1. Department of Agricultural Chemistry, Chiba University, 648, Matsudo, Matsudo-shi, Chiba 271, Japan
2. Department of Chemistry, Tokyo University, Hongo, Bunkyo-ku, Tokyo 113, Japan
3. Department of Botany, National Science Museum, Tokyo, 3–23–1, Hyakunin-cho, Shinjuku-ku, Tokyo 160, Japan
4. Institute of Applied Biochemistry, Tsukuba University, Tsukuba, Ibaraki 305, Japan