1. Yamada, Y., Tanaka, K., and Takahashi, E., Proc. Japan Acad., 43, 156 (1967).
2. Carter, O., Yamada, Y., and Takahashi, E., Nature, 214, 1029 (1967).
3. Yamada, Y., Nishi, T., Yasuda, T., and Takahashi, E., Gnotobiotic Life in Medical and Biological Research (edit. by Luckey, T. D.), 383 (Iliffe Books, Ltd, London, 1967).
4. Wilmer, C., and Hellendoorn, M., Nature, 217, 369 (1968).
5. Linsmaier, E. M., and Skoog, F., Physiol. Plant., 18, 100 (1964).