<PAGE>
EXHIBIT 23.8
PRUDENTIAL SECURITIES INCORPORATED CONSENT
October 30, 2000
The Board of Directors
Agritope, Inc.
16160 SW Upper Boones Ferry Road
Portland, OR 97224
Members of the Board of Directors:
We hereby consent to the inclusion of our opinion letter to the Board of
Directors of Agritope, Inc. ("Agritope") as Annex C to the Prospectus/Proxy
Statement of Agritope and Exelixis, Inc. ("Exelixis") relating to the proposed
merger involving Agritope and Exelixis and references thereto and to our opinion
letter dated September 7, 2000 to the Board of Directors of Agritope in such
Prospectus/Proxy Statement under the captions: SUMMARY--Reasons for the Merger;
SUMMARY--Opinion of Agritope's Financial Advisor; THE MERGER--Agritope's Reasons
for the Merger; and THE MERGER--Opinion of Agritope's Financial Advisor. In
giving such consent, we do not admit that we come within the category of persons
whose consent is required under, and we do not admit that we are "experts" for
purposes of, the Securities Act of 1933, as amended, and the rules and
regulations promulgated thereunder.
Sincerely,
PRUDENTIAL SECURITIES INCORPORATED
/s/ PRUDENTIAL SECURITIES
INCORPORATED