Received for publication 28 July 1986. The investigation reported in this paper (86-10-144) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director. We gratefully acknowledge the valuable suggestions of J. Buxton and R. Geneve. This work was done in part for an MS degree. 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.