Received for publication December 26, 1974, Paper No. 74-181 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh.
Research Plant Physiologist, Agricultural Research Service, USDA, (now retired); and Professor, Dept. of Horticultural Science, North Carolina State University respectively. The authors are indebted to John Skinner, Jr. and Eleanor P. Maness for assistance in carrying out the work.