Visiting Scholar, from Vegetable Research Institute, Chinese Academy of Agricultural Sciences, Beijing, P.R.C.
Received for publication January 13, 1983. This research was supported by the College of Agricultural and Life Sciences, University of Wisconsin-Madison, Madison, WI 53706 and Hatch Project No. 2378. We wish to thank S.A. Vicen for his assistance with the preparation of photographic materials. 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.