Received for publication April 1, 1977. Paper No. 5221 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, N.C. The use of trade names does not imply endorsement by the N.C. Agr. Expt. Sta. of the products named, nor criticism of similar ones not mentioned.
Director of Phytotron. The author wishes to express appreciation to the various lamp companies that provided assistance during the course of this study.