders thereunder, including, without limitation, the rights and
obligations to receive and pay accrued or deferred Contract Fees, shall
immediately and automatically terminate, without the necessity of any notice or
action by any Holder, the Unit Agent or the Company, if, on or prior to the
Stock Purchase Date, a Termination Event shall have occurred.  Upon and after
the occurrence of a Termination Event, the Collateral Agent shall release the
Pledged Securities from the Pledge.  The Normal Units shall thereafter 

                                      -2-
<PAGE>
 
represent the right to receive the Pledged Securities forming a part of such
Normal Units in accordance with the provisions of the Master Unit Agreement and
the Pledge Agreement.

          The Call Options evidenced hereby entitle the Call Option Holder to
acquire the Junior Subordinated Deferrable Debentures (the "Debentures")
evidenced hereby on or before November ., 2001 unless prior to the exercise
thereof there shall have occurred a Termination Event.  The Call Option Holder
may exercise such Call Options only in whole together with the Call Options
underlying the other Normal Units, by delivering to the Unit Agent a notice of
exercise and delivering to the Unit Agent the Aggregate Call Option Exercise
Consideration, whereupon the Debentures underlying the Normal Units will be
released from the Pledge and the Treasury Securities constituting all or part of
the Aggregate Call Option Exercise Consideration delivered to the Collateral
Agent will be substituted as the Pledged Securities underlying the Normal Units.

          The Company shall pay, on each January 15, April 15, July 15 and
October 15, commencing January 15, 1999 (each, a "Quarterly Payment Date"), in
respect of each Purchase Contract evidenced hereby, a fee (the "Contract Fee")
accruing on the Stated Amount of such Unit from and including the date of first
issuance of any Units at a rate per annum equal to .% (the "Contract Fee Rate")
(computed on the basis of a 360-day year of twelve 30-day months and subject to
deferral as described in the Master Unit Agreement), plus any additional fees
accrued thereon pursuant to Section 503 of the Master Unit Agreement.  The
Company's obligations with respect to Contract Fees shall be, to the extent
provided in the Master Unit Agreement, subordinate and subject in right of
payment to all Senior Indebtedness.

          Payments due to the Holder in respect of the Normal Units evidenced
hereby will be payable to the Person in whose name this Unit Certificate is
registered at the close of business on the Record Date next preceding the
relevant payment date.

          The transfer of any Unit Certificate will be registered and Unit
Certificates may be exchanged as provided in the Master Unit Agreement.  The
Unit Registrar may require a Holder, among other things, to furnish appropriate
endorsements and transfer documents permitted by the Master Unit Agreement.  No
service charge shall be required for any such registration of transfer or
exchange, but the Company and the Unit Agent may require payment of a sum
sufficient to cover any tax or other governmental charge payable in connection
therewith.  Except as provided in the Master Unit Agreement in connection with a
Stripped Unit Creation, for so long as the Purchase Contract underlying a Normal
Unit remains in effect, such Normal Unit shall not be separable into its
constituent parts, and the rights and obligations of the Holder of such Normal
Unit in respect of the Pledged Securities and Purchase Contract constituting
such Normal Unit may be transferred and exchanged only as an integrated Normal
Unit.

                                      -3-
<PAGE>
 
          Upon registration of transfer of this Unit Certificate, the transferee
shall be bound (without the necessity of any other action on the part of such
transferee) by the terms of the Purchase Contracts and Call Options evidenced
hereby and by the Pledge Agreement, and the transferor shall be released from
such obligations.  The Company covenants and agrees, and the Holder, by his
acceptance hereof, likewise covenants and agrees, to be bound by the provisions
of this paragraph.

          The Holder of this Unit Certificate, by his acceptance hereof,
irrevocably authorizes the Unit Agent to enter into and perform the related
Purchase Contracts and Call Options evidenced hereby on his behalf as his
attorney-in-fact, agrees to be bound by the terms and provisions thereof,
covenants and agrees to perform his obligations under such Purchase Contracts
and Call Options, consents to the provisions of the Principal Agreements,
irrevocably authorizes the Unit Agent to enter into and perform the Call Option
Agreement and the Pledge Agreement on his behalf as his attorney-in-fact, and
consents to and agrees to be bound by the Pledge evidenced hereby pursuant to
the Pledge Agreement.

          Subject to certain exceptions, the provisions of the Principal
Agreements may be amended with the consent of the Holders of at least a majority
of the Outstanding Units or, if the amendment affects only the Holders of the
Normal Units or only the Holders of the Stripped Units, at least a majority of
the Outstanding Units comprising Normal Units or Stripped Units, as the case may
be.

          THE PURCHASE CONTRACTS AND CALL OPTIONS SHALL FOR ALL PURPOSES BE
GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW
YORK, WITHOUT REGARD TO CONFLICTS OF LAWS PRINCIPLES THEREOF.

          The Company, the Unit Agent and any agent of the Company or the Unit
Agent may treat the Person in whose name this Unit Certificate is registered as
the owner of the Normal Units evidenced hereby for the purpose of receiving
payments of distributions or interest on the Pledged Securities, receiving the
rights and performing the obligations under the Purchase Contracts and for all
other purposes whatsoever, whether or not any payments in respect thereof be
overdue and notwithstanding any notice to the contrary, and neither the Company,
the Unit Agent nor any such agent shall be affected by notice to the contrary.

          THE PURCHASE CONTRACTS SHALL NOT, PRIOR TO THE SETTLEMENT THEREOF,
ENTITLE THE HOLDER TO ANY OF THE RIGHTS OF A HOLDER OF SHARES OF COMMON STOCK.

                                      -4-
<PAGE>
 
          Copies of the Principal Agreements are available for inspection at the
offices of the Unit Agent.

          Unless the certificate of authentication hereon has been executed by
the Unit Agent by manual signature, this Unit Certificate shall not be entitled
to any benefit under the Principal Agreements or be valid or obligatory for any
purpose.

                                      -5-
<PAGE>
 
          IN WITNESS WHEREOF, the Company and the Holder hereby agree to their
respective obligations under the Purchase Contracts evidenced by this
instrument, and the Holder hereby acknowledges that the Pledged Securities
evidenced by this instrument are subject to the Pledge under the Pledge
Agreement.

                                       MONSANTO COMPANY

                                       By:
                                          --------------------------------------

Attest:
        -----------------------------
 
                                       HOLDER SPECIFIED ABOVE

                                       By: THE FIRST NATIONAL
                                       BANK OF CHICAGO,
                                       as Attorney-in-Fact of such Holder

                                       By:
                                          --------------------------------------

          IN WITNESS WHEREOF, the Holder hereby agrees, for the benefit of the
Call Option Holder, to its obligations under any Call Options evidenced by this
instrument, and the Holder hereby acknowledges, for the benefit of the Call
Option Holder, that the Pledged Securities evidenced by this instrument are
subject to the Pledge under the Pledge Agreement.

                                       HOLDER SPECIFIED ABOVE

                                       By: THE FIRST NATIONAL
                                       BANK OF CHICAGO,
                                       as Attorney-in-Fact of such Holder
  
                                       By:
                                          --------------------------------------

Dated:

Unit Agent's Certificate of Authentication

          This is one of the Unit Certificates referred to in the within
mentioned Master Unit Agreement.

THE FIRST NATIONAL BANK OF CHICAGO,
as Unit Agent

                                      -6-
<PAGE>
 
By:
   --------------------------------------

                                      -7-
<PAGE>
 
                            Settlement Instructions


          The undersigned Holder directs that a certificate for shares of Common
Stock deliverable upon settlement on or after the Stock Purchase Date of the
Purchase Contracts underlying the number of Normal Units evidenced by this Unit
Certificate be registered in the name of, and delivered, together with a check
in payment for any fractional share, to the undersigned at the address indicated
below unless a different name and address have been indicated below.  If shares
are to be registered in the name of a Person other than the undersigned, the
undersigned will pay any transfer tax payable incident thereto.

Dated: _________________________________________________________________________
                                                   Signature*

<TABLE>
<CAPTION>

 If shares are to be registered in the                     REGISTERED HOLDER   
 name of and delivered to a Person                                            
 other than the Holder, please print           Please print name and address of
 such Person's name and address:               Registered Holder:              
- --------------------------------------------------------------------------------
<S>                                      <C>                                   
- --------------------------------------------------------------------------------
                Name                                       Name
- --------------------------------------------------------------------------------
                                                                               
- --------------------------------------------------------------------------------
               Address                                    Address
- --------------------------------------------------------------------------------
                                                                               
- --------------------------------------------------------------------------------
Social Security or other Taxpayer                                              
- --------------------------------------------------------------------------------
                                                                               
Identification Number, if any                                                  
- --------------------------------------------------------------------------------
</TABLE>

*/      Signature must be guaranteed by an eligible Guarantor Institution
(banks, stockbrokers, savings and loan associations and credit unions) with
membership in an approved signature medallion program pursuant to Securities and
Exchange Commission Rule 17Ad-15 if Common Stock is to be delivered other than
to, and in the name of, the registered Holder.                                  

                                      -8-
<PAGE>
 
- --------------------------------------------------------------------------------
 If shares are to be registered in the                     REGISTERED HOLDER
 name of and delivered to a Person
 other than the Holder, please print            Please print name and address of
 such Person's name and address:                Registered Holder:
- --------------------------------------------------------------------------------
Identification Number, if any  
- --------------------------------------------------------------------------------

                                      -9-
<PAGE>
 
 If shares are to be registered in the                      REGISTERED HOLDER
 name of and delivered to a Person
 other than the Holder, please print            Please print name and address of
 such Person's name and address:                Registered Holder:


               Name                                           Name

             Address                                        Address



Social Security or other Taxpayer
Identification Number, if any  

                                      -10-
<PAGE>
 
                            Election to Settle Early


          The undersigned Holder directs that a certificate for shares of Common
Stock deliverable upon settlement on or after the Special Early Settlement Date
of the Purchase Contracts underlying the number of Normal Units evidenced by
this Unit Certificate be registered in the name of, and delivered to the
undersigned at the address indicated below unless a different name and address
have been indicated below.  If shares are to be registered in the name of a
Person other than the undersigned, the undersigned will pay any transfer tax
payable incident thereto.

Dated: ___________________________________________________________
                                                   Signature*

- --------------------------------------------------------------------------------
 If shares are to be registered in the                     REGISTERED HOLDER
 name of and delivered to a Person
 other than the Holder, please print     Please print name and address of
 such Person's name and address:         Registered Holder:
 
- --------------------------------------------------------------------------------
                 Name                                        Name
- --------------------------------------------------------------------------------

- --------------------------------------------------------------------------------
                Address                                     Address
- --------------------------------------------------------------------------------
Social Security or other Taxpayer
Identification Number, if any
- --------------------------------------------------------------------------------

*    Signature must be guaranteed by an eligible Guarantor Institution (banks,
stockbrokers, savings and loan associations and credit unions) with membership
in an approved signature medallion program pursuant to Securities and Exchange
Commission Rule 17Ad-15 if Common Stock is to be delivered other than to, and in
the name of, the registered Holder.

                                      -11-
<PAGE>
 
                        Request to Create Stripped Units

          The undersigned Holder directs that (a) the Pledged Securities
underlying the number of Normal Units indicated below (which number does not
exceed the number of Normal Units evidenced by this Unit Certificate) be
released from the Pledge and registered in the name of, and delivered to, the
undersigned at the address indicated below unless a different name and address
have been indicated below and (b) a corresponding number of Stripped Units be
registered in the name of, and delivered to, the undersigned at the address
indicated below unless a different name and address have been indicated below.
If the released Pledged Securities or the Stripped Units are to be registered in
the name of a Person other than the undersigned, the undersigned will pay any
transfer tax payable incident thereto.

          The undersigned confirms that the requisite Treasury Securities, any
required cash and the instrument from the Call Option Holder have been delivered
to the Collateral Agent.

Dated: _________________________    ___________________________________
                                               Signature*

- --------------------------------------------------------------------------------
 If released Pledged Securities are to be                  REGISTERED HOLDER
 registered in the name of and delivered to
 a Person other than the Holder, please        Please print name and address
 print such Person's name and address:         of Registered Holder:

                 Name                                      Name

                Address                                   Address

Social Security or other Taxpayer
 Identification Number, if any
- -------------------------------------------------------------------------------

If Stripped Units are to be registered in
the name of and delivered to a Person
other than the Holder, please print such
Person's name and address:

          Name



                                     -12-


<PAGE>
 
          Address

Social Security or other Taxpayer
Identification Number, if any



*  Signature must be guaranteed by an eligible Guarantor Institution (banks,
   stockbrokers, savings and loan associations and credit unions) with      
   membership in an approved signature medallion program pursuant to        
   Securities and Exchange Commission Rule 17Ad-15 if Common Stock is to be 
   delivered other than to, and in the name of, the registered Holder.      

                                      -13-

<PAGE>
 
                                                                       EXHIBIT 6
Form of Stripped Unit Certificate

                               MONSANTO COMPANY

              .% Adjustable Conversion-rate Equity Security Units

                          (Stated Amount $. per Unit)

CUSIP No.

No.  _____                                                  _____ Stripped Units


     This Unit Certificate certifies that Cede & Co. is the registered Holder of
the number of Stripped Units set forth above. Each Stripped Unit represents the
right to purchase Common Stock under a Purchase Contract with Monsanto Company,
a Delaware corporation (the "Company"), together with ownership of the Treasury
Securities pledged to secure the obligations referred to in (a) below, subject
to (a) the obligations owed to the Company under such Purchase Contract and (b)
the pledge arrangements securing the foregoing obligations.

     Each Purchase Contract evidenced hereby is governed by a Master Unit
Agreement, dated as of November ., 1998 (the "Master Unit Agreement"), between
the Company and First National Bank of Chicago, as unit agent (herein called the
"Unit Agent"). All terms used herein which are not defined herein and which are
defined in the Master Unit Agreement have the meanings set forth therein. The
Pledge evidenced hereby is governed by the Pledge Agreement. Reference is hereby
made to the Master Unit Agreement and the Pledge Agreement, and any supplemental
agreements thereto, for a description of the respective rights, limitations of
rights, obligations, duties and immunities thereunder of the Unit Agent, the
Company, the Collateral Agent and the Holders. The summary contained herein is
qualified in its entirety by the provisions of the Principal Agreements, and the
Principal Agreements shall govern the rights of the parties to the extent that
there is any conflict between such summary and such provisions.

     Each Purchase Contract evidenced hereby obligates the Holder of this Unit
Certificate to purchase, and the Company to sell, on November ___, 2001 (the
"Stock Purchase Date"), at a price equal to $. (the "Stated Amount"), a number
of shares of Common Stock, no par value per share, having such terms as set
forth in the Company's certificate of incorporation, as amended from time to
time ("Common Stock"), of the Company equal to the Settlement Rate, unless on or
prior to the Stock Purchase Date there shall have occurred a Termination Event.
The "Settlement Rate" is equal to (a) if the Applicable Market Value (as defined
in the Master Unit Agreement) is greater than or equal to $. (the "Threshold
Appreciation Price"), . of a share of Common Stock per Purchase Contract, (b) if
the Applicable Market Value is less than the Threshold Appreciation Price but is
greater than the Stated Amount, a fractional share of Common Stock per Purchase
Contract equal to the Stated Amount divided by the Applicable Market Value
(rounded to the nearest 1/10,000th 
<PAGE>
 
of a share or, if there is no nearest 1/10,000th of a share, rounded downward to
the nearest 1/10,000th of a share) and (c) if the Applicable Market Amount is
less than or equal to the Stated Amount, one share of Common Stock per Purchase
Contract, in each case subject to adjustment as provided in the Master Unit
Agreement. No fractional shares of Common Stock will be issued upon settlement
of Purchase Contracts, but instead of any fractional interest the Company shall
make a cash payment as provided in the Master Unit Agreement. The purchase price
for the shares of Common Stock to be purchased pursuant to each Purchase
Contract evidenced hereby, if not paid by 10:00 a.m., New York City time, on the
Stock Purchase Date, shall be paid by application of payments received by the
Company on the Stock Purchase Date from the Collateral Agent pursuant to the
Pledge Agreement in respect of the Pledged Securities pledged to secure such
Holder's obligations under such Purchase Contract.

     The Purchase Contracts and the obligations and rights of the Company and
the Holders thereunder, including, without limitation, the rights and
obligations to receive and pay accrued or deferred Contract Fees, shall
immediately and automatically terminate, without the necessity of any notice or
action by any Holder, the Unit Agent or the Company, if, on or prior to the
Stock Purchase Date, a Termination Event shall have occurred. Upon and after the
occurrence of a Termination Event, the Collateral Agent shall release the
Pledged Securities from the Pledge. The Stripped Units shall thereafter
represent the right to receive the Pledged Securities forming a part of such
Stripped Units in accordance with the provisions of the Master Unit Agreement
and the Pledge Agreement.

     The Company shall pay, on each January 15, April 15, July 15 and 
October 15, commencing January 15, 1999 (each, a "Quarterly Payment Date"), in
respect of each Purchase Contract evidenced hereby, a fee (the "Contract Fee")
accruing on the Stated Amount of such Unit from and including the date of first
issuance of any Units at a rate per annum equal to .% (the "Contract Fee Rate")
(computed on the basis of a 360-day year of twelve 30-day months and subject to
deferral as described in the Master Unit Agreement), plus any additional fees
accrued thereon pursuant to Section 503 of the Master Unit Agreement. The
Company's obligations with respect to Contract Fees shall be, to the extent
provided in the Master Unit Agreement, subordinated and subject in right of
payment to all Senior Indebtedness.

     Payments due to the Holder in respect of the Stripped Units evidenced
hereby will be payable to the Person in whose name this Unit Certificate (or a
Predecessor Unit Certificate) is registered at the close of business on the
Record Date next preceding the relevant payment date.

     The transfer of any Unit Certificate will be registered and Unit
Certificates may be exchanged as provided in the Master Unit Agreement. The Unit
Registrar may require a Holder, among other things, to furnish appropriate
endorsements and transfer documents permitted by the Master Unit Agreement. No
service charge shall be required for any such registration of transfer or
exchange, but the Company and the Unit Agent may require payment of a sum
sufficient to cover any tax or other governmental charge payable in connection
therewith. For so long as the Purchase Contract underlying a Stripped Unit
remains in effect, such Stripped Unit shall not be separable into its
constituent parts, and the rights and obligations of the Holder of such Stripped
Unit in respect of the Pledged Securities and Purchase Contract constituting
such Stripped Unit may be transferred and exchanged only as an integrated
Stripped Unit.
<PAGE>
 
     Upon registration of transfer of this Unit Certificate, the transferee
shall be bound (without the necessity of any other action on the part of such
transferee) by the terms of the Purchase Contracts evidenced hereby and by the
Pledge Agreement, and the transferor shall be released from such obligations.
The Company covenants and agrees, and the Holder, by his acceptance hereof,
likewise covenants and agrees, to be bound by the provisions of this paragraph.

     The Holder of this Unit Certificate, by his acceptance hereof, irrevocably
authorizes the Unit Agent to enter into and perform the related Purchase
Contracts evidenced hereby on his behalf as his attorney-in-fact, agrees to be
bound by the terms and provisions thereof, covenants and agrees to perform his
obligations under such Purchase Contracts, consents to the provisions of the
Principal Agreements, irrevocably authorizes the Unit Agent to enter into and
perform the Pledge Agreement on his behalf as his attorney-in-fact, and consents
to and agrees to be bound by the Pledge of the Pledged Securities evidenced
hereby pursuant to the Pledge Agreement.

     Subject to certain exceptions, the provisions of the Principal Agreements
may be amended with the consent of the Holders of at least a majority of the
Outstanding Units or, if the amendment affects only the Holders of the Normal
Units or only the Holders of the Stripped Units, at least a majority of the
Outstanding Units comprising Normal Units or Stripped Units, as the case may be.

     THE PURCHASE CONTRACTS SHALL FOR ALL PURPOSES BE GOVERNED BY, AND CONSTRUED
IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO
CONFLICT OF LAWS PRINCIPLES THEREOF.

     The Company, the Unit Agent and any agent of the Company or the Unit Agent
may treat the Person in whose name this Unit Certificate is registered as the
owner of the Stripped Units evidenced hereby for the purpose of receiving
payments of distributions or interest on the Pledged Securities, receiving the
rights and performing the obligations under the Purchase Contracts and for all
other purposes whatsoever, whether or not any payments in respect thereof be
overdue and not  withstanding any notice to the contrary, and neither the
Company, the Unit Agent nor any such agent shall be affected by notice to the
contrary.

     THE PURCHASE CONTRACTS SHALL NOT, PRIOR TO THE SETTLEMENT THEREOF, ENTITLE
THE HOLDER TO ANY OF THE RIGHTS OF A HOLDER OF SHARES OF COMMON STOCK.

     Copies of the Principal Agreements are available for inspection at the
offices of the Unit Agent.

     Unless the certificate of authentication hereon has been executed by the
Unit Agent by manual signature, this Unit Certificate shall not be entitled to
any benefit under the Principal Agreements or be valid or obligatory for any
purpose.
<PAGE>
 
     IN WITNESS WHEREOF, the Company and the Holder hereby agree to their
respective obligations under the Purchase Contracts evidenced by this
instrument, and the Holder hereby acknowledges that the Pledged Securities
evidenced by this instrument are subject to the Pledge under the Pledge
Agreement.


                                     MONSANTO COMPANY

                                     By:
                                        ---------------------------------

Attest: 
        ----------------------

                                     HOLDER SPECIFIED ABOVE

                                     By: First National Bank of Chicago,
                                     as Attorney-in-Fact of such Holder

                                     By:
                                        ---------------------------------


Dated:

Unit Agent's Certificate of Authentication

     This is one of the Unit Certificates referred to in the within mentioned
Master Unit Agreement.

First National Bank of Chicago,
as Unit Agent

By:
    --------------------------
<PAGE>
 
                            Settlement Instructions

     The undersigned Holder directs that a certificate for shares of Common
Stock deliverable upon settlement on or after the Stock Purchase Date of the
Purchase Contracts underlying the number of Stripped Units evidenced by this
Unit Certificate be registered in the name of, and delivered, together with a
check in payment for any fractional share, to the undersigned at the address
indicated below unless a different name and address have been indicated below.
If shares are to be registered in the name of a Person other than the
undersigned, the undersigned will pay any transfer tax payable incident thereto.
 
Dated: 
       ---------------------------------    ------------------------------------
                                                          Signature*

If shares are to be registered in the                     REGISTERED HOLDER
name of and delivered to a Person
other than the Holder, please print         Please print name and address of
such Person's name and address:             Registered Holder:
- ----------------------------------------    ------------------------------------
 
 
          Name                                           Name
 
 
 
          Address                                        Address
 
 
 
Social Security or other Taxpayer
Identification Number, if any





* Signature must be guaranteed by an eligible Guarantor Institution (banks,
stockbrokers, savings and loan associations and credit unions) with membership
in an approved signature medallion program pursuant to Securities and Exchange
Commission Rule 17Ad-15 if Common Stock is to be delivered other than to, and in
the name of, the registered Holder.

<PAGE>
 
                                                                       EXHIBIT 8

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


                                MONSANTO COMPANY

                                      AND

                        FIRST NATIONAL BANK OF CHICAGO,
                                 as Unit Agent

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

                             MASTER UNIT AGREEMENT
                             
                               ----------------- 

                          Dated as of November ., 1998

                ----------------------------------------------
<PAGE>
 
                               TABLE OF CONTENTS
 
                                                                            Page
                                                                            ----

RECITALS.......................................................................1
 
ARTICLE ONE Definitions and Other Provisions of General Application
Section 101.  Definitions......................................................1
Section 102.  Reserved.........................................................9
Section 103.  Form of Documents Delivered to Unit Agent.......................10
Section 104.  Acts of Holders; Record Dates...................................10
Section 105.  Notices, etc. to Unit Agent and the Company.....................12
Section 106.  Notice to Holders; Waiver.......................................12
Section 107.  Effect of Headings and Table of Contents........................13
Section 108.  Successors and Assigns..........................................13
Section 109.  Separability Clause.............................................13
Section 110.  Benefits of Agreement...........................................13
Section 111.  Governing Law...................................................13
Section 112.  Legal Holidays..................................................13
Section 113.  Counterparts....................................................14
Section 114.  Inspection of Agreement.........................................14
 
ARTICLE TWO Unit Certificate Forms
Section 201.  Forms of Unit Certificates Generally............................14
Section 202.  Form of Unit Agent's Certificate of Authentication..............15
 
ARTICLE THREE The Units
Section 301.  Title and Terms; Denominations..................................15
Section 302.  Rights and Obligations Evidenced by the Unit Certificates.......16
Section 303.  Execution, Authentication, Delivery and Dating..................16
Section 304.  Temporary Unit Certificates.....................................17
Section 305.  Registration; Registration of Transfer and Exchange.............17
Section 306.  Mutilated, Destroyed, Lost and Stolen Unit Certificates.........20
Section 307.  Persons Deemed Owners...........................................21
Section 308.  Cancellation....................................................21
Section 309.  Substitution of Pledged Securities and Creation of Stripped Units;
                  Units Not Otherwise Separable...............................22
Section 310.  Payments on the Units...........................................24
 
ARTICLE FOUR The Pledged Securities
Section 401.  Payments on the Pledged Securities..............................24

                                      -i-
<PAGE>
 
Section 402.  Transfer of Pledged Securities Upon Occurrence of Termination 
                  Event.......................................................25
 
ARTICLE FIVE The Purchase Contracts
Section 501.  Purchase of Shares of Common Stock..............................26
Section 502.  Contract Fees...................................................27
Section 503.  Deferral of Payment Dates For Contract Fee......................28
Section 504.  Payment of Purchase Price.......................................29
Section 505.  Issuance of Shares of Common Stock..............................31
Section 506.  Adjustment of Settlement Rate...................................31
Section 507.  Notice of Adjustments and Certain Other Events..................36
Section 508.  No Fractional Shares............................................37
Section 509.  Charges and Taxes...............................................38
Section 510.  Termination Event; Notice.......................................38
Section 511.  Early Settlement................................................38
 
ARTICLE SIX Remedies
Section 601.  Unconditional Rights of Holders.................................39
Section 602.  Restoration of Rights and Remedies..............................39
Section 603.  Rights and Remedies Cumulative..................................39
Section 604.  Delay or Omission Not Waiver....................................39
Section 605.  Undertaking for Costs...........................................40
Section 606.  Waiver of Stay or Extension Laws................................40

                                     -ii-
<PAGE>
 
ARTICLE SEVEN The Unit Agent
Section 701.  Certain Duties and Responsibilities.............................40
Section 702.  Notice of Default...............................................41
Section 703.  Certain Rights of Unit Agent....................................41
Section 704.  Not Responsible for Recitals or Issuance of Units...............42
Section 705.  May Hold Units..................................................43
Section 706.  Money Held in Trust............................................ 43
Section 707.  Compensation and Reimbursement..................................43
Section 708.  Corporate Unit Agent Required; Eligibility......................44
Section 709.  Resignation and Removal; Appointment of Successor...............44
Section 710.  Acceptance of Appointment by Successor..........................45
Section 711.  Merger, Conversion, Consolidation or Succession to Business.....46
Section 712.  Preservation of Information; Communications to Holders..........46
Section 713.  No Obligations of Unit Agent....................................47
Section 714.  Tax Compliance..................................................47
 
ARTICLE EIGHT Supplemental Agreements
Section 801.  Supplemental Agreements Without Consent of Holders..............48
Section 802.  Supplemental Agreements with Consent of Holders.................48
Section 803.  Execution of Supplemental Agreements............................50
Section 804.  Effect of Supplemental Agreements...............................50
Section 805.  Reference to Supplemental Agreements............................50
 
ARTICLE NINE Consolidation, Merger, Sale or Conveyance
Section 901.  Covenant Not to Merge, Consolidate, Sell or Convey Property Except
                  Under Certain Conditions....................................51
Section 902.  Rights and Duties of Successor Corporation......................51
Section 903.  Opinion of Counsel to Unit Agent................................52


                                     -iii-
<PAGE>
 
ARTICLE TEN Covenants
Section 1001.  Performance Under Purchase Contracts...........................52
Section 1002.  Maintenance of Office or Agency................................53
Section 1003.  Company to Reserve Common Stock................................53
Section 1004.  Covenants as to Common Stock...................................53
Section 1005.  Statements of Officers of the Company as to Default............53

                                     -iv-
<PAGE>
 
TESTIMONIUM...................................................................54
SIGNATURES....................................................................54

EXHIBIT A  Form of Normal Unit Certificate
EXHIBIT B  Form of Stripped Unit Certificate
EXHIBIT C  Form of Call Option Agreement
EXHIBIT D  Form of Pledge Agreement

                                      -v-
<PAGE>
 
     MASTER UNIT AGREEMENT, dated as of November ., 1998, between MONSANTO
COMPANY, a Delaware corporation (the "Company"), and FIRST NATIONAL BANK OF
CHICAGO, a national banking corporation, acting as unit agent for the Holders of
Units from time to time (the "Unit Agent").

                                    RECITALS

     The Company has duly authorized the execution and delivery of this
Agreement and the Unit Certificates evidencing the Units.

     All things necessary to make the Company's obligations under the Units,
when the Unit Certificates are executed by the Company and authenticated,
executed on behalf of the Holders and delivered by the Unit Agent, as in this
Agreement provided, the valid obligations of the Company, and to constitute
these presents a valid agreement of the Company, in accordance with its terms,
have been done.

                                  WITNESSETH:

     For and in consideration of the premises and the purchase of the Units by
the Holders thereof, it is mutually agreed as follows:

                                  ARTICLE ONE

                        Definitions and Other Provisions
                             of General Application

 Section 101  Definitions.

     For all purposes of this Agreement, except as otherwise expressly provided
or unless the context otherwise requires:

          (a) the terms defined in this Article have the meanings assigned to
     them in this Article and include the plural as well as the singular; and

          (b) the words "herein", "hereof" and "hereunder" and other words of
     similar import refer to this Agreement as a whole and not to any particular
     Article, Section or other subdivision.

     "Act" has the meaning specified in Section 104.
<PAGE>
 
     "Affiliate" of any specified Person means any other Person directly or
indirectly controlling or controlled by or under direct or indirect common
control with such specified Person.  For the purposes of this definition,
"control" when used with respect to any specified Person means the power to
direct the management and policies of such Person, directly or indirectly,
whether through the ownership of voting securities, by contract or otherwise;
and the terms "controlling" and "controlled" have meanings correlative to the
foregoing.

     "Agreement" means this instrument as originally executed or as it may from
time to time be supplemented or amended by one or more agreements supplemental
hereto entered into pursuant to the applicable provisions hereof.

     "Aggregate Call Option Exercise Consideration" has the meaning set forth in
the Call Option Agreement.

     "Applicable Market Value" has the meaning specified in Section 501.

     "Board of Directors" means the board of directors of the Company or a duly
authorized committee of that board.

     "Board Resolution" means one or more resolutions of the Board of Directors,
a copy of which has been certified by the Secretary or an Assistant Secretary of
the Company to have been duly adopted by the Board of Directors and to be in
full force and effect on the date of such certification and delivered to the
Unit Agent.

     "Business Day" means any day other than Saturday, Sunday or any other day
on which  banking institutions in The City of New York are authorized or
obligated by law or executive order to be closed.

     "Call Option" means an option entitling the Call Option Holder to acquire
the Debentures underlying the related Normal Unit on the terms and subject to
the conditions set forth in the Call Option Agreement.

     "Call Option Agreement" means the Call Option Agreement, dated as of the
date hereof, between the Call Option Holder named therein and the Unit Agent, in
its capacity as Unit Agent and as attorney-in-fact for the Holders from time to
time of the Normal Units, the form of which is attached hereto as Exhibit C, as
the same may be amended from time to time in accordance with the terms hereof
and thereof.

     "Call Option Expiration Date" means November ., 2001 (or, if such date is
not a Trading Day, the next succeeding Trading Day).

                                      -2-
<PAGE>
 
     "Call Option Holder" means the Person named as the Call Option Holder in
the Call Option Agreement.

     "Call Settlement Date" means the date on which the Call Options are settled
pursuant to the Call Option Agreement.

     "Cash Merger" has the meaning specified in Section 511.

     "Closing Price" has the meaning specified in Section 501.

     "Collateral Agent" means First Union National Bank, as Collateral Agent
under the Pledge Agreement, until a successor Collateral Agent shall have become
such pursuant to the applicable provisions of the Pledge Agreement, and
thereafter "Collateral Agent" shall mean the Person who is then the Collateral
Agent thereunder.

     "Common Stock" means the Common Stock, no par value per share, of the
Company having such terms as set forth in the Company's certificate of
incorporation, as amended from time to time.

     "Company" means the Person designated as the "Company" in the first
paragraph of this instrument until a successor shall have become such, and
thereafter "Company" shall mean such successor.

     "Contract Fee" means, with respect to each Purchase Contract, a fee payable
[by the Company to the Holder] of the related Unit,  accruing on the Stated
Amount of such Unit from and including the date of first issuance of any Units
to but excluding the Stock Purchase Date and payable quarterly in arrears on
each Quarterly Payment Date to and including the Stock Purchase Date at a rate
per annum equal to the Contract Fee Rate (and computed on the basis of a 360-day
year of twelve 30-day months), plus any additional fees accrued thereon pursuant
to Section 503.

     "Contract Fee Rate" means .%.

     "Corporate Trust Office" means the principal office of the Unit Agent in
the Borough of Manhattan, The City of New York, at which at any particular time
its corporate trust business shall be administered, which office at the date
hereof is located at ___________, New York, New York _______.

     "Current Market Price" has the meaning specified in Section 506(a)(8).

                                      -3-
<PAGE>
 
     "Debenture Put Option" has the meaning specified for the term "Put Option"
in the Indenture.

     "Debentures" means the .% Junior Subordinated Deferrable Debentures due
November ., 2003 of the Company issued under the Indenture.

     "Deferral Rate" means .% per annum plus, for the period after the Call
Option Expiration Date, the amount (if any) by which the interest rate on the
Debentures shall have been increased on the Call Option Expiration Date in
accordance with the terms of the Debentures.

     "Depositary" means a clearing agency registered under the Exchange Act that
is designated to act as Depositary for Global Units as contemplated by Section
305.

     "Exchange Act" means the Securities Exchange Act of 1934 or any statute
successor thereto, in each case as amended from time to time.

     "Expiration Date" has the meaning specified in Section 104.

     "Global Unit Certificate" means a Unit Certificate that evidences all or
part of the Normal Units or a Unit Certificate that evidences all or a part of
the Stripped Units and is registered in the name of the Depositary or a nominee
thereof.

     "Holder" means a Person in whose name a Unit Certificate is registered in
the Unit Register; "Holder", when used with respect to any particular Unit
Certificate (or Unit), means a Person in whose name such Unit Certificate (or
the Unit Certificate evidencing such Unit) is registered in the relevant Unit
Register.

     "Indenture" means the Indenture, dated as of the date hereof, between the
Company and First National Bank of Chicago, as Trustee, as the same may be
amended or supplemented from time to time with respect to the terms of the
Debentures in accordance with the terms thereof.

     "Issuer Order" or "Issuer Request" means a written order or request signed
in the name of the Company by its Chairman of the Board, a Vice Chairman, its
Chief Executive Officer, its President or a Vice President, its Chief Financial
Officer, by its Treasurer, an Assistant Treasurer, its Controller, its Secretary
or an Assistant Secretary, and delivered to the Unit Agent.

     "Normal Unit" means the rights to purchase Common Stock under a Purchase
Contract, together with ownership of the Debentures or other Pledged Securities
pledged to secure the obligations referred to in (a) and (b) below, subject to
(a) the obligations owed to 

                                      -4-
<PAGE>
 
the Company under such Purchase Contract, (b) for so long as any Call Options
remain exercisable, the obligations owed to the Call Option Holder under a Call
Option and (c) the pledge arrangements securing the foregoing obligations;
provided, however, that the term "Normal Unit" will not include any Stripped
Unit.

     "NYSE" has the meaning specified in Section 501.

     "Officers' Certificate" means a certificate signed by the Chairman of the
Board, any Vice Chairman, the President or any Vice President and by the
Treasurer, an Assistant Treasurer, the Secretary or an Assistant Secretary of
the Company and delivered to the Unit Agent.

     "Opinion of Counsel" means an opinion in writing signed by legal counsel,
who may be an employee of or counsel to the Company.

     "Outstanding Unit Certificates" means, as of the date of determination, all
Unit Certificates theretofore authenticated, executed and delivered pursuant to
this Agreement, except:

          (a) Unit Certificates theretofore canceled by the Unit Agent or
     delivered to the Unit Agent for cancellation; and

          (b) Unit Certificates in exchange for or in lieu of which other Unit
     Certificates have been authenticated, executed on behalf of the Holder and
     delivered pursuant to this Agreement, other than any such Unit Certificate
     in respect of which there shall have been presented to the Unit Agent proof
     satisfactory to it that such Unit Certificate is held by a bona fide
     purchaser in whose hands the Units evidenced by such Unit Certificate are
     valid obligations of the Company.

     "Outstanding Units" means, as of the date of determination, all Units
evidenced by then Outstanding Unit Certificates, except, on or after the
Termination Date or Stock Purchase Date, Units for which the underlying Pledged
Securities or the Common Stock purchasable upon settlement of the underlying
Purchase Contracts, as the case may be, have been theretofore deposited with the
Unit Agent in trust for the Holders of such Units; provided, however, that in
determining whether the Holders of the requisite number of Units have given any
request, demand, authorization, direction, notice, consent or waiver hereunder,
Units owned by the Company or any Affiliate of the Company shall be disregarded
and deemed not to be outstanding, except that, in determining whether the Unit
Agent shall be protected in relying upon any such request, demand,
authorization, direction, notice, consent or waiver, only Units which the Unit
Agent actually knows to be so owned shall be so disregarded.  Units so owned
which have been pledged in good faith may be 

                                      -5-
<PAGE>
 
regarded as Outstanding Units if the pledgee establishes to the satisfaction of
the Unit Agent the pledgee's right so to act with respect to such Units and that
the pledgee is not the Company or any Affiliate of the Company.


     "Paid Units" has the meaning specified in Section 504(a).

     "Person" means any individual, corporation, limited liability company,
partnership, joint venture, association, joint-stock company, trust,
unincorporated organization or government or any agency or political subdivision
thereof.

     "Pledge" means the pledge of the Pledged Securities under the Pledge
Agreement.

     "Pledge Agreement" means the Pledge Agreement, dated as of the date hereof,
among the Company, the Call Option Holder, the Collateral Agent and the Unit
Agent, in its capacity as Unit Agent and as attorney-in-fact for the Holders
from time to time of the Units, the form of which is attached hereto as Exhibit
D, as the same may be amended from time to time in accordance with the terms
hereof and thereof.

     "Pledged Securities" has the meaning specified in the Pledge Agreement.

     "Predecessor Unit Certificate" of any particular Unit Certificate means
every previous Unit Certificate evidencing all or a portion of the rights and
obligations of the Holder under the Units evidenced thereby; and, for the
purposes of this definition, any Unit Certificate authenticated and delivered
under Section 306 in exchange for or in lieu of a mutilated, destroyed, lost or
stolen Unit Certificate shall be deemed to evidence the same rights and
obligations of the Holder as the mutilated, destroyed, lost or stolen Unit
Certificate.

     "Principal Agreements" means this Agreement (including the Purchase
Agreement), the Pledge Agreement and the Call Option Agreement.

     "Purchase Contract" means the obligation of the Company to sell and the
Holder of the related Unit to purchase Common Stock on the terms and subject to
the conditions set forth in Article Five hereof.

     "Purchase Contract Settlement Fund" has the meaning specified in Section
505.

     "Purchased Shares" has the meaning specified in Section 506(a)(6).

     "Put Agent" has the meaning specified in Section 504(b)(i).

                                      -6-
<PAGE>
 
     "Quarterly Payment Date" means each January 15, April 15, July 15 and
October 15, commencing January 15, 1999.

     "Record Date", when used with respect to any payment date, means the
Business Day next preceding such payment date; provided, however, that if any
Units are no longer evidenced by a Global Unit Certificate, "Record Date", when
used with respect to any payment date for such Units, means the first day of the
month in which such payment date falls; and provided further, that if payments
are in respect of Debentures underlying Normal Units, "Record Date", when used
with respect to such payments, means the record date for such payments
determined as provided under the Indenture.

     "Reorganization Event" has the meaning specified in Section 506(b).

     "Responsible Officer", when used with respect to the Unit Agent, means any
vice president, any assistant vice president, any assistant secretary, any
assistant treasurer, any trust officer or assistant trust officer, or any other
officer or assistant officer of the Unit Agent customarily performing functions
similar to those performed by any of the above designated officers and also
means, with respect to a particular corporate trust matter, any other officer to
whom such matter is referred because of his knowledge of and familiarity with
the particular subject.

     "Senior Indebtedness" has the meaning specified in the Indenture.

     "Settlement Rate" has the meaning specified in Section 501.

     "Stated Amount" means $________ per Unit.

     "Stock Purchase Date" means November ___, 2001 or such earlier date on
which the Purchase Contract may be settled pursuant to Section 511.

     "Stripped Unit" means the rights to purchase Common Stock under a Purchase
Contract, together with ownership of the Treasury Securities pledged to secure
the obligations referred to in (a) below, subject to (a) the obligations owed
to the Company under such Purchase Contract and (b) the pledge arrangements
securing the foregoing obligations; provided, however, that the term "Stripped
Unit" will only include Units issued as a result of a Stripped Unit Creation as
contemplated by Section 309.

     "Stripped Unit Creation" has the meaning specified in Section 309(a).

     "Termination Date" means the date, if any, on which a Termination Event
occurs.

                                      -7-
<PAGE>
 
     "Termination Event" means the occurrence of any of the following events at
any time on or prior to the Stock Purchase Date:  (a) a decree or order of a
court having jurisdiction in the premises shall have been entered adjudging the
Company a bankrupt or insolvent, or approving as properly filed a petition
seeking reorganization of the Company under the United States Bankruptcy Code or
any other similar applicable Federal or State law, and, unless such decree or
order shall have been entered within 90 days prior to the Stock Purchase Date,
such decree or order shall have continued undischarged and unstayed for a period
of 90 days, or (b) a decree or order of a court having jurisdiction in the
premises for the appointment of a receiver or liquidator or trustee or assignee
in bankruptcy or insolvency of the Company or of its property, or for the
winding up or liquidation of its affairs, shall have been entered, and, unless
such decree or order shall have been entered within 90 days prior to the Stock
Purchase Date, such decree or order shall have continued undischarged and
unstayed for a period of 90 days, or (c) the Company shall institute proceedings
to be adjudicated a bankrupt, or shall consent to the filing of a bankruptcy
proceeding against it, or shall file a petition or answer or consent seeking
reorganization under the United States Bankruptcy Code or any other similar
applicable Federal or State law, or shall consent to the filing of any such
petition, or shall consent to the appointment of a receiver or liquidator or
trustee or assignee in bankruptcy or insolvency of it or of its property, or
shall make an assignment for the benefit of creditors, or shall admit in writing
its inability to pay its debts generally as they become due.

     "Threshold Appreciation Price" has the meaning specified in Section 501.

     "TIA" means the Trust Indenture Act of 1939 or any statute successor
thereto, in each case as amended from time to time.

     "Trading Day" has the meaning specified in Section 501.

     "Treasury Securities" means United States Treasury Securities.

     "Underwriting Agreement" means the Underwriting Agreement dated November .,
1998, among the Company, and Goldman, Sachs & Co. and Solomon Smith Barney Inc.,
as the Underwriters named therein.

     "Unit Agent" means the Person named as the "Unit Agent" in the first
paragraph of this Agreement until a successor Unit Agent shall have become such
pursuant to the applicable provisions of this Agreement, and thereafter "Unit
Agent" shall mean the Person who is then the Unit Agent hereunder.

                                      -8-
<PAGE>
 
     "Unit Certificate" means a certificate evidencing the rights and
obligations of a Holder in respect of the number of Normal Units or Stripped
Units, as the case may be, specified on such certificate.

     "Unit Register" and "Unit Registrar" have the respective meanings specified
in Section 305.

     "Units" means the Normal Units and, if any are issued, the Stripped Units.
The Purchase Contracts, Call Options and/or Pledged Securities constituting a
part of any Units are sometimes referred to herein as "underlying" such Units
and are sometimes herein said to "underlie" such Units.

     "Unpaid Units" has the meaning specified in Section 504(a).

     "Vice President" means any vice president, whether or not designated by a
number or a word or words added before or after the title "vice president".

 Section 102  Reserved.

 Section 103  Form of Documents Delivered to Unit Agent.

     In any case where several matters are required to be certified by, or
covered by an opinion of, any specified Person, it is not necessary that all
such matters be certified by, or covered by the opinion of, only one such
Person, or that they be so certified or covered by only one document, but one
such Person may certify or give an opinion with respect to some matters and one
or more other such Persons as to other matters, and any such Person may certify
or give an opinion as to such matters in one or several documents.

     Any certificate or opinion of an officer of the Company may be based,
insofar as it relates to legal matters, upon a certificate or opinion of, or
representations by, counsel, unless such officer knows, or in the exercise of
reasonable care should know, that the certificate or opinion or representations
with respect to the matters upon which his certificate or opinion is based are
erroneous.  Any such certificate or Opinion of Counsel may be based, insofar as
it relates to factual matters, upon a certificate or opinion of, or
representations by, an officer or officers of the Company stating that the
information with respect to such factual matters is in the possession of the
Company, unless such counsel knows, or in the exercise of reasonable care should
know, that the certificate or opinion or representations with respect to such
matters are erroneous.

                                      -9-
<PAGE>
 
     Where any Person is required to make, give or execute two or more
applications, requests, consents, certificates, statements, opinions or other
instruments under this Agreement, they may, but need not, be consolidated and
form one instrument.

 Section 104  Acts of Holders; Record Dates.

     (a) Any request, demand, authorization, direction, notice, consent, waiver
or other action provided by this Agreement to be given or taken by Holders may
be embodied in and evidenced by one or more instruments of substantially similar
tenor signed by such Holders in person or by agent duly appointed in writing;
and, except as herein otherwise expressly provided, such action shall become
effective when such instrument or instruments are delivered to the Unit Agent
and, where it is hereby expressly required, to the Company. Such instrument or
instruments (and the action embodied therein and evidenced thereby) are herein
sometimes referred to as the "Act" of the Holders signing such instrument or
instruments.  Proof of execution of any such instrument or of a writing
appointing any such agent shall be sufficient for any purpose of this Agreement
and (subject to Section 701) conclusive in favor of the Unit Agent and the
Company, if made in the manner provided in this Section.

     (b) The fact and date of the execution by any Person of any such instrument
or writing may be proved by the affidavit of a witness of such execution or by a
certificate of a notary public or other officer authorized by law to take
acknowledgments of deeds, certifying that the individual signing such instrument
or writing acknowledged to him the execution thereof.  Where such execution is
by a signer acting in a capacity other than his individual capacity, such
certificate or affidavit shall also constitute sufficient proof of his
authority.  The fact and date of the execution of any such instrument or
writing, or the authority of the Person executing the same, may also be proved
in any other manner which the Unit Agent deems sufficient.

     (c) The ownership of Units shall be proved by the Unit Register.

     (d) Any request, demand, authorization, direction, notice, consent, waiver
or other Act of the Holder of any Unit shall bind every future Holder of the
same Unit and the Holder of every Unit Certificate evidencing such Unit issued
upon the registration of transfer thereof or in exchange therefor or in lieu
thereof in respect of anything done, omitted or suffered to be done by the Unit
Agent or the Company in reliance thereon, whether or not notation of such action
is made upon such Unit Certificate.

     (e) The Company may set any day as a record date for the purpose of
determining the Holders of Outstanding Units entitled to give, make or take any
request, demand, authorization, direction, notice, consent, waiver or other
action provided or permitted by this Agreement to be given, made or taken by
Holders of Units.  If any record 

                                      -10-
<PAGE>
 
date is set pursuant to this paragraph, the Holders of Outstanding Units on such
record date, and no other Holders, shall be entitled to take the relevant
action, whether or not such Holders remain Holders after such record date;
provided that no such action shall be effective hereunder unless taken on or
prior to the applicable Expiration Date by Holders of the requisite number of
Outstanding Units on such record date. Nothing in this paragraph shall be
construed to prevent the Company from setting a new record date for any action
for which a record date has previously been set pursuant to this paragraph
(whereupon the record date previously set shall automatically and with no action
by any Person be canceled and of no effect), and nothing in this paragraph shall
be construed to render ineffective any action taken by Holders of the requisite
number of Outstanding Units on the date such action is taken. Promptly after any
record date is set pursuant to this paragraph, the Company, at its own expense,
shall cause notice of such record date, the proposed action by Holders and the
applicable Expiration Date to be given to the Unit Agent in writing and to each
Holder of Units in the manner set forth in Section 106.

     With respect to any record date set pursuant to this Section, the Company
may designate any date as the "Expiration Date" and from time to time may change
the Expiration Date to any earlier or later day; provided that no such change
shall be effective unless notice of the proposed new Expiration Date is given to
the Unit Agent in writing, and to each Holder of Units in the manner set forth
in Section 106, on or prior to the existing Expiration Date.  If an Expiration
Date is not designated with respect to any record date set pursuant to this
Section, the Company shall be deemed to have initially designated the 180th day
after such record date as the Expiration Date with respect thereto, subject to
its right to change the Expiration Date as provided in this paragraph.
Notwithstanding the foregoing, no Expiration Date shall be later than the 180th
day after the applicable record date.

 Section 105  Notices, etc. to Unit Agent and the Company.

     Any request, demand, authorization, direction, notice, consent, waiver or
other Act of Holders or other document provided or permitted by this Agreement
to be made upon, given or furnished to, or filed with,

          (a) the Unit Agent by any Holder or by the Company shall be sufficient
     for every purpose hereunder (unless otherwise herein expressly provided) if
     made, given, furnished or filed in writing and personally delivered or
     mailed, first-class postage prepaid, to the Unit Agent at
     _______________________________, Attention:  ___________, or at any other
     address previously furnished in writing by the Unit Agent to the Holders
     and the Company, or

          (b) the Company by the Unit Agent or by any Holder shall be sufficient
     for every purpose hereunder (unless otherwise herein expressly provided) if
     made, 

                                      -11-
<PAGE>
 
     given, furnished or filed in writing and personally delivered or mailed,
     first-class postage prepaid, to the Company at 800 North Lindbergh
     Boulevard, St. Louis, Missouri 63167, Attention: Treasurer, or at any other
     address previously furnished in writing by the Company to the Unit Agent.

 Section 106  Notice to Holders; Waiver.

     Where this Agreement provides for notice to Holders of any event, such
notice shall be sufficiently given (unless otherwise herein expressly provided)
if in writing and mailed, first-class postage prepaid, to each Holder affected
by such event, at his address as it appears in the Unit Register, not later than
the latest date, and not earlier than the earliest date, prescribed for the
giving of such notice.  In any case where notice to Holders is given by mail,
neither the failure to mail such notice nor any defect in any notice so mailed
to any particular Holder shall affect the sufficiency of such notice with
respect to other Holders. Where this Agreement provides for notice in any
manner, such notice may be waived in writing by the Person entitled to receive
such notice, either before or after the event, and such waiver shall be the
equivalent of such notice.  Waivers of notice by Holders shall be filed with the
Unit Agent, but such filing shall not be a condition precedent to the validity
of any action taken in reliance upon such waiver.

     In case by reason of the suspension of regular mail service or by reason of
any other cause it shall be impracticable to give such notice by mail, then such
notification as shall be made with the approval of the Unit Agent shall
constitute a sufficient notification for every purpose hereunder.

 Section 107  Effect of Headings and Table of Contents.

     The Article and Section headings herein and the Table of Contents are for
convenience only and shall not affect the construction hereof.

 Section 108  Successors and Assigns.

     All covenants and agreements in this Agreement by the Company shall bind
its successors and assigns, whether so expressed or not.

 Section 109  Separability Clause.

     In case any provision in this Agreement or in the Units shall be invalid,
illegal or unenforceable, the validity, legality and enforceability of the
remaining provisions hereof and thereof shall not in any way be affected or
impaired thereby.

                                      -12-
<PAGE>
 
 Section 110.  Benefits of Agreement.

     Nothing in this Agreement or in the Unit Certificates, express or implied,
shall give to any Person, other than the parties hereto and their successors
hereunder and the Holders, any benefits or any legal or equitable right, remedy
or claim under this Agreement.  The Holders from time to time shall be
beneficiaries of this Agreement and shall be bound by all of the terms and
conditions hereof and of the Units evidenced by their Unit Certificates by their
acceptance of delivery thereof.

 Section 111.  Governing Law.

     THIS AGREEMENT AND THE UNITS SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO CONFLICTS
OF LAWS PRINCIPLES THEREOF.

 Section 112.  Legal Holidays.

     In any case where any Quarterly Payment Date or the Stock Purchase Date
shall not be a Business Day, then (notwithstanding any other provision of this
Agreement or of the Units) payment in respect of distributions or interest on or
principal of Pledged Securities or Contract Fees shall not be made, Purchase
Contracts shall not be performed and other actions described herein shall not
occur, but such payments shall be made, the Purchase Contracts shall be
performed and such other actions shall occur, as applicable, on the next
succeeding Business Day with the same force and effect as if made on such
Quarterly Payment Date or Stock Purchase Date, as the case may be; provided,
that to the extent such payment is made on the next succeeding Business Day, no
distributions or interest shall accrue or be payable by the Company or any
Holder for the period from and after any such Quarterly Payment Date or Stock
Purchase Date, as the case may be, to the date of payment or performance; except
that if such next succeeding Business Day is in the next succeeding calendar
year, such payment shall be made, the Purchase Contracts shall be performed or
such other action shall occur on the immediately preceding Business Day with the
same force and effect as if made on such Quarterly Payment Date or the Stock
Purchase Date.

 Section 113.  Counterparts.

     This Agreement may be executed in any number of counterparts, each of
which, when so executed, shall be deemed an original, but all such counterparts
shall together constitute one and the same instrument.

 Section 114.  Inspection of Agreement.

                                      -13-
<PAGE>
 
     A copy of this Agreement shall be available at all reasonable times at the
Corporate Trust Office for inspection by any Holder.

                                  ARTICLE TWO

                            Unit Certificate Forms

Section 201.  Forms of Unit Certificates Generally.

      Unit Certificates evidencing Normal Units shall be in substantially the
form set forth in Exhibit A hereto and Unit Certificates evidencing the Stripped
Units shall be in substantially the form of Exhibit B hereto, in each case with
such letters, numbers or other marks of identification or designation and such
legends or endorsements printed, litho graphed or engraved thereon as may be
required by the rules of any securities exchange on which the Units are listed
or Depositary therefor, or as may, consistently herewith, be determined by the
officers of the Company executing such Unit Certificates, as evidenced by their
execution of the Unit Certificates.

      The definitive Unit Certificates shall be printed, lithographed or
engraved on steel engraved borders or may be produced in any other manner, all
as determined by the officers of the Company executing the Unit Certificates,
consistent with the provisions of this Agreement, as evidenced by their
execution thereof.

      Every Global Unit Certificate authenticated, executed and delivered
hereunder shall bear a legend in substantially the following form:

      THIS UNIT CERTIFICATE IS A GLOBAL UNIT CERTIFICATE WITHIN THE MEANING OF
      THE MASTER UNIT AGREEMENT HEREINAFTER REFERRED TO AND IS REGISTERED IN THE
      NAME OF A DEPOSITARY OR A NOMINEE THEREOF. THIS UNIT CERTIFICATE MAY NOT
      BE EXCHANGED IN WHOLE OR IN PART FOR A UNIT CERTIFICATE REGISTERED, AND NO
      TRANSFER OF THIS UNIT CERTIFICATE IN WHOLE OR IN PART MAY BE REGISTERED,
      IN THE NAME OF ANY PERSON OTHER THAN SUCH DEPOSITARY OR A NOMINEE THEREOF,
      EXCEPT IN THE LIMITED CIRCUMSTANCES DESCRIBED IN THE MASTER UNIT
      AGREEMENT.

Section 202.  Form of Unit Agent's Certificate of Authentication.

      The form of the Unit Agent's certificate of authentication of the Units
shall be in substantially the form set forth on the form of the Unit
Certificates.

                                     -14-
<PAGE>
 
                                 ARTICLE THREE

                                   The Units

Section 301.  Title and Terms; Denominations.

      The aggregate number of Units evidenced by Unit Certificates
authenticated, executed on behalf of the Holders and delivered hereunder is
limited to . (subject to increase up to a maximum of . to the extent the over-
allotment option of the underwriters under the Underwriting Agreement is
exercised), except for Unit Certificates authenticated, executed and delivered
upon registration of transfer of, in exchange for, or in lieu of, other Unit
Certificates pursuant to Section 304, 305, 306 or 805.

      All of the Unit Certificates authenticated, executed and delivered
hereunder shall be Normal Units except for any Unit Certificates evidencing
Stripped Units issued in connection with a Stripped Unit Creation pursuant to
Section 309 and Unit Certificates authenticated, executed and delivered upon
registration of transfer of, in exchange for, or in lieu of, other Unit
Certificates evidencing Stripped Units pursuant to Section 304, 305, 306 or 805.

      Unit Certificates shall be issuable only in registered form and only in
denominations of a single Unit and any integral multiple thereof.

Section 302.  Rights and Obligations Evidenced by the Unit Certificates.

      Each Unit Certificate shall evidence the number of Units specified
therein. Prior to the purchase, if any, of shares of Common Stock under the
Purchase Contracts, the Units shall not entitle the Holders to any of the rights
or privileges of a holder of shares of Common Stock by virtue of holding such
Units, including, without limitation, the right to vote or receive any dividends
or other distributions or to consent or to receive notice as stockholders in
respect of the meetings of stockholders or for the election of directors of the
Company or for any other matter.

Section 303.  Execution, Authentication, Delivery and Dating.

      Subject to the provisions of Section 309 hereof, upon the execution and
delivery of this Agreement, and at any time and from time to time thereafter,
the Company may deliver Unit Certificates executed by the Company to the Unit
Agent for authentication, execution on behalf of the Holders and delivery,
together with its Issuer Order for authentication of such Unit Certificates, and
the Unit Agent in accordance with such Issuer Order shall

                                     -15-
<PAGE>
 
authenticate, execute on behalf of the Holders and make such Unit Certificates
available for delivery.

      The Unit Certificates shall be executed on behalf of the Company by its
Chairman of the Board, its Chief Executive Officer, its President, its Chief
Financial Officer or one of its Vice Presidents, under its corporate seal
reproduced thereon attested by its Secretary or one of its Assistant
Secretaries. The signature of any of these officers on the Unit Certificates may
be manual or facsimile.

      Unit Certificates bearing the manual or facsimile signatures of
individuals who were at any time the proper officers of the Company shall bind
the Company, notwithstanding that such individuals or any of them have ceased to
hold such offices prior to the authentication and delivery of such Unit
Certificates or did not hold such offices at the date of such Unit Certificates.

      Each Unit Certificate shall be dated the date of its authentication.

      No Purchase Contract or Call Option underlying a Unit evidenced by a Unit
Certificate shall be valid until such Unit Certificate has been executed on
behalf of the Holder by the manual signature of an authorized signatory of the
Unit Agent, as such Holder's attorney-in-fact. Such signature by an authorized
signatory of the Unit Agent shall be conclusive evidence that the Holder of such
Unit Certificate has entered into the Purchase Contracts and Call Options
underlying the Units evidenced by such Unit Certificate.

      No Unit Certificate shall be entitled to any benefit under this Agreement
or be valid or obligatory for any purpose unless there appears on such Unit
Certificate a certificate of authentication substantially in the form provided
for herein executed by an authorized signatory of the Unit Agent by manual
signature, and such certificate upon any Unit Certificate shall be conclusive
evidence, and the only evidence, that such Unit Certificate has been duly
authenticated and delivered hereunder.

Section 304.  Temporary Unit Certificates.

      Pending the preparation of definitive Unit Certificates, the Company shall
execute and deliver (together with an Issuer Order) to the Unit Agent, and the
Unit Agent shall authenticate, execute on behalf of the Holders, and deliver, in
lieu of such definitive Unit Certificates, temporary Unit Certificates which are
in substantially the form set forth in Exhibit A or Exhibit B hereto, with such
letters, numbers or other marks of identification or designation and such
legends or endorsements printed, lithographed or engraved thereon as may be
required by the rules of any securities exchange on which the Units are listed
or Depositary therefor, or as may, consistently herewith, be determined by the
officers of the

                                     -16-
<PAGE>
 
Company executing such Unit Certificates, as evidenced by their execution of the
Unit Certificates.

      If temporary Unit Certificates are issued, the Company will cause
definitive Unit Certificates to be prepared without unreasonable delay. After
the preparation of definitive Unit Certificates, the temporary Unit Certificates
shall be exchangeable for definitive Unit Certificates upon surrender of the
temporary Unit Certificates at the Corporate Trust Office, at the expense of the
Company and without charge to the Holder. Upon surrender for cancellation of any
one or more temporary Unit Certificates, the Company shall execute and deliver
to the Unit Agent, and the Unit Agent shall authenticate, execute on behalf of
the Holder, and deliver in exchange therefor, one or more definitive Unit
Certificates of authorized denominations and evidencing a like number of Normal
Units or Stripped Units, as the case may be, as the temporary Unit Certificate
or Unit Certificates so surrendered. Until so exchanged, the temporary Unit
Certificates shall in all respects evidence the same benefits and the same
obligations with respect to the Units evidenced thereby as definitive Unit
Certificates.

Section 305.  Registration; Registration of Transfer and Exchange.

      The Unit Agent shall keep at the Corporate Trust Office registers (the
registers maintained in such office being herein referred to as the "Unit
Registers") in which, subject to such reasonable regulations as it may
prescribe, the Unit Agent shall provide for the registration of Unit
Certificates evidencing the Normal Units and the Stripped Units and of transfers
of Unit Certificates evidencing the Normal Units and the Stripped Units (the
Unit Agent, in such capacity, the "Unit Registrar"). Upon request from any
Trustee or the Company, the Unit Agent shall furnish to such requesting party a
copy of the Unit Register for the Unit Certificates evidencing the Normal Units
as promptly as practicable.

      Upon surrender for registration of transfer of any Unit Certificate at the
Corporate Trust Office, the Company shall execute and deliver to the Unit Agent,
and the Unit Agent shall authenticate, execute on behalf of the designated
transferee or transferees, and deliver, in the name of the designated transferee
or transferees, one or more new Unit Certificates evidencing a like number of
Normal Units or Stripped Units, as the case may be.

      At the option of the Holder, Unit Certificates may be exchanged for other
Unit Certificates evidencing a like number of Normal Units or Stripped Units, as
the case may be, upon surrender of the Unit Certificates to be exchanged at the
Corporate Trust Office. Whenever any Unit Certificates are so surrendered for
exchange, the Company shall execute and deliver to the Unit Agent, and the Unit
Agent shall authenticate, execute on behalf of the Holder, and deliver the Unit
Certificates which the Holder making the exchange is entitled to receive.

                                     -17-
<PAGE>
 
      All Unit Certificates issued upon any registration of transfer or exchange
of a Unit Certificate shall evidence the ownership of the same number of Normal
Units or Stripped Units, as the case may be, and be entitled to the same
benefits and subject to the same obligations, under the Principal Agreements as
the Normal Units or Stripped Units, as the case may be, evidenced by the Unit
Certificate surrendered upon such registration of transfer or exchange.

      Every Unit Certificate presented or surrendered for registration of
transfer or for exchange shall (if so required by the Unit Agent) be duly
endorsed, or be accompanied by a written instrument of transfer in form
satisfactory to the Company and the Unit Agent duly executed, by the Holder
thereof or his attorney duly authorized in writing.

      No service charge shall be made for any registration of transfer or
exchange of a Unit Certificate, but the Company and the Unit Agent may require
payment from the Holder of a sum sufficient to cover any tax or other
governmental charge that may be imposed in connection with any registration of
transfer or exchange of Unit Certificates (which, for these purposes, includes a
Stripped Unit Creation or a transfer of Pledged Securities as contemplated by
Section 504(a)), other than any exchanges pursuant to Sections 304, 306 and 805
not involving any transfer.

      Notwithstanding the foregoing, the Company shall not be obligated to
execute and deliver to the Unit Agent, and the Unit Agent shall not be obligated
to authenticate, execute on behalf of the Holder and deliver any Unit
Certificate in respect of a Unit Certificate presented or surrendered for
registration of transfer or for exchange on or after the Stock Purchase Date or
the Termination Date. In lieu of delivery of a new Unit Certificate, upon
satisfaction of the applicable conditions specified above in this Section and
receipt of appropriate registration or transfer instructions from such Holder,
the Unit Agent shall (a) if the Stock Purchase Date has occurred, deliver the
shares of Common Stock issuable in respect of the Purchase Contracts forming a
part of the Units evidenced by such Unit Certificate, or (b) if a Termination
Event shall have occurred on or prior to the Stock Purchase Date, transfer the
liquidation or principal amount of the Pledged Securities evidenced thereby, in
each case subject to the applicable conditions and in accordance with the
applicable provisions of Article Five hereof.

     The provisions of Clauses (a), (b), (c) and (d) below shall apply only to
Global Unit Certificates:

          (a)  Each Global Unit Certificate authenticated and executed on behalf
     of the Holders under this Agreement shall be registered in the name of the
     Depositary designated for such Global Unit Certificate or a nominee thereof
     and delivered to

                                     -18-
<PAGE>
 
     such Depositary or a nominee thereof or custodian therefor, and each such
     Global Unit Certificate shall constitute a single Unit Certificate for all
     purposes of this Agreement.

          (b)  Notwithstanding any other provision in this Agreement, no Global
     Unit Certificate may be exchanged in whole or in part for Unit Certificates
     registered, and no transfer of a Global Unit Certificate in whole or in
     part may be registered, in the name of any Person other than the Depositary
     for such Global Unit Certificate or a nominee thereof unless (i) such
     Depositary (x) has notified the Company that it is unwilling or unable to
     continue as Depositary for such Global Unit Certificate or (y) has ceased
     to be a clearing agency registered under the Exchange Act or (ii) there
     shall have occurred and be continuing a default by the Company in respect
     of its obligations under one or more Principal Agreements.

          (c)  Subject to Clause (b) above, any exchange of a Global Unit
     Certificate for other Unit Certificates may be made in whole or in part,
     and all Unit Certificates issued in exchange for a Global Unit Certificate
     or any portion thereof shall be registered in such names as the Depositary
     for such Global Unit Certificate shall direct.

          (d)  Every Unit Certificate authenticated and delivered upon
     registration of transfer of, in exchange for or in lieu of a Global Unit
     Certificate or any portion thereof, whether pursuant to this Section,
     Section 304, 306 or 805 or otherwise, shall be authenticated, executed on
     behalf of the Holders and delivered in the form of, and shall be, a Global
     Unit Certificate, unless such Unit Certificate is registered in the name of
     a Person other than the Depositary for such Global Unit Certificate or a
     nominee thereof.

Section 306.  Mutilated, Destroyed, Lost and Stolen Unit Certificates.

      If any mutilated Unit Certificate is surrendered to the Unit Agent, the
Company shall execute and deliver to the Unit Agent, and the Unit Agent shall
authenticate, execute on behalf of the Holder, and deliver in exchange therefor,
a new Unit Certificate, evidencing the same number of Normal Units or Stripped
Units, as the case may be, and bearing a number not contemporaneously
outstanding.

      If there shall be delivered to the Company and the Unit Agent (a) evidence
to their satisfaction of the destruction, loss or theft of any Unit Certificate,
and (b) such security or indemnity as may be required by them to save each of
them and any agent of any of them harmless, then, in the absence of notice to
the Company or the Unit Agent that such Unit Certificate has been acquired by a
bona fide purchaser, the Company shall execute and

                                     -19-
<PAGE>
 
deliver to the Unit Agent, and the Unit Agent shall authenticate, execute on
behalf of the Holder, and deliver to the Holder, in lieu of any such destroyed,
lost or stolen Unit Certificate, a new Unit Certificate, evidencing the same
number of Normal Units or Stripped Units, as the case may be, and bearing a
number not contemporaneously outstanding.

      Notwithstanding the foregoing, the Company shall not be obligated to
execute and deliver to the Unit Agent, and the Unit Agent shall not be obligated
to authenticate, execute on behalf of the Holder, and deliver to the Holder, on
or after the Stock Purchase Date or the Termination Date, a Unit Certificate in
respect of any mutilated, destroyed, lost or stolen Unit Certificate. In lieu of
delivery of a new Unit Certificate, upon satisfaction of the applicable
conditions specified above in this Section and receipt of appropriate
registration or transfer instructions from such Holder, the Unit Agent shall (a)
if the Stock Purchase Date has occurred, deliver the shares of Common Stock
issuable in respect of the Purchase Contracts forming a part of the Units
evidenced by such Unit Certificate, or (b) if a Termination Event shall have
occurred on or prior to the Stock Purchase Date, transfer the liquidation or
principal amount of the Pledged Securities evidenced thereby, in each case
subject to the applicable conditions and in accordance with the applicable
provisions of Article Five hereof.

      Upon the issuance of any new Unit Certificate under this Section, the
Company and the Unit Agent may require the payment by the Holder of a sum
sufficient to cover any tax or other governmental charge that may be imposed in
relation thereto and any other expenses (including the fees and expenses of the
Unit Agent) connected therewith.

      Every new Unit Certificate issued pursuant to this Section in lieu of any
destroyed, lost or stolen Unit Certificate shall constitute an original
additional contractual obligation of the Company and of the Holder, whether or
not the destroyed, lost or stolen Unit Certificate shall be at any time
enforceable by anyone, and shall be entitled to all the benefits and be subject
to all the obligations of the Principal Agreements equally and proportionately
with any and all other Unit Certificates delivered hereunder.

      The provisions of this Section are exclusive and shall preclude (to the
extent lawful) all other rights and remedies with respect to the replacement or
settlement of mutilated, destroyed, lost or stolen Unit Certificates.

Section 307.  Persons Deemed Owners.

      Prior to due presentment of a Unit Certificate for registration of
transfer, the Company and the Unit Agent, and any agent of the Company or the
Unit Agent, may treat the Person in whose name such Unit Certificate is
registered as the owner of the Units evidenced thereby, for the purpose of
receiving payments of distributions or interest on the

                                     -20-
<PAGE>
 
Pledged Securities, receiving or making payments of Contract Fees and
performance of the underlying Purchase Contracts and Call Options and for all
other purposes whatsoever, whether or not the payment of distributions or
interest on the Pledged Securities or any Contract Fee payable in respect of the
Purchase Contracts constituting a part of the Units evidenced thereby shall be
overdue and notwithstanding any notice to the contrary, and neither the Company
nor the Unit Agent, nor any agent of the Company or the Unit Agent, shall be
affected by notice to the contrary.

      Notwithstanding the foregoing, with respect to any Global Unit
Certificate, nothing herein shall prevent the Company, the Unit Agent or any
agent of the Company or the Unit Agent, from giving effect to any written
certification, proxy or other authorization furnished by any Depositary (or its
nominee), as a Holder, with respect to such Global Unit Certificate or impair,
as between such Depositary and owners of beneficial interests in such Global
Unit Certificate, the operation of customary practices governing the exercise of
rights of such Depositary (or its nominee) as Holder of such Global Unit
Certificate.

Section 308.  Cancellation.

      All Unit Certificates surrendered for delivery of shares of Common Stock
on or after the Stock Purchase Date, transfer of Pledged Securities after the
occurrence of a Termination Event or registration of transfer or exchange shall,
if surrendered to any Person other than the Unit Agent, be delivered to the Unit
Agent and, if not already canceled, shall be promptly canceled by it. The
Company may at any time deliver to the Unit Agent for cancellation any Unit
Certificates previously authenticated, executed and delivered hereunder which
the Company may have acquired in any manner whatsoever, and all Unit
Certificates so delivered shall, upon Issuer Order, be promptly canceled by the
Unit Agent. No Unit Certificates shall be authenticated, executed on behalf of
the Holder and delivered upon transfer of, in exchange for or in lieu of any
Unit Certificates canceled as provided in this Section, except as expressly
permitted by this Agreement. All canceled Unit Certificates held by the Unit
Agent shall be disposed of as directed by Issuer Order.

     If the Company or any Affiliate of the Company shall acquire any Unit
Certificate, such acquisition shall not operate as a cancellation of such Unit
Certificate unless and until such Unit Certificate is delivered to the Unit
Agent canceled or for cancellation.

Section 309.  Substitution of Pledged Securities and Creation of Stripped
              Units; Units Not Otherwise Separable.

      (a)     A Holder of Normal Units may obtain the release from the Pledge of
such Holder's Pledged Securities underlying such Normal Units, free and clear of
the Company's and the Call Option Holder's security interests therein, and
convert such Normal Units into

                                     -21-
<PAGE>
 
Stripped Units (collectively, a "Stripped Unit Creation") at any time after the
original issuance of such Normal Units and on or prior to the second Business
Day immediately preceding the Stock Purchase Date by:

          (i)  delivering to the Collateral Agent: (w) Treasury Securities that
     through their scheduled payments will generate not later than the Stock
     Purchase Date an amount of cash that is at least equal to the aggregate
     Stated Amount of such Normal Units, (x) if any Contract Fees are or will be
     payable by the Holders to the Company, Treasury Securities that through
     their scheduled payments will generate not later than each Quarterly
     Payment Date falling after the date on which the requirements for such
     Stripped Unit Creation contained in this Section 309(a) are satisfied and
     on or before the Stock Purchase Date an amount of cash that is at least
     equal to the aggregate Contract Fees that are scheduled to be payable in
     respect of the Purchase Contracts underlying such Normal Units on each such
     Quarterly Payment Date (assuming for this purpose that no Contract Fees
     will then have been deferred under Section 503); (y) if there are any
     deferred Contract Fees payable by such Holder to the Company on the date on
     which the requirements for such Stripped Unit Creation contained in this
     Section 309(a) are satisfied, an amount of cash equal to (1) the aggregate
     unpaid amount of such Contract Fees accrued to such date, if such date is a
     Quarterly Payment Date, and (2) the aggregate unpaid amount of such
     Contract Fees accrued to the Quarterly Payment Date immediately preceding
     such date plus interest thereon at a rate per annum equal to the Deferral
     Rate for the period from and including such Quarterly Payment Date to but
     excluding such date (calculated on the basis 
     of a 360-day year of twelve 30-day months), if such date is not a Quarterly
     Payment Date; and (z) if the Call Options underlying such Normal Units
     remain exercisable on the date on which the requirements contained in this
     Section 309(a) for such Stripped Unit Creation are satisfied, an instrument
     from the Call Option Holder releasing its security interest in the Pledged
     Securities securing such Call Options and agreeing that such Call Options
     no longer underlie such Normal Units (or the Stripped Units they become);
     and

          (ii)  surrendering the Unit Certificate evidencing such Normal Units,
     with the form of Request to Create Stripped Units thereon duly completed
     and executed, to the Unit Agent, whereupon the Unit Agent shall promptly
     request the Collateral Agent to release the Pledged Securities underlying
     such Normal Units;

provided, however, that if Treasury Securities are the Pledged Securities
underlying such Normal Units, a Stripped Unit Creation may only be effected with
respect to a number of Normal Units that will result in the release from the
Pledge of Treasury Securities in denominations of $1,000 and integral multiples
thereof.

                                     -22-
<PAGE>
 
     (b)   Upon receipt of the items described in clause (i) of Section 309(a)
above and the request from the Unit Agent described in clause (ii) of Section
309(a) above, the Collateral Agent will, in accordance with the terms of the
Pledge Agreement, release to the Unit Agent, on behalf of the Holder, from the
Pledge, free and clear of the Company's and the Call Option Holders's security
interests therein, the securities that theretofore had been the Pledged
Securities underlying such Normal Units, and upon receipt thereof the Unit Agent
shall promptly:

          (i)   cancel the Unit Certificate for such Normal Units;

          (ii)  transfer such released Pledged Securities to the Holder or,
     subject to Section 305, the Holder's designee;

          (iii) authenticate, execute on behalf of such Holder and deliver to
     the Holder or, subject to Section 305, the Holder's designee a Unit
     Certificate executed by the Company in accordance with Section 303
     evidencing a number of Stripped Units equal to the number of such Normal
     Units.

Concurrently with the release of the securities that theretofore had been the
Pledged Securities underlying such Normal Units as contemplated by the preceding
sentence, the Treasury Securities delivered to the Collateral Agent as
contemplated by clause (i) of Section 309(a) above shall thereupon be
substituted for such securities as Pledged Securities underlying the Stripped
Units created from such Normal Units.

     (c)  Except for a Stripped Unit Creation effected in compliance with this
Section 309, for so long as the Purchase Contract underlying a Normal Unit
remains in effect such Normal Unit shall not be separable into its constituent
parts, and the rights and obligations of the Holder of such Normal Unit in
respect of the Pledged Securities, Purchase Contract and Call Option underlying
such Normal Unit may be acquired, and may be transferred and exchanged, only as
an integrated Normal Unit. For so long as the Purchase Contract underlying a
Stripped Unit remains in effect such Stripped Unit shall not be separable into
its constituent parts, and the rights and obligations of the Holder of such
Stripped Unit in respect of the Pledged Securities and Purchase Contract
underlying such Stripped Unit may be acquired, and may be transferred and
exchanged, only as an integrated Stripped Unit. Other than a Unit Certificate,
no Holder of a Unit, nor any transferee thereof, shall be entitled to receive a
certificate evidencing the ownership of Pledged Securities or any other rights
or obligations underlying such Unit for so long as the Purchase Contract
underlying such Unit remains in effect.

 Section 310.  Payments on the Units.

                                     -23-
<PAGE>
 
     Contract Fees payable by the Company to the Holders, and all amounts
payable to Holders as required by Section 401 or 504(b), will be payable at the
office of the Unit Agent in The City of New York maintained for that purpose or,
at the option of the Company, by check mailed to the address of the Person
entitled thereto at such address as it appears on the relevant Unit Register on
the Record Date; provided, however, that for so long as any Units are evidenced
by Global Certificates, the Unit Agent will pay each such amount payable in
respect of such Units by wire transfer in same-day funds, no later than 2:00
p.m., New York City time, on the Business Day such amount is received by the
Unit Agent from the Collateral Agent or the Company (or, if such amount is
received by the Unit Agent after 1:00 p.m., New York City time, on a Business
Day or on a day that is not a Business Day, no later than 10:00 a.m., New York
City time, on the next succeeding Business Day), to the Depositary, to the
account or accounts designated by it for such purpose.

                                 ARTICLE FOUR

                            The Pledged Securities

Section 401.  Payments on the Pledged Securities.

      On each Quarterly Payment Date, as provided by the terms of the Pledge
Agreement, subject to receipt by the Collateral Agent of the relevant payments
in respect of the Pledged Securities underlying any Holder's Units, (a) the
Collateral Agent shall, subject to Section 504(b), remit to the Unit Agent the
amount of such payments and (b) the Unit Agent shall pay the amount referred to
in clause (a) above, subject to receipt thereof by the Unit Agent from the
Collateral Agent, to the Person in whose name the Unit Certificate (or one or
more Predecessor Unit Certificates) evidencing such Units is registered at the
close of business on the Record Date next preceding such Quarterly Payment Date.

      Payments on the Pledged Securities on the Stock Purchase Date are
discussed at Section 504.

Section 402.  Transfer of Pledged Securities Upon Occurrence of Termination
Event.

      Upon the occurrence of a Termination Event and the transfer of the Pledged
Securities underlying each Holder's Units to the Unit Agent pursuant to the
terms of the Pledge Agreement, the Unit Agent shall request transfer
instructions with respect to such Pledged Securities from such Holder by written
request mailed to such Holder at his address as it appears in the relevant Unit
Register and shall give notice of such Termination Event to the Collateral
Agent. Thereafter, upon surrender to the Unit Agent of a Unit Certificate
evidencing a Holder's Units, with transfer instructions in proper form for
transfer of the underlying Pledged Securities, the Unit Agent shall transfer the
Pledged Securities evidenced

                                     -24-
<PAGE>
 
by such Unit Certificate to such Holder in accordance with such instructions;
provided, however, that if the Pledged Securities are to be transferred to a
Person other than the Person in whose name such Unit Certificate is registered,
no such transfer shall be made unless the Person requesting the transfer has
paid any transfer and other taxes required by reason of such transfer to a
Person other than the registered Holder of such Unit Certificate or has
established to the satisfaction of the Company that such tax either has been
paid or is not payable. Until the foregoing conditions to transfer any of the
Pledged Securities underlying any Units has been met, the Unit Agent shall hold
such Pledged Securities as custodian for the Holder of such Units.

      If upon a Termination Event any Holder of Units would, after satisfying
the foregoing conditions, otherwise be entitled to receive (or have transferred
to such Holder's designee) Treasury Securities of any series having a principal
amount that is not an integral multiple of $1,000, such Holder shall instead be
entitled to receive (or have transferred to such Holder's designee) Treasury
Securities of such series in a principal amount equal to the next lower integral
multiple of $1,000 plus a portion of the net proceeds from the sale of Treasury
Securities of such series contemplated by the succeeding sentence representing
such Holder's interest therein. As soon as practicable after transfer to the
Unit Agent of the Pledged Securities as provided in the Pledge Agreement, the
Unit Agent shall, on behalf of all Holders who, by virtue of the preceding
sentence, will not be entitled to a portion of the Treasury Securities of any
series to which they would otherwise be entitled, aggregate and sell the
Treasury Securities of such series representing such portion to or through one
or more U.S. government securities dealers at then prevailing prices, deduct
from the proceeds of such sales all commissions and other out-of-pocket
transaction costs incurred in connection with such sales and, until the net
proceeds therefrom have been distributed to the Holders entitled thereto or
their designees, hold such proceeds in trust for such Holders.

                                 ARTICLE FIVE

                            The Purchase Contracts

Section 501.  Purchase of Shares of Common Stock.

      Each Purchase Contract underlying a Unit shall obligate the Holder of such
Unit to purchase, and the Company to sell, on the Stock Purchase Date, at a
price equal to the Stated Amount, a number of shares of Common Stock equal to
the Settlement Rate, unless, on or prior to the Stock Purchase Date, there shall
have occurred a Termination Event. The "Settlement Rate" is equal to (a) if the
Applicable Market Value (as defined below) is greater than or equal to $. (the
"Threshold Appreciation Price"), . of a share of Common Stock per Purchase
Contract, (b) if the Applicable Market Value is less than the Threshold
Appreciation Price but is greater than the Stated Amount, a fractional share of
Common

                                     -25-
<PAGE>
 
Stock per Purchase Contract equal to the Stated Amount divided by the Applicable
Market Value (rounded upward or downward to the nearest 1/10,000th of a share
or, if there is not a nearest 1/10,000th of a share, to the next lower
1/10,000th of a share) and (c) if the Applicable Market Value is less than or
equal to the Stated Amount, one share of Common Stock per Purchase Contract, in
each case subject to adjustment as provided in Section 506. As provided in
Section 509, no fractional shares of Common Stock will be issued upon settlement
of Purchase Contracts.

      The "Applicable Market Value" means the average of the Closing Prices per
share of Common Stock on each of the twenty consecutive Trading Days ending on
the last Trading Day immediately preceding the Stock Purchase Date. The "Closing
Price" of the Common Stock on any date of determination means the closing sale
price (or, if no closing price is reported, the last reported sale price) of the
Common Stock on the New York Stock Exchange (the "NYSE") on such date or, if the
Common Stock is not listed for trading on the NYSE on any such date, as reported
in the composite transactions for the principal United States securities
exchange on which the Common Stock is so listed, or if the Common Stock is not
so listed on a United States national or regional securities exchange, as
reported by The NASDAQ Stock Market, or, if the Common Stock is not so reported,
the last quoted bid price for the Common Stock in the over-the-counter market as
reported by the National Quotation Bureau or similar organization, or, if such
bid price is not available, the market value of the Common Stock on such date as
determined by a nationally recognized investment banking firm retained for this
purpose by the Company. A "Trading Day" means a day on which the Common Stock
(A) is not suspended from trading on any national or regional securities
exchange or association or over-the-counter market at the close of business and
(B) has traded at least once on the national or regional securities exchange or
association or over-the-counter market that is the primary market for the
trading of the Common Stock.

      Each Holder of a Unit Certificate evidencing Normal Units, by his
acceptance thereof, irrevocably authorizes the Unit Agent to enter into and
perform the underlying Purchase Contracts and Call Options on his behalf as his
attorney-in-fact, agrees to be bound by the terms and provisions thereof,
covenants and agrees to perform his obligations under such Purchase Contracts
and Call Options, consents to the provisions of the Principal Agreements,
irrevocably authorizes the Unit Agent to enter into and perform the Call Option
Agreement and the Pledge Agreement on his 

                                     -26-
<PAGE>
 
behalf as his attorney-in-fact, and consents to and agrees to be bound by the
Pledge of the Pledged Securities underlying such Normal Units pursuant to the
Pledge Agreement. Each Holder of a Unit Certificate evidencing Stripped Units,
by his acceptance thereof, irrevocably authorizes the Unit Agent to enter into
and perform the underlying Purchase Contracts on his behalf as his attorney-in-
fact, agrees to be bound by the terms and provisions thereof, covenants and
agrees to perform his obligations under such Purchase Contracts, consents to the
provisions of the Principal Agreements, irrevocably authorizes the Unit Agent to
perform the Pledge Agreement on his behalf as his attorney-in-fact, and consents
to and agrees to be bound by the Pledge of the Pledged Securities underlying
such Stripped Units pursuant to the Pledge Agreement. Each Holder of Units, by
his acceptance thereof, further irrevocably covenants and agrees that, unless
such Holder satisfies its obligations to the Company under the Purchase
Contracts underlying such Units as provided in Section 504(a), then to the
extent and in the manner provided in Section 504(b) and the Pledge Agreement,
but subject to the terms thereof, payments in respect of all or a portion of the
principal of or proceeds from the Pledged Securities on the Stock Purchase Date
shall be paid by the Collateral Agent to the Company in satisfaction of such
Holder's obligations under such Purchase Contract and such Holder shall acquire
no right, title or interest in such payments.

      Upon registration of transfer of a Unit Certificate, the transferee shall
be bound (without the necessity of any other action on the part of such
transferee) by the terms of the Purchase Contracts and any Call Options
evidenced thereby and by the Pledge Agreement and the transferor shall be
released from all such obligations evidenced by the Unit Certificate so
transferred. The Company covenants and agrees, and each Holder of a Unit
Certificate, by his acceptance thereof, likewise covenants and agrees, to be
bound by the provisions of this paragraph.

Section 502.  Contract Fees.

      Subject to Section 503, if any Contract Fees are or will be payable by the
Company to the Holders, the Company shall pay, prior to 1:00 p.m., New York City
time, on each Quarterly Payment Date to and including the Stock Purchase Date,
the Contract Fees payable in respect of each Purchase Contract to the Person in
whose name the Unit Certificate (or one or more Predecessor Unit Certificates)
evidencing such Purchase Contract is registered at the close of business on the
Record Date next preceding such Quarterly Payment Date. The Company's
obligations with respect to such Contract Fees are hereby expressly subordinated
in right of payment to the prior payment in full of all Senior Indebtedness, to
the extent and in the manner set forth in the Indenture.

      Each Unit Certificate delivered under this Agreement upon registration of
transfer of, in exchange for or in lieu of any other Unit Certificate shall
carry the rights to receive and obligations to pay Contract Fees accrued and
unpaid, and to accrue, which were carried by the Purchase Contracts evidenced by
such other Unit Certificate.

Section 503.  Deferral of Payment Dates For Contract Fee.

      So long as no default in the Company's obligations under the Principal
Agreements has occurred and is continuing, the Company shall have the right, at
any time prior to the Stock Purchase Date, to defer the payment of any or all of
the Contract Fees otherwise payable by the Company on any Quarterly Payment
Date, but only if the Company shall give

                                     -27-
<PAGE>
 
the Holders and the Unit Agent written notice of its election to defer such
payment (specifying the amount to be deferred) at least five Business Days prior
to the earlier of (a) the next succeeding Quarterly Payment Date or (b) the date
the Company is required to give notice of the Record Date or Quarterly Payment
Date with respect to payment of such Contract Fee to the NYSE or other
applicable self-regulatory organization or to Holders, or (c) the Record Date
for such Quarterly Payment Date. Any Contract Fees so deferred shall bear
additional Contract Fees thereon at a rate per annum equal to the Deferral Rate
(computed on the basis of a 360-day year of twelve 30-day months), compounding
on each succeeding Quarterly Payment Date, until paid in full. Deferred Contract
Fees (and additional Contract Fees accrued thereon) shall be due on the next
succeeding Quarterly Payment Date except to the extent that payment is deferred
pursuant to this Section. No Contract Fees may be deferred to a date that is
after the Stock Purchase Date.

      In the event the Company exercises its option to defer the payment of
Contract Fees payable by it, then, until all deferred Contract Fees (including
additional Contract Fees accrued thereon) have been paid in full, the Company
shall not (a) declare or pay any dividends or distributions on, or redeem,
purchase, acquire, or make a liquidation payment with respect to, any of the
Company's capital stock, (b) make any payment of principal, interest or premium,
if any, on or repay, repurchase or redeem any debt securities of the Company
that rank pari passu with or junior in right of payment to the Contract Fees or
(c) make any guarantee payments with respect to any guarantee by the Company of
any securities of any subsidiary of the Company if such guarantee ranks pari
passu or junior in right of payment to the Contract Fees (other than, in the
case of clauses (a), (b) and (c), (i) dividends or distributions in shares of,
or options, warrants or rights to subscribe for or purchase shares of, common
stock of the Company, (ii) any declaration of a dividend in connection with the
implementation of a stockholder's rights plan, or the issuance of stock under
any such plan in the future, or the redemption or repurchase of any such rights
pursuant thereto, (iii) as a result of a reclassification of the Company's
capital stock solely into shares of one or more classes or series of the
Company's capital stock or the exchange or conversion of one class or series of
the Company's capital stock for another class or series of the Company's capital
stock, (iv) the purchase of fractional interests in shares of the Company's
capital stock pursuant to the conversion or exchange provisions of such capital
stock or the securities being converted or exchanged and (v) purchases of common
stock in connection with the satisfaction by the Company of its obligations
under any of the Company's benefit plans for its and its subsidiaries'
directors, officers or employees or any of the company's dividend reinvestment
plans).

Section 504.  Payment of Purchase Price.

      (a)     A Holder of Units shall, by no later than 10:00 a.m., New York
City time, on the Stock Purchase Date, deliver to the Unit Agent payment of the
purchase price for the

                                     -28-
<PAGE>
 
shares of Common Stock to be purchased pursuant to the Purchase Contracts
underlying such Units, which payment shall be made in lawful money of the United
States by certified or cashier's check payable to the order of the Company in
immediately available funds in an amount equal to the aggregate Stated Amount of
such Holder's Units.

      By 11:00 a.m., New York City time, on the Stock Purchase Date, the Unit
Agent shall (i) transfer to the Company all of the payments the Company is
entitled to receive as contemplated by the preceding sentence, (ii) notify the
Collateral Agent and the Company as to the number of Normal Units and the number
of Stripped Units, respectively, with respect to which payment has been received
as aforesaid (such Units being collectively referred to as "Paid Units") and the
number of Normal Units and the number of Stripped Units, respectively, with
respect to which payment has not been received as aforesaid (such Units being
collectively referred to as "Unpaid Units"), and (iii) request the Collateral
Agent (with notice of such request to the Company) to release the Pledged
Securities underlying the Paid Units (or, in the case of Treasury Securities,
the cash payments received thereon) from the Pledge and transfer such released
Pledged Securities (or such cash) to the Unit Agent for delivery to the Holders
of such Units entitled thereto, free and clear of the Company's security
interest therein.

      By 1:00 p.m., New York City time, on the Stock Purchase Date, the
Collateral Agent shall, as provided by the terms of the Pledge Agreement, comply
with the request referred to in clause (iii) of the preceding sentence (subject
to the Company's right under the Pledge Agreement to prevent the Collateral
Agent from doing so to the extent the aggregate amount the Company has received
as contemplated by clause (i) of the preceding sentence is less than the
aggregate amount payable with respect to the Units referred to in such request).
The Unit Agent shall thereupon, subject to its receipt from the Collateral Agent
of the Pledged Securities (or cash) referred to in such request and subject to
Section 305, transfer such released Pledged Securities (or cash) to the
respective Holders entitled thereto in accordance with the settlement
instructions specified in the form of Settlement Instructions appearing on the
Unit Certificates evidencing the Paid Units; provided, however, that if any such
Unit Certificate is not surrendered to the Unit Agent with the form of
Settlement Instructions thereon duly completed and executed, the Unit Agent
shall hold such Pledged Securities (or cash), and any distributions or interest
received on such Pledged Securities, as custodian for the Holder entitled
thereto, to be delivered to such Holder (without any interest thereon and
subject to Section 305) upon surrender of such Unit Certificate to the Unit
Agent (with the form of Settlement Instructions thereon duly completed and
executed).

      (b)  With respect to each Holder's Unpaid Units, pursuant to the terms of
the Pledge Agreement,

                                     -29-
<PAGE>
 
          (i)    if Debentures underlie such Unpaid Units, the Collateral Agent,
     on behalf of such Holder, shall, as Put Agent, exercise the Debenture Put
     Option with respect thereto;

          (ii)   the Collateral Agent shall deliver to the Company, out of  the
     proceeds from the exercise of such Debenture Put Option or, if Treasury
     Securities underlie such Unpaid Units, the proceeds from the payment of
     such Treasury Securities at maturity, an amount equal to the aggregate
     Stated Amount of such Unpaid Units plus the unpaid Contract Fees, if any,
     payable by such Holder to the Company in respect of such Unpaid Units to
     satisfy in full such Holder's obligations under such Unpaid Units; and

          (iii)  the Collateral Agent shall remit to the Unit Agent, on behalf
     of such Holder, the remainder of the proceeds, if any, from the Pledged
     Securities underlying such Unpaid Units for distribution to such Holder.

The amount referred to in clause (iii) above shall, subject to receipt thereof
by the Unit Agent from the Collateral Agent, be paid to the Person in whose name
the Unit Certificate (or one or more Predecessor Unit Certificates) evidencing
such Unpaid Units is registered at the close of business on the Record Date next
preceding the Stock Purchase Date.

     (c) Each Holder will be entitled to apply any unpaid amounts owing by the
Company to such Holder as a set-off to reduce, dollar-for-dollar, any amounts
then owing by such Holder to the Company in respect of such Holder's Units, and
such set-off amounts will be treated for all purposes as having been paid in
full by such Holder as required hereby.

     (d) The Company shall not be obligated to issue any shares of Common Stock
in respect of a Purchase Contract or deliver any certificates therefor to the
Holder of the related Unit unless the Company shall have received payment in
full of the aggregate purchase price for the shares of Common Stock to be
purchased thereunder in the manner herein set forth (either directly or by
operation of set-off as contemplated by the preceding sentence).

 Section 505.  Issuance of Shares of Common Stock.

     As promptly as practicable on or after the Stock Purchase Date, upon
receipt by the Company of payment in full of the aggregate purchase price for
the shares of Common Stock purchased by the Holders pursuant to the foregoing
provisions of this Article, and subject to Section 506(b), the Company shall
deposit with the Unit Agent, for the benefit of the Holders of the Units, one or
more certificates representing the shares of Common Stock registered in the name
of the Unit Agent (or its nominee) as custodian for the Holders (such
certificates 

                                      -30-
<PAGE>
 
for shares of Common Stock, together with any dividends or distributions with
respect thereto, being hereinafter referred to as the "Purchase Contract
Settlement Fund") to which the Holders are entitled hereunder. Subject to the
foregoing, upon surrender of a Unit Certificate to the Unit Agent on or after
the Stock Purchase Date, with the form of Settlement Instructions thereon duly
completed and executed, the Holder of such Unit Certificate shall be entitled to
receive in exchange therefor a certificate representing that number of whole
shares of Common Stock which such Holder is entitled to receive pursuant to the
provisions of this Article Five (after taking into account all Units then held
by such Holder) together with cash in lieu of fractional shares as provided in
Section 509 and any dividends or distributions with respect to such shares
constituting part of the Purchase Contract Settlement Fund, but without any
interest thereon, and the Unit Certificate so surrendered shall forthwith be
cancelled. Such shares shall be registered in the name of the Holder or the
Holder's designee as specified in the form of Settlement Instructions appearing
on the surrendered Unit Certificate.

     If any shares of Common Stock issued in respect of a Purchase Contract are
to be registered to a Person other than the Person in whose name the Unit
Certificate evidencing such Purchase Contract is registered, no such
registration shall be made unless the Person requesting such registration has
paid any transfer and other taxes required by reason of such registration in a
name other than that of the registered Holder of the Unit Certificate evi-
dencing such Purchase Contract or has established to the satisfaction of the
Company that such tax either has been paid or is not payable.

 Section 506.  Adjustment of Settlement Rate.

     (a) Adjustments for Dividends, Distributions, Stock Splits, Etc.

     (1) In case the Company shall pay or make a dividend or other distribution
on any class of Common Stock of the Company in Common Stock, the Settlement Rate
in effect at the opening of business on the day following the date fixed for the
determination of stockholders entitled to receive such dividend or other
distribution shall be increased by dividing such Settlement Rate by a fraction
of which the numerator shall be the number of shares of Common Stock outstanding
at the close of business on the date fixed for such determination and the
denominator shall be the sum of such number of shares and the total number of
shares constituting such dividend or other distribution, such increase to become
effective immediately after the opening of business on the day following the
date fixed for such determination.  For the purposes of this paragraph (1), the
number of shares of Common Stock at any time outstanding shall not include
shares held in the treasury of the Company but shall include shares issuable in
respect of scrip certificates issued in lieu of fractions of shares of Common
Stock.  The Company will not pay any dividend or make any distribution on shares
of Common Stock held in the treasury of the Company.

                                      -31-
<PAGE>
 
     (2) In case the Company shall issue rights, options or warrants to all
holders of its Common Stock (not being available on an equivalent basis to
Holders of the Units upon settlement of the Purchase Contracts underlying such
Units) entitling them, for a period expiring within 45 days after the record
date for the determination of stockholders entitled to receive such rights,
options or warrants, to subscribe for or purchase shares of Common Stock at a
price per share less than the Current Market Price per share of the Common Stock
on the date fixed for the determination of stockholders entitled to receive such
rights, options or warrants (other than pursuant to a dividend reinvestment
plan), the Settlement Rate in effect at the opening of business on the day
following the date fixed for such determination shall be increased by dividing
such Settlement Rate by a fraction of which the numerator shall be the number of
shares of Common Stock outstanding at the close of business on the date fixed
for such determination plus the number of shares of Common Stock which the
aggregate of the offering price of the total number of shares of Common Stock so
offered for subscription or purchase would purchase at such Current Market Price
and the denominator shall be the number of shares of Common Stock outstanding at
the close of business on the date fixed for such determination plus the number
of shares of Common Stock so offered for subscription or purchase, such increase
to become effective immediately after the opening of business on the day
following the date fixed for such determination.  For the purposes of this
paragraph (2), the number of shares of Common Stock at any time outstanding
shall not include shares held in the treasury of the Company but shall include
shares issuable in respect of scrip certificates issued in lieu of fractions of
shares of Common Stock.  The Company shall not issue any such rights, options or
warrants in respect of shares of Common Stock held in the treasury of the
Company.

     (3) In case outstanding shares of Common Stock shall be subdivided into a
greater number of shares of Common Stock, the Settlement Rate in effect at the
opening of business on the day following the day upon which such subdivision
becomes effective shall be proportionately increased, and, conversely, in case
outstanding shares of Common Stock shall each be combined into a smaller number
of shares of Common Stock, the Settlement Rate in effect at the opening of
business on the day following the day upon which such combination becomes
effective shall be proportionately reduced, such increase or reduction, as the
case may be, to become effective immediately after the opening of business on
the day following the day upon which such subdivision or combination becomes
effective.

     (4) In case the Company shall, by dividend or otherwise, distribute to all
holders of its Common Stock evidences of its indebtedness or assets (including
securities, but excluding any rights or warrants referred to in paragraph (2) of
this Section, any dividend or distribution paid exclusively in cash and any
dividend or distribution referred to in para  graph (1) of this Section), the
Settlement Rate shall be increased so that the same shall equal the rate
determined by dividing the Settlement Rate in effect immediately prior to the
close 

                                      -32-
<PAGE>
 
of business on the date fixed for the determination of stockholders entitled to
receive such distribution by a fraction of which the numerator shall be the
Current Market Price per share of the Common Stock on the date fixed for such
determination less the then fair market value (as determined by the Board of
Directors, whose determination shall be conclusive and described in a Board
Resolution filed with the Unit Agent) of the portion of the assets or evidences
of indebtedness so distributed applicable to one share of Common Stock and the
denominator shall all be such Current Market Price per share of the Common
Stock, such adjustment to become effective immediately prior to the opening of
business on the day following the date fixed for the determination of
stockholders entitled to receive such distribution. In any case in which this
paragraph (4) is applicable, paragraph (2) of this Section shall not be
applicable.

     (5) In case the Company shall, by dividend or otherwise, distribute to all
holders of its Common Stock cash (excluding any cash that is distributed in a
Reorganization Event to which Section 506(b) applies or as part of a
distribution referred to in paragraph (4) of this Section) in an aggregate
amount that, when combined with (I) the aggregate amount of any other
distributions to all holders of its Common Stock made exclusively in cash within
the 12 months preceding the date of payment of such distribution to the extent
such amount has not already been applied in a prior adjustment pursuant to this
paragraph (5) and (II) the aggregate of the cash plus the fair market value (as
determined by the Board of Directors, whose determination shall be conclusive
and described in a Board Resolution), as of the date of expiration of such
tender or exchange offer, of the consideration paid in respect of any tender or
exchange offer by the Company or any of its subsidiaries for all or any portion
of the Common Stock expiring within the 12 months preceding the date of payment
of such distribution and in respect of which no adjustment pursuant to paragraph
(6) of this Section has been made, exceeds 12.5% of the product of the Current
Market Price per share of the Common Stock on the date fixed for the
determination of stockholders entitled to receive such distribution times the
number of shares of Common Stock outstanding on such date (such excess portion
of such distribution being herein referred to as the "Excess Amount"), the
Settlement Rate shall be increased so that the same shall equal the rate
determined by dividing the Settlement Rate in effect immediately prior to the
close of business on the date fixed for the determination of stockholders
entitled to receive such distribution by a fraction of which (i) the numerator
shall be the Current Market Price per share of the Common Stock on the date
fixed for such determination less an amount equal to  (x) such Excess Amount
divided by (y) the number of shares of Common Stock outstanding at the close of
- ----------                                                                     
business on the date fixed for such determination and (ii) the denominator shall
be the Current Market Price per share of the Common Stock on the date fixed for
such determination, such adjustment to become effective immediately prior to the
opening of business on the day following the date fixed for the determination of
stockholders entitled to receive such distribution.

                                      -33-
<PAGE>
 
     (6) In case the Company or any subsidiary of the Company shall consummate a
tender or exchange offer for all or any portion of the Common Stock and pay an
aggregate consideration in respect thereof having a fair market value (as
determined by the Board of Directors, whose determination shall be conclusive
and described in a Board Resolution) that, when combined with (I) the aggregate
of the cash plus the fair market value (as determined by the Board of Directors,
whose determination shall be conclusive and described in a Board Resolution), as
of the date of expiration of such tender or exchange offer, of the consideration
paid in respect of any other tender or exchange offer by the Company or any of
its subsidiaries for all or any portion of the Common Stock expiring within the
12 months preceding the date of expiration of such tender or exchange offer and
in respect of which no adjustment pursuant to this paragraph (6) has been made
and (II) the aggregate amount of any distributions to all holders of the
Company's Common Stock made exclusively in cash within 12 months preceding the
date of expiration of such tender or exchange offer to the extent such amount
has not already been applied in a prior adjustment pursuant to paragraph (5) of
this Section, exceeds 12.5% of the product of the Current Market Price per share
of the Common Stock on the date of expiration of such tender or exchange offer
times the number of shares of Common Stock outstanding (including any tendered
shares) at the close of business on the date of such expiration, the Settlement
Rate shall be increased so that the same shall equal the rate determined by
dividing the Settlement Rate in effect immediately prior to the close of
business on the date of such expiration by a fraction  of which (i) the
numerator shall be (A) the product of (I) the Current Market Price per share of
the Common Stock on the date of such expiration and (II) the number of shares of
Common Stock outstanding (including any tendered shares) at the close of
business on the date of such expiration less (B) the amount of cash plus the
fair market value (determined as aforesaid) of the aggregate consideration paid
in respect of such tender or exchange offer and (ii) the denominator shall be
the product of (A) the Current Market Price per share of the Common Stock on the
date of such expiration and (B) the number of shares of Common Stock outstanding
(including any tendered shares) at the close of business on the date of such
expiration less the number of shares acquired pursuant to such tender or
exchange, such adjustment to become effective immediately prior to the opening
of business on the day following the date of such expiration.

     (7) The reclassification of Common Stock into securities including
securities other than Common Stock (other than any reclassification upon a
Reorganization Event to which Section 506(b) applies) shall be deemed to involve
(i) a distribution of such securities other than Common Stock to all holders of
Common Stock (and the effective date of such reclassification shall be deemed to
be "the date fixed for the determination of stockholders entitled to receive
such distribution" and the "date fixed for such determination" within the
meaning of paragraph (4) of this Section), and (ii) a subdivision or
combination, as the case may be, of the number of shares of Common Stock
outstanding immediately prior to such reclassification into the number of shares
of Common Stock outstanding immediately

                                      -34-
<PAGE>
 
thereafter (and the effective date of such reclassification shall be deemed to
be "the day upon which such subdivision becomes effective" or "the day upon
which such combination becomes effective", as the case may be, and "the day upon
which such subdivision or combination becomes effective" within the meaning of
paragraph (3) of this Section).

     (8) The "Current Market Price" per share of Common Stock on any day means
the average of the daily Closing Prices for the 5 consecutive Trading Days
selected by the Company commencing not more than 20 Trading Days before, and
ending not later than, the earlier of the day in question and the day before the
"ex" date with respect to the issuance or distribution requiring such
computation.  For purposes of this paragraph, the term " 'ex' date", when used
with respect to any issuance or distribution, shall mean the first date on which
the Common Stock trades regular way on such exchange or in such market without
the right to receive such issuance or distribution.

     (9) All adjustments to the Settlement Rate shall be calculated to the
nearest 1/10,000th of a share of Common Stock (or, if there is not a nearest
1/10,000th of a share, to the next lower 1/10,000th of a share).  No adjustment
in the Settlement Rate shall be required unless such adjustment would require an
increase or decrease of at least one percent therein; provided, however, that
any adjustments which by reason of this subparagraph are not required to be made
shall be carried forward and taken into account in any subsequent adjustment.
If an adjustment is made to the Settlement Rate pursuant to paragraph (1), (2),
(3), (4), (5), (6), (7) or (10) of this Section 506(a), an adjustment shall also
be made to the Applicable Market Value solely to determine which of clauses (a),
(b) or (c) of the definition of Settlement Rate in Section 501 will apply on the
Stock Purchase Date.  Such adjustment shall be made by multiplying the
Applicable Market Value by a fraction of which the numerator shall be the
Settlement Rate immediately after such adjustment pursuant to para  graph (1),
(2), (3), (4), (5), (6), (7) or (10) of this Section 506(a) and the denominator
shall be the Settlement Rate immediately before such adjustment.

     (10) The Company may make such increases in the Settlement Rate, in
addition to those required by this Section, as it considers to be advisable in
order to avoid or diminish any income tax to any holders of shares of Common
Stock resulting from any dividend or distribution of stock or issuance of rights
or warrants to purchase or subscribe for stock or from any event treated as such
for income tax purposes or for any other reasons.

     (b) Adjustment for Consolidation, Merger or Other Reorganization Event.
In the event of (i) any consolidation or merger of the Company with or into
another Person (other than a merger or consolidation in which the Company is the
continuing corporation and in which the Common Stock outstanding immediately
prior to the merger or consolidation is not exchanged for cash, securities or
other property of the Company or another corporation), (ii) any sale, transfer,
lease or conveyance to another Person of the 

                                      -35-
<PAGE>
 
property of the Company as an entirety or substantially as an entirety, (iii)
any statutory exchange of securities of the Company with another Person (other
than in connection with a merger or acquisition) or (iv) any liquidation,
dissolution or winding up of the Company (any such event, a "Reorganization
Event"), the Settlement Rate will be adjusted to provide that each Holder of
Units will receive on the Stock Purchase Date with respect to each Purchase
Contract forming a part thereof, the kind and amount of securities, cash and
other property receivable upon such Reorganization Event by a Holder of the
number of shares of Common Stock issuable on account of each Purchase Contract
if the Stock Purchase Date had occurred immediately prior to such Reorganization
Event, assuming such Holder of Common Stock is not a Person with which the
Company consolidated or into which the Company merged or which merged into the
Company or to which such sale or transfer was made, as the case may be
("constituent Person"), or an Affiliate of a constituent Person, and failed to
exercise his rights of election, if any, as to the kind or amount of securities,
cash and other property receivable upon such Reorganization Event (provided that
if the kind or amount of securities, cash and other property receivable upon
such Reorganization Event is not the same for each share of Common Stock held
immediately prior to such Reorganization Event by other than a constituent
Person or an Affiliate thereof and in respect of which such rights of election
shall not have been exercised ("non-electing share"), then for the purpose of
this Section the kind and amount of securities, cash and other property
receivable upon such Reorganization Event by each non-electing share shall be
deemed to be the kind and amount so receivable per share by a plurality of the
non-electing shares). In the event of such a Reorganization Event, the Person
formed by such consolidation, merger or exchange or the Person which acquires
the assets of the Company or, in the event of a liquidation or dissolution of
the Company, the Company or a liquidating trust created in connection therewith,
shall execute and deliver to the Unit Agent an agreement supplemental hereto
providing that the Holders of each Outstanding Unit shall have the rights
provided by this Section 506. Such supplemental agreement shall provide for
adjustments which, for events subsequent to the effective date of such
supplemental agreement, shall be as nearly equivalent as may be practicable to
the adjustments provided for in this Section. The above provisions of this
Section shall similarly apply to successive Reorganization Events.

 Section 507.  Notice of Adjustments and Certain Other Events.

     (a) Whenever the Settlement Rate is adjusted as herein provided, the
Company shall:

          (i)   forthwith compute the adjusted Settlement Rate in accordance
     with Section 506 and prepare and transmit to the Unit Agent an Officers'
     Certificate setting forth the Settlement Rate, the method of calculation
     thereof in reasonable detail, and the facts requiring such adjustment and
     upon which such adjustment is based; and

                                      -36-
<PAGE>
 
          (ii)  within 10 Business Days following the occurrence of an event
     that permits or requires an adjustment to the Settlement Rate pursuant to
     Section 506 (or if the Company is not aware of such occurrence, as soon as
     practicable after becoming so aware), provide a written notice to the
     Holders of the Units of the occurrence of such event and a statement in
     reasonable detail setting forth the method by which the adjustment to the
     Settlement Rate was determined and setting forth the adjusted Settlement
     Rate.

     (b) The Unit Agent shall not at any time be under any duty or
responsibility to any holder of Units to determine whether any facts exist which
may require any adjustment of the Settlement Rate, or with respect to the nature
or extent or calculation of any such adjustment when made, or with respect to
the method employed in making the same.  The Unit Agent shall not be accountable
with respect to the validity or value (or the kind or amount) of any shares of
Common Stock, or of any securities or property, which may at the time be issued
or delivered with respect to any Purchase Contract; and the Unit Agent makes no
representation with respect thereto.  The Unit Agent shall not be responsible
for any failure of the Company to issue, transfer or deliver any shares of
Common Stock pursuant to a Purchase Contract or to comply with any of the
duties, responsibilities or covenants of the Company contained in this Article.

 Section 508.  No Fractional Shares.

     No fractional shares or scrip representing fractional shares of Common
Stock shall be issued or delivered upon settlement on the Stock Purchase Date.
If Unit Certificates evidencing more than one Purchase Contract shall be
surrendered for settlement at one time by the same Holder, the number of full
shares of Common Stock which shall be delivered upon settlement shall be
computed on the basis of the aggregate number of Purchase Contracts evidenced by
the Unit Certificates so surrendered.  Instead of any fractional share of Common
Stock which would otherwise be deliverable upon settlement of any Purchase
Contracts on the Stock Purchase Date, the Company, through the Unit Agent, shall
make a cash payment in respect of such fractional interest in an amount equal to
such fraction times the Applicable Market Value.  The Company shall provide the
Unit Agent from time to time with sufficient funds to permit the Unit Agent to
make all cash payments required by this Section 508 in a timely manner.

 Section 509.  Charges and Taxes.

     The Company will pay all stock transfer and similar taxes attributable to
the initial issuance and delivery of the shares of Common Stock pursuant to the
Purchase Contracts; provided, however, that the Company shall not be required to
pay any such tax or taxes 

                                      -37-
<PAGE>
 
which may be payable in respect of any exchange of or substitution for a Unit
Certificate evidencing a Purchase Contract or any issuance of a share of Common
Stock in a name other than that of the registered Holder of a Unit Certificate
surrendered in respect of the Purchase Contracts evidenced thereby, other than
in the name of the Unit Agent, as custodian for such Holder, and the Company
shall not be required to issue or deliver such share certificates or Unit
Certificates unless or until the Person or Persons requesting the transfer or
issuance thereof shall have paid to the Company the amount of such tax or shall
have established to the satisfaction of the Company that such tax has been paid.

 Section 510.  Termination Event; Notice.

     The Purchase Contracts and the obligations and rights of the Company and
the Holders thereunder, including, without limitation, all obligations and
rights to pay or receive any accrued or deferred Contract Fees or to settle such
Purchase Contracts pursuant to this Article Five, shall immediately and
automatically terminate, without the necessity of any notice or action by any
Holder, the Unit Agent or the Company, if, on or prior to the Stock Purchase
Date, a Termination Event shall have occurred.  Upon the occurrence of a
Termination Event, the Company shall give written notice to the Unit Agent and
the Collateral Agent, at their addresses as they appear in the Unit Registers.
Upon and after the occurrence of a Termination Event, the provisions of this
Article Five (other than this Section 510) shall automatically terminate and be
of no further force or effect, and the Unit Certificates shall thereafter
represent only the right to receive the Pledged Securities forming a part of the
Units theretofore evidenced thereby in accordance with the provisions of Section
402 and the Pledge Agreement.

Section 511.  Early Settlement.

     (a) In the event of a merger or consolidation of the Company of the type
described in clause (i) of Section 506(b) in which the Common Stock outstanding
immediately prior to such merger or consolidation is exchanged for consideration
consisting of at least 30% cash or cash equivalents (any such event a "Cash
Merger"), then the Company (or the successor to the Company hereunder) shall be
required to offer the Holder of each Unit the right to settle the Purchase
Contract underlying such Unit prior to the Stock Purchase Date ("Early
Settlement") as provided herein.  On or before the fifth Business Day after the
consummation of a Cash Merger the Company or, at the request and expense of the
Company, the Unit Agent shall give all Holders notice, in the manner provided in
Section 106, of the occurrence of the Cash Merger and of the right of Early
Settlement arising as a result thereof.  The Company shall also deliver a copy
of such notice to the Unit Agent, the Collateral Agent and, if the Call Options
have not been exercised,  the Call Option Holder.

     Each such notice shall contain:

                                      -38-
<PAGE>
 
          (i)   the date, which shall be not less than 20 nor more than 30 days
     after the date of such notice, on which the Early Settlement will be
     effected (the "Early Settlement Date");

          (ii)  the date, which shall be not more than three Business Days prior
     to the Early Settlement Date, by which the Early Settlement right must be
     exercised;

          (iii) the Settlement Rate in effect as a result of such Cash Merger
     and the kind and amount of securities, cash and other property receivable
     by the Holder upon settlement of each Purchase Contract pursuant to Section
     506(b);

          (iv)  a statement to the effect that all or a portion of the Stated
     Amount payable by the Holder to settle the Purchase Contract will be offset
     against the amount of cash so receivable upon exercise of Early Settlement,
     as applicable;

          (v)   the instructions a Holder must follow to exercise the Early
     Settlement Right; and

          (vi)  a statement to the effect that accrued and unpaid Contract Fees
     in respect of the Purchase Contracts for which Early Settlement shall have
     been effected shall be payable on the Early Settlement Date and that upon
     such payment Contract Fees on such Purchase Contracts shall cease to
     accrue.

     (b) To exercise an Early Settlement right, a Holder shall deliver to the
Unit Agent on or before 5:00 p.m. on the date specified in the notice the Unit
Certificate(s) with respect to which the Early Settlement right is being
exercised with the form of Election to Settle Early on the reverse thereof duly
completed accompanied by payment of the purchase price for the property to be
purchased pursuant to the Purchase Contracts underlying such Units, which
payment shall be made in lawful money of the United States by certified or
cashier's check payable to the order of the Company in immediately available
funds in an amount equal to the aggregate Stated Amount of the Units in respect
of which the Early Settlement is being effected less the amount of cash that
otherwise would be deliverable by the Company or its successor upon settlement
of the Purchase Contract in lieu of Common Stock pursuant to Section 506(b) and
as described in the Company Notice.

     (c)  In the event a Early Settlement right shall be exercised by a Holder
in accordance with the terms hereof, (i) on the Early Settlement Date the
Company shall deliver or cause to be delivered by the Unit Agent to each such
exercising Holder the net cash, securities and other property to be received, as
provided herein,  by such exercising Holder in respect of the number of
Purchase Contracts for which such Early Settlement right was exercised, together
with all accrued and unpaid Contract Fees to the Early Settlement Date 

                                      -39-
<PAGE>
 
payable on such Purchase Contracts, in accordance with the settlement
instructions provided by such Holder and (ii) all references herein to Stock
Purchase Date shall be deemed to refer to such Early Settlement Date and all
references to form of Settlement Instruction shall be deemed to refer to the
form of Election to Settle Early, as applicable.

     (d)  In the event that Early Settlement is effected with respect to less
than all of the Purchase Contracts underlying the Units evidenced by a Unit
Certificate, upon such Early Settlement the Company shall execute and the Unit
Agent shall authenticate, execute on behalf of the Holders and deliver to the
Holder thereof, at the expense of the Company, a Unit Certificate evidencing the
Units as to which Early Settlement was not effected.

                                  ARTICLE SIX

                                   Remedies

 Section 601.  Unconditional Rights of Holders.

     Notwithstanding any other provision in this Agreement, the Holder of any
Unit shall have the right, which is absolute and unconditional but which is
subject to Section 510, to purchase Common Stock pursuant to the Purchase
Contract underlying such Unit and to receive payment of Contract Fees payable by
the Company to such Holder with respect to such Purchase Contract and, in each
such case, to institute suit for the enforcement of any such right, and such
rights shall not be impaired without the consent of such Holder.

Section 602.  Restoration of Rights and Remedies.

     If any Holder of Units has instituted any proceeding to enforce any right
or remedy under this Agreement and such proceeding has been discontinued or
abandoned for any reason, or has been determined adversely to such Holder, then
and in every such case, subject to any determination in such proceeding, the
Company and such Holder shall be restored severally and respectively to their
former positions hereunder and thereafter all rights and remedies of such Holder
shall continue as though no such proceeding had been instituted.

Section 603.  Rights and Remedies Cumulative.

     Except as otherwise provided with respect to the replacement of mutilated,
destroyed, lost or stolen Unit Certificates in the last paragraph of Section
306, no right or remedy herein conferred upon or reserved to the Holders of
Units is intended to be exclusive of any other right or remedy, and every right
and remedy shall, to the extent permitted by law, be cumulative and in addition
to every other right and remedy given hereunder or now or hereafter existing at
law or in equity or otherwise. The assertion or employment of any right or

                                      -40-
<PAGE>
 
remedy hereunder, or otherwise, shall not prevent the concurrent assertion or
employment of any other appropriate right or remedy.

Section 604.  Delay or Omission Not Waiver.

     No delay or omission of any Holder to exercise any right or remedy shall
impair any such right or remedy or constitute a waiver of any such right.  Every
right and remedy given by this Article or by law to the Holders may be exercised
from time to time, and as often as may be deemed expedient, by such Holders.

Section 605.  Undertaking for Costs.

     All parties to this Agreement agree, and each Holder of any Unit by his
acceptance of the Unit Certificate evidencing such Unit shall be deemed to have
agreed, that any court may in its discretion require, in any suit for the
enforcement of any right or remedy under this Agreement, or in any suit against
the Unit Agent for any action taken, suffered or omitted by it as Unit Agent,
the filing by any party litigant in such suit of an undertaking to pay the costs
of such suit, and that such court may in its discretion assess reasonable costs,
including reasonable attorneys' fees, against any party litigant in such suit,
having due regard to the merits and good faith of the claims or defenses made by
such party litigant; provided that the provisions of this Section shall not
apply to any suit instituted by the Company, to any suit instituted by the Unit
Agent, to any suit instituted by any Holder of Units, or group of Holders,
holding in the aggregate more than 10% of the number of Outstanding Units, or to
any suit instituted by any Holder of Units for the enforcement of payments due
in respect of Pledged Securities or Contract Fees on Purchase Contracts
underlying such Units on or after the respective due dates therefor, or for
enforcement of the right to purchase shares of Common Stock under the Purchase
Contracts constituting a part of such Units.

Section 606.  Waiver of Stay or Extension Laws.

     The Company covenants (to the extent that it may lawfully do so) that it
will not at any time insist upon, or plead, or in any manner whatsoever claim or
take the benefit or advantage of, any stay or extension law wherever enacted,
now or at any time hereafter in force, which may affect the covenants or the
performance of this Agreement; and the Company (to the extent that it may
lawfully do so) hereby expressly waives all benefit or advantage of any such law
and covenants that it will not hinder, delay or impede the execution of any
power herein granted to the Unit Agent or the Holders, but will suffer and
permit the execution of every such power as though no such law had been enacted.


                                 ARTICLE SEVEN

                                The Unit Agent

                                      -41-
<PAGE>
 
Section 701.  Certain Duties and Responsibilities.

          (a)(i) The Unit Agent undertakes to perform, with respect to the
     Units, such duties and only such duties as are specifically set forth in
     this Agreement, and no implied covenants or obligations shall be read into
     this Agreement against the Unit Agent; and

          (ii) in the absence of bad faith or negligence on its part, the Unit
     Agent may, with respect to the Units, conclusively rely, as to the truth of
     the statements and the correctness of the opinions expressed therein, upon
     certificates or opinions furnished to the Unit Agent and conforming to the
     requirements of this Agreement, but in the case of any certificates or
     opinions which by any provision hereof are specifically required to be
     furnished to the Unit Agent, the Unit Agent shall be under a duty to
     examine the same to determine whether or not they conform to the
     requirements of this Agreement.

     (b) No provision of this Agreement shall be construed to relieve the Unit
Agent from liability for its own negligent action, its own negligent failure to
act, or its own willful misconduct, except that

          (i)   this Subsection shall not be construed to limit the effect of
     Subsection (a) of this Section;

          (ii)  the Unit Agent shall not be liable for any error of judgment
     made in good faith by a Responsible Officer, unless it shall be proved that
     the Unit Agent was negligent in ascertaining the pertinent facts; and

          (iii)  no provision of this Agreement shall require the Unit Agent to
     expend or risk its own funds or otherwise incur any financial liability in
     the performance of any of its duties hereunder, or in the exercise of any
     of its rights or powers, if it shall have reasonable grounds for believing
     that repayment of such funds or adequate indemnity against such risk or
     liability is not reasonably assured to it.

     (c) Whether or not therein expressly so provided, every provision of this
Agreement relating to the conduct or affecting the liability of or affording
protection to the Unit Agent shall be subject to the provisions of this Section.

 Section 702.  Notice of Default.

                                      -42-
<PAGE>
 
     Within 90 days after the occurrence of any default by the Company
hereunder, of which a Responsible Officer of the Unit Agent has actual
knowledge, the Unit Agent shall transmit by mail to all Holders of Units, as
their names and addresses appear in the Unit Registers, notice of such default
hereunder, unless such default shall have been cured or waived.

 Section 703.  Certain Rights of Unit Agent.

     Subject to the provisions of Section 701:

          (a) the Unit Agent may rely and shall be protected in acting or
     refraining from acting upon any resolution, certificate, statement,
     instrument, opinion, report, notice, request, direction, consent, order,
     bond, debenture, note, other evidence of indebtedness or other paper or
     document believed by it to be genuine and to have been signed or presented
     by the proper party or parties;

          (b) any request or direction of the Company mentioned herein shall be
     sufficiently evidenced by an Officers' Certificate, Issuer Order or Issuer
     Request, and any resolution of the Board of Directors of the Company may be
     sufficiently evidenced by a Board Resolution;

          (c) whenever in the administration of this Agreement the Unit Agent
     shall deem it desirable that a matter be proved or established prior to
     taking, suffering or omitting any action hereunder, the Unit Agent (unless
     other evidence be herein specifically prescribed) may, in the absence of
     bad faith on its part, rely upon an Officers' Certificate of the Company;

          (d) the Unit Agent may consult with counsel and the advice of such
     counsel or any Opinion of Counsel shall be full and complete authorization
     and protection in respect of any action taken, suffered or omitted by it
     hereunder in good faith and in reliance thereon;

          (e) the Unit Agent shall not be bound to make any investigation into
     the facts or matters stated in any resolution, certificate, statement,
     instrument, opinion, report, notice, request, direction, consent, order,
     bond, debenture, note, other evidence of indebtedness or other paper or
     document, but the Unit Agent, in its discretion, may make reasonable
     further inquiry or investigation into such facts or matters related to the
     issuance of the Units and the execution, delivery and performance of the
     Purchase Contracts as it may see fit, and, if the Unit Agent shall
     determine to make such further inquiry or investigation, it shall be
     entitled to 

                                      -43-
<PAGE>
 
     examine the books, records and promises of the Company, personally or by
     agent or attorney; and

          (f)   the Unit Agent may execute any of its powers hereunder or
     perform any duties hereunder either directly or by or through agents or
     attorneys and the Unit Agent shall not be responsible for any misconduct or
     negligence on the part of any agent or attorney appointed with due care by
     it hereunder.

Section 704.  Not Responsible for Recitals or Issuance of Units.

     The recitals contained herein and in the Unit Certificates shall be taken
as the statements of the Company and the Unit Agent assumes no responsibility
for their correctness.  The Unit Agent makes no representations as to the
validity or sufficiency of this Agreement or of the Units.  The Unit Agent shall
not be accountable for the use or application by the Company of the proceeds in
respect of the Debentures or Purchase Contracts.

Section 705.  May Hold Units.

     Any Unit Registrar or any other agent of the Company, or the Unit Agent, in
its individual or any other capacity, may become the owner or pledgee of Units
and may otherwise deal with the Company with the same rights it would have if it
were not Unit Registrar or such other agent, or the Unit Agent.

Section 706.  Money Held in Trust.

     Money held by the Unit Agent in trust hereunder need not be segregated from
other funds except to the extent required by law.  The Unit Agent shall be under
no obligation to invest or pay interest on any money received by it hereunder
except as otherwise agreed with the Company.

Section 707.  Compensation and Reimbursement.

     The Company agrees:

          (a)   to pay to the Unit Agent from time to time reasonable
     compensation for all services rendered by it hereunder as the Company and
     the Unit Agent shall from time to time agree in writing;

          (b)   except as otherwise expressly provided herein, to reimburse the
     Unit Agent upon its request for all reasonable expenses, disbursements and
     advances incurred or made by the Unit Agent in accordance with any
     provision of this 

                                      -44-
<PAGE>
 
     Agreement (including the reasonable compensation and the expenses and
     disbursements of its agents and counsel), except any such expense,
     disbursement or advance as may be attributable to its negligence or bad
     faith; and

          (c)   to indemnify the Unit Agent and any predecessor Unit Agent and
     their agents for, and to hold each of them harmless against, any and all
     loss, damage, claim, liability or expense, including taxes (other than
     taxes based upon, measured by or determined by the income of the Unit
     Agent), incurred without negligence or bad faith on its part, arising out
     of or in connection with the acceptance or administration of its duties
     hereunder, including the costs and expenses of defending itself against any
     claim or liability in connection with the exercise or performance of any of
     its powers or duties hereunder.

Section 708.  Corporate Unit Agent Required; Eligibility.

     There shall at all times be an Unit Agent hereunder which shall be a
corporation organized and doing business under the laws of the United States of
America, any State thereof or the District of Columbia, authorized under such
laws to exercise corporate trust powers, having a combined capital and surplus
of at least $50,000,000, subject to supervision or examination by Federal or
State authority and having its Corporate Trust Office in the Borough of
Manhattan, The City of New York, if there be such a corporation in the Borough
of Manhattan, The City of New York qualified and eligible under this Article and
willing to act on reasonable terms.  If such corporation publishes reports of
condition at least annually, pursuant to law or to the requirements of said
supervising or examining authority, then for the purposes of this Section, the
combined capital and surplus of such corporation shall be deemed to be its
combined capital and surplus as set forth in its most recent report of condition
so published.  If at any time the Unit Agent shall cease to be eligible in
accordance with the provisions of this Section, it shall resign immediately in
the manner and with the effect hereinafter specified in this Article.

Section 709.  Resignation and Removal; Appointment of Successor.

     (a)   No resignation or removal of the Unit Agent and no appointment of a
successor Unit Agent pursuant to this Article shall become effective until the
acceptance of appointment by the successor Unit Agent in accordance with the
applicable requirements of Section 710.

     (b)   The Unit Agent may resign at any time by giving written notice
thereof to the Company 60 days prior to the effective date of such resignation.
If the instrument of acceptance by a successor Unit Agent required by 
Section 710 shall not have been delivered to the Unit Agent within 30 days after
the giving of such notice of resignation, the resigning 

                                      -45-
<PAGE>
 
Unit Agent may petition any court of competent jurisdiction for the appointment
of a successor Unit Agent.

     (c)   The Unit Agent may be removed at any time by Act of the Holders of a
majority in number of the Outstanding Units delivered to the Unit Agent and the
Company.

     (d)   If at any time

           (i)   the Unit Agent fails to comply with Section 310(b) of the TIA,
     as if the Unit Agent were an indenture trustee under an indenture qualified
     under the TIA, after written request therefor by the Company or by any
     Holder who has been a bona fide Holder of a Unit for at least six months,
     or

           (ii)  the Unit Agent shall cease to be eligible under Section 708 and
     shall fail to resign after written request therefor by the Company or by
     any such Holder, or

           (iii) the Unit Agent shall become incapable of acting or shall be
     adjudged a bankrupt or insolvent or a receiver of the Unit Agent or of its
     property shall be appointed or any public officer shall take charge or
     control of the Unit Agent or of its property or affairs for the purpose of
     rehabilitation, conservation or liquidation,

then, in any such case, (x) the Company by a Board Resolution may remove the
Unit Agent, or (y) any Holder who has been a bona fide Holder of a Unit for at
least six months may, on behalf of himself and all others similarly situated,
petition any court of competent jurisdiction for the removal of the Unit Agent
and the appointment of a successor Unit Agent.

     (e)   If the Unit Agent shall resign, be removed or become incapable of
acting, or if a vacancy shall occur in the office of Unit Agent for any cause,
the Company, by a Board Resolution, shall promptly appoint a successor Unit
Agent and shall comply with the applicable requirements of Section 710.  If no
successor Unit Agent shall have been so appointed by the Company and accepted
appointment in the manner required by Section 710, any Holder who has been a
bona fide Holder of a Unit for at least six months may, on behalf of himself and
all others similarly situated, petition any court of competent jurisdiction for
the appointment of a successor Unit Agent.

     (f)   The Company shall give, or shall cause such successor Unit Agent to
give, notice of each resignation and each removal of the Unit Agent and each
appointment of a successor Unit Agent by mailing written notice of such event by
first-class mail, postage prepaid, to all Holders of Units as their names and
addresses appear in the Unit Registers. 

                                      -46-
<PAGE>
 
Each notice shall include the name of the successor Unit Agent and the address
of its Corporate Trust Office.

Section 710.  Acceptance of Appointment by Successor.

     (a)   In case of the appointment hereunder of a successor Unit Agent, every
such successor Unit Agent so appointed shall execute, acknowledge and deliver to
the Company and to the retiring Unit Agent an instrument accepting such
appointment, and thereupon the resignation or removal of the retiring Unit Agent
shall become effective and such successor Unit Agent, without any further act,
deed or conveyance, shall become vested with all the rights, powers, agencies
and duties of the retiring Unit Agent; but, on the request of the Company or the
successor Unit Agent, such retiring Unit Agent shall, upon payment of its
charges, execute and deliver an instrument transferring to such successor Unit
Agent all the rights, powers and trusts of the retiring Unit Agent and shall
duly assign, transfer and deliver to such successor Unit Agent all property and
money held by such retiring Unit Agent hereunder.

     (b)   Upon request of any such successor Unit Agent, the Company shall
execute any and all instruments for more fully and certainly vesting in and
confirming to such successor Unit Agent all such rights, powers and agencies
referred to in paragraph (a) of this Section.

     (c)   No successor Unit Agent shall accept its appointment unless at the
time of such acceptance such successor Unit Agent shall be qualified and
eligible under this Article.

Section 711.  Merger, Conversion, Consolidation or Succession to Business.

     Any corporation into which the Unit Agent may be merged or converted or
with which it may be consolidated, or any corporation resulting from any merger,
conversion or consolidation to which the Unit Agent shall be a party, or any
corporation succeeding to all or substantially all the corporate trust business
of the Unit Agent, shall be the successor of the Unit Agent hereunder, provided
such corporation shall be otherwise qualified and eligible under this Article,
without the execution or filing of any paper or any further act on the part of
any of the parties hereto.  In case any Unit Certificates shall have been
authenticated and executed on behalf of the Holders, but not delivered, by the
Unit Agent then in office, any successor by merger, conversion or consolidation
to such Unit Agent may adopt such authentication and execution and deliver the
Unit Certificates so authenticated and executed with the same effect as if such
successor Unit Agent had itself authenticated and executed such Units.

Section 712.  Preservation of Information; Communications to Holders.

                                      -47-
<PAGE>
 
     (a)   The Unit Agent shall preserve, in as current a form as is reasonably
practicable, the names and addresses of Holders received by the Unit Agent in
its capacity as Unit Registrar.

     (b)   If three or more Holders (herein referred to as "applicants") apply
in writing to the Unit Agent, and furnish to the Unit Agent reasonable proof
that each such applicant has owned a Unit for a period of at least six months
preceding the date of such application, and such application states that the
applicants desire to communicate with other Holders with respect to their rights
under this Agreement or under the Units and is accompanied by a copy of the form
of proxy or other communication which such applicants propose to transmit, then
the Unit Agent shall, within five Business Days after the receipt of such
application, afford such applicants access to the information preserved at the
time by the Unit Agent in accordance with Section 712(a).

     (c)   Every Holder of Units, by receiving and holding the Unit Certificates
evidencing the same, agrees with the Company and the Unit Agent that none of the
Company, the Unit Agent nor any agent of any of them shall be held accountable
by reason of the disclosure of any such information as to the names and
addresses of the Holders in accordance with Section 712(b), regardless of the
source from which such information was derived.

Section 713.  No Obligations of Unit Agent.

     Except to the extent otherwise provided in this Agreement, the Unit Agent
assumes no obligations and shall not be subject to any liability under this
Agreement or any Purchase Contract or Call Option in respect of the obligations
of the Holder of any Unit thereunder. The Company agrees, and each Holder of a
Unit Certificate, by his acceptance thereof, shall be deemed to have agreed,
that the Unit Agent's execution of the Unit Certificates on behalf of the
Holders shall be solely as agent and attorney-in-fact for the Holders, and that
the Unit Agent shall have no obligation to perform such Purchase Contracts or
Call Options on behalf of the Holders, except to the extent expressly provided
in Article Five hereof.

Section 714.  Tax Compliance.

     (a)   The Unit Agent, on its own behalf and on behalf of the Company, will
comply with all applicable certification, information reporting and withholding
(including "backup" withholding) requirements imposed by applicable tax laws,
regulations or administrative practice with respect to (i) any payments made
with respect to the Units or (ii) the issuance, delivery, holding, transfer,
redemption or exercise of rights under the Units.  Such compliance shall
include, without limitation, the preparation and timely filing of 

                                      -48-
<PAGE>
 
required returns and the timely payment of all amounts required to be withheld
to the appropriate taxing authority or its designated agent.

     (b)   The Unit Agent shall comply with any direction received from the
Company with respect to the application of such requirements to particular
payments or Holders or in other particular circumstances, and may for purposes
of this Agreement rely on any such direction in accordance with the provisions
of Section 701(a)(ii) hereof.

     (c)   The Unit Agent shall maintain all appropriate records documenting 
compliance with such requirements, and shall make such records available, on
written request, to the Company or to its authorized representative within a
reasonable period of time after receipt of such request.

                                 ARTICLE EIGHT

                            Supplemental Agreements

Section 801.  Supplemental Agreements Without Consent of Holders.

     Without the consent of any Holders, the parties to any Principal Agreement,
at any time and from time to time, may enter into one or more agreements
supplemental hereto or thereto, in form satisfactory to such parties, for any of
the following purposes:

           (1)   to evidence the succession of another Person to any such party,
     and the assumption by any such successor of the covenants of such party
     herein or therein and under the Units; or

           (2)   to add to the covenants of the Company for the benefit of the
     Holders, or to surrender any right or power herein conferred upon the
     Company; or

           (3)   to evidence and provide for the acceptance of appointment
     hereunder by a successor Unit Agent; or

           (4)   to evidence the succession of another Person to the rights of
     the Call Option Holder under the Call Options, in connection with a
     transfer of such rights by the Call Option Holder to such Person; or

           (5)   to make provision with respect to the rights of Holders
     pursuant to the requirements of Section 506(b); or

                                      -49-
<PAGE>
 
           (6)   to cure any ambiguity, to correct or supplement any provisions
     herein or therein which may be inconsistent with any other provisions
     herein or therein, or to make any other provisions with respect to such
     matters or questions arising under such Principal Agreement, provided such
     action shall not adversely affect the interests of the Holders.

Section 802.  Supplemental Agreements with Consent of Holders.

     With the consent of the Holders of not less than a majority of the
Outstanding Units (or, with respect to modifications that adversely affect only
the Holders of Normal Units or only the Holders of Stripped Units, with the
consent of the Holders of not less than a majority of the Outstanding Units that
comprise Normal Units or Stripped Units, as the case may be), by Act of said
Holders delivered to the parties to any Principal Agreement, such parties (when
authorized, in the case of the Company, by a Board Resolution) may enter into an
agreement or agreements supplemental to such Principal Agreement for the purpose
of modifying in any manner the terms of the Units, or the provisions of such
Principal Agreement or the rights of the Holders in respect of the Units;
provided, however, that no such supplemental agreement shall, without the
consent of the Holder of each Outstanding Unit affected thereby,

           (1)   change any payment date;

           (2)   change the amount or type of Pledged Securities underlying a
     Unit, impair the right of the Holder of any Unit to receive distributions
     or interest payments on the underlying Pledged Securities or otherwise
     adversely affect the Holder's rights in or to such Pledged Securities
     (including the rights of Holders of Normal Units to effect a Stripped Unit
     Creation);

           (3)   reduce the Contract Fees or other amounts receivable by Holders
     in respect of Units or increase other amounts payable by Holders in respect
     of Units or change any place where, or the coin or currency in which, any
     Contract Fees or other amounts receivable or payable in respect of Units
     are payable;

           (4)   impair the right to institute suit for the enforcement of any
     Purchase Contract;

           (5)   reduce the number of shares of Common Stock to be purchased
     pursuant to any Purchase Contract, increase the price to purchase shares of
     Common Stock upon settlement of any Purchase Contract, change the Stock
     Purchase Date or otherwise adversely affect the Holder's rights under any
     Purchase Contract; or

                                      -50-
<PAGE>
 
           (6)   reduce the amount payable on exercise of any Call Option,
     extend the Call Option Expiration Date (as defined in the Call Option
     Agreement) or otherwise adversely affect any Holder's rights under any Call
     Option; or

           (7)   reduce the percentage of the Outstanding Units the consent of
     whose Holders is required for any such supplemental agreement.

     It shall not be necessary for any Act of Holders under this Section to
approve the particular form of any proposed supplemental agreement, but it shall
be sufficient if such Act shall approve the substance thereof.

     The Company may, but shall not be obligated to, fix a record date for the
purpose of determining the Persons entitled to consent to any supplemental
agreement to any Principal Agreement.  If a record date is fixed, the Holders on
such record date, or their duly designated proxies, and only such Persons, shall
be entitled to consent to such supplemental agreement, whether or not such
Holders remain Holders after such record date; provided, that unless such
consent shall have become effective by virtue of the requisite percentage having
been obtained prior to the date which is 90 days after such record date, any
such consent previously given shall automatically and without further action by
any Holder be cancelled and of no further effect.

Section 803.  Execution of Supplemental Agreements.

     In executing, or accepting the additional agencies created by, any
supplemental agreement permitted by this Article or the modifications thereby of
the agencies created by the Principal Agreements, the Unit Agent shall be
entitled to receive and (subject to Section 701) shall be fully protected in
relying upon, an Opinion of Counsel stating that the execution of such
supplemental agreement is authorized or permitted by this Agreement. The Unit
Agent may, but shall not be obligated to, enter into any such supplemental
agreement which affects the Unit Agent's own rights, duties or immunities under
this Agreement or otherwise.

Section 804.  Effect of Supplemental Agreements.

     Upon the execution of any supplemental agreement under this Article, the
relevant Principal Agreement shall be modified in accordance therewith, and such
supplemental agreement shall form a part of such Principal Agreement for all
purposes; and every Holder of Unit Certificates theretofore or thereafter
authenticated, executed on behalf of the Holder and delivered hereunder shall be
bound thereby.

Section 805.  Reference to Supplemental Agreements.

                                      -51-
<PAGE>
 
     Unit Certificates authenticated, executed on behalf of the Holders and
delivered after the execution of any supplemental agreement pursuant to this
Article may, and shall if required by the Unit Agent, bear a notation in form
approved by the Unit Agent as to any matter provided for in such supplemental
agreement.  If the Company shall so determine, new Unit Certificates so modified
as to conform, in the opinion of the Unit Agent and the Company, to any such
supplemental agreement may be prepared and executed by the Company and
authenticated, executed on behalf of the Holders and delivered by the Unit Agent
in exchange for Outstanding Unit Certificates evidencing the same number of
Normal Units or Stripped Units, as the case may be.

                                  ARTICLE NINE

                   Consolidation, Merger, Sale or Conveyance

Section 901.  Covenant Not to Merge, Consolidate, Sell or Convey Property
              Except Under Certain Conditions.

     The Company covenants that it will not merge or consolidate with any other
Person or sell or convey all or substantially all of its assets to any Person,
except that the Company may merge or consolidate with, or sell or convey all or
substantially all of its assets to, any other Person, provided that (a) the
Company shall be the continuing corporation, or the successor (if other than the
Company) shall be a corporation organized and existing under the laws of the
United States of America or a State thereof and such corporation shall assume
the obligations of the Company under the Purchase Contracts and the Pledge
Agreement by one or more supplemental agreements in form satisfactory to the
Unit Agent and, in the case of the Pledge Agreement, the Collateral Agent,
executed and delivered to the Unit Agent, and, in the case of the Pledge
Agreement, the Collateral Agent by such corporation, and (b) the Company or such
successor corporation, as the case may be, shall not, immediately after such
merger or consolidation, or such sale or conveyance, be in default in the
performance of any covenant or condition under any Principal Agreement or under
any of the Units.

Section 902.  Rights and Duties of Successor Corporation.

     In case of any such consolidation, merger, sale or conveyance and upon any
such assumption by the successor corporation, such successor corporation shall
succeed to and be substituted for the Company with the same effect as if it had
been named in the Principal Agreements as the Company.  Such successor
corporation thereupon may cause to be signed, and may issue either in its own
name or in the name of Monsanto Company, any or all of the Unit Certificates
evidencing Units issuable hereunder which theretofore shall not have been 

                                      -52-
<PAGE>
 
signed by the Company and delivered to the Unit Agent; and, upon the order of
such successor corporation, instead of the Company, and subject to all the
terms, conditions and limitations in this Agreement prescribed, the Unit Agent
shall authenticate and execute on behalf of the Holders and deliver any Unit
Certificates which previously shall have been signed and delivered by the
officers of the Company to the Unit Agent for authentication and execution, and
any Unit Certificate evidencing Units which such successor corporation
thereafter shall cause to be signed and delivered to the Unit Agent for that
purpose. All the Unit Certificates so issued shall in all respects have the same
legal rank and benefit under this Agreement as the Unit Certificates theretofore
or thereafter issued in accordance with the terms of this Agreement as though
all of such Unit Certificates had been issued at the date of the execution
hereof.

     In case of any such consolidation, merger, sale or conveyance such change
in phraseology and form (but not in substance) may be made in the Unit
Certificates evidencing Units thereafter to be issued as may be appropriate.

Section 903.  Opinion of Counsel to Unit Agent.

     The Unit Agent, subject to Sections 701 and 703, may receive an Opinion of
Counsel as conclusive evidence that any such consolidation, merger, sale or
conveyance, and any such assumption, complies with the provisions of this
Article.

                                  ARTICLE TEN

                                   Covenants

Section 1001.  Performance Under Purchase Contracts.

     The Company covenants and agrees for the benefit of the Holders from time
to time of the Units that it will duly and punctually perform its obligations
under the Purchase Contracts in accordance with the terms of the Purchase
Contracts and this Agreement.

Section 1002.  Maintenance of Office or Agency.

     The Company will maintain in the Borough of Manhattan, The City of New York
an office or agency where Unit Certificates may be presented or surrendered for
acquisition of shares of Common Stock upon settlement and for transfer of
Pledged Securities upon occurrence of a Termination Event, where Unit
Certificates may be surrendered for registration of transfer or exchange or
for effecting Stripped Unit Creations, where payment of Contract Fees payable by
the Company to the Holders may be made and where notices and demands to or upon
the Company in respect of the Units and this Agreement may be served. 

                                      -53-
<PAGE>
 
The Company will give prompt written notice to the Unit Agent of the location,
and any change in the location, of such office or agency. If at any time the
Company shall fail to maintain any such required office or agency or shall fail
to furnish the Unit Agent with the address thereof, such presentations,
surrenders, notices and demands may be made or served at the Corporate Trust
Office, and the Company hereby appoints the Unit Agent as its agent to receive
all such presentations, surrenders, notices and demands.

     The Company may also from time to time designate one or more other offices
or agencies where Unit Certificates may be presented or surrendered for any or
all such purposes and may from time to time rescind such designations; provided,
however, that no such designation or rescission shall in any manner relieve the
Company of its obligation to maintain an office or agency in the Borough of
Manhattan, The City of New York for such purposes.  The Company will give prompt
written notice to the Unit Agent of any such designation or rescission and of
any change in the location of any such other office or agency.  The Company
hereby designates as the place of payment for the Units the Corporate Trust
Office and appoints the Unit Agent at its Corporate Trust Office as paying agent
in such city.

Section 1003.  Company to Reserve Common Stock.

     The Company shall at all times prior to the Stock Purchase Date reserve and
keep available, free from preemptive rights, out of its authorized but unissued
Common Stock the full number of shares of Common Stock issuable against tender
of payment in respect of all Purchase Contracts underlying the Units.

Section 1004.  Covenants as to Common Stock.

     The Company covenants that all shares of Common Stock which may be issued
against tender of payment in respect of the Purchase Contracts underlying the
Units will, upon issuance, be newly issued (i.e., not issued out of treasury
shares) and be duly authorized, validly issued, fully paid and nonassessable.

Section 1005.  Statements of Officers of the Company as to Default.

     The Company will deliver to the Unit Agent, on or before May 1 in each year
(beginning the first May 1 after the date of the original issuance of the Units
hereunder) a brief certificate from the principal executive, financial or
accounting officer of the Company stating that in the course of the performance
by the signer of his or her duties as an officer of the Company he or she would
normally have knowledge of any default or non-compliance by the Company in the
performance of any covenants or conditions contained in this Agreement, stating
whether or not he or she has knowledge of any such default or non-

                                      -54-
<PAGE>
 
compliance and, if so, specifying each such default or non-compliance of which
the signer has knowledge and the nature thereof. For purposes of this Section
1005, non-compliance or default shall be determined without regard to any grace
period or requirement of notice.

                                      -55-
<PAGE>
 
     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the day and year first above written.

                                     MONSANTO COMPANY



                                     By:
                                        -------------------------------
 


                                     FIRST NATIONAL BANK OF CHICAGO,
                                     as Unit Agent
    


                                     By:
                                        -------------------------------

                                      A-1
 

<PAGE>
 
                                                                       EXHIBIT 9


           =========================================================




                             GOLDMAN, SACHS & CO.,

                             as Call Option Holder

                                      AND

                        FIRST NATIONAL BANK OF CHICAGO,

                     as Unit Agent and as Attorney-In-Fact

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

                             CALL OPTION AGREEMENT

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


                         Dated as of November __, 1998




           =========================================================
<PAGE>
 
                             CALL OPTION AGREEMENT


          CALL OPTION AGREEMENT, dated as of November __, 1998, between GOLDMAN,
SACHS & CO., as Call Option Holder, and FIRST NATIONAL BANK OF CHICAGO, as Unit
Agent and as attorney-in-fact of the Holders from time to time of the Normal
Units.


                                   RECITALS


          Monsanto Company and the Unit Agent are parties to the Master Unit
Agreement, dated as the date hereof (as the same may be supplemented or amended
in accordance with the terms thereof, the "Master Unit Agreement").  The Master
Unit Agreement contemplates that the Company will issue Debentures, and that
Debentures will underlie Normal Units outstanding from time to time thereunder.

          It is intended that the Holders from time to time of the Normal Units
grant Call Options entitling the Call Option Holder to acquire the Debentures
underlying the related Normal Units on the terms and subject to the conditions
set forth herein.  Pursuant to the terms of the Principal Agreements and the
Unit Certificates for the Normal Units, the Holders from time to time of the
Normal Units irrevocably authorize the Unit Agent, as attorney-in-fact of such
Holders, to enter into such Call Options and execute and deliver this Agreement
on behalf of such Holders.

          Accordingly, the Call Option Holder and the Unit Agent, on its own
behalf and as attorney-in-fact of the Holders from time to time of the Normal
Units, agree as follows:


                                  ARTICLE ONE

                                  Definitions

          Section 1.  Definitions.  For all purposes of this Agreement, except
as otherwise expressly provided or unless the context otherwise requires:

          (a)   capitalized terms used herein and not defined are used herein as
     defined in the Master Unit Agreement; and
<PAGE>
 
          (b)   the words "herein", "hereof" and "hereunder" and other words of
     similar import refer to this Agreement as a whole and not to any particular
     Article, Section or other subdivision.

          "Aggregate Call Option Exercise Consideration" means consideration
     comprised of:

          (a)   Treasury Securities that through their scheduled payments will
                generate by each Quarterly Payment Date falling after the Call
                Settlement Date and on or before the Stock Purchase Date an
                amount of cash equal to the aggregate interest payments that are
                scheduled to be payable in respect of the Debentures underlying
                the Normal Units on such Quarterly Payment Date (assuming for
                this purpose, even if not true, that (i) no distributions or
                interest payments will then have been deferred and (ii) that the
                rate of interest on the Debentures remains at ____%);

          (b)   Treasury Securities that through their scheduled payments will
                generate by the Stock Purchase Date an amount of cash equal to
                the aggregate Stated Amount of the Normal Units; and
 
          (c)   if the Company is, at the Call Settlement Date, deferring
                interest payments on the Debentures, an amount in cash equal to
                (i) the aggregate unpaid  interest payments on the Debentures
                underlying the Normal Units accrued to the Call Settlement Date,
                if the Call Settlement Date is a Quarterly Payment Date, or (ii)
                the aggregate unpaid interest payments on the Debentures
                underlying the Normal Units accrued to the Quarterly Payment
                Date immediately preceding the Call Settlement Date plus
                interest thereon at the Deferral Rate for the period from and
                including such Quarterly Payment Date to but excluding such Call
                Settlement Date (computed on the basis of a 360-day year of
                twelve 30-day months), if the Call Settlement Date is not a
                Quarterly Payment Date.

          "Call Option Expiration Date" means _________________ (or, if such
     date is not a Business Day, the next succeeding Business Day).


                                  ARTICLE TWO

                                  Call Option

                                      -2-
<PAGE>
 
          Section 2.1  Grant.  The Unit Agent, on behalf of and as attorney-in-
fact for the Holders from time to time of the Normal Units, hereby grants the
Call Options to the Call Option Holder on the terms and subject to the
conditions set forth herein.

          Section 2.2  Consideration.  As consideration for such Call Options,
concurrently with the execution hereof, the Call Option Holder is paying to the
underwriters under the Underwriting Agreement (who are acting in this regard on
behalf of the initial investors in the Normal Units) an amount equal to ________
per Call Option.

          Section 2.3  Expiration or Termination of Call Options.  The Call
Options shall be irrevocable, but the Call Options and the rights of the Call
Option Holder and the obligations of the Holders of Normal Units thereunder
shall (a) expire on the Call Option Expiration Date if the Call Settlement Date
has not occurred on or prior to such date and (b) automatically terminate upon
the occurrence of a Termination Event.


                                 ARTICLE THREE

                            Exercise of Call Options


          Section 3.1  Exercise Mechanics.



          (a)  The Call Option Holder may exercise all (but not less than all)
the Call Options by (i) delivering to the Unit Agent and the Collateral Agent,
on or prior to the Call Option Expiration Date, a notice, substantially in the
form set forth in Annex A attached hereto, stating that the Call Option Holder
is exercising its Call Options and specifying the Call Settlement Date therefor
(which must be a Business Day falling on or before the Call Option Expiration
Date) and (ii) delivering to the Collateral Agent, by Noon, New York City time,
on the Call Settlement Date, the Aggregate Call Option Exercise Consideration.

          (b)  Pursuant to the Pledge Agreement, upon receipt by the Collateral
Agent of the Aggregate Call Option Exercise Consideration in the manner
contemplated hereby and by the Pledge Agreement, the Collateral Agent shall
release the Debentures underlying the Normal Units, free and clear of any lien,
pledge or security interest created by the Pledge Agreement, and transfer such
released Debentures to the Call Option Holder or its designee as specified in
the notice referred to in Section 3.1(a) above.

          (c)  The Unit Agent shall, not later than three Business Days
following the Call Settlement Date, mail notice of the exercise of the Call
Options to the Holders of Normal Units in the manner prescribed by the Master
Unit Agreement.

                                      -3-
<PAGE>
 
                                 ARTICLE FOUR

                                 Miscellaneous


     4.1 Amendments.  This Agreement may be amended in the manner set forth in
Section 801 of the Master Unit Agreement with respect to supplemental
agreements.

     4.2  Governing Law.  THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO CONFLICTS
OF LAWS PRINCIPLES THEREOF.  The Call Option Holder, the Unit Agent and the
Holders from time to time of the Normal Units, acting through the Unit Agent as
their attorney-in-fact, hereby submit to the nonexclusive jurisdiction of the
United States District Court for the Southern District of New York and of any
New York state court sitting in New York City for the purposes of all legal
proceedings arising out of or relating to this Agreement or the transactions
contemplated hereby.  The Call Option Holder, the Unit Agent and the Holders
from time to time of the Normal Units, acting through the Unit Agent as their
attorney-in-fact, irrevocably waive, to the fullest extent permitted by
applicable law, any objection which they may now or hereafter have to the laying
of the venue of any such proceeding brought in such a court and any claim that
any such proceeding brought in such a court has been brought in an inconvenient
forum.

     4.3  Notices.  All notices, requests, consents and other communications
provided for herein (including, without limitation, any modifications of, or
waivers or consents under, this Agreement) shall be given or made in writing
(including, without limitation, by telecopy) delivered to the intended recipient
at the "Address for Notices" specified below its name on the signature pages
hereof or, as to any party, at such other address as shall be designated by such
party in a notice to the other party.  Except as otherwise provided in this
Agreement, all such communications shall be deemed to have been duly given when
transmitted by telecopier or personally delivered or, in the case of a mailed
notice, upon receipt, in each case given or addressed as aforesaid.

     4.4  Successors and Assigns.  This Agreement shall be binding upon and
inure to the benefit of the respective successors and assigns of the Call Option
Holder and the Unit Agent, and the Holders from time to time of the Normal
Units, by their acceptance of the same, shall be deemed to have agreed to be
bound by the provisions hereof and to have ratified the agreements of, and the
grant of the Call Options hereunder by, the Unit Agent.

     4.5  Counterparts.  This Agreement may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
instrument, and any of the parties hereto may execute this Agreement by signing
any such counterpart.

                                      -4-
<PAGE>
 
     4.6  Severability.  If any provision hereof is invalid or unenforceable in
any jurisdiction, then, to the fullest extent permitted by law, (a) the other
provisions hereof shall remain in full force and effect in such jurisdiction and
shall be liberally construed in order to carry out the intentions of the parties
hereto as nearly as may be possible and (b) the invalidity or unenforceability
of any provision hereof in any jurisdiction shall not affect the validity or
enforceability of such provision in any other jurisdiction.

                                      -5-
<PAGE>
 
     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the day and year first above written.

                                  GOLDMAN, SACHS & CO.,
                                  as Call Option Holder


                                  ----------------------------
                                    (Goldman, Sachs & Co.)

                                  Address for Notices:

                                  85 Broad Street
                                  New York, New York  10004
                                  Attention:  Registration Department



                                  FIRST NATIONAL BANK OF CHICAGO,
                                  as Unit Agent and as attorney-in-fact of the 
                                  Holders from time to time of the Normal Units

                                  By:
                                     -------------------------------------------
                                     Name:
                                     Title:

                                  Address for Notices:
<PAGE>
 
                                EXERCISE NOTICE


          Reference is made to the Call Option Agreement, dated as of 
November __, 1998 (the "Call Option Agreement"), between Goldman, Sachs & Co.,
as Call Option Holder, and First National Bank of Chicago, as Unit Agent and
attorney-in-fact of the Holders from time to time of the Normal Units.
Capitalized terms used herein but not defined are used herein as defined in the
Call Option Agreement.

          The undersigned hereby exercises all of the Call Options underlying
the Normal Units and specifies ____________________ as the Call Settlement Date.
Certificates representing the Debentures underlying the  Normal Units should be
registered in the name of ______________________________ and delivered to
[insert address].


                                      GOLDMAN, SACHS & CO.,
                                      As Call Option Holder




                                      (Goldman, Sachs & Co.)



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

                                      A-1

<PAGE>
 
                                                                      EXHIBIT 10

================================================================================



                                MONSANTO COMPANY

                             GOLDMAN, SACHS & CO.,
                             as Call Option Holder

                           FIRST UNION NATIONAL BANK
                as Collateral Agent and Securities Intermediary

                                      AND

                         FIRST NATIONAL BANK OF CHICAGO
                     as Unit Agent and as Attorney-In-Fact


                                 --------------
                                PLEDGE AGREEMENT
                                 --------------


                         Dated as of November __, 1998


================================================================================
<PAGE>
 
                                PLEDGE AGREEMENT

     PLEDGE AGREEMENT, dated as of November __, 1998, among MONSANTO COMPANY, a
Delaware corporation (the "Company", as such term is more fully defined in the
Master Unit Agreement referred to below), GOLDMAN, SACHS & CO., as Call Option
Holder, FIRST UNION NATIONAL BANK, as Collateral Agent and in its capacity as a
"securities intermediary" as defined in Section 8-102(a)(14) of the Code (as
defined herein) (in such capacity, the "Securities Intermediary"), and FIRST
NATIONAL BANK OF CHICAGO, as Unit Agent and as attorney-in-fact of the Holders
from time to time of the Units.


                                    RECITALS

     The Company and the Unit Agent are parties to the Master Unit Agreement,
dated as of the date hereof (as the same may be supplemented or amended from
time to time in accordance with the terms thereof, the "Master Unit Agreement").
The Master Unit Agreement contemplates that the Debentures or Treasury
Securities that from time to time underlie the Units be pledged to the
Collateral Agent to secure the obligations of the Holders of Units under the
Purchase Contracts and Call Options that underlie such Units.

     Pursuant to the terms of the Principal Agreements and the Unit
Certificates, the Holders from time to time of the Units irrevocably authorize
the Unit Agent, as attorney-in-fact of such Holders,  to execute and deliver
this Agreement on behalf of such Holders and to grant the pledge provided hereby
of the Pledged Securities underlying such Units as provided herein and subject
to the terms hereof.

     Accordingly, the Company, the Call Option Holder, the Collateral Agent and
the Unit Agent, in its capacity as Unit Agent and as attorney-in-fact of the
Holders from time to time of the Units, agree as follows:

     Section 1.  Definitions.  For all purposes of this Agreement, except as
otherwise expressly provided or unless the context otherwise requires:

          (a) capitalized terms used herein and not defined are used herein as
     defined in the Master Unit Agreement;

          (b) the words "herein", "hereof" and "hereunder" and other words of
     similar import refer to this Agreement as a whole and not to any particular
     Article, Section or other subdivision; and
<PAGE>
 
          (c) all other terms contained herein shall, unless the context
     indicates otherwise, have the meanings assigned to such terms by the Code
     (as defined herein) to the extent the same are defined therein.

     "Aggregate Call Option Exercise Consideration" has the meaning specified in
the Call Option Agreement.

     "Agreement" means this instrument as originally executed or as it may from
time to time be supplemented or amended by one or more agreements supplemental
hereto entered into pursuant to the applicable provisions hereof.

     "Applicable Treasury Regulations" means Part 357 of Title 31 of the Code of
Federal Regulations (31 CFR (S)(S) 357 et seq.) and any other regulations of the
United States Treasury Department from time to time applicable to the transfer
or pledge of book-entry Treasury Securities.

     "Code" has the meaning specified in Section 2 hereof.

     "Collateral" has the meaning specified in Section 2 hereof.

     "Collateral Account" means the trust account (number [______]) maintained
at [__________________] in the name of "[____________________], as Collateral
Agent".

     "Date of Deemed Receipt" means, with respect to any payment received by the
Collateral Agent, the date of receipt thereof; provided, however, that if such
payment is received on a date which is not a Quarterly Payment Date and is not
either a payment in respect of defaulted interest on Debentures or a payment
comprising a part of the Aggregate Call Option Exercise Consideration,  "Date of
Deemed Receipt" means, with respect to such payment, the Quarterly Payment Date
next succeeding such date of receipt.

     "Pledged Securities" means all Debentures constituting a part of the Units
and any Treasury Securities delivered in exchange for Debentures in accordance
with Section 5(b) and (c) hereof (or securities entitlements thereto) in each
case that have been delivered to the Collateral Agent and not released by the
Collateral Agent to the Unit Agent under the provisions of this Agreement.

     "Proceeds" means all interest, dividends, cash, instruments, securities,
financial assets (as defined in Article 8 of the Code) and other property and
proceeds from time to time received, receivable or otherwise distributed in
respect of or in exchange for any or all of the Pledged Securities.
<PAGE>
 
     Section 2.  The Pledge.  The Holders from time to time of the Units acting
through the Unit Agent, as their attorney-in-fact, hereby pledge to the
Collateral Agent (for the benefit of the Company and the Call Option Holder as
their interests may appear), and grant to the Collateral Agent, for the benefit
of the Company and the Call Option Holder (as their interests may appear) a
security interest in all of the right, title and interest of such Holders in and
to (i) the Pledged Securities, (ii) the Collateral Account and all securities,
financial assets and other property credited thereto and all security
entitlements related thereto and (iii) all proceeds from each of the foregoing
(collectively, the "Collateral"), as collateral security to ensure the
performance when due by such Holders of their respective obligations under the
Purchase Contracts and Call Options underlying such Units.  Concurrently with
the execution of this Agreement, the initial Holders of the first
[__________________] Normal Units issued under the Master Unit Agreement, the
Unit Agent and the Collateral Agent are causing [____________] Debentures to be
delivered to, and registered in the name of, the Collateral Agent, and such
Debentures will thereupon constitute Pledged Securities forming a part of such
Normal Units.  As used in this Section 2, the term "delivery" shall have the
meaning ascribed to it in the Uniform Commercial Code as in effect in the State
of New York (the "Code").  In the event that any or all of the additional
[__________] Normal Units that may be issued as a result of an exercise of the
overallotment option of the underwriters under the Underwriting Agreement are
issued pursuant to the Master Unit Agreement at or after the execution of this
Agreement, the initial Holders of such Normal Units, the Unit Agent and the
Collateral Agent shall cause a number of Debentures equal to the number of such
Normal Units to be delivered to, and registered in the name of, the Collateral
Agent, and such Debentures will thereupon constitute Pledged Securities forming
a part of such Normal Units. In addition, the execution hereof by the Unit Agent
and the Collateral Agent shall constitute an acknowledgment by the Collateral
Agent and Securities Intermediary of the Pledge and of the Securities
Intermediary's holding of such Debentures or other Pledged Securities
substituted therefor in accordance with the provisions hereof subject to the
Pledge and of the Securities Intermediary's crediting such Debentures or other
Pledged Securities to the Collateral Account for purposes of perfecting the
Pledge under applicable law, including, to the extent applicable, the Uniform
Commercial Code as adopted and in effect in any applicable jurisdiction and the
Applicable Treasury Regulations.  Subject to the Pledge, the Holders from time
to time of the Units shall have full beneficial ownership of the Pledged
Securities underlying such Units, and shall be entitled (directly or through the
Collateral Agent) to all of the rights provided by such Pledged Securities, and
the Company and the Call Option Holder shall have no rights with respect to such
Pledged Securities other than their respective security interests therein.

     Section 3.  Payments in Respect of the Pledged Securities.  Any payment
received by the Collateral Agent in respect of the Pledged Securities underlying
any Normal Units or Stripped Units shall be paid by the Collateral Agent, by
wire transfer in same day funds no 

                                      -3-
<PAGE>
 
later than [1:00 p.m.], New York City time, on the Date of Deemed Receipt (or,
if the Date of Deemed Receipt is not a Business Day or if such payment is
received by the Collateral Agent after noon, New York City time, on the Date of
Deemed Receipt, then such payment shall be made by the Collateral Agent no later
than [10:00 a.m.], New York City time, on the next succeeding Business Day), as
follows:

          (a) in the case of payments not scheduled to fall on and that are not
     in respect of amounts due on the Stock Purchase Date or Early Settlement
     Date, as applicable, to the Unit Agent, to the account designated by it for
     payments in respect of Normal Units or the account designated by it for
     payments in respect of Stripped Units, as the case may be; and

          (b) in the case of payments scheduled to fall on or that are in
     respect of amounts due on the Stock Purchase Date or Early Settlement Date,
     as applicable, (i) with respect to payments received in respect of Units
     which are Paid Units (as specified in the notice from the Unit Agent
     referred to in Section 4), to the Unit Agent, to the account designated by
     it for payments in respect of Paid Units which are Normal Units or the
     account designated by it for payments in respect of Paid Units which are
     Stripped Units, as the case may be; and (ii) with respect to payments
     received in respect of Units which are Unpaid Units (as specified in the
     notice from the Unit Agent referred to in Section 4), (x) first, to the
     Company, to the account designated by it for such purpose, in an amount
     equal to the aggregate amount payable to the Company in respect of such
     Unpaid Units, and (y) second, to the extent of any amount remaining after
     the payment (if any) referred to in (x) above, to the Unit Agent, to the
     account designated by it for payments in respect of Unpaid Units which are
     Normal Units; provided, however, that if the Company disputes the notice
     from the Unit Agent referred to in Section 4 and notifies the Collateral
     Agent in writing, prior to noon, New York City time, on the Stock Purchase
     Date or Early Settlement Date, as applicable, that the number of Paid Units
     or the number of Unpaid Units (or both) is different from that indicated in
     such notice, the foregoing payments with respect to any Paid Units or
     Unpaid Units subject to dispute shall not be paid until such dispute is
     resolved.

          All payments received by the Unit Agent as provided herein shall be
applied by the Unit Agent pursuant to the provisions of the Master Unit
Agreement.

     Section 4.  Notice with Respect to Numbers of Paid Units and Unpaid Units;
Exercise of Debenture Put Options with Respect to Unpaid Units.  By [11:00
a.m.], New York City time, on the Stock Purchase Date or Early Settlement Date,
as applicable, the Unit Agent shall, as provided in the Master Unit Agreement,
notify the Company and the Collateral Agent as to the number of Normal Units and
the number of Stripped Units, respectively, which are Paid Units and the number
of Normal Units and the number of Stripped Units, 

                                      -4-
<PAGE>
 
respectively, which are Unpaid Units. Promptly after receiving such
notification, the Collateral Agent, on behalf of such Holder, shall, as Put
Agent, exercise the Debenture Put Option with respect thereto. The payment
received by the Collateral Agent from the exercise of any Debenture Put Option
shall then be applied by the Collateral Agent in accordance with Section 3(b).

     Section 5.  Release and Substitution of Pledged Securities.  (a)  Upon
notice to the Collateral Agent by the Company or the Unit Agent that there has
occurred a Termination Event, the Collateral Agent shall release all Pledged
Securities from the Pledge and shall transfer, without recourse, such released
Pledged Securities, free and clear of any lien, pledge or security interest
created hereby, to the Unit Agent for delivery by the Unit Agent pursuant to the
provisions of the Master Unit Agreement.

     (b) Upon notice to the Collateral Agent by the Call Option Holder that the
Call Option Holder is exercising the Call Options in accordance with the terms
of the Call Option Agreement with respect to the Debentures underlying the
Normal Units, provided that the Collateral Agent receives the requisite
Aggregate Call Option Exercise Consideration on the Call Settlement Date
specified in such notice, the Collateral Agent shall release such Debentures
from the Pledge and transfer, without recourse, such released Debentures, free
and clear of any lien, pledge or security interest created hereby, to the Call
Option Holder or its designee as specified in such notice, whereupon (i) the
Treasury Securities constituting all or a part of the Aggregate Call Option
Exercise Consideration so received by the Collateral Agent shall be subject to
the Pledge with respect to the Normal Units and (ii) the Pledge shall cease to
constitute a security interest for the benefit of the Call Option Holder.

     (c) In connection with a Stripped Unit Creation, upon request by the Unit
Agent to the Collateral Agent to release the then Pledged Securities underlying
the number of Normal Units indicated in such request, provided that the
Collateral Agent has received (i) the Treasury Securities and cash required by
Section 309(a)(i) of the Master Unit Agreement for a Stripped Unit Creation
relating to such Normal Units and (ii) if the Call Options underlying such
Normal Units remain exercisable on the date of receipt of such instruction, an
instrument from the Call Option Holder releasing its security interest in the
Pledged Securities underlying such Normal Units and agreeing that such Call
Options no longer underlie such Normal Units (or the Stripped Units they
become), the Collateral Agent shall release such Pledged Securities from the
Pledge and transfer, without recourse, such released Pledged Securities, free
and clear of any lien, pledge or security interest created hereby, to the Unit
Agent for delivery by the Unit Agent pursuant to the provisions of the Master
Unit Agreement, whereupon the Treasury Securities so received by the Collateral
Agent in connection with such Stripped Unit Creation shall be subject to the
Pledge and constitute the Pledged Securities underlying the Stripped Units so
created.

                                      -5-
<PAGE>
 
     (d) In connection with the delivery to the Collateral Agent of Treasury
Securities pursuant to Section 5(b) or (c), such delivery shall be by Federal
Reserve Bank-Wire to the account of the Securities Intermediary designated by it
for such purpose, and the Securities Intermediary and the Call Option Holder or
transferring Holder of Normal Units, as the case may be, shall take appropriate
action (i) so that the applicable Federal Reserve Bank through which such
Treasury Securities have been purchased will reflect such transfer and the
Securities Intermediary shall credit a security entitlement with respect to such
Treasury Securities in the Collateral Account in accordance with Applicable
Treasury Regulations and (ii) as may be required to perfect the Pledge under
Applicable Treasury Regulations and applicable law.

     (e) On the Stock Purchase Date or Early Settlement Date, as applicable, the
Collateral Agent shall release the Debentures underlying Units which are Paid
Units (as specified in the notice from the Unit Agent referred to in Section 4)
from the Pledge and transfer, without recourse, such released Debentures, free
and clear of any lien, pledge or security interest created hereby, to the Unit
Agent for delivery pursuant to the provisions of the Master Unit Agreement;
provided, however, that if the Company disputes the notice from the Unit Agent
referred to in Section 4 and notifies the Collateral Agent, prior to noon, New
York City time, on the Stock Purchase Date or Early Settlement Date, as
applicable, that the number of Paid Units is different from that indicated in
such notice, the foregoing release with respect to any Paid Units subject to
dispute shall not be made until such dispute is resolved.

     Section 6.  Rights and Remedies.  (a) The Collateral Agent shall have all
of the rights and remedies with respect to the Collateral of a secured party
under the Code (whether or not said Code is in effect in the jurisdiction where
the rights and remedies are asserted) and, with respect to Pledged Securities
which are Treasury Securities, the Applicable Treasury Regulations, and such
additional rights and remedies to which a secured party is entitled under the
laws in effect in any jurisdiction where any rights and remedies hereunder may
be asserted.

     (b) Without limiting any rights or powers otherwise granted by this
Agreement to the Collateral Agent, in the event the Collateral Agent is unable
to make payments due to the Company pursuant to the Purchase Contracts
underlying any Units, the Collateral Agent shall have and shall exercise, upon
the written direction of the Company and, if the Call Options are outstanding,
the Call Option Holder, with reference to the Pledged Securities underlying such
Units and the obligations of the Holders of such Units, any and all of the
rights and remedies available to a secured party under the Code and the
Applicable Treasury Regulations after default by a debtor, and as otherwise
granted herein or under any other law.

                                      -6-
<PAGE>
 
     (c) Without limiting any rights or powers otherwise granted by this
Agreement to the Collateral Agent, the Collateral Agent is hereby irrevocably
authorized to receive and collect all payments of principal of or distributions
or interest on the Pledged Securities, in each case subject to the provisions
hereof.

     (d) The Unit Agent, the Call Option Holder and each Holder of  Units agree
that, from time to time, upon the written request of the Collateral Agent, the
Unit Agent, the Call Option Holder or such Holder of Units shall execute and
deliver such further documents and do such other acts and things as the
Collateral Agent may reasonably request in order to maintain the Pledge, and the
perfection and priority thereof, and to confirm the rights of the Collateral
Agent hereunder.

     Section 7.  The Collateral Agent.  The Collateral Agent, the Company and
the Call Option Holder hereby agree among themselves as follows (it being
understood and agreed that, except as provided in Section 7.08, neither the Unit
Agent nor any Holder of Units shall have any rights or duties under this Section
7):

     7.01  Appointment, Powers and Immunities.  The Collateral Agent shall act
hereunder as agent for the Company and the Call Option Holder, with such powers
as are specifically vested in the Collateral Agent by the terms of this
Agreement, together with such other powers as are reasonably incidental thereto.
The Collateral Agent:  (a) shall have no duties or responsibilities except those
expressly set forth in this Agreement and no implied covenants or obligations
shall be inferred from this Agreement against the Collateral Agent, nor shall
the Collateral Agent be bound by the provisions of any agreement by any party
hereto beyond the specific terms hereof; (b) shall not be responsible to the
Company or the Call Option Holder for any recitals contained in this Agreement,
or in any certificate or other document referred to or provided for in, or
received by it under, this Agreement, the Units, the Master Unit Agreement, or
the Call Option Agreement or for the value, validity, effectiveness,
genuineness, enforceability or sufficiency of this Agreement (other than as
against the Collateral Agent), the Units, the Master Unit Agreement or the Call
Option Agreement or any other document referred to or provided for herein or
therein or for any failure by the Company, the Call Option Holder, or any other
Person (except the Collateral Agent) to perform any of its obligations hereunder
or thereunder; (c) shall not be required to initiate or conduct any litigation
or collection proceedings hereunder (except pursuant to directions furnished
under Section 7.02 hereof); (d) shall not be responsible for any action taken or
omitted to be taken by it hereunder or under any other document or instrument
referred to or provided for herein or in connection herewith or therewith,
except for its own negligence or wilful misconduct; and (e) shall not be
required to advise any party as to selling or retaining, or taking or refraining
from taking any action with respect to, any Units or any property deposited
hereunder.  Subject to the foregoing, during the term of this 

                                      -7-
<PAGE>
 
Agreement the Collateral Agent shall take all reasonable action in connection
with the safekeeping and preservation of the Pledged Securities hereunder.

     No provision of this Agreement shall require the Collateral Agent to expend
or risk its own funds or otherwise incur any financial liability in the
performance of any of its duties hereunder.  In no event shall the Collateral
Agent be liable for any amount in excess of the value of the Pledged Securities.

     7.02  Instructions of the Company.  The Company (or, with respect to
matters relating to the Call Options, the Call Option Holder) shall have the
right, by one or more instruments in writing executed and delivered to the
Collateral Agent, to direct the time, method and place of conducting any
proceeding for any right or remedy available to the Collateral Agent, or of
exercising any power conferred on the Collateral Agent, or to direct the taking
or refraining from taking of any action authorized by this Agreement; provided,
however, that (a) the Company shall not give any direction that in any way
adversely affects the rights of the Call Option Holder hereunder or under the
Call Options and the Call Option Holder shall not give any direction that in any
way adversely affects the rights of the Company hereunder or under the Purchase
Contracts, (b) such direction shall not conflict with the provisions of any law
or of this Agreement and (c) the Collateral Agent shall be adequately
indemnified as provided herein.  Nothing in this Section 7.02 shall impair the
right of the Collateral Agent in its discretion to take any action or omit to
take any action which it deems proper and which is not inconsistent with such
direction.

     7.03  Reliance by Collateral Agent.  The Collateral Agent shall be entitled
to rely upon any certification, order, judgment, opinion, notice or other
communication (including, without limitation, any thereof by telephone,
telecopy, telex, telegram or cable) believed by it to be genuine and correct and
to have been signed or sent by or on behalf of the proper Person or Persons
(without being required to determine the correctness of any fact stated
therein), and upon advice and statements of legal counsel and other experts
selected by the Collateral Agent.  As to any matters not expressly provided for
by this Agreement, the Collateral Agent shall in all cases be fully protected in
acting, or in refraining from acting, hereunder in accordance with instructions
given by the Company or the Call Option Holder, as the case may be, in
accordance with this Agreement.

     7.04  Rights in Other Capacities.  The Collateral Agent and its affiliates
may (without having to account therefor to the Company or the Call Option
Holder) accept deposits from, lend money to, make investments in and generally
engage in any kind of banking, trust or other business with the Company, the
Call Option Holder, the Unit Agent and any Holder of Units as if it were not
acting as the Collateral Agent, and the Collateral Agent and its affiliates may
accept fees and other consideration from the Company, the Call Option Holder,
the Unit Agent and any Holder of Units without having to account for the same to
the Company or the Call Option Holder, provided that the Collateral Agent

                                      -8-
<PAGE>
 
covenants and agrees with the Company and the Call Option Holder that the
Collateral Agent shall not accept, receive or permit there to be created in its
favor any security interest, lien or other encumbrance of any kind in or upon
the Pledged Securities, except as contemplated by the terms hereof.

     7.05  Non-Reliance on Collateral Agent.  The Collateral Agent shall not be
required to keep itself informed as to the performance or observance by the Unit
Agent or any Holder of Units of this Agreement, the Master Unit Agreement, the
Call Option Agreement, the Units or any other document referred to or provided
for herein or therein or to inspect the properties or books of the Unit Agent or
any Holder of Units.  The Collateral Agent shall not have any duty or
responsibility to provide the Company or the Call Option Holder with any credit
or other information concerning the affairs, financial condition or business of
the Unit Agent or any Holder of Units that may come into the possession of the
Collateral Agent or any of its affiliates.

     7.06  Compensation and Indemnity.  The Company agrees: (a) to pay the
Collateral Agent from time to time reasonable compensation for all services
rendered by it hereunder and (b) to indemnify the Collateral Agent for, and to
hold it harmless against, any loss, liability or expense including taxes (other
than taxes based upon, measured by or determined by the income of the Collateral
Agent) incurred without negligence or bad faith on its part, arising out of or
in connection with the acceptance or administration of its powers and duties
under this Agreement, including the costs and expenses of defending itself
against any claim or liability in connection with the exercise or performance of
such powers and duties.  The provisions of this Section 7.06 shall survive the
resignation or removal of the Collateral Agent and the termination of this
Agreement.

     7.07  Failure to Act.  In the event of any ambiguity in the provisions of
this Agreement or any dispute between or conflicting claims by or among the
undersigned and/or any other Person with respect to any funds or property
deposited hereunder, the Collateral Agent shall be entitled, at its sole option,
to refuse to comply with any and all claims, demands or instructions with
respect to such property or funds so long as such dispute or conflict shall
continue, and the Collateral Agent shall not be or become liable in any way to
any of the undersigned for its failure or refusal to comply with such
conflicting claims, demands or instructions.  The Collateral Agent shall be
entitled to refuse to act until either (a) such conflicting or adverse claims or
demands shall have been finally determined by a court of competent jurisdiction
or settled by agreement between the conflicting parties as evidenced in a
writing satisfactory to the Collateral Agent or (b) the Collateral Agent shall
have received security or an indemnity satisfactory to the Collateral Agent
sufficient to save the Collateral Agent harmless from and against any and all
loss, liability or expense which the Collateral Agent may incur by reason of its
acting.  The Collateral Agent may in addition elect to commence an interpleader
action or seek other judicial relief or orders as the 

                                      -9-
<PAGE>
 
Collateral Agent may deem necessary. Notwithstanding anything contained herein
to the contrary, the Collateral Agent shall not be required to take any action
that is in its opinion contrary to law or to the terms of this Agreement, or
which would in its opinion subject it or any of its officers, employees or
directors to liability.

     7.08  Resignation of Collateral Agent.  Subject to the appointment and
acceptance of a successor Collateral Agent as provided below, (a) the Collateral
Agent may resign at any time by giving notice thereof to the Company, the Unit
Agent and, if the Call Options are exercisable or have been exercised but not
settled, the Call Option Holder, (b) the Collateral Agent may be removed at any
time by the Company (provided, that, if the Call Options are exercisable or have
been exercised but not settled, the Call Option Holder shall have consented to
such removal), and (c) if the Collateral Agent fails to perform any of its
material obligations hereunder in any material respect for a period of not less
than [20] days after receiving notice of such failure by the Unit Agent and such
failure shall be continuing, the Collateral Agent may be removed by the Unit
Agent.  The Unit Agent shall promptly notify the Company and, if the Call
Options are exercisable or have been exercised but not settled, the Call Option
Holder of any removal of the Collateral Agent pursuant to clause (c) of the
immediately preceding sentence.  Upon any such resignation or removal, the
Company and, if the Call Options are exercisable or have been exercised but not
settled, the Call Option Holder shall have the right to appoint a successor
Collateral Agent.  If no successor Collateral Agent shall have been so appointed
and shall have accepted such appointment within [30] days after the retiring
Collateral Agent's giving of notice of resignation or such removal, then the
retiring Collateral Agent may petition any court of competent jurisdiction for
the appointment of a successor Collateral Agent.  The Collateral Agent shall be
a bank which has an office in New York, New York with a combined capital and
surplus of at least $50,000,000.  Upon the acceptance of any appointment as
Collateral Agent hereunder by a successor Collateral Agent, such successor
Collateral Agent shall thereupon succeed to and become vested with all the
rights, powers, privileges and duties of the retiring Collateral Agent, and the
retiring Collateral Agent shall take all appropriate action to transfer any
money and property held by it hereunder (including the Pledged Securities) to
such successor Collateral Agent.  The retiring Collateral Agent shall, upon such
succession, be discharged from its duties and obligations as Collateral Agent
hereunder.  After any retiring Collateral Agent's resignation hereunder as
Collateral Agent, the provisions of this Section 7 shall continue in effect for
its benefit in respect of any actions taken or omitted to be taken by it while
it was acting as the Collateral Agent.

     7.09  Right to Appoint Agent or Advisor.  The Collateral Agent shall have
the right to appoint agents or advisors in connection with any of its duties
hereunder, and the Collateral Agent shall not be liable for any action taken or
omitted by such agents or advisors selected in good faith.

                                     -10-
<PAGE>
 
     7.10  Survival.  The provisions of this Section 7 shall survive termination
of this Agreement and the resignation or removal of the Collateral Agent.

     Section 8  Miscellaneous.

     8.01 Amendments.  This Agreement may be amended in the manner set forth in
Section 801 of the Master Unit Agreement for supplemental agreements.  In
executing any amendment permitted by this Section, the Collateral Agent shall be
entitled to receive and (subject to Section 7.01 hereof) shall be fully
protected in relying upon, an Opinion of Counsel stating that the execution of
such amendment is authorized or permitted by this Agreement and is for a purpose
set forth in Section 801 of the Master Unit Agreement, and that all conditions
precedent herein and in the Principal Agreements related to such amendment have
been satisfied.

     8.02  No Waiver.  No failure on the part of the Collateral Agent or any of
its agents to exercise, and no course of dealing with respect to, and no delay
in exercising, any right, power or remedy hereunder shall operate as a waiver
thereof; nor shall any single or partial exercise by the Collateral Agent or any
of its agents of any right, power or remedy hereunder preclude any other or
further exercise thereof or the exercise of any other right, power or remedy.
The remedies herein are cumulative and are not exclusive of any remedies
provided by law.

     8.03  Governing Law.  THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK, WITHOUT REGARD TO CONFLICTS
OF LAWS PRINCIPLES THEREOF.  The Company, the Call Option Holder, the Collateral
Agent and the Holders from time to time of the Units, acting through the Unit
Agent as their attorney-in-fact, hereby submit to the nonexclusive jurisdiction
of the United States District Court for the Southern District of New York and of
any New York state court sitting in New York City for the purposes of all legal
proceedings arising out of or relating to this Agreement or the transactions
contemplated hereby.  The Company, the Call Option Holder, the Collateral Agent
and the Holders from time to time of the Units, acting through the Unit Agent as
their attorney-in-fact, irrevocably waive, to the fullest extent permitted by
applicable law, any objection which they may now or hereafter have to the laying
of the venue of any such proceeding brought in such a court and any claim that
any such proceeding brought in such a court has been brought in an inconvenient
forum.

     8.04  Legal Holidays.  In any case where any Quarterly Payment Date or the
Stock Purchase Date shall not be a Business Day, then (notwithstanding any other
provision of this Agreement or of the Units) the actions required by this
Agreement to occur on such date shall not occur on such date, but instead shall
occur on the next succeeding Business Day 

                                     -11-
<PAGE>
 
with the same force and effect as if they had occurred on such Quarterly Payment
Date or Stock Purchase Date, as the case may be; except that if such next
succeeding Business Day is in the next calendar year, such actions shall occur
on the immediately preceding Business Day with the same force and effect as if
made on such Quarterly Payment Date or Stock Purchase Date.

     8.05  Notices.  All notices, requests, consents and other communications
provided for herein (including, without limitation, any modifications of, or
waivers or consents under, this Agreement) shall be given or made in writing
(including, without limitation, by telecopy) delivered to the intended recipient
at the "Address for Notices" specified below its name on the signature pages
hereof or, as to any party, at such other address as shall be designated by such
party in a notice to the other parties.  Except as otherwise provided in this
Agreement, all such communications shall be deemed to have been duly given when
transmitted by telecopier or personally delivered or, in the case of a mailed
notice, upon receipt, in each case given or addressed as aforesaid.

     8.06  Successors and Assigns.  This Agreement shall be binding upon and
inure to the benefit of the respective successors and assigns of the Company,
the Call Option Holder, the Collateral Agent and the Unit Agent, and the Holders
from time to time of the Units, by their acceptance of the same, shall be deemed
to have agreed to be bound by the provisions hereof and to have ratified the
agreements of, and the grant of the Pledge hereunder by, the Unit Agent, as
their attorney-in-fact.

     8.07  Counterparts.  This Agreement may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
instrument, and any of the parties hereto may execute this Agreement by signing
any such counterpart.

     8.08  Severability.  If any provision hereof is invalid or unenforceable in
any jurisdiction, then, to the fullest extent permitted by law, (a) the other
provisions hereof shall remain in full force and effect in such jurisdiction and
shall be liberally construed in order to carry out the intentions of the parties
hereto as nearly as may be possible and (b) the invalidity or unenforceability
of any provision hereof in any jurisdiction shall not affect the validity or
enforceability of such provision in any other jurisdiction.

     8.09  Expenses, etc.  The Company agrees to reimburse the Collateral Agent
for: (a) all reasonable out-of-pocket costs and expenses of the Collateral Agent
(including, without limitation, the reasonable fees and expenses of counsel to
the Collateral Agent), in connection with (i) the negotiation, preparation,
execution and delivery or performance of this Agreement and (ii) any
modification, supplement or waiver of any of the terms of this Agreement; (b)
all reasonable costs and expenses of the Collateral Agent (including, without
limitation, reasonable fees and expenses of counsel) in connection with (i) any
enforcement 

                                     -12-
<PAGE>
 
or proceedings resulting or incurred in connection with causing any Holder of
Units to satisfy its obligations under the Purchase Contracts or Call Options
forming a part of the Units and (ii) the enforcement of this Section 8.09; and
(c) all transfer, stamp, documentary or other similar taxes, assessments or
charges levied by any governmental or revenue authority in respect of this
Agreement or any other document referred to herein and all costs, expenses,
taxes, assessments and other charges incurred in connection with any filing,
registration, recording or perfection of any security interest contemplated
hereby.

     8.10  Security Interest Absolute.  All rights of the Collateral Agent and
security interests hereunder, and all obligations of the Holders from time to
time of the Units hereunder, shall be absolute and unconditional irrespective
of:

          (a) any lack of validity or enforceability of any provision of the
     Units or any other agreement or instrument relating thereto;

          (b) any change in the time, manner or place of payment of, or any
     other term of, or any increase in the amount of, all or any of the
     obligations of Holders of Units under the related Purchase Contracts or
     Call Options or any other amendment or waiver of any term of, or any
     consent to any departure from any requirement of, the Master Unit Agreement
     or any Units or any other agreement or instrument relating thereto; or

          (c) any other circumstance which might otherwise constitute a defense
     available to, or discharge of, a borrower, a guarantor or a pledgor.

                            [SIGNATURE PAGE FOLLOWS]

                                     -13-
<PAGE>
 
     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the day and year first above written.

                            MONSANTO COMPANY                                 
                                                                             
                                                                             
                            By:                                              
                               --------------------------------------
                               Name:                                          
                               Title:                                         
                                                                             
                                                                             
                            Address for Notices:                             
                                                                             
                            Attention:                                       
                            Telecopy:                                        
                                                                             
                                                                             
                            GOLDMAN, SACHS & CO.,                            
                            as Call Option Holder                            
                                                                             
                                                                             
                                                                             
                              (Goldman, Sachs & Co.)                         
                                                                             
                            Address for Notices:                             
                                                                             
                            85 Broad Street                                  
                            New York, New York  10004                        
                            Attention:  Registration Department              
                            Telecopy:  212-357-1557                          
                                                                             
                                                                             
                            FIRST NATIONAL BANK OF CHICAGO,                  
                            as Unit Agent and as attorney-in-fact of the 
                            Holders from time to time of the Units 
                                                                   
                                                                   
                            By:                                    
                               -------------------------------------- 
                               Name:                                
                               Title:                               
                                                                    
                            Address for Notices:                   
<PAGE>
 
                            Attention:
                            Telecopy:
                            FIRST UNION NATIONAL BANK,
                            as Collateral Agent
                            
                            
                            By:
                               --------------------------------------
                               Name:
                               Title:
                            
                            Address for Notices:
                            
                            Attention:
                            Telecopy:
 


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