Received for publication 8 Sept. 1987. The investigation reported in this paper (87-10-131) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director. We are grateful to Douglas D. Archbold and Robert G. Anderson for their careful review and corrections. The plant materials used in this study were obtained from Faber Greenhouses, Kankakee, IL 60901. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.