EXHIBIT 4.2


                             AMENDED AND RESTATED

                               RIGHTS AGREEMENT

                                BY AND BETWEEN

                              MYCOGEN CORPORATION

                                      AND

                       THE FIRST NATIONAL BANK OF BOSTON

                                      AS

                                 RIGHTS AGENT



                         DATED AS OF OCTOBER 19, 1995
                                        

 
                     AMENDED AND RESTATED RIGHTS AGREEMENT
                     -------------------------------------

     This Amended and Restated Rights Agreement (the "Agreement"), dated as of
October 19, 1995, is entered into by and between Mycogen Corporation, a
California corporation (the "Company"), and The First National Bank of Boston, a
national banking association (the "Rights Agent").

     WHEREAS, the Company wishes to restate and amend that certain Rights
Agreement by and between Mycogen Corporation, a Delaware Corporation, ("Mycogen-
Delaware") and the Rights Agent dated February 21, 1992, as amended by that
certain Amendment No. 1 to Rights Agreement by and between Mycogen-Delaware and
the Rights Agent dated as of December 1, 1992; that certain Amendment No. 2 to
Rights Agreement by and between Mycogen-Delaware and the Rights Agent dated as
of December 31, 1993; and that certain Amendment No. 3 to Rights Agreement by
and between Mycogen-Delaware and the Rights Agent dated as of January 23, 1995
(collectively, the "Original Rights Agreement").

     WHEREAS, the Board of Directors of Mycogen-Delaware authorized and declared
a dividend of one preferred share purchase right (a "Right") for each Common
Share (as hereinafter defined) of Mycogen Delaware outstanding as of the Close
of Business (as hereinafter defined) on March 6, 1992 (the "Record Date"), each
Right representing the right to purchase one one-hundredth of a Preferred Share
(as hereinafter defined) upon the terms and subject to the conditions herein set
forth, and further authorized and directed the issuance of one Right with
respect to each Common Share that shall become outstanding between the Record
Date and the earliest of the Distribution Date, the Redemption Date or the Final
Expiration Date (as such terms are hereinafter defined).

     WHEREAS, by that certain Agreement and Plan of Merger ("Merger Agreement")
by and between Mycogen-Delaware and the Company, dated as of October 19,1995,
the Company assumed all of the rights and obligations of Mycogen-Delaware
including, but not limited to its rights and obligations under the Original
Rights Agreement.

     Accordingly, in consideration of the premises and the mutual agreements
herein set forth, the parties hereby agree as follows:

SECTION 1.  CERTAIN DEFINITIONS.

     For purposes of this Agreement, the following terms have the meanings
indicated:

     (a)  "Acquiring Person" shall mean any Person (as such term is hereinafter
          defined) who or which, together with all Affiliates and Associates (as
          such terms are hereinafter defined) of such Person, shall be the
          Beneficial Owner (as such term is hereinafter defined) of 25% or more
          of the Common Shares of the Company then outstanding, but shall not
          include (i) the Company, any

                                       2

 
          Subsidiary (as such term is hereinafter defined) of the Company, any
          employee benefit plan of the Company or any Subsidiary of the Company,
          or any entity holding Common Shares for or pursuant to the terms of
          any such plan, (ii) The Lubrizol Corporation ("Lubrizol"), or any
          Affiliates or Associates of Lubrizol (collectively with Lubrizol, the
          "Lubrizol Investor Group") in the event that the members of the
          Lubrizol Investor Group shall become the Beneficial Owner in the
          aggregate of (A) up to 40% of the total combined voting power of the
          Company's voting securities then outstanding pursuant to (1) the Stock
          Exchange Agreement dated August 25, 1992 between Lubrizol and Mycogen-
          Delaware, predecessor in interest to the Company, (2) the Stock
          Purchase Agreement dated August 25, 1992 between Lubrizol and Mycogen-
          Delaware, predecessor in interest to the Company, (3) the Partnership
          Interest Purchase Agreement dated December 31, 1993 between Lubrizol
          and Mycogen-Delaware, predecessor in interest to the Company, (4) the
          acquisition of voting securities pursuant to any compensatory plan
          adopted by the Company's Board of Directors, (5) the acquisition of
          voting securities pursuant to the terms of the Series A Convertible
          Redeemable Preferred Stock of the Company, (6) the acquisition of
          voting securities pursuant to Paragraph V of the Amended and Restated
          Equity Investment Agreement dated December 31, 1993 between Lubrizol
          and Mycogen-Delaware, predecessor in interest to the Company, (7) the
          acquisition of voting securities by members of the Lubrizol Investor
          Group other than Lubrizol in an amount not exceeding 1.5% of the total
          combined voting power of the voting securities in the aggregate, or
          (B) up to 25% of the total combined voting power of the Company's
          voting securities pursuant to Paragraph VIII.B. of the Amended and
          Restated Equity Investment Agreement, and (iii) any Person who or
          which (together with all Affiliates or Associates of such Person)
          shall become the Beneficial Owner of 25% or more of the Common Shares
          of the Company then outstanding, if the transaction or series of
          related transactions in which such Person (together with all
          Affiliates or Associates of such Person) became the Beneficial Owner
          of 25% or more of the Common Shares of the Company then outstanding,
          had received prior approval of a majority of the Continuing Directors
          (such Person (together with all Affiliates or Associates of such
          Person), an "Approved Person"); provided, that in the event a Person
          is not an Acquiring Person by reason of clause (iii) of this Section
          1(a), such Person shall become an Acquiring Person, in the event such
          Person thereafter acquires Beneficial Ownership of any additional
          Common Shares or other voting securities unless such acquisition of
          such additional Common Shares or voting securities would not result in
          such Person becoming an Acquiring Person by reason of any provision of
          this Agreement, including, without limitation, clause (iii) of this
          Section 1(a). Notwithstanding the foregoing, (A) the exemptions set
          forth in clauses (ii) and (iii) above shall not apply to any
          acquisition by the members of the Lubrizol Investor Group of voting
          securities, other than (i) the acquisition of voting 

                                       3

 
          securities pursuant to the Stock Purchase Agreement and the Stock
          Exchange Agreement, (ii) the acquisition of voting securities pursuant
          to any compensatory plan adopted by the Company's Board of Directors,
          (iii) the acquisition of voting securities pursuant to the terms of
          the Series A Convertible Redeemable Preferred Stock of the Company,
          (iv) the acquisition of voting securities by members of the Lubrizol
          Investor Group other than Lubrizol in an amount not exceeding 1.5% of
          the total combined voting power of the voting securities in the
          aggregate, or (v) in accordance with Paragraph VIII.B. of the Amended
          and Restated Equity Investment Agreement, if immediately following
          such acquisition the Lubrizol Investor Group would be the Beneficial
          Owner of more than 25% of the total combined voting power of the
          voting securities in the aggregate, and (B) no Person shall become an
          "Acquiring Person" as the result of any recapitalization of the
          Company or any other action taken by the Company or its Affiliates or
          Associates (other than, in determining whether the Lubrizol Investor
          Group shall be an "Acquiring Person," an action or series of actions
          taken by any of the members of the Lubrizol Investor Group, including,
          without limitation, any repurchase of voting securities by the Company
          that has the effect of increasing the proportionate number of shares
          beneficially owned by such Person to more than 25% of the Common
          Shares of the Company then outstanding (or, in the case of the
          Lubrizol Investor Group, more than 40% of the total combined voting
          power of the voting securities then outstanding); provided, however,
          that if any Person shall become the Beneficial Owner of 25% or more of
          the Common Shares of the Company then outstanding (or, in the case of
          the Lubrizol Investor Group, more than 40% of the voting securities
          then outstanding), by reason of the taking of such action or series of
          actions by the Company or such Affiliates or Associates and such
          Person shall, after such action or series of actions, increase its
          beneficial ownership of Common Shares of the Company (or, in the case
          of the members of the Lubrizol Investor Group or an Approved Person,
          increase its beneficial ownership of voting securities), then such
          Person shall be deemed to be an "Acquiring Person." Notwithstanding
          any provision to the contrary in this Agreement, no amendment shall be
          made to this definition without the consent of Lubrizol or an Approved
          Person if the effect of such amendment would be to reduce the
          aggregate percentage ownership of the total combined voting power of
          the voting securities that the Lubrizol Investor Group or such
          Approved Person, respectively, would be permitted to beneficially own
          at any time without being deemed an "Acquiring Person" hereunder.

     (b)  "Affiliate" and "Associate" shall have the respective meanings
          ascribed to such terms in Rule 12b-2 of the General Rules and
          Regulations under the Exchange Act (as such term is hereinafter
          defined).

                                       4

 
     (c)  A Person shall be deemed the "Beneficial Owner" of and shall be deemed
          to "beneficially own" any securities:

          (i)    which such Person or any of such Person's Affiliates or
                 Associates beneficially owns, directly or indirectly;

          (ii)   which such Person or any of such Person's Affiliates or
                 Associates has (A) the right to acquire (whether such right is
                 exercisable immediately or only after the passage of time)
                 pursuant to any agreement, arrangement or understanding (other
                 than customary agreements with and between underwriters and
                 selling group members with respect to a bona fide public
                 offering of securities), or upon the exercise of conversion
                 rights, exchange rights, rights (other than these Rights),
                 warrants or options, or otherwise; provided, however that a
                                                    --------  -------  
                 Person shall not be deemed the Beneficial Owner of, or to
                 beneficially own, (1) securities tendered pursuant to a tender
                 or exchange offer made by or on behalf of such Person or any of
                 such Person's Affiliates or Associates until such tendered
                 securities are accepted for purchase or exchange or (2)
                 securities which a Person or any Person's Affiliates or
                 Associates may be deemed to have the right to acquire pursuant
                 to any merger or other acquisition agreement between the
                 Company and such Person (or one or more of such Person's
                 Affiliates or Associates) if such agreement has been approved
                 by the Board of Directors of the Company, upon the affirmative
                 vote of a majority of the Continuing Directors, prior to there
                 being an Acquiring Person; or (B) the right to vote pursuant to
                 any agreement, arrangement or understanding; provided, however,
                                                              --------  -------
                 that a Person shall not be deemed the Beneficial Owner of, or
                 to beneficially own, any security if the agreement, arrangement
                 or understanding to vote such security (1) arises solely from a
                 revocable proxy or consent given to such Person in response to
                 a public proxy or consent solicitation made pursuant to, and in
                 accordance with, the applicable rules and regulations
                 promulgated under the Exchange Act and (2) is not also then
                 reportable on Schedule 13D under the Exchange Act (or any
                 comparable or successor report); or

          (iii)  which are beneficially owned, directly or indirectly, by any
                 other Person with which such Person or any of such Person's
                 Affiliates or Associates has any agreement, arrangement or
                 understanding (other than customary agreements with and between
                 underwriters and selling group members with respect to a bona
                 fide public offering of securities) for the purpose of
                 acquiring, holding, voting (except to the extent contemplated
                 by the proviso to Section 1(c)(ii)(B)) or disposing of any
                 securities of the Company.

                 Notwithstanding anything in this definition of Beneficial
                 Ownership to the contrary, the phrase "then outstanding," when
                 used with reference to a Person's Beneficial Ownership of
                 securities of the Company, shall mean the 

                                       5

 
                 number of such securities then issued and outstanding together
                 with the number of such securities not then actually issued and
                 outstanding which such Person would be deemed to own
                 beneficially hereunder.

     (d)  "Business Day" shall mean any day other than a Saturday, a Sunday, or
          a day on which banking institutions in The Commonwealth of
          Massachusetts are authorized or obligated by law or executive order to
          close.

     (e)  "Close of Business" on any given date shall mean 5:00 P.M., Boston,
          Massachusetts time, on such date; provided, however, that if such date
                                            --------  -------
          is not a Business Day it shall mean 5:00 P.M., Boston, Massachusetts
          time, on the next succeeding Business Day.

     (f)  "Company" shall have the meaning set forth in the first paragraph at
          the beginning of this Agreement.

     (g)  "Common Shares" when used with reference to the Company shall mean the
          shares of common stock, par value $.001 per share, of the Company.
          "Common Shares" when used with reference to any Person other than the
          Company shall mean the capital stock (or other equity interest) with
          the greatest voting power of such other Person or, if such other
          Person is a Subsidiary of another Person, the Person or Persons which
          ultimately control such first-mentioned Person.

     (h)  "Common stock equivalents" shall have the meaning set forth in Section
          11(a)(iv)  hereof.

     (i)  "Continuing Director" shall mean (i) any person who is a member of the
          Board of Directors of the Company, while such person is a member of
          the Board of Directors, who is not an Acquiring Person, or an
          Affiliate or Associate of an Acquiring Person, or a representative or
          agent of an Acquiring Person or of any such Affiliate or Associate,
          and who was a member of the Board of Directors prior to the date of
          this Agreement, or (ii) any person who subsequently becomes a member
          of the Board of Directors and who, while such person is a member of
          the Board of Directors, is not an Acquiring Person or an Affiliate or
          Associate of an Acquiring Person, or a representative or agent of an
          Acquiring Person or of any such Affiliate or Associate, if such
          Person's nomination for election or such Person's election to the
          Board of Directors is recommended or approved by a majority of the
          Continuing Directors then on the Board of Directors.

     (j)  "Current per share market price" shall have the meaning set forth in
          Section 11 hereof.

     (k)  "Current Value" shall have the respective meanings set forth in
          Section 11(a)(iv) hereof and Section 24(d) hereof.

                                       6

 
     (l)  "Distribution Date" shall have the meaning set forth in Section 3(a)
          hereof.

     (m)  "Effective Date" shall have the meaning set forth in Section 35
          hereof.

     (n)  "Equivalent preferred shares" shall have the meaning set forth in
          Section 11(b) hereof.

     (o)  "Exchange Act" shall mean the Securities Exchange Act of 1934, as
          amended, as in effect on the date of this Agreement.

     (p)  "Exchange ratio" shall have the meaning set forth in Section 24(a)
          hereof.

     (q)  "Final Expiration Date" shall have the meaning set forth in Section
          7(a) hereof.

     (r)  "Issuer" shall have the meaning set forth in Section 13 hereof.

     (s)  "NASDAQ" shall have the meaning set forth in Section 11(d)(i) hereof.

     (t)  "Person" shall mean any individual, firm, corporation or other entity,
          and shall include any successor (by merger or otherwise) of such
          entity.

     (u)  "Preferred Shares" shall mean shares of Series B Junior Participating
          Preferred Shares par value $.001 per share, of the Company having the
          rights and preferences set forth in the Form of Certificate of
          Determination attached to this Agreement as Exhibit A.
                                                      --------- 

     (v)  "Purchase Price" shall have the meaning set forth in Section 4 hereof.

     (w)  "Record Date" shall have the meaning set forth in the third paragraph
          at the beginning of this Agreement.

     (x)  "Redemption Date" shall have the meaning set forth in Section 7(a)
          hereof.

     (y)  "Redemption Price" shall have the meaning set forth in Section 23(a)
          hereof.

     (z)  "Right" shall have the meaning set forth in the third paragraph at the
          beginning of this Agreement.

     (aa) "Right Certificate" shall have the meaning set forth in Section 3(a)
          hereof.

     (bb) "Rights Agent" shall have the meaning set forth in the first paragraph
          at the beginning of this Agreement.

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     (cc) "Securities Act" shall have the meaning set forth in Section 9(c)
          hereof.

     (dd) "Security" shall have the meaning set forth in Section 11(d)(i)
          hereof.

     (ee) "Shares Acquisition Date" shall mean the first date of public
          announcement (which, for purposes of this definition, shall include,
          without limitation, a report filed pursuant to Section 13(d) of the
          Exchange Act) by the Company or an Acquiring Person that an Acquiring
          Person has become such.

     (ff) "Spread" shall have the meaning set forth in Section 11(a)(iv) hereof.

     (gg) "Subsidiary" of any Person shall mean any corporation or other entity
          of which a majority of the voting power of the voting equity
          securities or equity interest is owned, directly or indirectly, by
          such Person.

     (hh) "Substitution Period" shall have the meaning set forth in Section
          11(a)(iv) hereof.

     (ii) "Summary of Rights" shall have the meaning set forth in Section 3(b)
          hereof.

     (jj) "Trading Day" shall have the meaning set forth in Section 11(d)(i)
          hereof.

SECTION 2.  APPOINTMENT OF RIGHTS AGENT.

     The Company hereby appoints the Rights Agent to act as agent for the
Company in accordance with the terms and conditions hereof, and the Rights Agent
hereby accepts such appointment.  The Company may from time to time appoint such
co-Rights Agents as it may deem necessary or desirable.

SECTION 3.  ISSUE OF RIGHTS CERTIFICATES.

     (a)  Until the earlier of (i) the tenth day after the Shares Acquisition
Date or (ii) the tenth business day (or such later date as may be determined by
action of the Board of Directors (upon approval by a majority of the Continuing
Directors) prior to such time as any Person becomes an Acquiring Person) after
the date of the commencement by any Person (other than the Company, any
Subsidiary of the Company, any employee benefit plan of the Company or of any
Subsidiary of the Company or any entity holding Common Shares for or pursuant to
the terms of any such plan) of, or of the first public announcement of the
intention of any Person (other than the Company, any Subsidiary of the Company,
any employee benefit plan of the Company or of any Subsidiary of the Company or
any entity holding Common Shares for or pursuant to the terms of any such plan)
to commence, a tender or exchange offer the consummation of which would result
in any Person becoming the Beneficial Owner of Common Shares aggregating 15% or
more of the then outstanding Common Shares (including any such date which is
after the date of this Agreement and prior to the issuance of the Rights; the
earlier of such dates being herein referred to as the "Distribution Date"), (x)
the Rights will be evidenced (subject to the provisions 

                                       8

 
of Section 3(b) hereof) by the certificates for Common Shares registered in the
names of the holders thereof (which certificates shall also be deemed to be
Right Certificates) and not by separate Right Certificates, and (y) the right to
receive Right Certificates will be transferable only in connection with the
transfer of Common Shares. As soon as practicable after the Distribution Date,
the Company will notify the Rights Agent thereof and the Company will prepare
and execute, the Rights Agent will countersign, and the Company will send or
cause to be sent (and the Rights Agent will, if requested, send) by first-class,
insured, postage-prepaid mail, to each record holder of Common Shares as of the
Close of Business on the Distribution Date, at the address of such holder shown
on the records of the Company, a Right Certificate, in substantially the form of
Exhibit B hereto (a "Right Certificate"), evidencing one Right for each Common
Share so held. As of the Distribution Date, the Rights will be evidenced solely
by such Right Certificates.

     (b)  On the Effective Date, or as soon as practicable thereafter, the
Company will send a revised copy of a Summary of Rights to Purchase Preferred
Shares, in substantially the form of Exhibit C hereto (the "Summary of Rights"),
by first-class, postage-prepaid mail, to each record holder of Common Shares as
of the Close of Business on the Effective Date, at the address of such holder
shown on the records of the Company.  With respect to certificates for Common
Shares outstanding as of the Effective Date, until the Distribution Date, the
Rights will be evidenced by such certificates registered in the names of the
holders thereof together with a copy of the Summary of Rights attached thereto.
Until the Distribution Date (or the earlier of the Redemption Date or the Final
Expiration Date), the surrender for transfer of any certificate for Common
Shares outstanding on the Effective Date, with or without a copy of the Summary
of Rights attached thereto, shall also constitute the transfer of the Rights
associated with the Common Shares represented thereby.

     (c)  Certificates for Common Shares which become outstanding (including,
without limitation, reacquired Common Shares referred to in the last sentence of
this paragraph (c)) after the Effective Date but prior to the earliest of the
Distribution Date, the Redemption Date or the Final Expiration Date shall have
impressed on, printed on, written on or otherwise affixed to them the following
legend:

     This certificate also evidences and entitles the holder hereof to certain
     rights as set forth in an Amended and Restated Rights Agreement between
     Mycogen Corporation, a California corporation and The First National Bank
     of Boston dated as of October 19, 1995  (the "Rights Agreement"), the terms
     of which are hereby incorporated herein by reference and a copy of which is
     on file at the principal executive offices of Mycogen Corporation.  Under
     certain circumstances, as set forth in the Rights Agreement, such Rights
     will be evidenced by separate certificates and will no longer be evidenced
     by this certificate.  Mycogen Corporation will mail to the holder of this
     certificate a copy of the Rights Agreement without charge after receipt of
     a written request therefor.  Under certain circumstances, as set forth in
     the Rights Agreement, Rights issued 

                                       9

 
     to any Person who becomes an Acquiring Person (as defined in the Rights
     Agreement) may become null and void.

          With respect to such certificates containing the foregoing legend,
until the Distribution Date, the Rights associated with the Common Shares
represented by such certificates shall be evidenced by such certificates alone,
and the surrender for transfer of any such certificate shall also constitute the
transfer of the Rights associated with the Common Shares represented thereby.
In the event that the Company purchases or acquires any Common Shares after the
Record Date but prior to the Distribution Date, any Rights associated with such
Common Shares shall be deemed cancelled and retired so that the Company shall
not be entitled to exercise any Rights associated with the Common Shares which
are no longer outstanding.

SECTION 4.  FORM OF RIGHT CERTIFICATES.

     The Right Certificates (and the forms of election to purchase Preferred
Shares and of assignment to be printed on the reverse thereof) shall be
substantially the same as Exhibit B hereto and may have such marks of
identification or designation and such legends, summaries or endorsements
printed thereon as the Company may deem appropriate and as are not inconsistent
with the provisions of this Agreement, or as may be required to comply with any
applicable law or with any rule or regulation made pursuant thereto or with any
rule or regulation of any stock exchange or transaction reporting system on
which the Rights may from time to time be listed, or to conform to usage.
Subject to the provisions of Section 22 hereof, the Right Certificates shall
entitle the holders thereof to purchase such number of one one-hundredths of a
Preferred Share as shall be set forth therein at the price per one one-hundredth
of a Preferred Share set forth therein (the "Purchase Price"), but the number of
such one one-hundredths of a Preferred Share and the Purchase Price shall be
subject to adjustment as provided herein.

SECTION 5.  COUNTERSIGNATURE AND REGISTRATION.

     The Right Certificates shall be executed on behalf of the Company by its
Chairman of the Board, its President, any of its Vice Presidents, or its Chief
Financial Officer, either manually or by facsimile signature, shall have affixed
thereto the Company's seal or a facsimile thereof, and shall be attested by the
Secretary or an Assistant Secretary of the Company, either manually or by
facsimile signature.  The Right Certificates shall be manually or by facsimile
countersigned by the Rights Agent and shall not be valid for any purpose unless
countersigned.  In case any officer of the Company who shall have signed any of
the Right Certificates shall cease to be such officer of the Company before
countersignature by the Rights Agent and issuance and delivery by the Company,
such Right Certificates, nevertheless, may be countersigned by the Rights Agent
and issued and delivered by the Company with the same force and effect as though
the person who signed such Right Certificates had not ceased to be such officer
of the Company; and any Right Certificate may be signed on behalf of the Company
by any person who, at the actual date of the execution of such Right
Certificate, shall be a proper officer of the Company to sign such Right
Certificate, although at the date of the execution of this Rights Agreement any
such person was not such an officer.

                                       10

 
     Following the Distribution Date, the Rights Agent will keep or cause to be
kept, at its office designated for such purpose, books for registration and
transfer of the Right Certificates issued hereunder.  Such books shall show the
names and addresses of the respective holders of the Right Certificates, the
number of Rights evidenced on its face by each of the Right Certificates and the
date of each of the Right Certificates.

SECTION 6.  TRANSFER, SPLIT-UP, COMBINATION AND EXCHANGE OF RIGHT CERTIFICATES;
MUTILATED, DESTROYED, LOST OR STOLEN RIGHT CERTIFICATES.

     Subject to the provisions of Section 14 hereof, at any time after the Close
of Business on the Distribution Date, and at or prior to the Close of Business
on the earlier of the Redemption Date or the Final Expiration Date, any Right
Certificate or Right Certificates (other than Right Certificates representing
Rights that have become void pursuant to Section 11(a)(ii) hereof or that have
been exchanged pursuant to Section 24 hereof) may be transferred, split up,
combined or exchanged for another Right Certificate or Right Certificates,
entitling the registered holder to purchase a like number of one one-hundredths
of a Preferred Share (or other securities or property) as the Right Certificate
or Right Certificates surrendered then entitled such holder to purchase.  Any
registered holder desiring to transfer, split up, combine or exchange any Right
Certificate or Right Certificates shall make such request in writing delivered
to the Rights Agent, and shall surrender the Right Certificate or Right
Certificates to be transferred, split up, combined or exchanged at the office of
the Rights Agent designated for such purpose.  Thereupon the Rights Agent shall
countersign and deliver to the person entitled thereto a Right Certificate or
Right Certificates, as the case may be, as so requested.  The Company may
require payment of a sum sufficient to cover any tax or governmental charge that
may be imposed in connection with any transfer, split up, combination or
exchange of Right Certificates.

     Upon receipt by the Company and the Rights Agent of evidence reasonably
satisfactory to them of the loss, theft, destruction or mutilation of a Right
Certificate, and, in case of loss, theft or destruction, of indemnity or
security reasonably satisfactory to them, and, at the Company's request,
reimbursement to the Company and the Rights Agent of all reasonable expenses
incidental thereto, and upon surrender to the Rights Agent and cancellation of
the Right Certificate if mutilated, the Company will make and deliver a new
Right Certificate of like tenor to the Rights Agent for delivery to the
registered holder in lieu of the Right Certificate so lost, stolen, destroyed or
mutilated.

SECTION 7.  EXERCISE OF RIGHTS; PURCHASE PRICE; EXPIRATION DATE OF RIGHTS.
 
     (a)  The registered holder of any Right Certificate may exercise the Rights
evidenced thereby (except as otherwise provided herein) in whole or in part at
any time after the Distribution Date upon surrender of the Right Certificate,
with the form of election to purchase and certification on the reverse side
thereof duly executed, to the Rights Agent at the office of the Rights Agent
designated for such purpose, together with payment of the Purchase Price for
each one one-hundredth of a Preferred Share as to which the Rights are
exercised, at or prior to the 

                                       11

 
earliest of (i) the Close of Business on February 20, 2002 (the "Final
Expiration Date"), (ii) the time at which the Rights are redeemed as provided in
Section 23 hereof (the "Redemption Date"), (iii) the time at which such Rights
are exchanged as provided in Section 24 hereof, or (iv) the consummation of any
merger or other acquisition involving the Company pursuant to an agreement
described in Section 1(c)(ii)(A)(2) hereof.

     (b)  The Purchase Price for each one one-hundredth of a Preferred Share
pursuant to the exercise of a Right shall initially be $65.00, shall be subject
to adjustment from time to time as provided in Sections 11 and 13 hereof and
shall be payable in lawful money of the United States of America in accordance
with paragraph (c) below.

     (c)  Upon receipt of a Right Certificate representing exercisable Rights,
with the form of election to purchase duly executed, accompanied by payment of
the Purchase Price for the shares to be purchased and an amount equal to any
applicable transfer tax required to be paid by the holder of such Right
Certificate in accordance with Section 9 hereof by certified check, cashier's
check or money order payable to the order of the Company, the Rights Agent shall
thereupon promptly (i) (A) requisition from any transfer agent of the Preferred
Shares certificates for the number of Preferred Shares to be purchased and the
Company hereby irrevocably authorizes its transfer agent to comply with all such
requests, or (B) requisition from a depositary agent properly appointed by the
Company depositary receipts representing such number of one one-hundredths of a
Preferred Share as are to be purchased (in which case certificates for the
Preferred Shares represented by such receipts shall be deposited by the transfer
agent with the depositary agent) and the Company hereby directs the depositary
agent to comply with such request, (ii) when appropriate, requisition from the
Company the amount of cash to be paid in lieu of issuance of fractional shares
in accordance with Section 14 hereof, (iii) after receipt of such certificates
or depositary receipts, cause the same to be delivered to or upon the order of
the registered holder of such Right Certificate, registered in such name or
names as may be designated by such holder and (iv) when appropriate, after
receipt, deliver such cash to or upon the order of the registered holder of such
Right Certificate.

     (d)  In case the registered holder of any Right Certificate shall exercise
less than all the Rights evidenced thereby, a new Right Certificate evidencing
Rights equivalent to the Rights remaining unexercised shall be issued by the
Rights Agent to the registered holder of such Right Certificate or to its duly
authorized assigns, subject to the provisions of Section 14 hereof.

     (e)  The Company covenants and agrees that it will cause to be reserved and
kept available out of its authorized and unissued Preferred Shares or any
Preferred Shares held in its treasury, the number of Preferred Shares that will
be sufficient to permit the exercise in full of all outstanding Rights in
accordance with this Section 7.

     (f)  Notwithstanding anything in this Agreement to the contrary, neither
the Rights Agent nor the Company shall be obligated to undertake any action with
respect to a registered holder upon the occurrence of any purported exercise as
set forth in this Section 7 unless such registered holder shall have (i)
completed and signed the certificate contained in the form of 

                                       12

 
election to purchase set forth on the reverse side of the Right Certificate
surrendered for such exercise, and (ii) provided such additional evidence of the
identity of the Beneficial Owner (or former Beneficial Owner) or Affiliates or
Associates thereof as the Company shall reasonably request.

SECTION 8.  CANCELLATION AND DESTRUCTION OF RIGHT CERTIFICATES.

     All Right Certificates surrendered for the purpose of exercise, transfer,
split up, combination or exchange shall, if surrendered to the Company or to any
of its agents, be delivered to the Rights Agent for cancellation or in cancelled
form, or, if surrendered to the Rights Agent, shall be cancelled by it, and no
Right Certificates shall be issued in lieu thereof except as expressly permitted
by any of the provisions of this Rights Agreement.  The Company shall deliver to
the Rights Agent for cancellation and retirement, and the Rights Agent shall so
cancel and retire, any other Right Certificate purchased or acquired by the
Company otherwise than upon the exercise thereof.  The Rights Agent shall
deliver all cancelled Right Certificates to the Company, or shall, at the
written request of the Company, destroy such cancelled Right Certificates, and
in such case shall deliver a certificate of destruction thereof to the Company.

SECTION 9.  AVAILABILITY OF PREFERRED SHARES.

     (a)  The Company covenants and agrees that it will use its best efforts to
cause to be reserved and kept available out of and to the extent of its
authorized and unissued Preferred Shares not reserved for another purpose (and,
following the occurrence of an event described in Section 11(a)(ii) or Section
13(a), out of its authorized and unissued shares of Common Stock and/or other
securities), the number of Preferred Shares (and, following the occurrence of
any such event, Common Stock and/or other Securities) that will be sufficient to
permit the exercise in full of all outstanding Rights.

     (b)  If the Preferred Shares (or, following the occurrence of an event
described in Section 11(a)(ii) or Section 13(a), the Common Shares and/or other
Securities) are at any time listed on a national securities exchange or included
for quotation on any transaction reporting system, then so long as the Preferred
Shares (and, following the occurrence of any such event, Common Shares and/or
other securities) issuable and deliverable upon exercise of the Rights may be
listed on such exchange or included for quotation on any such transaction
reporting system, the Company shall use its best efforts to cause, from and
after such time as the Rights become exercisable (but only to the extent that it
is reasonably likely that the Rights will be exercised), all shares reserved for
such issuance to be listed on such exchange or included for quotation on any
such transaction reporting system upon official notice of issuance upon such
exercise.

     (c)  The Company shall use its best efforts to:  (i) file, as soon as
practicable following the earliest date after the first occurrence of an event
described in Section 11(a)(ii) in which the consideration to be delivered by the
Company upon exercise of the Rights has been determined in accordance with
Section 11(a)(iv) hereof, or as soon as is required by law following the

                                       13

 
Distribution Date, as the case may be, a registration statement under the
Securities Act of 1933, as amended (the "Securities Act"), with respect to the
securities purchasable upon exercise of the Rights on an appropriate form; (ii)
cause such registration statement to become effective as soon as practicable
after such filing; and (iii) cause such registration statement to remain
effective (with a prospectus at all times meeting the requirements of the
Securities Act) until the earlier of (A) the date as of which the Rights are no
longer exercisable for such securities or (B) the date of expiration of the
Rights. The Company may temporarily suspend, for a period not to exceed ninety
(90) days after the date set forth in clause (i) of the first sentence of this
Section 9(c), the exercisability of the Rights in order to prepare and file such
registration statement and permit it to become effective. Upon any such
suspension, the Company shall issue a public announcement stating, and notify
the Rights Agent, that the exercisability of the Rights has been temporarily
suspended, as well as a public announcement and notification to the Rights Agent
at such time as the suspension is no longer in effect. The Company will also
take such action as may be appropriate under, or to ensure compliance with, the
securities or "blue sky" laws of the various states in connection with the
exercisability of the Rights. Notwithstanding any provision of this Agreement to
the contrary, the Rights shall not be exercisable in any jurisdiction, unless
the requisite qualification in such jurisdiction shall have been obtained, or an
exemption therefrom shall be available and until a registration statement has
been declared effective.

     (d)  The Company covenants and agrees that it will take all such action as
may be necessary to ensure that all Preferred Shares delivered upon exercise of
Rights shall, at the time of delivery of the certificates for such Preferred
Shares (subject to payment of the Purchase Price), be duly and validly
authorized and issued and fully paid and nonassessable shares.

     (e)  The Company further covenants and agrees that it will pay when due and
payable any and all federal and state transfer taxes and charges which may be
payable in respect of the issuance or delivery of the Right Certificates or of
any Preferred Shares upon the exercise of Rights.  The Company shall not,
however, be required to pay any transfer tax which may be payable in respect of
any transfer or delivery of Right Certificates to a person other than, or the
issuance or delivery of certificates or depositary receipts for the Preferred
Shares in a name other than that of, the registered holder of the Right
Certificate evidencing Rights surrendered for exercise or to issue or to deliver
any certificates or depositary receipts for Preferred Shares upon the exercise
of any Rights until any such tax shall have been paid (any such tax being
payable by the holder of such Right Certificate at the time of surrender) or
until it has been established to the Company's reasonable satisfaction that no
such tax is due.

SECTION 10. PREFERRED SHARES RECORD DATE.

     Each person in whose name any certificate for Preferred Shares is issued
upon the exercise of Rights shall for all purposes be deemed to have become the
holder of record of the Preferred Shares represented thereby on, and such
certificate shall be dated, the date upon which the Right Certificate evidencing
such Rights was duly surrendered and payment of the Purchase Price (and any
applicable transfer taxes) was made; provided, however, that if the date of such
                                     --------  --------                         
surrender and payment is a date upon which the Preferred Shares transfer books
of the Company 

                                       14

 
are closed, such person shall be deemed to have become the record holder of such
shares on, and such certificate shall be dated, the next succeeding Business Day
on which the Preferred Shares transfer books of the Company are open. Prior to
the exercise of the Rights evidenced thereby, the holder of a Right Certificate
shall not be entitled to any rights of a holder of Preferred Shares for which
the Rights shall be exercisable, including, without limitation, the right to
vote, to receive dividends or other distributions or to exercise any preemptive
rights, and shall not be entitled to receive any notice of any proceedings of
the Company, except as provided herein.

SECTION 11. ADJUSTMENT OF PURCHASE PRICE, NUMBER OF SHARES OR NUMBER OF RIGHTS.

     The Purchase Price, the number of Preferred Shares covered by each Right
and the number of Rights outstanding are subject to adjustment from time to time
as provided in this Section 11.

     (a)(i)   In the event the Company shall at any time after the date of this
              Agreement (A) declare a dividend on the Preferred Shares payable
              in Preferred Shares; (B) subdivide the outstanding Preferred
              Shares; (C) combine the outstanding Preferred Shares into a
              smaller number of Preferred Shares; or (D) issue any shares of its
              capital stock in a reclassification of the Preferred Shares
              (including any such reclassification in connection with a
              consolidation or merger in which the Company is the continuing or
              surviving corporation), except as otherwise provided in this
              Section 11(a), the Purchase Price in effect at the time of the
              record date for such dividend or of the effective date of such
              subdivision, combination or reclassification, and the number and
              kind of shares of capital stock issuable on such date, shall be
              proportionately adjusted so that the holder of any Right exercised
              after such time shall be entitled to receive the aggregate number
              and kind of shares of capital stock which, if such Right had been
              exercised immediately prior to such date and at a time when the
              Preferred Shares transfer books of the Company were open, such
              holder would have owned upon such exercise and been entitled to
              receive by virtue of such dividend, subdivision, combination or
              reclassification; provided, however, that in no event shall the
                                --------  -------
              consideration to be paid upon the exercise of one Right be less
              than the aggregate par value of the shares of capital stock of the
              Company issuable upon exercise of one Right. If an event occurs
              which would require an adjustment under both Section 11(a)(i) and
              Section 11(a)(ii), the adjustment provided for in this Section
              11(a)(i) shall be in addition to, and shall be made prior to any
              adjustment required pursuant to Section 11(a)(ii).

     (a)(ii)  Subject to Section 24 of this Agreement, in the event that any
              Person becomes an Acquiring Person, each holder of a Right shall
              thereafter have a right to receive, upon exercise thereof at a
              price equal to the then current Purchase Price multiplied by the
              number of one one-hundredths of a Preferred Share for which a
              Right is then exercisable, in accordance with the terms of this
              Agreement and in lieu of Preferred Shares, such number of Common
              Shares of the Company as shall equal 

                                       15

 
              the result obtained by (x) multiplying the then current Purchase
              Price by the number of one one-hundredths of a Preferred Share for
              which a Right is then exercisable and dividing that product by (y)
              50% of the then current per share market price of the Company's
              Common Shares (determined pursuant to Section 11(d) hereof) on the
              date of the occurrence of such event. Except as provided in
              Section 23, in the event that any Person shall become an Acquiring
              Person and the Rights shall then be outstanding, the Company shall
              not take any action which would eliminate or diminish the benefits
              intended to be afforded by the Rights.

              Notwithstanding anything in this Agreement to the contrary, from
              and after the first occurrence of an event in which any Person
              shall become an Acquiring Person, any Rights beneficially owned by
              (A) an Acquiring Person or an Associate or Affiliate of an
              Acquiring Person, (B) a transferee of an Acquiring Person (or of
              any such Associate or Affiliate) who becomes a transferee after
              the Acquiring Person becomes such, or (C) a transferee of an
              Acquiring Person (or of any such Associate or Affiliate) who
              becomes a transferee prior to or concurrently with the Acquiring
              Person becoming such and receives such Rights pursuant to either
              (1) a transfer (whether or not for consideration) from the
              Acquiring Person to holders of equity interests in such Acquiring
              Person or to any Person with whom the Acquiring Person has any
              continuing agreement, arrangement or understanding regarding the
              transferred Rights or (2) a transfer which the Board of Directors,
              upon approval by a majority of the Continuing Directors, has
              determined is part of a plan, arrangement or understanding which
              has as a primary purpose or effect the avoidance of this Section
              11(a)(ii), shall become null and void without any further action
              and no holder of such Rights shall have any rights whatsoever with
              respect to such Rights, whether under any provision of this
              Agreement or otherwise. No Right Certificate shall be issued
              pursuant to Section 3 that represents Rights beneficially owned by
              an Acquiring Person whose Rights would be void pursuant to the
              preceding sentence or any Associate or Affiliate thereof; no Right
              Certificate shall be issued at any time upon the transfer of any
              Rights to an Acquiring Person whose Rights would be void pursuant
              to the preceding sentence or any Associate or Affiliate thereof or
              to any nominee of such Acquiring Person, Associate or Affiliate;
              and any Right Certificate delivered to the Rights Agent for
              transfer to an Acquiring Person whose Rights would be void
              pursuant to the preceding sentence shall be cancelled. The Company
              shall use all reasonable efforts to ensure that the provisions of
              this Section 11(a)(ii) are complied with, but shall have no
              liability to any holder of Right Certificates or other Person as a
              result of its failure to make any determinations with respect to
              an Acquiring person or its Affiliates, Associates or transferees
              hereunder.

     (a)(iii) The right to buy Common Shares of the Company pursuant to
              subparagraph (ii) of this paragraph (a) shall not arise if the
              event causing such Person to become an Acquiring Person (A) is a
              consolidation, merger, sale, transfer or similar transaction
              subject to Section 13 hereof, or (B) is an acquisition of shares
              of 

                                       16

 
              Common Stock pursuant to a tender offer or an exchange offer for
              all outstanding Common Shares at a price and on terms determined
              by at least a majority of the Continuing Directors, and after
              receiving advice from one or more investment banking firms, to be
              (1) at a price which is fair to stockholders (taking into account
              all factors which such members of the Board of Directors deem
              relevant including, without limitation, prices which could
              reasonably be achieved if the Company or its assets were sold in
              an orderly basis designed to realize maximum value) and (2)
              otherwise in the best interests of the Company and its
              stockholders.

     (a)(iv)  In lieu of issuing Common Shares in accordance with Section
              11(a)(ii) hereof, the Company may, if the Board of Directors of
              the Company, upon approval by a majority of the Continuing
              Directors, determines that such action is necessary or appropriate
              and not contrary to the interest of holders of Rights (and, in the
              event that the number of Common Shares which are authorized by the
              Company's Articles of Incorporation but not outstanding or
              reserved for issuance for purposes other than upon exercise of the
              Rights are not sufficient to permit the exercise in full of the
              Rights, or if any necessary regulatory approval for such issuance
              has not been obtained by the Company, the Company shall): (A)
              determine the excess of (1) the value of the Common Shares
              issuable upon the exercise of a Right (the "Current Value") over
              (2) the Purchase Price (such excess being referred to as the
              "Spread") and (B) with respect to each Right, make adequate
              provision to substitute for such Common Shares, upon exercise of
              the Rights, (1) cash, (2) a reduction in the Purchase Price, (3)
              other equity securities of the Company (including, without
              limitation, shares or units of shares of any series of preferred
              stock which the Board of Directors of the Company, upon approval
              by a majority of the Continuing Directors, has deemed to have the
              same value as Common Shares (such shares or units of shares of
              preferred stock are herein called "common stock equivalents")),
              except to the extent that the Company has not obtained any
              necessary regulatory approval for such issuance, (4) debt
              securities of the Company, except to the extent that the Company
              has not obtained any necessary regulatory approval for such
              issuance, (5) other assets or (6) any combination of the
              foregoing, having an aggregate value equal to the Current Value,
              where such aggregate value has been determined by the Board of
              Directors of the Company, upon approval by a majority of the
              Continuing Directors, based upon the advice of a nationally
              recognized investment banking firm selected by the Board of
              Directors of the Company, upon approval by a majority of the
              Continuing Directors; provided, however, if the Company shall not
                                    --------  ------- 
              have made adequate provision to deliver value pursuant to clause
              (B) above within thirty (30) days following the occurrence of an
              event described in Section 11(a)(ii), then the Company shall be
              obligated to deliver, upon the surrender for exercise of a Right
              and without requiring payment of the Purchase Price, Common Shares
              (to the extent available), except to the extent that the Company
              has not obtained any necessary regulatory approval for such
              issuance, and then, if necessary, cash, which shares and/or cash
              have an aggregate value equal to the Spread. If the 

                                       17

 
              Board of Directors, upon approval by a majority of the Continuing
              Directors, shall determine in good faith that it is likely that
              sufficient additional Common Shares could be authorized for
              issuance upon exercise in full of the Rights or that any necessary
              regulatory approval for such issuance will be obtained, the thirty
              (30) day period set forth above may be extended to the extent
              necessary, but not more than ninety (90) days after the occurrence
              of an event described in Section 11(a)(ii), in order that the
              Company may seek stockholder approval for the authorization of
              such additional shares or take action to obtain such regulatory
              approval (such period, as it may be extended, the "Substitution
              Period"). To the extent that the Company determines that some
              action need be taken pursuant to the first and/or second sentences
              of this Section 11(a)(iv), the Company (x) shall provide that such
              action shall apply uniformly to all outstanding Rights held by
              holders entitled to receive Common Shares or other securities or
              property upon exercise of such Rights and (y) may suspend the
              exercisability of the Rights until the expiration of the
              Substitution Period in order to seek any authorization of
              additional shares, to take any action to obtain any required
              regulatory approval and/or to decide the appropriate form of
              distribution to be made pursuant to such first sentence and to
              determine the value thereof. In the event of any such suspension,
              the Company shall issue a public announcement stating that the
              exercisability of the Rights has been temporarily suspended, as
              well as a public announcement at such time as the suspension is no
              longer in effect and shall promptly notify the Rights Agent of
              such suspension. For purposes of this Section 11(a)(iv), the value
              of the Common Shares shall be the current per share market price
              (as determined pursuant to Section 11(d) hereof) of the Common
              Shares at the Close of Business on the date of the occurrence of
              one of the events described in Section 11(a)(ii) and the value of
              any "common stock equivalent" shall be deemed to have the same
              value as the Common Shares on such date.

     (b)      In the event that the Company shall fix a record date for the
              issuance of rights, options or warrants to all holders of
              Preferred Shares entitling them (for a period expiring within
              forty-five (45) calendar days after such record date) to subscribe
              for or purchase Preferred Shares (or shares having the same
              rights, privileges and preferences as the Preferred Shares
              ("equivalent preferred shares")) or securities convertible into
              Preferred Shares or equivalent preferred shares at a price per
              Preferred Share or equivalent preferred share (or having a
              conversion price per share, if a security convertible into
              Preferred Shares or equivalent preferred shares) less than the
              then current per share market price of the Preferred Shares (as
              defined in Section 11(d)) on such record date, the Purchase Price
              to be in effect after such record date shall be determined by
              multiplying the Purchase Price in effect immediately prior to such
              record date by a fraction, the numerator of which shall be the
              number of Preferred Shares outstanding on such record date plus
              the number of Preferred Shares which the aggregate offering price
              of the total number of Preferred Shares and/or equivalent
              preferred shares so to be offered (and/or the aggregate initial
              conversion price of the convertible securities so to be offered)

                                       18

 
              would purchase at such current market price and the denominator of
              which shall be the number of Preferred Shares outstanding on such
              record date plus the number of additional Preferred Shares and/or
              equivalent preferred shares to be offered for subscription or
              purchase (or into which the convertible securities so to be
              offered are initially convertible); provided, however, that in no
                                                  --------  -------
              event shall the consideration to be paid upon the exercise of one
              Right be less than the aggregate par value of the shares of
              capital stock of the Company issuable upon exercise of one Right.
              In case such subscription price may be paid in a consideration
              part or all of which shall be in a form other than cash, the value
              of such consideration shall be as determined in good faith by the
              Board of Directors of the Company, upon approval by a majority of
              the Continuing Directors, whose determination shall be described
              in a statement filed with the Rights Agent and shall be binding on
              the Rights Agent and the holders of the Rights. Preferred Shares
              owned by or held for the account of the Company shall not be
              deemed outstanding for the purpose of any such computation. Such
              adjustment shall be made successively whenever such a record date
              is fixed; and in the event that such rights, options or warrants
              are not so issued, the Purchase Price shall be adjusted to be the
              Purchase Price which would then be in effect if such record date
              had not been fixed.

                    (c)    In case the Company shall fix a record date for the
              making of a distribution to all holders of the Preferred Shares
              (including any such distribution made in connection with a
              consolidation or merger in which the Company is the continuing or
              surviving corporation) of evidences of indebtedness or assets
              (other than a regular quarterly cash dividend or a dividend
              payable in Preferred Shares) or subscription rights or warrants
              (excluding those referred to in Section 11(b) hereof), the
              Purchase Price to be in effect after such record date shall be
              determined by multiplying the Purchase Price in effect immediately
              prior to such record date by a fraction, the numerator of which
              shall be the then current per share market price of the Preferred
              Shares on such record date, less the fair market value (as
              determined in good faith by the Board of Directors of the Company,
              upon approval by a majority of the Continuing Directors, whose
              determination shall be described in a statement filed with the
              Rights Agent) of the portion of the assets or evidences of
              indebtedness so to be distributed or of such subscription rights
              or warrants applicable to one Preferred Share and the denominator
              of which shall be such current per share market price of the
              Preferred Shares; provided, however, that in no event shall the
                                --------  ------- 
              consideration to be paid upon the exercise of one Right be less
              than the aggregate par value of the shares of capital stock of the
              Company to be issued upon exercise of one Right. Such adjustments
              shall be made successively whenever such a record date is fixed;
              and in the event that such distribution is not so made, the
              Purchase Price shall again be adjusted to be the Purchase Price
              which would then be in effect if such record date had not been
              fixed.

                                       19

 
                    (d)(i) For the purpose of any computation hereunder, the
              "current per share market price" of any security (a "Security" for
              the purpose of this Section 11(d)(i)) on any date shall be deemed
              to be the average of the daily closing prices per share of such
              Security for the thirty (30) consecutive Trading Days (as such
              term is hereinafter defined) immediately prior to such date;
              provided, however, that in the event that the current per share
              --------  -------         
              market price of the Security is determined during a period
              following the announcement by the issuer of such Security of (A) a
              dividend or distribution on such Security payable in shares of
              such Security or securities convertible into such shares, or (B)
              any subdivision, combination or reclassification of such Security
              and prior to the expiration of thirty (30) Trading Days after the
              ex-dividend date for such dividend or distribution, or the record
              date for such subdivision, combination or reclassification, then,
              and in each such case, the current per share market price shall be
              appropriately adjusted to reflect the current market price per
              share equivalent of such Security. The closing price for each day
              shall be the last sale price, regular way, or, in case no such
              sale takes place on such day, the average of the closing bid and
              asked prices, regular way, in either case as reported in the
              principal consolidated transaction reporting system with respect
              to securities listed or admitted to trading on the New York Stock
              Exchange or, if the Security is not listed or admitted to trading
              on the New York Stock Exchange, as reported in the principal
              consolidated transaction reporting system with respect to
              securities listed on the principal national securities exchange on
              which the Security is listed or admitted to trading or, if the
              Security is not listed or admitted to trading on any national
              securities exchange, the last quoted price or, if not so quoted,
              the average of the high bid and low asked prices in the over-the-
              counter market, as reported by the National Association of
              Securities Dealers, Inc. Automated Quotations System ("NASDAQ") or
              such other system then in use, or, if on any such date the
              Security is not quoted by any such organization, the average of
              the closing bid and asked prices as furnished by a professional
              market maker making a market in the Security selected by the Board
              of Directors of the Company, upon approval by a majority of the
              Continuing Directors. If on any such date no market maker is
              making a market in the Security, the "current per share market
              price" of such Security on such date as determined in good faith
              by the Board of Directors of the Company as provided for above
              shall be used. The term "Trading Day" shall mean a day on which
              the principal national securities exchange on which the Security
              is listed or admitted to trading is open for the transaction of
              business or, if the Security is not listed or admitted to trading
              on any national securities exchange, a Business Day.

     (d)(ii)  For the purpose of any computation hereunder, the "current per
              share market share price" of the Preferred Shares shall be
              determined in accordance with the method set forth in Section
              11(d)(i). If the Preferred Shares are not publicly traded, the
              "current per share market price" of the Preferred Shares shall be
              conclusively deemed to be the current per share market price of
              the Common Shares as deter-

                                       20

 
              mined pursuant to Section 11(d)(i) (appropriately adjusted to
              reflect any stock split, stock dividend or similar transaction
              occurring after the date hereof), multiplied by one hundred. If
              neither the Common Shares nor the Preferred Shares are publicly
              held or so listed or traded, "current per share market price"
              shall mean the fair value per share as determined in good faith by
              the Board of Directors of the Company, upon approval by a majority
              of the Continuing Directors, whose determination shall be
              described in a statement filed with the Rights Agent.

     (e)      No adjustment in the Purchase Price shall be required unless such
              adjustment would require an increase or decrease of at least 1% in
              the Purchase Price; provided, however, that any adjustments which
                                  --------  ------- 
              by reason of this Section 11(e) are not required to be made shall
              be carried forward and taken into account in any subsequent
              adjustment. All calculations under this Section 11 shall be made
              to the nearest cent or to the nearest one one-millionth of a
              Preferred Share or one ten-thousandth of any other share or
              security as the case may be. Notwithstanding the first sentence of
              this Section 11(e), any adjustment required by this Section 11
              shall be made no later than the earlier of (i) three (3) years
              from the date of the transaction which requires such adjustment or
              (ii) the date of the expiration of the right to exercise any
              Rights.

     (f)      If as a result of an adjustment made pursuant to Section 11(a)
              hereof, the holder of any Right thereafter exercised shall become
              entitled to receive any shares of capital stock of the Company
              other than Preferred Shares, thereafter the number of such other
              shares so receivable upon exercise of any Right shall be subject
              to adjustment from time to time in a manner and on terms as nearly
              equivalent as practicable to the provisions with respect to the
              Preferred Shares contained in Section 11(a) through (c),
              inclusive, and the provisions of Sections 7, 9, 10, 13 and 14 with
              respect to the Preferred Shares shall apply on like terms to any
              such other shares.

     (g)      All Rights originally issued by the Company subsequent to any
              adjustment made to the Purchase Price hereunder shall evidence the
              right to purchase, at the adjusted Purchase Price, the number of
              one one-hundredths of a Preferred Share purchasable from time to
              time hereunder upon exercise of the Rights, all subject to further
              adjustment as provided herein.

     (h)      Unless the Company shall have exercised its election as provided
              in Section 11(i), upon each adjustment of the Purchase Price as a
              result of the calculations made in Sections 11(b) and (c), each
              Right outstanding immediately prior to the making of such
              adjustment shall thereafter evidence the right to purchase, at the
              adjusted Purchase Price, that number of one one-hundredths of a
              Preferred Share (calculated to the nearest one one-millionth of a
              Preferred Share) obtained by (i) multiplying (x) the number of one
              one-hundredths of a share covered by a Right 

                                       21

 
              immediately prior to this adjustment by (y) the Purchase Price in
              effect immediately prior to such adjustment of the Purchase Price
              and (ii) dividing the product so obtained by the Purchase Price in
              effect immediately after such adjustment of the Purchase Price.

     (i)      The Company may elect on or after the date of any adjustment of
              the Purchase Price to adjust the number of Rights, in substitution
              for any adjustment in the number of one one-hundredths of a
              Preferred Share purchasable upon the exercise of a Right. Each of
              the Rights outstanding after such adjustment of the number of
              Rights shall be exercisable for the number of one one-hundredths
              of a Preferred Share for which a Right was exercisable immediately
              prior to such adjustment. Each Right held of record prior to such
              adjustment of the number of Rights shall become that number of
              Rights (calculated to the nearest one ten-thousandth) obtained by
              dividing the Purchase Price in effect immediately prior to
              adjustment of the Purchase Price by the Purchase Price in effect
              immediately after adjustment of the Purchase Price. The Company
              shall make a public announcement of its election to adjust the
              number of Rights, indicating the record date for the adjustment,
              and, if known at the time, the amount of the adjustment to be
              made. This record date may be the date on which the Purchase Price
              is adjusted or any day thereafter, but, if the Right Certificates
              have been issued, shall be at least 10 days later than the date of
              the public announcement. If Right Certificates have been issued,
              upon each adjustment of the number of Rights pursuant to this
              Section 11(i), the Company shall, as promptly as practicable,
              cause to be distributed to holders of record of Right Certificates
              on such record date Right Certificates evidencing, subject to
              Section 14 hereof, the additional Rights to which such holders
              shall be entitled as a result of such adjustment, or, at the
              option of the Company, shall cause to be distributed to such
              holders of record in substitution and replacement for the Right
              Certificates held by such holders prior to the date of adjustment,
              and upon surrender thereof, if required by the Company, new Right
              Certificates evidencing all the Rights to which such holders shall
              be entitled after such adjustment. Right Certificates so to be
              distributed shall be issued, executed and countersigned in the
              manner provided for herein and shall be registered in the names of
              the holders of record of Right Certificates on the record date
              specified in the public announcement.

     (j)      Irrespective of any adjustment or change in the Purchase Price or
              the number of one one-hundredths of a Preferred Share issuable
              upon the exercise of the Rights, the Right Certificates
              theretofore and thereafter issued may continue to express the
              Purchase Price and the number of one one-hundredths of a Preferred
              Share which were expressed in the initial Right Certificates
              issued hereunder.

     (k)      Before taking any action that would cause an adjustment reducing
              the Purchase Price below one one-hundredth of the then par value,
              if any, of the Preferred Shares issuable upon exercise of the
              Rights, the Company shall take any corporate 

                                       22

 
              action which may, in the opinion of its counsel, be necessary in
              order that the Company may validly and legally issue fully paid
              and nonassessable Preferred Shares at such adjusted Purchase
              Price.

     (l)      In any case in which this Section 11 shall require that an
              adjustment in the Purchase Price be made effective as of a record
              date for a specified event, the Company may elect to defer until
              the occurrence of such event the issuing to the holder of any
              Right exercised after such record date of the Preferred Shares and
              other capital stock or securities of the Company, if any, issuable
              upon such exercise over and above the Preferred Shares and other
              capital stock or securities of the Company, if any, issuable upon
              such exercise on the basis of the Purchase Price in effect prior
              to such adjustment; provided, however that the Company shall
                                  --------  -------
              deliver to such holder a due bill or other appropriate instrument
              evidencing such holder's right to receive such additional shares
              upon the occurrence of the event requiring such adjustment.

     (m)      Anything in this Section 11 to the contrary notwithstanding, the
              Company shall be entitled to make such reductions in the Purchase
              Price, in addition to those adjustments expressly required by this
              Section 11, as and to the extent that it in its sole discretion
              shall determine to be advisable in order that any consolidation or
              subdivision of the Preferred Shares, issuance wholly for cash of
              any Preferred Shares at less than the current market price,
              issuance wholly for cash of Preferred Shares or securities which
              by their terms are convertible into or exchangeable for Preferred
              Shares, dividends on Preferred Shares payable in Preferred Shares
              or issuance of rights, options or warrants referred to hereinabove
              in Section 11(b), hereafter made by the Company to holders of its
              Preferred Shares shall not be taxable to such stockholders.

     (n)      In the event that at any time after the date of this Agreement and
              prior to the Distribution Date, the Company shall (i) declare or
              pay any dividend on the Common Shares payable in Common Shares or
              (ii) effect a subdivision, combination or consolidation of the
              Common Shares (by reclassification or otherwise than by payment of
              dividends in Common Shares) into a greater or lesser number of
              Common Shares, then in any such case (A) the number of one one-
              hundredths of a Preferred Share purchasable after such event upon
              proper exercise of each Right shall be determined by multiplying
              the number of one one-hundredths of a Preferred Share so
              purchasable immediately prior to such event by a fraction, the
              numerator of which is the number of Common Shares outstanding
              immediately before such event and the denominator of which is the
              number of Common Shares outstanding immediately after such event,
              and (B) each Common Share outstanding immediately after such event
              shall have issued with respect to it that number of Rights which
              each Common Share outstanding immediately prior to such event had
              issued with respect to it. The adjustments provided for in this

                                       23

 
              Section 11(n) shall be made successively whenever such a dividend
              is declared or paid or such a subdivision, combination or
              consolidation is effected.

SECTION 12.  CERTIFICATE OF ADJUSTED PURCHASE PRICE OR NUMBER OF SHARES.

     Whenever an adjustment is made as provided in Sections 11 and 13 hereof,
the Company shall promptly (a) prepare a certificate setting forth such
adjustment, and a brief statement of the facts accounting for such adjustment,
(b) file with the Rights Agent and with each transfer agent for the Common
Shares or the Preferred Shares a copy of such certificate and (c) mail a brief
summary thereof to each holder of a Right Certificate in accordance with Section
25 hereof.  Notwithstanding the foregoing sentence, the failure by the Company
to make such certification or give such notice shall not affect the validity of
or the force or effect of the requirement for such adjustment.  The Rights Agent
shall be fully protected in relying on any such certificate and on any
adjustment contained therein and shall not be deemed to have knowledge of such
adjustment unless and until it shall have received such certificate.

SECTION 13.  CONSOLIDATION, MERGER OR SALE OR TRANSFER OF ASSETS OR EARNING
POWER.

     (a)  Except as provided in Section 13(b) hereof, in the event, directly or
indirectly, (1) the Company shall consolidate with, or merge with and into, any
other Person, (2) any Person shall consolidate with the Company, or merge with
and into the Company and the Company shall be the continuing or surviving
corporation of such consolidation or merger and, in connection with such
consolidation or merger, all or part of the Common Shares shall be changed into
or exchanged for stock or other securities of any other Person (or the Company)
or cash or any other property, or (3) the Company shall sell or otherwise
transfer (or one or more of its Subsidiaries shall sell or otherwise transfer),
in one or more transactions, directly or indirectly, assets or earning power
aggregating 50% or more of the assets or earning power of the Company and its
Subsidiaries (taken as a whole) to any other Person other than the Company or
one or more of its wholly-owned Subsidiaries, then, and in each such case,
proper provision shall be made so that (i) each holder of a Right (except as
otherwise provided herein) shall thereafter have the right to receive, upon the
exercise thereof at a price equal to the then current Purchase Price multiplied
by the number of one one-hundredths of a Preferred Share for which a Right is
then exercisable, in accordance with the terms of this Agreement and in lieu of
Preferred Shares, such number of Common Shares of such other Person (including
the Company as successor thereto or as the surviving corporation) as shall equal
the result obtained by (A) multiplying the then current Purchase Price by the
number of one one-hundredths of a Preferred Share for which a Right is then
exercisable and dividing that product by (B) 50% of the then current per share
market price of the Common Shares of such other Person (determined pursuant to
Section 11(d) hereof) on the date of consummation of such consolidation, merger,
sale or transfer; (ii) the issuer of such Common Shares shall thereafter be
liable for, and shall assume, by virtue of such consolidation, merger, sale or
transfer, all the obligations and duties of the Company pursuant to this
Agreement; (iii) the term "Company" shall thereafter be deemed to refer to such
issuer; and (iv) such issuer shall take such steps (including, but not limited
to, the reservation of a sufficient number of its Common Shares in accordance
with Section 9 hereof) in connection with such 

                                       24

 
consummation as may be necessary to assure that the provisions hereof shall
thereafter be applicable, as nearly as reasonably may be, in relation to the
Common Shares thereafter deliverable upon the exercise of the Rights. The
Company shall not consummate any such consolidation, merger, sale or transfer
unless prior thereto the Company and such issuer shall have executed and
delivered to the Rights Agent a supplemental agreement so providing. The Company
shall not enter into any transaction of the kind referred to in this Section 13
if at the time of such transaction there are any rights, warrants, instruments
or securities outstanding or any agreements or arrangements which, as a result
of the consummation of such transaction, would eliminate or substantially
diminish the benefits intended to be afforded by the Rights. The provisions of
this Section 13 shall similarly apply to successive mergers or consolidations or
sales or other transfers.

          The supplemental agreement referred to above in this Section 13(a) to
be entered into by the Company and the Rights Agent shall also provide that, as
soon as practicable after the date of any of the events described in Section
13(a), such issuer shall:

     (a)(i)   prepare and file a registration statement under the Securities Act
              with respect to the Rights and the securities purchasable upon
              exercise of the Rights on an appropriate form, use its best
              efforts to cause such registration statement to become effective
              as soon as practicable after such filing and use its best efforts
              to cause such registration statement to remain effective (with a
              prospectus at all times meeting the requirements of the Securities
              Act) until the Final Expiration Date, and similarly comply with
              applicable state securities laws;

     (a)(ii)  use its best efforts to list (or continue the listing of) the
              Rights and the securities purchasable upon exercise of the Rights
              on a national securities exchange or to meet the eligibility
              requirements for quotation on NASDAQ; and

     (a)(iii) deliver to holders of the Rights historical financial statements
              for such issuer which comply in all respects with the requirements
              for registration on Form 10 (or any successor form) under the
              Exchange Act.

     (b)  In the event of any merger or other acquisition transaction involving
the Company pursuant to an agreement described in Section 1(c)(ii)(A)(2), the
provisions of Section 13(a) hereof shall not be applicable to such transaction
and this Rights Agreement and the rights of holders of Rights hereunder shall be
terminated in accordance with Section 7(a) hereof.

     (c)  The term "issuer," for purposes of this Section 13, shall refer to the
Person (or Affiliate or Associate) referred to in Section 13(a); provided,
however, that (i) if such Person (or Affiliate or Associate) is a direct or
indirect Subsidiary of another Person, the term "issuer" shall refer to such
other Person, and (ii) in case such Person is a Subsidiary, directly or
indirectly, of more than one Person, the term "issuer" shall refer to whichever
of such Persons is the issuer of such Common Shares having the greatest
aggregate value.

                                       25

 
     (d)  If, for any reason, the Rights cannot be exercised for Common Shares
of such issuer as provided in Section 13(a), then each holder of Rights shall
have the right to exchange its Rights for cash from such issuer in an amount
equal to the number of Common Shares that it would otherwise be entitled to
purchase multiplied by 50% of the current per share market price, as determined
pursuant to Section 11(d) hereof, of such Common Shares of such issuer. If, for
any reason, the foregoing provision cannot be applied to determine the cash
amount into which the Rights are exchangeable, then the Board of Directors of
the Company, upon approval by a majority of the Continuing Directors, based upon
the advice of one or more nationally recognized investment banking firms, shall
determine such amount reasonably and with good faith to the holders of Rights.
Any such determination shall be final and binding on the Rights Agent and the
holders of Rights.

SECTION 14.  FRACTIONAL RIGHTS AND FRACTIONAL SHARES.

     (a)  The Company shall not be required to issue fractions of Rights or to
distribute Right Certificates which evidence fractional Rights.  In lieu of such
fractional Rights, there shall be paid to the registered holders of the Right
Certificates with regard to which such fractional Rights would otherwise be
issuable, an amount in cash equal to the same fraction of the current market
value of a whole Right.  For the purposes of this Section 14(a), the current
market value of a whole Right shall be the closing price of the Rights for the
Trading Day immediately prior to the date on which such fractional Rights would
have been otherwise issuable.  The closing price for any day shall be the last
sale price, regular way, or, in case no such sale takes place on such day, the
average of the closing bid and asked prices, regular way, in either case as
reported in the principal consolidated transaction reporting system with respect
to securities listed or admitted to trading on the New York Stock Exchange or,
if the Rights are not listed or admitted to trading on the New York Stock
Exchange, as reported in the principal consolidated transaction reporting system
with respect to securities listed on the principal national securities exchange
on which the Rights are listed or admitted to trading or, if the Rights are not
listed or admitted to trading on any national securities exchange, the last
quoted price or, if not so quoted, the average of the high bid and low asked
prices in the over-the-counter market, as reported by NASDAQ or such other
system then in use or, if on any such date the Rights are not quoted by any such
organization, the average of the closing bid and asked prices as furnished by a
professional market maker making a market in the Rights selected by the Board of
Directors of the Company, upon approval by a majority of the Continuing
Directors.  If on any such date no such market maker is making a market in the
Rights, the fair value of the Rights on such date as determined in good faith by
the Board of Directors of the Company, upon approval by a majority of the
Continuing Directors, shall be used.

(b)  The Company shall not be required to issue fractions of Preferred Shares
(other than fractions which are integral multiples of one one-hundredth of a
Preferred Share) upon exercise of the Rights or to distribute certificates which
evidence fractional Preferred Shares (other than fractions which are integral
multiples of one one-hundredth of a Preferred Share). Fractions of Preferred
Shares in integral multiples of one one-hundredth of a Preferred Share may, at
the election of the Company, be evidenced by depositary receipts, pursuant to an

                                       26

 
appropriate agreement between the Company and a depositary selected by it;
provided, that such agreement shall provide that the holders of such depositary
- --------                                                                       
receipts shall have all the rights, privileges and preferences to which they are
entitled as beneficial owners of the Preferred Shares represented by such
depositary receipts.  In lieu of fractional Preferred Shares that are not
integral multiples of one one-hundredth of a Preferred Share, the Company shall
pay to the registered holders of Right Certificates at the time such Rights are
exercised as herein provided an amount in cash equal to the same fraction of the
current market value of one Preferred Share.  For the purposes of this Section
14(b), the current market value of a Preferred Share shall be the closing price
of a Preferred Share (as determined pursuant to the second sentence of Section
11(d)(i) hereof) for the Trading Day immediately prior to the date of such
exercise.

(c)  The holder of a Right by the acceptance of the Right expressly waives his
right to receive any fractional Rights or any fractional shares upon exercise of
a Right (except as provided above).

SECTION 15.  RIGHT OF ACTION.

     All rights of action in respect of this Agreement, excepting the rights of
action given to the Rights Agent under Section 18 hereof, are vested in the
respective registered holders of the Right Certificates (and, prior to the
Distribution Date, the registered holders of the Common Shares); and any
registered holder of any Right Certificate (or, prior to the Distribution Date,
of the Common Shares), without the consent of the Rights Agent or of the holder
of any other Right Certificate (or, prior to the Distribution Date, of the
Common Shares), may, in such holder's own behalf and for such holder's own
benefit, enforce, and may institute and maintain any suit, action or proceeding
against the Company to enforce, or otherwise act in respect of, such holder's
right to exercise the Rights evidenced by such Right Certificate in the manner
provided in such Right Certificate and in this Agreement.  Without limiting the
foregoing or any remedies available to the holders of Rights, it is specifically
acknowledged that the holders of Rights would not have an adequate remedy at law
for any breach of this Agreement and will be entitled to specific performance of
the obligations hereunder, and injunctive relief against actual or threatened
violations of the obligations of any Person subject to, this Agreement.

SECTION 16.  AGREEMENT OF RIGHT HOLDERS.

     Every holder of a Right, by accepting the same, consents and agrees with
the Company and the Rights Agent and with every other holder of a Right that:

     (a)  prior to the Distribution Date, the Rights will be transferable only
          in connection with the transfer of the Common Shares;

     (b)  after the Distribution Date, the Right Certificates are transferable
          only on the registry books of the Rights Agent if surrendered at the
          principal office of the Rights Agent, duly endorsed or accompanied by
          a proper instrument of transfer; and

                                       27

 
     (c)  subject to Sections 6 and 7(f) hereof, the Company and the Rights
          Agent may deem and treat the person in whose name the Right
          Certificate (or, prior to the Distribution Date, the associated Common
          Shares certificate) is registered as the absolute owner thereof and of
          the Rights evidenced thereby (notwithstanding any notations of
          ownership or writing on the Right Certificates or the associated
          Common Shares certificate made by anyone other than the Company or the
          Rights Agent) for all purposes whatsoever, and neither the Company nor
          the Rights Agent shall be affected by any notice to the contrary.

     (d)  notwithstanding anything in this Agreement to the contrary, neither
          the Company nor the Rights Agent shall have any liability to any
          holder of a Right or other Person as a result of its inability to
          perform any of its obligations under this Agreement by reason of any
          preliminary or permanent injunction or other order, decree or ruling
          issued by a court of competent jurisdiction or by a governmental,
          regulatory or administrative agency or commission, or any statute,
          rule, regulation or executive order promulgated or enacted by any
          governmental authority, prohibiting or otherwise restraining
          performance of such obligation; provided, however, the Company must
                                          --------  -------                  
          use its best efforts to have any such order, decree or ruling lifted
          or otherwise overturned as soon as possible.

SECTION 17.  RIGHT CERTIFICATE HOLDER NOT DEEMED A STOCKHOLDER.

     No holder, as such, of any Right Certificate shall be entitled to vote,
receive dividends or be deemed for any purpose the holder of the Preferred
Shares or any other securities of the Company which may at any time be issuable
on the exercise of the Rights represented thereby, nor shall anything contained
herein or in any Right Certificate be construed to confer upon the holder of any
Right Certificate, as such, any of the rights of a stockholder of the Company or
any right to vote for the election of directors or upon any matter submitted to
stockholders at any meeting thereof, or to give or withhold consent to any
corporate action, or to receive notice of meetings or other actions affecting
stockholders (except as provided in Section 25 hereof), or to receive dividends
or subscription rights, or otherwise, until the Right or Rights evidenced by
such Right Certificate shall have been exercised in accordance with the
provisions hereof.
 
SECTION 18.  CONCERNING THE RIGHTS AGENT.

     (a)  The Company agrees to pay to the Rights Agent reasonable compensation
for all services rendered by it hereunder and, from time to time, on demand of
the Rights Agent, its reasonable expenses and counsel fees and other
disbursements incurred in the administration and execution of this Agreement and
the exercise and performance of its duties hereunder.  The Company also agrees
to indemnify the Rights Agent for, and to hold it harmless against, any loss,
liability, suit, action, proceeding or expense, incurred without gross
negligence, bad faith or willful misconduct on the part of the Rights Agent, for
any action taken, suffered or omitted by the Rights Agent in connection with the
execution, acceptance and administration of this 

                                       28

 
Agreement and the exercise and performance hereunder of its duties, including
the costs and expenses of defending against and appealing any claim of liability
arising therefrom. The indemnity provided herein shall survive the termination
of this Agreement and the expiration of the Rights.

     (b)  The Rights Agent shall be protected and shall incur no liability for,
or in respect of any action taken, suffered or omitted by it in connection with,
its administration of this Agreement or the exercise and performance of its
duties hereunder in reliance upon any Right Certificate or certificate for the
Preferred Shares or Common Shares or for other securities of the Company,
instrument of assignment or transfer, power of attorney, endorsement, affidavit,
letter, notice, direction, consent, certificate, statement, or other paper or
document believed by it to be genuine and to be signed, executed and, where
necessary, verified or acknowledged, by the proper person or persons, or
otherwise upon the advice of counsel as set forth in Section 20 hereof.

SECTION 19.  MERGER OR CONSOLIDATION OR CHANGE OF NAME OF RIGHTS AGENT.

     (a)  Any corporation into which the Rights Agent or any successor Rights
Agent may be merged or with which it may be consolidated, or any corporation
resulting from any merger or consolidation to which the Rights Agent or any
successor Rights Agent shall be a party, or any corporation succeeding to the
stock transfer or corporate trust business of the Rights Agent or any successor
Rights Agent, shall be the successor to the Rights Agent under this Agreement
without the execution or filing of any paper or any further act on the part of
any of the parties hereto, provided that such corporation would be eligible for
appointment as a successor Rights Agent under the provisions of Section 21
hereof.  In case at the time such successor Rights Agent shall succeed to the
agency created by this Agreement any of the Right Certificates shall have been
countersigned but not delivered, any such successor Rights Agent may adopt the
countersignature of the predecessor Rights Agent and deliver such Right
Certificates so countersigned; and in case at that time any of the Right
Certificates shall not have been countersigned, any successor Rights Agent may
countersign such Right Certificates either in the name of the predecessor Rights
Agent or in the name of the successor Rights Agent; and in all such cases such
Right Certificates shall have the full force provided in the Right Certificates
and in this Agreement.

     (b)  In case at any time the name of the Rights Agent shall be changed and
at such time any of the Right Certificates shall have been countersigned but not
delivered, the Rights Agent may adopt the countersignature under its prior name
and deliver Right Certificates so countersigned; and in case at that time any of
the Right Certificates shall not have been countersigned, the Rights Agent may
countersign such Right Certificates either in its prior name or in its changed
name; and in all such cases such Right Certificates shall have the full force
provided in the Right Certificates and in this Agreement.

                                       29

 
SECTION 20.  DUTIES OF RIGHTS AGENT.
 
     The Rights Agent undertakes the duties and obligations imposed by this
Agreement upon the following terms and conditions, by all of which the Company
and the holders of Right Certificates, by their acceptance thereof, shall be
bound:

     (a)  The Rights Agent may consult with legal counsel of its choice (who may
be legal counsel for the Company), and the opinion of such counsel shall be full
and complete authorization and protection to the Rights Agent as to any action
taken, suffered or omitted by it in good faith and in accordance with such
opinion.

     (b)  Whenever in the administration, exercise and performance of its duties
under this Agreement the Rights Agent shall deem it necessary or desirable that
any fact or matter be proved or established by the Company prior to taking,
suffering or omitting any action hereunder, such fact or matter (unless other
evidence in respect thereof be herein specifically prescribed) may be deemed to
be conclusively proved and established by a certificate signed by any one of the
Chairman of the Board, the Chief Executive Officer, the President, any Vice
President, the Treasurer or the Secretary of the Company and delivered to the
Rights Agent; and such certificate shall be full authorization to the Rights
Agent for any action taken, suffered or omitted in good faith by it under the
provisions of this Agreement in reliance upon such certificate.

     (c)  The Rights Agent shall be liable hereunder to the Company and any
other Person only for its own negligence, bad faith or willful misconduct.

     (d)  The Rights Agent shall not be liable for or by reason of any of the
representations, warranties, or statements of fact or recitals contained in this
Agreement or in the Right Certificates (except its countersignature thereof) or
be required to verify the same, but all such representations, warranties, or
statements and recitals are and shall be deemed to have been made by the Company
only.

     (e)  The Rights Agent shall not be under any liability or responsibility in
respect of the legality, validity or enforceability of this Agreement or the
execution and delivery hereof (except the due execution hereof by the Rights
Agent) or in respect of the legality, validity or enforceability or the
execution of any Right Certificate (except its countersignature thereof); nor
shall it be liable or responsible for any breach by the Company of any covenant
or condition contained in this Agreement or in any Right Certificate; nor shall
it be liable or responsible for any change in the exercisability of the Rights
(including the Rights becoming void pursuant to Section 11(a)(ii) hereof) or any
adjustment in the terms of the Rights (including the manner, method or amount
thereof) provided for in Section 3, 11, 13, 23 or 24, or the ascertaining of the
existence of facts that would require any such change or adjustment (except with
respect to the exercise of Rights evidenced by Right Certificates after receipt
of the certificate described in Section 12 hereof); nor shall it by any act
hereunder be deemed to make any representation or warranty as to the
authorization or reservation of any Preferred Shares to be issued pursuant to

                                       30

 
this Agreement or any Right Certificate or as to whether any Preferred Shares
will, when issued, be validly authorized and issued, fully paid and
nonassessable.

     (f)  The Company agrees that it will perform, execute, acknowledge and
deliver or cause to be performed, executed, acknowledged and delivered all such
further and other acts, instruments and assurances as may reasonably be required
by the Rights Agent for the carrying out or performing by the Rights Agent of
the provisions of this Agreement.

     (g)  The Rights Agent is hereby authorized and directed to accept
instructions with respect to the administration, exercise and performance of its
duties hereunder from any one of the Chairman of the Board, the Chief Executive
Officer, the President, any Vice President, the Secretary or the Chief Financial
Officer of the Company, and to apply to such officers for advice or instructions
in connection with its duties, and it shall not be responsible or liable for any
action taken, suffered or omitted by it in good faith in accordance with
instructions of any such officer or for any delay in acting while waiting for
those instructions.  Any application by the Rights Agent for written
instructions from the Company may, at the option of the Rights Agent, set forth
in writing any action proposed to be taken or omitted by the Rights Agent under
this Rights Agreement and the date on and/or after which such action shall be
taken or such omission shall be effective.  The Rights Agent shall not be liable
for any action taken by, or omission of, the Rights Agent in accordance with a
proposal included in any such application on or after the date specified in such
application (which date shall not be less than five (5) Business Days after the
date any officer of the Company actually received such application, unless any
such officer shall have consented in writing to an earlier date) unless, prior
to taking any such action (or the effective date in the case of an omission),
the Rights Agent shall have received written instructions in response to such
application specifying the action to be taken or omitted.

     (h)  The Rights Agent and any stockholder, director, officer or employee of
the Rights Agent may buy, sell or deal in any of the Rights or other securities
of the Company or become pecuniarily interested in any transaction in which the
Company may be interested, or contract with or lend money to the Company or
otherwise act as fully and freely as though it were not Rights Agent under this
Agreement.  Nothing herein shall preclude the Rights Agent from acting in any
other capacity for the Company or for any other legal entity.

     (i)  The Rights Agent may execute and exercise any of the rights or powers
hereby vested in it or perform any duty hereunder either itself or by or through
its attorneys or agents, and the Rights Agent shall not be liable or accountable
for any act, default, omission, neglect or misconduct of any such attorneys or
agents or for any loss to the Company resulting from any such act, default,
omission, neglect or misconduct, provided reasonable care was exercised in the
selection and continued employment thereof.

     (j)  No provision of this Agreement shall require the Rights 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 its rights if
there shall be reasonable grounds for believing that

                                       31

 
repayment of such funds or adequate indemnification against such risk or
liability is not reasonably assured to it.

     (k)  If, with respect to any Right Certificate surrendered to the Rights
Agent for exercise or transfer, split-up, combination or exchange, the
certification on the form of assignment or form of election to purchase, as the
case may be, that the Rights evidenced by the Right Certificate are not owned by
an Acquiring Person, or an Affiliate or Associate thereof, has either not been
completed or in any manner indicates any other response thereto, the Rights
Agent shall not take any further action with respect to such requested exercise,
transfer, split-up, combination or exchange, without first consulting with the
Company.

SECTION 21.  CHANGE OF RIGHTS AGENT.

     The Rights Agent or any successor Rights Agent may resign and be discharged
from its duties under this Agreement upon thirty (30) days' notice in writing
mailed to the Company and to each transfer agent of the Common Shares or
Preferred Shares (as to which the Rights Agent has received prior written
notice) by registered or certified mail, and the Company shall mail notice
thereof to the holders of the Right Certificates by first-class mail.  The
Company may remove the Rights Agent or any successor Rights Agent upon thirty
(30) days' notice in writing, mailed to the Rights Agent or successor Rights
Agent, as the case may be, and to each transfer agent of the Common Shares or
Preferred Shares (as to which the Rights Agent has received prior written
notice) by registered or certified mail, and to the holders of the Right
Certificates by first-class mail.  If the Rights Agent shall resign or be
removed or shall otherwise become incapable of acting, the Company shall appoint
a successor to the Rights Agent.  If the Company shall fail to make such
appointment within a period of thirty (30) days after giving notice of such
removal or after it has been notified in writing of such resignation or
incapacity by the resigning or incapacitated Rights Agent or by the holder of a
Right Certificate (who shall, with such notice, submit such holder's Right
Certificate for inspection by the Company), then the registered holder of any
Right Certificate may apply to any court of competent jurisdiction for the
appointment of a new Rights Agent.  Any successor Rights Agent, whether
appointed by the Company or by such a court, shall be a corporation organized
and doing business under the laws of the United States or of any state of the
United States so long as such corporation is authorized to do business as a
banking institution, is in good standing, and is authorized under such laws to
exercise corporate trust or stock transfer powers and is subject to supervision
or examination by federal or state authority and which has at the time of its
appointment as Rights Agent a combined capital and surplus of at least $50
million.  After appointment, the successor Rights Agent shall be vested with the
same powers, rights, duties and responsibilities as if it had been originally
named as Rights Agent without further act or deed; but the predecessor Rights
Agent shall deliver and transfer to the successor Rights Agent any property at
the time held by it hereunder, and execute and deliver any further assurance,
conveyance, act or deed necessary for the purpose.  Not later than the effective
date of any such appointment the Company shall file notice thereof in writing
with the predecessor Rights Agent and each transfer agent of the Common Shares
or Preferred Shares, and mail a notice thereof in writing to the registered
holders of the Right Certificates.  Failure to give any notice provided for in
this Section 21, however, or any defect therein, shall 

                                       32

 
not affect the legality or validity of the resignation or removal of the Rights
Agent or the appointment of the successor Rights Agent, as the case may be.

SECTION 22.  ISSUANCE OF NEW RIGHT CERTIFICATES.

     Notwithstanding any of the provisions of this Agreement or of the Rights to
the contrary, the Company may, at its option, issue new Right Certificates
evidencing Rights in such form as may be approved by its Board of Directors,
upon approval by a majority of the Continuing Directors, to reflect any
adjustment or change in the Purchase Price and the number or kind or class of
shares or other securities or property purchasable under the Right Certificates
made in accordance with the provisions of this Agreement. In addition, in
connection with the issuance or sale of Common Shares following the Distribution
Date and prior to the redemption or expiration of the Rights, the Company (a)
shall, with respect to Common Shares so issued or sold pursuant to the exercise
of stock options or under any employee benefit plan or arrangement or upon the
exercise, conversion or exchange of securities of the Company currently
outstanding or issued at any time in the future by the Company and (b) may, in
any other case, if deemed necessary or appropriate by the Board of Directors of
the Company, upon approval by a majority of the Continuing Directors, issue
Right Certificates representing the appropriate number of Rights in connection
with such issuance or sale; provided, however, that (i) no such Right
                            --------  -------                        
Certificate shall be issued and this sentence shall be null and void ab initio
                                                                     -- ------
if, and to the extent that, such issuance or this sentence would create a
significant risk of or result in material adverse tax consequences to the
Company or the Person to whom such Right Certificate would be issued or would
create a significant risk of or result in such options' or employee plans' or
arrangements' failing to qualify for otherwise available special tax treatment
and (ii) no such Right Certificate shall be issued if, and to the extent that,
appropriate adjustment shall otherwise have been made in lieu of the issuance
thereof.

SECTION 23.  REDEMPTION.

     (a)  The Company may, at its option, upon approval by a majority of the
Continuing Directors, at any time prior to the earliest of (i) the tenth (10th)
business day following the Shares Acquisition Date, or (ii) such date or dates
on or after the tenth (10th) business day following the Shares Acquisition Date
to which such option may be extended by a majority of the Continuing Directors
(for one or more successive ten (10) day periods) by vote(s) first taken or
written consent(s) first given prior to the tenth (10th) business day following
the Shares Acquisition Date and, thereafter, prior to the completion of any such
(ten) 10 day extension or extensions (or, if the Shares Acquisition Date shall
have occurred prior to the Record Date, prior to (A) the tenth (10th) business
day following the Record Date or (B) such date or dates on or after the tenth
business day after the Record Date to which such option may be extended by a
majority of the Continuing Directors (for one or more successive ten (10) day
periods) by vote(s) first taken or written consent(s) first given prior to the
tenth business day following the Record Date and, thereafter, prior to the
completion of any such 10 day extension or extensions), redeem all but not less
than all the then outstanding Rights at a redemption price of $.01 per Right,
appropriately adjusted to reflect any stock split, stock dividend or similar
transaction occurring after the date 

                                       33

 
hereof (such redemption price being hereinafter referred to as the "Redemption
Price"), and the Company may, at its option, pay the Redemption Price either in
cash, Common Shares (based on the current per share market price thereof (as
determined pursuant to Section 11(d)) at the time of redemption), or any other
form of consideration deemed appropriate by the Board of Directors. The
redemption of the Rights by the Board of Directors may be made effective at such
time on such basis and with such conditions as the Board of Directors in its
sole discretion may establish, upon approval by a majority of the Continuing
Directors.

     (b)  Immediately upon the action of the Board of Directors of the Company
ordering the redemption of the Rights pursuant to Section 23(a), and without any
further action and without any notice, the right to exercise the Rights will
terminate and the only right thereafter of the holders of Rights shall be to
receive the Redemption Price. The Company shall promptly give public notice of
any such redemption; provided, however, that the failure to give, or any defect
in, any such notice shall not affect the validity of such redemption. Within ten
(10) days after such action of the Board of Directors ordering the redemption of
the Rights, the Company shall give notice of such redemption to the Rights Agent
and shall mail a notice of redemption to all the holders of the then outstanding
Rights at their last addresses as they appear upon the registry books of the
Rights Agent or, prior to the Distribution Date, on the registry books of the
transfer agent for the Common Shares. Any notice which is mailed in the manner
herein provided shall be deemed given, whether or not the holder receives the
notice. Each such notice of redemption will state the method by which the
payment of the Redemption Price will be made. Neither the Company nor any of its
Affiliates or Associates may redeem, acquire or purchase for value any Rights at
any time in any manner other than that specifically set forth in this Section 23
or in Section 24 hereof, and other than in connection with the purchase of
Common Shares prior to the Distribution Date. Notwithstanding anything contained
in this Agreement to the contrary, the Rights shall not be exercisable pursuant
to Section 11(a)(ii) at any time when the Rights are redeemable under this
Section 23.

SECTION 24.  EXCHANGE.

     (a)  The Company, at its option, upon approval by a majority of the
Continuing Directors, at any time after any Person becomes an Acquiring Person,
may exchange all or part of the then outstanding and exercisable Rights (which
shall not include Rights that have become void pursuant to the provisions of
Section 11(a)(ii) hereof) for Common Shares at an exchange ratio of one Common
Share per Right, appropriately adjusted to reflect any stock split, stock
dividend or similar transaction occurring after the date hereof (such exchange
ratio being hereinafter referred to as the "Exchange Ratio").  Notwithstanding
the foregoing, the Board of Directors shall not be empowered to effect such
exchange at any time after any Person (other than the Company, any Subsidiary of
the Company, any employee benefit plan of the Company or any such Subsidiary, or
any entity holding Common Shares for or pursuant to the terms of any such plan),
together with all Affiliates and Associates of such Person, becomes the
Beneficial Owner of 50% or more of the Common Shares then outstanding.

                                       34

 
     (b)  Immediately upon the action of the Board of Directors of the Company
ordering the exchange of any Rights pursuant to Section 24(a) and without any
further action and without any notice, the right to exercise such Rights shall
terminate and the only right thereafter of a holder of such Rights shall be to
receive that number of Common Shares equal to the number of such Rights held by
such holder multiplied by the Exchange Ratio.  The Company shall promptly give
public notice of any such exchange; provided, however that the failure to give,
or any defect in, such notice shall not affect the validity of such exchange.
The Company promptly shall mail a notice of any such exchange to all of the
holders of such Rights at their last addresses as they appear upon the registry
books of the Rights Agent.  Any notice which is mailed in the manner herein
provided shall be deemed given, whether or not the holder receives the notice.
Each such notice of exchange will state the method by which the exchange of the
Common Shares for Rights will be effected and, in the event of any partial
exchange, the number of Rights which will be exchanged.  Any partial exchange
shall be effected pro rata based on the number of Rights (other than Rights
which have become void pursuant to the provisions of Section 11(a)(ii) hereof)
held by each holder of Rights.

     (c)  In any exchange pursuant to this Section 24, the Company, at its
option, may substitute Preferred Shares (or equivalent preferred shares, as such
term is defined in Section 11(b) hereof) for Common Shares exchangeable for
Rights, at the initial rate of one one-hundredth of a Preferred Share (or
equivalent preferred share) for each Common Share, as appropriately adjusted to
reflect adjustments in the voting rights of the Preferred Shares pursuant to the
terms thereof, so that the fraction of a Preferred Share delivered in lieu of
each Common Share shall have the same voting rights as one Common Share.

     (d)  In the event that there shall not be sufficient Common Shares or
Preferred Shares issued but not outstanding or authorized but unissued to permit
any exchange of Rights as contemplated in accordance with Section 24(a), the
Company shall either take such action as may be necessary to authorize
additional Common Shares or Preferred Shares for issuance upon exchange of the
Rights or alternatively, at the option of the Board of Directors, upon approval
by a majority of the Continuing Directors, with respect to each Right (i) pay
cash in an amount equal to the Purchase Price, in lieu of issuing Common Shares
or Preferred Shares in exchange therefor, or (ii) issue debt or equity
securities, or a combination thereof, having a value equal to the Current Value
(as hereinafter defined) of the Common Shares or Preferred Shares exchangeable
for each such Right, where the value of such securities shall be determined by a
nationally recognized investment banking firm selected by the Board of
Directors, upon approval by a majority of the Continuing Directors, or (iii)
deliver any combination of cash, property, Common Shares, Preferred Shares
and/or other securities having a value equal to the Current Value in exchange
for each Right.  The term "Current Value", for the purposes of this Section 24,
shall mean the product of the current per share market price of Common Shares
(determined pursuant to Section 11(d) on the date of the occurrence of the event
described above in subparagraph (a)) multiplied by the number of Common Shares
for which the Right otherwise would be exchangeable if there were sufficient
shares available.  To the extent that the Company determines that some action
need be taken pursuant to clauses (i), (ii) or (iii) of this Section 24(d), the
Board of Directors, upon approval by a majority of the Continuing Directors, may

                                       35

 
temporarily suspend the exercisability of the Rights for a period of up to sixty
(60) days following the date on which the event described in Section 24(a) shall
have occurred, in order to seek any authorization of additional Common Shares or
Preferred Shares and/or to decide the appropriate form of distribution to be
made pursuant to the above provision and to determine the value thereof.  In the
event of any such suspension, the Company shall issue a public announcement
stating that the exercisability of the Rights has been temporarily suspended.

     (e)  The Company shall not be required to issue fractions of Common Shares
or to distribute certificates which evidence fractional Common Shares.  In lieu
of such fractional Common Shares, the Company shall pay to the registered
holders of the Right Certificates with regard to which such fractional Common
Shares would otherwise be issuable an amount in cash equal to the same fraction
of the current market value of a whole Common Share.  For the purposes of this
paragraph (e), the current market value of a whole Common Share shall be the
closing price of a Common Share (as determined pursuant to the second sentence
of Section 11(d)(i) hereof) for the Trading Day immediately prior to the date of
exchange pursuant to this Section 24.

SECTION 25.  NOTICE OF CERTAIN EVENTS.

     (a)  In case the Company shall propose:  (i) to pay any dividend payable in
stock of any class to the holders of its Preferred Shares or to make any other
distribution to the holders of its Preferred Shares (other than a regular
quarterly cash dividend); (ii) to offer to the holders of its Preferred Shares
rights or warrants to subscribe for or to purchase any additional Preferred
Shares or shares of stock of any class or any other securities, rights or
options; (iii) to effect any reclassification of its Preferred Shares (other
than a reclassification involving only the subdivision of outstanding Preferred
Shares); (iv) to effect any consolidation or merger into or with, or to effect
any sale or other transfer (or to permit one or more of its Subsidiaries to
effect any sale or other transfer), in one or more transactions, of 50% or more
of the assets or earning power of the Company and its Subsidiaries (taken as a
whole) to, any other Person; (v) to effect the liquidation, dissolution or
winding up of the Company; or (vi) to declare or pay any dividend on the Common
Shares payable in Common Shares or to effect a subdivision, combination or
consolidation of the Common Shares (by reclassification or otherwise than by
payment of dividends in Common Shares), then, in each such case, the Company
shall give to each holder of a Right Certificate, in accordance with Section 26
hereof, a notice of such proposed action, which shall specify the record date
for the purposes of such stock dividend, or distribution of rights or warrants,
or the date on which such reclassification, consolidation, merger, sale,
transfer, liquidation, dissolution, or winding up is to take place and the date
of participation therein by the holders of the Common Shares and/or Preferred
Shares, if any such date is to be fixed, and such notice shall be so given in
the case of any action covered by clause (i) or (ii) above at least ten (10)
days prior to the record date for determining holders of the Preferred Shares
for purposes of such action, and in the case of any such other action, at least
ten (10) days prior to the date of the taking of such proposed action or the
date of participation therein by the holders of the Common Shares and/or
Preferred Shares, whichever shall be the earlier.

                                       36

 
     (b)  In case any of the events set forth in Section 11(a)(ii) hereof shall
occur, then the Company shall as soon as practicable thereafter give to each
holder of a Right Certificate, in accordance with Section 26 hereof, a notice of
the occurrence of such event, which notice shall describe such event and the
consequences of such event to holders of Rights under Section 11(a)(ii) hereof.
In the event any Person becomes an Acquiring Person, the Company will promptly
notify the Rights Agent thereof.

SECTION 26.  NOTICES.

     Notices or demands authorized by this Agreement to be given or made by the
Rights Agent or by the holder of any Right Certificate to or on the Company
shall be sufficiently given or made if sent by first-class mail, postage
prepaid, addressed (until another address is filed in writing with the Rights
Agent) as follows:

               Mycogen Corporation
               5501 Oberlin Drive
               San Diego, California  92121
               Attention: Carlton J. Eibl

     Subject to the provisions of Section 21 hereof, any notice or demand
authorized by this Agreement to be given or made by the Company or by the holder
of any Right Certificate to or on the Rights Agent shall be sufficiently given
or made if sent by first-class mail, postage prepaid, addressed (until another
address is filed in writing with the Company) as follows:        

               The First National Bank of Boston
               435 Tasso Street
               Suite 250
               Palo Alto, California  94301
               Attention:  Geoffrey Anderson

     Notices or demands authorized by this Agreement to be given or made by the
Company or the Rights Agent to the holder of any Right Certificate shall be
sufficiently given or made if sent by first-class mail, postage prepaid,
addressed to such holder at the address of such holder as shown on the registry
books of the Company.

SECTION 27.  SUPPLEMENTS AND AMENDMENTS.

     Prior to the Distribution Date, the Company may supplement or amend this
Agreement in any respect, without the approval of any holders of Rights, by
action of its Board of Directors upon approval by a majority of the Continuing
Directors, and the Rights Agent shall, if the Company so directs, execute such
supplement or amendment. From and after the Distribution Date, the Company may
from time to time supplement or amend this Agreement without the approval of any
holders of Rights, by action of its Board of Directors, upon approval by a
majority of the Continuing Directors, in order to cure any ambiguity, to correct
or supplement 

                                       37

 
any provision contained herein which may be defective or inconsistent with any
other provisions herein, or to make any other provisions with respect to the
Rights which the Company may deem necessary or desirable and which shall be
consistent with, and for the purpose of fulfilling, the objectives of the Board
of Directors in adopting this Agreement, including, without limitation, to
change the Purchase Price, the Redemption Price, any time periods herein
specified, and any other term hereof, any such supplement or amendment to be
evidenced by a writing signed by the Company and the Rights Agent; provided,
                                                                   --------
however, that from and after such time as any Person becomes an Acquiring
- -------
Person, this Agreement shall not be amended in any manner which would adversely
affect the interests of the holders of Rights. Upon receipt of a certificate
from an appropriate officer of the Company that the proposed supplement or
amendment is consistent with this Section 27 and, after such time as any Person
has become an Acquiring Person, that the proposed supplement or amendment does
not adversely affect the interests of the holders of Rights, the Rights Agent
shall execute such supplement or amendment. Without limiting the foregoing, the
Company may at any time prior to such time as any Person becomes an Acquiring
Person, by action of its Board of Directors, upon approval by a majority of the
Continuing Directors, amend this Agreement to lower the thresholds set forth in
Sections 1(a) and 3(a) to not less than the greater of (i) any percentage
greater than the largest percentage of the outstanding Common Shares then known
by the Company to be beneficially owned by any Person (other than the Company,
any Subsidiary of the Company, any employee benefit plan of the Company or any
Subsidiary of the Company, or any entity holding Common Shares for or pursuant
to the terms of any such plan) and (ii) 10%.

SECTION 28.  SUCCESSORS.

     All the covenants and provisions of this Agreement by or for the benefit of
the Company or the Rights Agent shall bind and inure to the benefit of their
respective successors and assigns hereunder.

SECTION 29.  DETERMINATIONS AND ACTIONS BY THE BOARD OF DIRECTORS.

     For all purposes of this Agreement, any calculation of the number of Common
Shares outstanding at any particular time, including for purposes of determining
the particular percentage of such outstanding Common Shares of which any Person
is the Beneficial Owner, shall be made in accordance with the last sentence of
Rule 13d-3(d)(1)(i) of the General Rules and Regulations under the Exchange Act.
The Board of Directors of the Company (and, where specifically provided for
herein, only upon approval by a majority of the Continuing Directors) shall have
the exclusive power and authority to administer this Agreement and to exercise
all rights and powers specifically granted to the Board, or the Company, or as
may be necessary or advisable in the administration of this Agreement,
including, without limitation, the right and power to (i) interpret the
provisions of this Agreement and (ii) make all determinations deemed necessary
or advisable for the administration of this Agreement (including a determination
to redeem or not redeem the Rights or to amend the Agreement).  All such
actions, calculations, interpretations and determinations (including, for
purposes of clause (y) below, all omissions with respect to the foregoing),
which are done or made by the Board of Directors (or, where 

                                       38

 
specifically provided for herein, upon approval by a majority of the Continuing
Directors) in good faith, shall (x) be final, conclusive and binding on the
Company, the Rights Agent, the holders of the Right Certificates and all other
parties and (y) not subject the Board or the Continuing Directors to any
liability to the holders of the Rights.

SECTION 30.  BENEFITS OF THIS AGREEMENT.

     Nothing in this Agreement shall be construed to give to any person or
corporation other than the Company, the Rights Agent and the registered holders
of the Right Certificates (and, prior to the Distribution Date, the Common
Shares) any legal or equitable right, remedy or claim under this Agreement; but
this Agreement shall be for the sole and exclusive benefit of the Company, the
Rights Agent and the registered holders of the Right Certificates (and, prior to
the Distribution Date, the Common Shares).

SECTION 31.  SEVERABILITY.

     If any term, provision, covenant or restriction of this Agreement is held
by a court of competent jurisdiction or other authority to be invalid, void or
unenforceable, the remainder of the terms, provisions, covenants and
restrictions of this Agreement shall remain in full force and effect and shall
in no way be affected, impaired or invalidated; provided, however, that
                                                --------  -------      
notwithstanding anything in this Agreement to the contrary, if any such term,
provision, covenant or restriction is held by such court or authority to be
invalid, void or unenforceable and the Board of Directors of the Company, upon
approval by a majority of the Continuing Directors, determines in its good faith
judgment that severing the invalid language from this Agreement would adversely
affect the purpose or effect of this Agreement, the right of redemption set
forth in Section 23 hereof shall be reinstated and shall not expire until the
tenth business day following the date of such determination by the Board of
Directors of the Company.

SECTION 32.  GOVERNING LAW.

     This Agreement and each Right Certificate issued hereunder shall be deemed
to be a contract made under the laws of the State of California and for all
purposes shall be governed by and construed in accordance with the laws of such
State applicable to contracts to be made and performed entirely within such
State.

SECTION 33.  COUNTERPARTS.

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

                                       39

 
SECTION 34.  DESCRIPTIVE HEADINGS.

     Descriptive headings of the several Sections of this Agreement are inserted
or convenience only and shall not control or affect the meaning or construction
of any of the provisions hereof.

SECTION 35.  EFFECTIVE DATE.

     This Agreement will be effective as of the effective date of the merger as
contemplated by the Merger Agreement (the "Effective Date").

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed and attested, all as of the day and year first above written.

ATTEST:                                   MYCOGEN CORPORATION, a   
                                          California Corporation
 

By:___________________________            By:_________________________________
   Arthur J. Chatroo                         Jerry D. Caulder, Ph.D.
   Assistant Secretary                       Chairman of the Board
                                             and Chief Executive Officer


                                          By:_________________________________
                                             Carlton J. Eibl
                                             President, Chief Operating Officer
                                             and Secretary


ATTEST:                                   THE FIRST NATIONAL BANK OF
                                          BOSTON, a National Banking Association


By:___________________________               By:______________________________
  Name:_______________________                 Name:__________________________
  Title:______________________                 Title:_________________________

                                       40

 
                                   EXHIBIT A
                                   ---------

                      FORM OF CERTIFICATE OF DETERMINATION
                                       OF
                       RIGHTS, PREFERENCES AND PRIVILEGES
                                       OF
                 SERIES B JUNIOR PARTICIPATING PREFERRED STOCK
                                       OF
                              MYCOGEN CORPORATION






                                   [ATTACHED]

                                       41

 
                         CERTIFICATE OF DETERMINATION
                                      OF
                     RIGHTS, PREFERENCES AND PRIVILEGES OF
                 SERIES B JUNIOR PARTICIPATING PREFERRED STOCK
                                      OF
                              MYCOGEN CORPORATION



          The undersigned, Jerry D. Caulder and Carlton J. Eibl, do hereby
certify:

          (a)  That Jerry D. Caulder is the duly elected and acting Chief
Executive Officer of  Mycogen Corporation, a California corporation (the
"Corporation") and Carlton J. Eibl is the duly elected and acting President,
Chief Operating Officer and Secretary of the Corporation.

          (b)  That pursuant to the authority conferred upon the Board of
Directors of the Corporation (the "Board") by the Articles of Incorporation of
the Corporation, the Board on October 19, 1995, adopted the following
resolutions creating a series of 200,000 shares of Preferred Stock designated as
Series B Junior Participating Preferred Stock:

     NOW, THEREFORE, BE IT RESOLVED, that pursuant to the authority granted to
     and vested in the Board in accordance with the provisions of the Articles
     of Incorporation of the Corporation, the Board hereby creates a series of
     Preferred Stock, par value $.001 per share (the "Preferred Stock"), of the
     Corporation and hereby states the designation and number of shares and
     fixes the relative rights, preferences and limitations thereof (in addition
     to the provisions set forth in the Articles of Incorporation of the
     Corporation, which are applicable to the Preferred Stock of all classes and
     series), as Series B Junior Participating Preferred Stock as set forth in
     the Certificate of  Determination, attached to the Amended and Restated
     Rights Agreement as Exhibit "A".

     RESOLVED FURTHER, that two hundred thousand (200,000) Preferred Shares be,
     as of the Effective Date of the Merger (as such term is defined in the
     Rights Agreement), initially reserved for issuance upon exercise of the
     Rights, such number to be subject to adjustment from time to time in
     accordance with the Rights Agreement.

          1.   DESIGNATION AND AMOUNT.  The shares of such series shall be
               ----------------------                                     
designated as "Series B Junior Participating Preferred Stock" (the "Series B
Preferred Stock") and the number of shares constituting the Series B Preferred
Stock shall be Two Hundred Thousand (200,000).  Such number of shares may be
increased or decreased by resolution of the Board; provided, that no decrease
                                                   --------                  
shall reduce the number of shares of Series B Preferred Stock to a number less
than the number of shares then outstanding plus the number of shares reserved
for issuance upon the exercise of outstanding options, 

                                       42

 
rights or warrants or upon the conversion of any outstanding securities issued
by the Corporation convertible into Series B Preferred Stock.

          2.   DIVIDENDS AND DISTRIBUTIONS.
               --------------------------- 

          (a)  Subject to the rights of the holders of any shares of any series
of Preferred Stock (or any similar stock) ranking prior and superior to the
Series B Preferred Stock with respect to dividends, the holders of shares of
Series B Preferred Stock, in preference to the holders of Common Stock, par
value $.001 per share (the "Common Stock"), of the Corporation, and of any other
junior stock, shall be entitled to receive, when, as and if declared by the
Board out of funds legally available for the purpose, quarterly dividends
payable in cash on the first day of March, June, September and December in each
year (each such date being referred to herein as a "Quarterly Dividend Payment
Date"), commencing on the first Quarterly Dividend Payment Date after the first
issuance of a share or fraction of a share of Series B Preferred Stock, in an
amount per share (rounded to the nearest cent) equal to the greater of (a) $1 or
(b) subject to the provision for adjustment hereinafter set forth, 100 times the
aggregate per share amount of all cash dividends, and 100 times the aggregate
per share amount (payable in kind) of all non-cash dividends or other
distributions, other than a dividend payable in shares of Common Stock or a
subdivision of the outstanding shares of Common Stock (by reclassification or
otherwise), declared on the Common Stock since the immediately preceding
Quarterly Dividend Payment Date or, with respect to the first Quarterly Dividend
Payment Date, since the first issuance of any share or fraction of a share of
Series B Preferred Stock.  In the event the Corporation shall at any time
declare or pay any dividend on the Common Stock payable in shares of Common
Stock, or effect a subdivision or combination or consolidation of the
outstanding shares of Common Stock (by reclassification or otherwise than by
payment of a dividend in shares of Common Stock) into a greater or lesser number
of shares of Common Stock, then in each such case the amount to which holders of
shares of Series B Preferred Stock were entitled immediately prior to such event
under clause (b) of the preceding sentence shall be adjusted by multiplying such
amount by a fraction, the numerator of which is the number of shares of Common
Stock outstanding immediately after such event and the denominator of which is
the number of shares of Common Stock that were outstanding immediately prior to
such event.

          (b)  The Corporation shall declare a dividend or distribution on the
Series B Preferred Stock as provided in paragraph (a) of this Section
immediately after it declares a dividend or distribution on the Common Stock
(other than a dividend payable in shares of Common Stock); provided that, in the
event no dividend or distribution shall have been declared on the Common Stock
during the period between any Quarterly Dividend Payment Date and the next
subsequent Quarterly Dividend Payment Date, a dividend of $1 per share on the
Series B Preferred Stock shall nevertheless be payable on such subsequent
Quarterly Dividend Payment Date.

          (c)  Dividends shall begin to accrue and be cumulative on outstanding
shares of Series B Preferred Stock from the Quarterly Dividend Payment Date next
preceding the date of issue of such shares, unless the date of issue of such
shares is prior to the record date for the first Quarterly Dividend Payment
Date, in which case dividends on such shares shall begin to accrue from the date
of issue of such shares, or unless the date of issue is a Quarterly Dividend
Payment Date or is a date after the record 

                                       43

 
date for the determination of holders of shares of Series B Preferred Stock
entitled to receive a quarterly dividend and before such Quarterly Dividend
Payment Date, in either of which events such dividends shall begin to accrue and
be cumulative from such Quarterly Dividend Payment Date. Accrued but unpaid
dividends shall not bear interest. Dividends paid on the shares of Series B
Preferred Stock in an amount less than the total amount of such dividends at the
time accrued and payable on such shares shall be allocated pro rata on a share-
by-share basis among all such shares at the time outstanding. The Board may fix
a record date for the determination of holders of shares of Series B Preferred
Stock entitled to receive payment of a dividend or distribution declared
thereon, which record date shall be not more than 60 days prior to the date
fixed for the payment thereof.

          3.   VOTING RIGHTS.  The holders of shares of Series B Preferred Stock
               -------------                                                    
shall have the following voting rights:

          (a)  Subject to the provision for adjustment hereinafter set forth,
each share of Series B Preferred Stock shall entitle the holder thereof to 100
votes on all matters submitted to a vote of the stockholders of the Corporation.
In the event the Corporation shall at any time declare or pay any dividend on
the Common Stock payable in shares of Common Stock, or effect a subdivision or
combination or consolidation of the outstanding shares of Common Stock (by
reclassification or otherwise than by payment of a dividend in shares of Common
Stock) into a greater or lesser number of shares of Common Stock, then in each
such case the number of votes per share to which holders of shares of Series B
Preferred Stock were entitled immediately prior to such event shall be adjusted
by multiplying such number by a fraction, the numerator of which is the number
of shares of Common Stock outstanding immediately after such event and the
denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

          (b)  Except as otherwise provided herein, in any other Certificate of
Determination creating a series of Preferred Stock or any similar stock, or by
law, the holders of shares of Series B Preferred Stock and the holders of shares
of Common Stock and any other capital stock of the Corporation having general
voting rights shall vote together as one class on all matters submitted to a
vote of stockholders of the Corporation.

          (c) Except as set forth herein, or as otherwise provided by law,
holders of Series B Preferred Stock shall have no special voting rights and
their consent shall not be required (except to the extent they are entitled to
vote with holders of Common Stock as set forth herein) for taking any corporate
action.

          4.   CERTAIN RESTRICTIONS.
               -------------------- 

          (a)  Whenever quarterly dividends or other dividends or distributions
payable on the Series B Preferred Stock as provided in Section 2 are in arrears,
thereafter and until all accrued and unpaid dividends and distributions, whether
or not declared, on shares of Series B Preferred Stock outstanding shall have
been paid in full, the Corporation shall not:

                                       44

 
           (i)  declare or pay dividends, or make any other distributions, on
any shares of stock ranking junior (either as to dividends or upon liquidation,
dissolution or winding up) to the Series B Preferred Stock;

          (ii)  declare or pay dividends, or make any other distributions, on
any shares of stock ranking on a parity (either as to dividends or upon
liquidation, dissolution or winding up) with the Series B Preferred Stock,
except dividends paid ratably on the Series B Preferred Stock and all such
parity stock on which dividends are payable or in arrears in proportion to the
total amounts to which the holders of all such shares are then entitled;

         (iii)  redeem or purchase or otherwise acquire for consideration
shares of any stock ranking junior (either as to dividends or upon liquidation,
dissolution or winding up) to the Series B Preferred Stock, provided that the
Corporation may at any time redeem, purchase or otherwise acquire shares of any
such junior stock in exchange for shares of any stock of the Corporation ranking
junior (either as to dividends or upon dissolution, liquidation or winding up)
to the Series B Preferred Stock; or

          (iv)  redeem or purchase or otherwise acquire for consideration any
shares of Series B Preferred Stock, or any shares of stock ranking on a parity
with the Series B Preferred Stock, except in accordance with a purchase offer
made in writing or by publication (as determined by the Board) to all holders of
such shares upon such terms as the Board, after consideration of the respective
annual dividend rates and other relative rights and preferences of the
respective series and classes, shall determine in good faith will result in fair
and equitable treatment among the respective series or classes.

          (b) The Corporation shall not permit any subsidiary of the Corporation
to purchase or otherwise acquire for consideration any shares of stock of the
Corporation unless the Corporation could, under paragraph (a) of this Section 4,
purchase or otherwise acquire such shares at such time and in such manner.

          5.   RE-ACQUIRED SHARES.  Any shares of Series B Preferred Stock
               ------------------                                         
purchased or otherwise acquired by the Corporation in any manner whatsoever
shall be retired and canceled promptly after the acquisition thereof.  All such
shares shall upon their cancellation become authorized but unissued shares of
Preferred Stock and may be reissued as part of a new series of Preferred Stock
subject to the conditions and restrictions on issuance set forth herein, in the
Articles of Incorporation, or in any other Certificate of Determination creating
a series of Preferred Stock or any similar stock or as otherwise required by
law.

          6.   LIQUIDATION, DISSOLUTION OR WINDING UP.  Upon any liquidation,
               --------------------------------------                        
dissolution or winding up of the Corporation, no distribution shall be made (1)
to the holders of shares of stock ranking junior (either as to dividends or upon
liquidation, dissolution or winding up) to the Series B Preferred Stock unless,
prior thereto, the holders of shares of Series B Preferred Stock shall have
received $100 per share, plus an amount equal to accrued and unpaid dividends
and distributions thereon, whether or not declared, to the date of such payment,
provided that the holders of shares of Series B Preferred Stock shall be
entitled to receive an aggregate amount per share, subject to the provisions for
adjustment hereinafter set forth, equal to 100 times the aggregate amount to be
distributed per share to holders of 

                                       45

 
shares of Common Stock, or (2) to the holders of shares of stock ranking on a
parity (either as to dividends or upon liquidation, dissolution or winding up)
with the Series B Preferred Stock, except distributions made ratably on the
Series B Preferred Stock and all such parity stock in proportion to the total
amounts to which the holders of all such shares are entitled upon such
liquidation, dissolution or winding up. In the event the Corporation shall at
any time declare or pay any dividend on the Common Stock payable in shares of
Common Stock, or effect a subdivision or combination or consolidation of the
outstanding shares of Common Stock (by reclassification or otherwise than by
payment of a dividend in shares of Common Stock) into a greater or lesser number
of shares of Common Stock, then in each such case the aggregate amount to which
holders of shares of Series B Preferred Stock were entitled immediately prior to
such event under the proviso in clause (1) of the preceding sentence shall be
adjusted by multiplying such amount by a fraction, the numerator of which is the
number of shares of Common Stock outstanding immediately after such event and
the denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

          7.   CONSOLIDATION, MERGER, ETC.  In case the Corporation shall enter
               --------------------------                                      
into any consolidation, merger, combination or other transaction in which the
shares of Common Stock are exchanged for or changed into other stock or
securities, cash and/or any other property, then in any such case each share of
Series B Preferred Stock shall at the same time be similarly exchanged or
changed into an amount per share, subject to the provision for adjustment
hereinafter set forth, equal to 100 times the aggregate amount of stock,
securities, cash and/or any other property (payable in kind), as the case may
be, into which or for which each share of Common Stock is changed or exchanged.
In the event the Corporation shall at any time declare or pay any dividend on
the Common Stock payable in shares of Common Stock, or effect a subdivision or
combination or consolidation of the outstanding shares of Common Stock (by
reclassification or otherwise than by payment of a dividend in shares of Common
Stock) into a greater or lesser number of shares of Common Stock, then in each
such case the amount set forth in the preceding sentence with respect to the
exchange or change of shares of Series B Preferred Stock shall be adjusted by
multiplying such amount by a fraction, the numerator of which is the number of
shares of Common Stock outstanding immediately after such event and the
denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event.

          8.   NO REDEMPTION.  The shares of Series B Preferred Stock shall not
               -------------                                                   
be redeemable.

          9.   RANK.  The Series B Preferred Stock shall rank, with respect to
               ----                                                           
the payment of dividends and the distribution of assets, junior to all series of
any other class of the Corporation's Preferred Stock.

          10.  AMENDMENT.  The Articles of Incorporation of the Corporation
               ---------                                                   
shall not be amended in any manner which would materially alter or change the
powers, preferences or special rights of the Series B Preferred Stock so as to
effect them adversely without the affirmative vote of the holders of at least a
majority of the outstanding shares of Series B Preferred Stock, voting together
as a single class.

                                       46

 
          We further declare under penalty of perjury that the matters set forth
in the foregoing Certification of Determination are true and correct of our own
knowledge.

Executed at San Diego, California on October 19, 1995.


                                           ___________________________
                                           Jerry D. Caulder,
                                           Chief Executive Officer


                                           ___________________________
                                           Carlton J. Eibl, President,    
                                           Chief Operating Officer     
                                           and Secretary

                                       47

 
                                   EXHIBIT B
                                   ---------

                           Form of Right Certificate

Certificate No. R-                                               ________ Rights


          NOT EXERCISABLE AFTER FEBRUARY 20, 2002 OR EARLIER IF REDEMPTION OR
          EXCHANGE OCCURS.  THE RIGHTS ARE SUBJECT TO REDEMPTION AT THE OPTION
          OF THE COMPANY AT $.01 PER RIGHT AND TO EXCHANGE ON THE TERMS SET
          FORTH IN THE AMENDED AND RESTATED RIGHTS AGREEMENT.  UNDER CERTAIN
          CIRCUMSTANCES, RIGHTS BENEFICIALLY OWNED BY AN ACQUIRING PERSON OR AN
          AFFILIATE OR ASSOCIATE OF AN ACQUIRING PERSON (AS SUCH TERMS ARE
          DEFINED IN THE AMENDED AND RESTATED RIGHTS AGREEMENT) AND ANY
          SUBSEQUENT HOLDER OF SUCH RIGHTS MAY BECOME NULL AND VOID.  [THE
          RIGHTS REPRESENTED BY THIS RIGHT CERTIFICATE ARE OR WERE BENEFICIALLY
          OWNED BY A PERSON WHO WAS OR BECAME AN ACQUIRING PERSON OR AN
          AFFILIATE OR ASSOCIATE OF AN ACQUIRING PERSON (AS SUCH TERMS ARE
          DEFINED IN THE AMENDED AND RESTATED RIGHTS AGREEMENT).  ACCORDINGLY,
          THIS RIGHT CERTIFICATE AND THE RIGHTS REPRESENTED HEREBY MAY BECOME
          NULL AND VOID IN THE CIRCUMSTANCES SPECIFIED IN SUCH AMENDED AND
          RESTATED RIGHTS AGREEMENT.]/*/
                                     --




                                 Right Certificate

                                 MYCOGEN CORPORATION


          This certifies that____________________, or registered assigns, is the
registered owner of the number of Rights set forth above, each of which entitles
the owner thereof, subject to the terms, provisions and conditions of the
Amended and Restated Rights Agreement, dated as 

______________________________
   /*//  The portion of the legend in bracket shall be inserted only if
   --                                                                 
applicable and shall replace the preceding sentence.

                                       48

 
of October 19, 1995 (the "Rights Agreement"), by and between Mycogen
Corporation, a California corporation (the "Company"), and The First National
Bank of Boston (the "Rights Agent"), to purchase from the Company at any time
after the Distribution Date (as such term is defined in the Rights Agreement)
and prior to 5:00 P.M., Boston, Massachusetts time, on February 20, 2002 at the
office of the Rights Agent designated for such purpose, or at the office of its
successor as Rights Agent, one one-hundredth of a fully paid non-assessable
share of Series B Junior Participating Preferred Stock, par value $.001 per
share (the "Preferred Shares") of the Company, at a purchase price of $65.00 per
one one-hundredth of a Preferred Share (the "Purchase Price"), upon presentation
and surrender of this Right Certificate with the Form of Election to Purchase
duly executed. The number of Rights evidenced by this Right Certificate (and the
number of one one-hundredths of a Preferred Share which may be purchased upon
exercise hereof) set forth above, and the Purchase Price set forth above, are
the number and Purchase Price as of February 21, 1992 based on the Preferred
Shares as constituted at such date. As provided in the Rights Agreement, the
Purchase Price and the number of one one-hundredths of a Preferred Share which
may be purchased upon the exercise of the Rights evidenced by this Right
Certificate are subject to modification and adjustment upon the happening of
certain events.

          This Right Certificate is subject to all of the terms, provisions and
conditions of the Rights Agreement, which terms, provisions and conditions are
hereby incorporated herein by reference and made a part hereof and to which
Rights Agreement reference is hereby made for a full description of the rights,
limitations of rights, obligations, duties and immunities hereunder of the
Rights Agent, the Company and the holders of the Right Certificates.  Copies of
the Rights Agreement are on file at the principal executive offices of the
Company and at the office of the Rights Agent.

          This Right Certificate, with or without other Right Certificates, upon
surrender at the office of the Rights Agent designated for such purpose, may be
exchanged for another Right Certificate or Right Certificates of like tenor and
date evidencing Rights entitling the holder to purchase a like aggregate number
of Preferred Shares as the Rights evidenced by the Right Certificate or Right
Certificates surrendered shall have entitled such holder to purchase.  If this
Right Certificate shall be exercised in part, the holder shall be entitled to
receive upon surrender hereof another Right Certificate or Right Certificates
for the number of whole Rights not exercised.

          Subject to the provisions of the Rights Agreement, the Rights
evidenced by this Certificate (i) may be redeemed by the Company at a redemption
price of $.01 per Right or (ii) may be exchanged in whole or in part for
Preferred Shares, shares of the Company's Common Stock, par value $.001 per
share, or substantially equivalent rights or other consideration as determined
by the Company.

          No fractional Preferred Shares will be issued upon the exercise of any
Right or Rights evidenced hereby (other than fractions which are integral
multiples of one one-hundredth 

                                       49

 
of a Preferred Share, which may, at the election of the Company, be evidenced by
depositary receipts), but in lieu thereof a cash payment will be made, as
provided in the Rights Agreement.

          No holder of this Right Certificate, as such, shall be entitled to
vote or receive dividends or be deemed for any purpose the holder of the
Preferred Shares or of any other securities of the Company which may at any time
be issuable on the exercise hereof, nor shall anything contained in the Rights
Agreement or herein be construed to confer upon the holder hereof, as such, any
of the rights of a stockholder of the Company or any right to vote for the
election of directors or upon any matter submitted to stockholders at any
meeting thereof, or to give or withhold consent to any corporate action, or to
receive notice of meetings or other actions affecting stockholders (except as
provided in the Rights Agreement), or to receive dividends or subscription
rights, or otherwise, until the Right or Rights evidenced by this Right
Certificate shall have been exercised as provided in the Rights Agreement.

          This Right Certificate shall not be valid or obligatory for any
purpose until it shall have been countersigned by the Rights Agent.

                                       50

 
WITNESS the signature of the proper officers of the Company and its corporate
seal.  Dated as of ___________, 19__.



[SEAL]

ATTEST:                            MYCOGEN CORPORATION,
                                   a California Corporation
 

By /s/ Arthur J. Chatroo           By: /s/ Jerry D. Caulder
   ---------------------              --------------------
  Arthur J. Chatroo                   Jerry D. Caulder, Ph.D.
  Assistant Secretary                 Chairman of the Board
                                      and Chief Executive Officer



                                   By:/s/ Carlton J. Eibl
                                      -------------------
                                      Carlton J. Eibl
                                      President, Chief Operating Officer
                                      and Secretary


ATTEST:                               THE FIRST NATIONAL BANK OF
                                      BOSTON, a National Bank Association


By: __________________________         By: ____________________________
  Name:______________________             Name:________________________
  Title:_______________________           Title:_________________________

                                       51

 
                   Form of Reverse Side of Right Certificate

                              FORM OF ASSIGNMENT
                              ------------------


          (To be executed by the registered holder if such holder desires to
          transfer the Right Certificate.)

          FOR VALUE RECEIVED _____________ hereby sells, assigns and transfers 
unto _______________________________________________________________________
         (Please print name and address of transferee)

__________________________________________________________________________this 
Right Certificate, together with all right, title and interest therein, and
does hereby irrevocably constitute and appoint ___________________ Attorney, to
transfer the within Right Certificate on the books of the within-named Company,
with full power of substitution.


Dated:  _______________, 19__


                                   ______________________________  
                                   Signature
 
Signature Guaranteed:

          Signature(s) must be guaranteed by an eligible guarantor institution
(banks, savings banks, savings & loan institutions and credit unions with
membership in an approved Signature Guaranty Medallion Program), pursuant to SEC
Rule 17Ad-15.

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

                                 CERTIFICATION
                                 -------------

          The undersigned hereby certifies that the Rights evidenced by this
Right Certificate are not beneficially owned by an Acquiring Person or an
Affiliate or Associate thereof (as defined in the Rights Agreement).


                                   ______________________
                                   Signature

            Form of Reverse Side of Right Certificate -- continued

                                       52

 
                         FORM OF ELECTION TO PURCHASE
                         ----------------------------

     (To be executed if holder desires to exercise the Right Certificate.)


To MYCOGEN CORPORATION

          The undersigned hereby irrevocably elects to exercise________________
_________________________ Rights represented by this Right Certificate to
purchase the Preferred Shares issuable upon the exercise of such Rights and
requests that certificates for such Preferred Shares be issued in the name of:


Please insert social security
or other identifying number                            _________________________

________________________________________________________________________________
                        (Please print name and address)

________________________________________________________________________________

If such number of Rights shall not be all the Rights evidenced by this Right
Certificate, a new Right Certificate for the balance remaining of such Rights
shall be registered in the name of and delivered to:

Please insert social security
or other identifying number                            _________________________

- --------------------------------------------------------------------------------
                        (Please print name and address)

Dated:  __________________, 19__


                                   _________________________
                                   Signature


Signature Guaranteed
Signatures must be guaranteed by a member firm of a registered national
securities exchange, a member of the National Association of Securities Dealers,
Inc., or a commercial bank or trust company having an office or correspondent in
the United States.

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

                                       53

 
                                 CERTIFICATION
                                 -------------


          The undersigned hereby certifies that the Rights evidenced by this
Right Certificate are not beneficially owned by an Acquiring Person or an
Affiliate or Associate thereof (as defined in the Rights Agreement).

                                   _____________________
                                   Signature

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

                                    NOTICE
                                    ------


          The signature in the foregoing Forms of Assignment and Election to
Purchase must conform to the name as written upon the face of this Right
Certificate in every particular, without alteration or enlargement or any change
whatsoever.

          In the event the certification set forth above in the Form of
Assignment or the Form of Election to Purchase, as the case may be, is not
completed, the Company and the Rights Agent will deem the beneficial owner of
the Rights evidenced by this Right Certificate to be an Acquiring Person or an
Affiliate or Associate thereof (as defined in the Rights Agreement) and such
Assignment or Election to Purchase will not be honored.

                                       54

 
                                   EXHIBIT C
                                   ---------

                              MYCOGEN CORPORATION

                         SUMMARY OF RIGHTS TO PURCHASE
                               PREFERRED SHARES


          On February 21, 1992, the Board of Directors of Mycogen-Delaware the
predecessor in interest to Mycogen Corporation, a California corporation (the
"Company") declared a dividend of one preferred share purchase right (a "Right")
for each outstanding share of common stock, par value $.001 per share (the
"Common Shares"), of the Company.  The dividend was payable on March 6, 1992
(the "Record Date") to the stockholders of record as of the close of business on
that date.  Each Right entitles the registered holder to purchase from the
Company one one-hundredth of a share of Series B Junior Participating Preferred
Stock, par value $.001 per share (the "Preferred Shares"), of the Company at a
price of $65.00 per one one-hundredth of a Preferred Share (the "Purchase
Price"), subject to adjustment.  The description and terms of the Rights are set
forth in an Amended and Restated Rights Agreement dated as of _______________,
1995 (the "Rights Agreement") between the Company and The First National Bank of
Boston, as Rights Agent (the "Rights Agent").

          Pursuant to a merger agreement, Mycogen Corporation, a California
Corporation (the "Company") assumed all of the rights and obligations of
Mycogen-Delaware under the original Rights Agreement dated February 21, 1992 as
amended (collectively, the "Original Rights Agreement").  A Summary of Rights
was originally mailed to all shareholders of record as of the Record Date.  This
new summary of Rights reflects the assumption by the Company of Mycogen-Delaware
rights and incorporates all amendments to the Original Rights Agreement

          Until the earlier to occur of (i) 10 days following a public
announcement that a person or group of affiliated or associated persons (an
"Acquiring Person") have acquired beneficial ownership of 25% or more of the
outstanding Common Shares or (ii) 10 business days (or such later date as may be
determined by action of the Board of Directors prior to such time as any Person
becomes an Acquiring Person) following the commencement of, or announcement of
an intention to make, a tender offer or exchange offer the consummation of which
would result in the beneficial ownership by a person or group of 25% or more of
such outstanding Common Shares (the earlier of such dates being called the
"Distribution Date"), the Rights will be evidenced, with respect to any of the
Common Share certificates outstanding as of the Record Date, by such Common
Share certificate with a copy of this Summary of Rights attached thereto.

          The Rights Agreement provides that, until the Distribution Date, the
Rights will be transferred with and only with the Common Shares.  Until the
Distribution Date (or earlier redemption or expiration of the Rights), new
Common Share certificates issued after the Record 

                                       55

 
Date, upon transfer or new issuance of Common Shares will contain a notation
incorporating the Rights Agreement by reference. Until the Distribution Date (or
earlier redemption or expiration of the Rights), the surrender for transfer of
any certificates for Common Shares, outstanding as of the Record Date, even
without such notation or a copy of this Summary of Rights being attached
thereto, will also constitute the transfer of the Rights associated with the
Common Shares represented by such certificate. As soon as practicable following
the Distribution Date, separate certificates evidencing the Rights ("Right
Certificates") will be mailed to holders of record of the Common Shares as of
the Close of Business on the Distribution Date and such separate Right
Certificates alone will evidence the Rights.

          The Rights are not exercisable until the Distribution Date. The Rights
will expire on February 20, 2002 (the "Final Expiration Date"), unless the Final
Expiration Date is extended or unless the Rights are earlier redeemed by the
Company, in each case as described below.

          The Purchase Price payable, and the number of Preferred Shares or
other securities or property issuable, upon exercise of the Rights are subject
to adjustment from time to time to prevent dilution (i) in the event of a stock
dividend on, or a subdivision, combination or reclassification of, the Preferred
Shares, (ii) upon the grant to holders of the Preferred Shares of certain rights
or warrants to subscribe for or purchase Preferred Shares at a price, or
securities convertible into Preferred Shares with a conversion price, less than
the then current market price of the Preferred Shares or (iii) upon the
distribution to holders of the Preferred Shares of evidences of indebtedness or
assets (excluding regular periodic cash dividends paid out of earnings or
retained earnings or dividends payable in Preferred Shares) or of subscription
rights or warrants (other than those referred to above).

          The number of outstanding Rights and the number of one one-hundredths
of a Preferred Share issuable upon exercise of each Right are also subject to
adjustment in the event of a stock split of the Common Shares or a stock
dividend on the Common Shares payable in Common Shares or subdivisions,
consolidations or combinations of the Common Shares occurring, in any such case,
prior to the Distribution Date.

          Preferred Shares purchasable upon exercise of the Rights will not be
redeemable.  Each Preferred Share will be entitled to a minimum preferential
quarterly dividend payment of $1.00 per share but will be entitled to an
aggregate dividend of 100 times the dividend declared per Common Share.  In the
event of liquidation, the holders of the Preferred Shares will be entitled to a
minimum preferential liquidation payment of $1.00 per share but will be entitled
to an aggregate payment of 100 times the payment made per Common Share.  Each
Preferred Share will have 100 votes, voting together with the Common Shares.
Finally, in the event of any merger, consolidation or other transaction in which
Common Shares are exchanged, each Preferred Share will be entitled to receive
100 times the amount received per Common Share.  These rights are protected by
customary antidilution provisions.

                                       56

 
          Because of the nature of the Preferred Shares' dividend, liquidation
and voting rights, the value of the one one-hundredth interest in a Preferred
Share purchasable upon exercise of each Right should approximate the value of
one Common Share.

          In the event that, after the Rights become exercisable, the Company is
acquired in a merger or other business combination transaction with an Acquiring
Person or an affiliate thereof, or 50% or more of its consolidated assets or
earning power are sold to an Acquiring Person or an affiliate thereof, proper
provision will be made so that each holder of a Right will thereafter have the
right to receive, upon exercise thereof at the then current exercise price of
the Right, that number of shares of common stock of the acquiring company which
at the time of such transaction will have a market value of two times the
exercise price of the Right.

          In the event that any person or group of affiliated or associated
persons becomes the beneficial owner of 25% or more of the outstanding Common
Shares (except pursuant to a tender offer for all of the Common Shares at a
price and on terms determined by a majority of the Continuing Directors to be
fair to and otherwise in the best interests of the Company and its stockholders)
proper provision shall be made so that each holder of a Right, other than Rights
beneficially owned by the Acquiring Person (which will thereafter be void), will
thereafter have the right to receive upon exercise that number of Common Shares
(or cash, other securities or property) having a market value of two times the
exercise price of the Right.

          At any time after the acquisition by a person or group of affiliated
or associated persons of beneficial ownership of 25% or more of the outstanding
Common Shares and prior to the acquisition by such person or group of 50% or
more of the outstanding Common Shares, the Board of Directors of the Company may
exchange the Rights (other than Rights owned by such person or group which have
become void), in whole or in part, at an exchange ratio of one Common Share (or
a fraction of a Preferred Share having equivalent market value) per Right
(subject to adjustment).

          With certain exceptions, no adjustment in the Purchase Price will be
required until cumulative adjustments require an adjustment of at least 1% in
such Purchase Price.  No fractional Preferred Shares will be issued (other than
fractions which are integral multiples of one one-hundredth of a Preferred
Share, which may, at the election of the Company, be evidenced by depositary
receipts) and, in lieu thereof, an adjustment in cash will be made based on the
market price of the Preferred Shares on the last trading day prior to the date
of exercise.

          At any time within ten (10) days after a person or group of affiliated
or associated persons acquire beneficial ownership of 25% or more of the
outstanding Common Shares (unless the Board of Directors extends such ten-day
period), the Board of Directors of the Company may redeem the Rights in whole,
but not in part, at a price of $.001 per Right (the "Redemption Price"), upon
the approval of a majority of the Continuing Directors.  The redemption of the
rights may be made effective at such time on such basis and with such conditions
as the Board of Directors in its sole discretion may establish.  Immediately
upon any redemption of the Rights, the right to exercise the Rights will
terminate and the only right of the holders of Rights will be 

                                       57

 
to receive the Redemption Price. The Rights are also redeemable under other
circumstances as specified in the Rights Agreement.

          The terms of the Rights may be amended by the Board of Directors of
the Company without the consent of the holders of the Rights upon the approval
of a majority of the Continuing Directors, including an amendment to lower
certain thresholds described above to not less than the greater of (i) any
percentage greater than the largest percentage of the outstanding Common Shares
then known to the Company to be beneficially owned by any person or group of
affiliated or associated persons and (ii) 10%, except that from and after such
time as any person becomes an Acquiring Person no such amendment may adversely
affect the interests of the holders of the Rights.

          Until a Right is exercised, the holder thereof, as such, will have no
rights as a stockholder of the Company, including, without limitation, the right
to vote or to receive dividends.

          A copy of the Rights Agreement has been filed with the Securities and
Exchange Commission as an Exhibit to a Registration Statement on Form 8-A.  A
copy of the Rights Agreement is available free of charge from the Company.  This
summary description of the Rights does not purport to be complete and is
qualified in its entirety by reference to the Rights Agreement, which is hereby
incorporated herein by reference.

                                       58