1. Weed Science Center, Utsunomiya University, 350 Mine-machi, Utsunomiya 321, Japan, K·I Chemical Research Institute Company Ltd., Shioshinden Fukude-cho, Iwata-gun, Shizuoka, 437-12, Japan, and Kumiai Chemical Industry Company Ltd., 1-4-26, Ikenohata, Taitoh-ku, Tokyo 110, Japan