1) The filtrate of a Cephalothecium sp. from 2-months old culture in Tochinai's nutrient solution has been tested for effect upon the germination of conidia of Piricularia oryzae and growth of rice seedlings.
2) The filtrate was found capable of inhibiting completely the germination of conidia, when diluted 1:32. At a dilution of 1:64, it allowed to germinate and form appressoria in a few con idia. It checked remarkably up to a dilution of 1:128.
3) Since the pH of the filtrate (7.0) and osmotic pressure (0.4-0.5mol in sucrose) was not inhibitory, it may be considered that the toxity of the filtrate is attributed to the metabolic product of Cephalothecium.
4) No effect was observed upon the consequent growth of rice seedlings by soaking the roots for 2 days in a filtrate diluted 1:15-240. Susceptibility to blast, however, appeares to be lowered by the treatment, being the number of leaf-spots remarkably less than the nontreated.
