Assistant Professor. Present address: Dept. of Horticulture and Landscape Architecture, Washington State Univ., Pullman, WA.
Received for publication 29 Oct. 1984. Salaries and research support provided by State and Federal funds appropriated to the Ohio Agricultural Research and Development Center, The Ohio State Univ. Journal Article No. 180-84. 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.