AMENDMENT NO.2 TO LOAN AGREEMENT

This Amendment No. 2 to Loan Agreement ("Amendment") is made as of November 
14, 1997 between DowElanco LLC, a Delaware corporation, f/k/a DowElanco, an 
Indiana general partnership (the "Lender"), and Mycogen Corporation, a 
California corporation (the "Borrower") (together, the "parties").

WHEREAS, the parties executed a Loan Agreement as of April 1, 1997, and 
Amendment No. 1 as of September 29, 1997 (the "Agreement"); and

WHEREAS, the parties wish to amend the Agreement;

NOW THEREFORE, the parties hereto have agreed and do hereby agree to amend 
the Agreement as follows:

     Section 1.1 The Advance is hereby deleted in its entirety and 
     replaced with the following:

     1.1 The Advance
         From the date of this Amendment No. 2 to April 1, 1998, the Lender 
         agrees to make from time to time advances to the Borrower ("Advances"),
         in an aggregate amount not exceeding $75,000,000 (seventy-five million
         U.S. dollars), at any time outstanding ("Commitment"). Lender must 
         receive Borrower's request for an advance by 9:00 a.m. Eastern Standard
         Time if the advance is to be made that day. Advances repaid prior to 
         April 1, 1998, may be reborrowed. This Agreement involves U.S. dollars 
         only.

     All other terms and conditions of the Agreement shall remain in full 
     force and effect.

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

LENDER:                                  BORROWER:

DowElanco LLC                            Mycogen Corporation


By: /s/ Sean S. Skinner                  By: /s/ James A. Baumker
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Printed: Sean S. Skinner                    Printed: James A. Baumker
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Title: Treasurer                            Title: VP CFO
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Date: 11/14/97                               Date: 11/17/97
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