1. The present paper deals with the results of the writers' investigations on Polyporus rhodophaeus LÉV., which has been treated by many authors under the name of Polyporus semilaccatus BERK. 2. A number of broadleaf species are listed as hosts, and it has been reported that the fungus is found most commonly on various species of cherry trees in Japan. According to the writers' collections and observations, Robinia pseudoacacia is apparently one of the most susceptible hosts of the fungus. 3. In the present paper the morphological characters of the fungus as well as the diagnostic characters of decay in the wood of Robinia pseudoacacia affected by it were described. The investigations were mostly carried out on specimens which had been contributed to the writers' Herbarium from Sapporo in Hokkaido and Utunomiya in Totigi. 4. The decay of this plant caused by the present fungus starts from the sapwood and advances inward causing peripheral rot, but sometimes very irregularly, so that, while the central portion of the heartwood is attacked, there remain sound tissues in the outer portion. The rotted wood becomes soft and light, changing uniformly to whitish color. 5. By the characters of decay in the wood and also by the cultural experiment using BAVENDAMM'S method, the writers classified the fungus as belonging to the group of lignin dissolving fungi (Korrosionspilze). 6. The relation of temperature to the growth of the fungus was studied by growing the mycelium on poured plates of apricot decoction agar, of potato decoction agar and of soy agar incubated at different temperatures. It was found that the fungus in culture grows at from ca. 11°C to ca. 40°C and the optimum temperature for the mycelial growth seems to lie at approximately 31°-32°C.
With Poria vaporaria (PERS.) FR., Polystictus sanguineus (L.) FR., and Schizophyllum commune FR. as test fungi, experiments were carried out for determining the checking effect of electricity upon the growth of wood-destroying fungi. Electric current (direct, alternating, and high-frequency) was run (1) through a piece of wood placed upon a fungous mat which has been reared on culture medium, (2) through the fungi inoculated upon culture medium, (3) through the fungi cultivated upon a piece of wood. The results were as follows: (1) electric current had a checking effect upon the growth of fungi, (2) the fungi were destroyed at a spot where density of current was great, (3) direct current had a greater effect than alternating current, (4) high-frequency current could not be expected to have a very great effect. As the causes of such a checking effect of current may be mentioned (i) heat, (ii) production of toxic substances due to electrolysis, (iii) movement of charged substances and migration of nutritive elements due to electro-endosmose, and (iv) destructive action. The results of test have shown, however, that (i) and (ii) are not so effective as to check the growth of the fungi. From the fact that the colouring matter was segregated out of the cells of Polystictus sanguineus (L.) FR., it seems that the electro-endosmose greatly affects the growth of the fungi.
In Japan the method of cultivation of the rice plant is quite different from that of other cereals and the proper preparation of the land for the seedlings later to be transplanted, is most important in order to obtain strong and healthy plants. For this purpose the nursery-beds with or without covering water are most commonly used. Among the grown rice plants transplanted from these nursery-beds in their seedling stage, there seems to exist a difference of susceptibility to the blast disease. It is clear that the plants originated from humid soil are more resistant than those from arid soil. In the present paper, the writer has discussed the results of comparison of the ash figures in leaves of rice plants transplanted from these two nursery-beds. The number of silicated epidermal cells per unit area of leaf, especially of the bulliform cells, is larger in plants transplanted from the former than in those transplanted from the latter. It seems to be very interesting that the number of silicated cells in the bulliform cells, which are more easily penetrated by the causal fungus (Piricularia Oryzae B. et C.) than the long and short cells, varies in accordance with such different conditions in the seedling stage.