LOAN AGREEMENT

This Loan Agreement ("Agreement") is made as of April 1, 1997 between Mycogen
Corporation, a California corporation (the "Lender"), and DowElanco, an 
Indiana general partnership (the "Borrower").

The parties hereto have agreed and do hereby agree as follows:

1.   THE LOAN

     1.1  The Advance

          From the above date to April 1, 1998, the Lender agrees to make 
          from time to time advances to the Borrower ("Advances"), in an 
          aggregate amount not exceeding $50,000,000 (fifty million U.S. 
          dollars), at any time outstanding ("Commitment").  Lender must 
          receive Borrower's request for an advance by 9:00 a.m. Eastern
          Standard Time if the advance is to be made that day.  Advances
          repaid prior to April 1, 1998, may be reborrowed.  This Agreement
          involves U.S. dollars only.

     1.2  Repayment

          Repayment may be made at any time, provided that the final 
          repayment be made on or prior to April 1, 1998.

     1.3  Cancellation/Reduction

          From time to time and upon 30 days written notice, the Borrower or 
          Lender may at any time permanently reduce the Commitment and the 
          unpaid principal and all interest shall be due and payable 
          immediately.
          
     1.4  Evidence of Debt

          The Lender shall maintain in accordance with its usual practice an 
          account or accounts evidencing the indebtedness of the Borrower 
          resulting from the Loan and the amounts of principal and interest 
          payable and paid from time to time hereunder.  In any legal action 
          or proceeding in respect of the Agreement, the entries made in such 
          account or accounts shall, unless in case of obvious or manifest 
          error, be conclusive evidence of the existence and amounts of the 
          obligations of the Borrower therein recorded.
          
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     1.5  Interest

          The Loan shall bear interest from day to day at Borrower's rate of 
          deposit, as advised from time to time by Borrower, minus 1/8% per 
          annum payable every three months from the date hereof to maturity 
          on the outstanding balance.

2.   EVENTS OF DEFAULT

     In the event that:

     (A)  The Borrower fails to pay any sum payable hereunder when due; or

     (B)  The Borrower defaults in the due performance and observance of 
          any other term of this Agreement and such default is not 
          remedied within 15 days after notice of such default; or

     (C)  The Borrower goes bankrupt or becomes insolvent or is subject 
          to a receivership either voluntary or compulsory; or

     (D)  Any order is made or law, decree, regulation or resolution 
          passed for the liquidation, winding up or dissolution of the 
          Borrower; or

     (E)  All or any substantial part of the business or assets of the 
          Borrower is expropriated, nationalized, compulsorily acquired 
          or taken into public ownership or the Borrower ceases to be 
          able or entitled to exercise the rights of control or 
          ownership of the same; or

     (F)  The Borrower ceases to be directly or indirectly controlled by 
          The Dow Chemical Company, Midland, Michigan, U.S.A.,

     then and in any such event, and at any time thereafter if any such event 
     shall then be continuing, the Lender may, by written notice to the Borrower
     declare the Loan immediately due and payable whereupon the same shall 
     become immediately due and payable together with all interest accrued 
     thereon and all other amounts payable hereunder, including all interest 
     accrued on any past due principal, to the extent permitted by law.

3.   REPRESENTATIONS AND WARRANTIES OF BORROWER.  The Borrower represents and 
     warrants as follows:

     (A)  The Borrower is an Indiana general partnership;

     (B)  The execution, delivery and performance by the Borrower of 
          this Agreement are within the Borrower's powers, have been duly 
          authorized by all necessary action, and do not contravene (i) the 
          Borrower's 

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          Partnership Agreement or Authorization Policy or (ii) any law or
          any judgment or contractual restriction binding on or affecting
          the Borrower;

     (C)  No authorization or approval or other action by, and no notice 
          to or filing with, any governmental authority or regulatory 
          body which has not already been obtained or made is required 
          for the due execution, delivery and performance by the 
          Borrower of this Agreement; and

     (D)  This Agreement is the legal, valid and binding obligation of 
          the Borrower enforceable against the Borrower in accordance 
          with its terms.

4.   COVENANTS OF THE BORROWER; REPORTING REQUIREMENTS.  So long as the Loan 
     shall remain unpaid, the Borrower will, unless the Lender shall otherwise
     consent in writing, furnish to the Lender:

     (A)  As soon as practicable, in any event within five Business Days 
          after the occurrence of each Event of Default, or each event 
          which with notice or lapse of time or both would become an 
          Event of Default, which is continuing on the date of such 
          statement, a statement of an authorized representative of the 
          Borrower setting forth details of such Event of Default or 
          event and the action which the Borrower proposes to take with 
          respect thereto; and

     (B)  Such other information respecting the business, properties or 
          the condition or operations, financial or otherwise, of the 
          Borrower as the Lender may from time to time reasonably 
          request.

5.   COSTS AND EXPENSES

     The Borrower agrees to pay on demand all losses and all costs and 
     expenses, if any, in connection with the enforcement of this Agreement 
     and any instruments or other documents delivered hereunder, including, 
     without limitation, losses, costs and expenses sustained as a result of 
     a default by the Borrower in the performance of its obligations 
     contained in this Agreement or any instrument or document delivered 
     hereunder.

6.   ALTERNATIVE DISPUTE RESOLUTION

     The parties shall negotiate in good faith to resolve any dispute arising 
     out of or relating to this Agreement.  In the event that the parties 
     fail to resolve a dispute by good faith negotiations, or if either party 
     deems a resolution by such means to be improbable, either party may 
     initiate mediation of the dispute upon written notice to the other 
     party.  Such mediation shall be conducted promptly in accordance with 
     the Center for Public Resources Model Procedure for Mediation of 
     Business Disputes.  If, within 60 days after notice of mediation, the 
     parties have failed to resolve the dispute by mediation, either party 
     may propose binding arbitration or 

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     initiate litigation. If either party requests mediation, it shall occur 
     in Indianapolis, Indiana.

7.   CHANGE OF CONTROL. After any change of Control (as defined below) of the 
     Borrower, the Lender may, at its option, upon notice to the Borrower 
     declare all principal, interest, and other amounts payable under this 
     Agreement to be immediately due and payable, whereupon the same shall 
     become immediately due and payable.

8.   DEFINITIONS. Capitalized terms as to which such capitalization would not 
     be required in accordance with standard rules of grammar shall have the 
     meanings specified below.

     "Affiliate" means, with respect to each party hereto, a party that 
     directly, or indirectly, through one or more intermediaries, controls or 
     is controlled by, or is under common control with, the party specified. 
     The term "control" is defined below. For purposes of this Agreement, 
     Lender is not an Affiliate of Borrower.

     "Business Day" means any day other than a Saturday, Sunday or other day 
     on which banking institutions in Indianapolis, Indiana are required or 
     authorized by law to suspend operations.

     "Control" means the possession, directly or indirectly, of the power to 
     direct or cause the direction of the management and policies of any 
     individual, corporation, partnership, unincorporated association or 
     other entity, whether through the ownership of voting stock, by contract 
     or otherwise. A person who is the owner of 20% or more of a 
     corporation's outstanding voting stock shall be deemed to have Control 
     of such corporation.

9.   MISCELLANEOUS

     The Borrower agrees to take all such steps and actions and to execute 
     and to deliver and/or cause to be delivered all such further documents 
     and instruments as may be necessary at any time or times in the 
     reasonable opinion of the Lender to establish, maintain and protect the 
     rights of the Lender hereunder and generally to carry out the true intent 
     of this Agreement.

10.  ASSIGNMENT

     This agreement may not be assigned in whole or in part by Lender 
     without the express written consent of the other party. This Agreement 
     may be assigned by Borrower to any Affiliate.


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11.  SUCCESSORS

     This Agreement and any instrument or document executed in accordance 
     herewith shall be binding upon and shall inure to the benefit of the 
     parties hereto and their respective successors and assignees.

12.  GOVERNING LAW

     This Agreement and any instruments or other documents executed in 
     accordance herewith shall be governed by and construed in accordance 
     with the laws of the State of Indiana.

13.  AMENDMENTS, ETC.

     No amendment or waiver of any provision of this Agreement or any 
     instrument delivered hereunder, nor consent to any departure by the 
     Borrower therefrom, shall in any event be effective unless the same 
     shall be in writing and signed by an authorized representative of the 
     Lender and then such waiver or consent shall be effective only in the 
     specific instance and for the specific purpose for which given.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly 
executed on the date first written above.

LENDER:                                     BORROWER:

DowElanco                                   Mycogen Corporation


By: /s/ Sean S. Skinner                     By: /s/ James A. Baumker
   ----------------------------                ---------------------------

Printed: Sean S. Skinner                    Printed: James A. Baumker
        -----------------------                     ----------------------

Title: Treasurer                            Title: VP CFO
      -------------------------                   ------------------------

Date: 5/20/97                               Date: 6/10/97
     --------------------------                  -------------------------
                                                         [Illegible]


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