杉樹ノ心材腐朽ヲ基因スルおほしろさるのこしかけノ研究

Abstract

1. When the writers visited the Nara Park together with Dr. C. J. HUMPHREY on June 22, 1926, they first noticed the present heartwood rot of Cryptomeria japonica. On that occasion, however, they found only the rotting of the lumber, but no evidence as to the nature of the causal organism.2. By careful searches the writers collected soon afterwards a fungus belonging to the genus Fomes on the trunks of many living trees in the Nara Park and also in other places, where large cryptomerias are growing.3. The writers′ investigations on the morphology as well as its taxonomy have not only led them to prove the fungus to be Fomes ulmarius Fr., which has been known commonly as a pest of elms, but to recognize that Fomes geotropus COOKE is also identical in every respect with the present fungus. The writers consider, therefore, the latter to be the synonym of the former.4. According to the writers′ investigations, the present fungus is widely distributed in the southern part of Honshû an well as in Kiushû and parasitic not only on Cryptomeria joponica, an indigenous coniferous tree common in Japan, but also on several deciduous trees.5. By microchemical test and also by the cultural experiment using BAVENDAMM′s method the writers classified the fungus as belonging to the group of lignin dissolving fungi. This fungus causes the brown pocket rot of the heartwood of cryptomeria. These pockets or cavities are partially filled with a yellowish brown powder and occasionally also with white mycelium, and sometimes fibrous masses of partially decayed wood are found mixed with the brown powder. In the advanced stage, the pockets usually become entirely empty.6. In the present paper the results of the writer′s investigations on the morphological characters as well as its taxonomy are first described.7. Pure cultures of the fungus were readily obtained by placing a piece of the fungus tissue and also of the rotting wood on an agar plate in PETRI dishes. The growth habit of the mycelium on fourteen different media were compared. Among the favorable agar and liquid media, the potato decoction proved to be the best. The mycelium grown on artificial media was almost white, changing afterward slowly to a dirty yellowish color.8. 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, according to SAITO′s formula, incubated at different temperatures. It was found that the fungus in culture grows very vigorously at from 24°to 40°C. and the optimum temperature for the mycelial growth seems to lie at approximately 36°C.