(1) The cultural characters of Piricularia Oryzae collected from various localities are not identical to each other on various cultural media. (2) On apricot juice agar medium the growth-types are classified into six, on onion decoction agar into four, on rice-plant decoction agar and pepton-sucrose synthetic agar into three each. (3) Considering the relative differences of the cultural characters on these four kinds of media, they are classified into nine physiologic forms. (4) On rice-plant decoction agar Forms show better growth at the temperature of 25°C. than at 28°C., while the remaining Forms VI-IX show the converse relation. (5) Measuring the length of conidia produced by these different physiologic forms cultured on steamed rice-straw, the conidia of Forms I, II, IV, V. and IX are somewhat longer than those of Forms III, VI, VII, and VIII. Moreover the apex of the conidia are attenuate in the former group of Forms and round in the latter ones.
1. Further studies on the growth promoting substance excreted by “Bakanae” fungus were carried out in its extractive nature and its effect on some other plants, not rice-plant. 2. The extraction-experiments were made on the following materials (1) the filtrate which was dried up by gentle heat, (2) the animal black which adsorbed the substace, and (3) the animal black which adsorbed the substance passed through a semipermeable membrane. From the material (1), the substance was extracted by distilled water, alcohol, ether, aceton and chloroform, and from the materials (2) and (3), it can not be extracted by distilled water. As a whole, the growth promoting substance is extractable by some solvents after various treatments, approaching to the relatively pure state. 3. By the action of the alcohol extracted substance from the filtrate, the seedlings of wheat, barley, Indian corn, Azuki bean and soy bean also grew taller than normal.