Received for publication 27 Apr. 1984. Published with the approval of the Director of the Clemson Univ. Agricultural Experiment Station as Technical Contribution No. 2185. 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.
Associate Professor of Horticulture.
Former Graduate Research Assistant. Present address: Dept. of Horticultural Science, N.C. State Univ., Raleigh, NC 27695-7609.