2 5 8 
ON A NEW CANKEK-DISEASE OF PRUNUS YEDOENSIS, etc. 
standing its wide cultivation, shows the plant is immune to the disease. As 
the result of my studies this destructive canker disease was proved to be 
caused by the attack of a new species of Valsa acting as a wound parasite. 
I wish to express here my heartiest thanks to Prof. K. Miyabe for his 
constant and kind direction ; and to Assistant Prof. S. Pro to whom I am also 
indebted for his many valuable suggestions. I wish also to express my 
sincere thanks to Prof. H. Köriba, Messrs. Y. Kudö, S. Nishida and other 
gentlemen, who have kindly helped me in many ways. 
2. Historical Review of Valsa-Diseases. 
Valsa is a large Pyrenomycetous genus, having more than 400 species, 
most of which are generally described as saprophytes in mycological litera- 
ture. Up to the present time only five species have been recognized as the 
cause of plant diseases. They are, namely, — Valsa leucostoma (Peks.) Fk., 
Valsa oxysloma Kehm, Valsa ambiens Fk., Valsa (Eutypclla) Pntnastri (Peks.) 
Fk. and Valsa Mali Miyabe et Yamada. 
Among them, Valsa leucostoma (Peks.) Fk. is most widely known as the 
cause of a destructive disease of the drupaceous trees throughout Europe, 
Australia and N. America. This fungus attacks the cherry, peach and other 
drupaceous fruit-trees, causing the disease known as the "Die-back" of the 
twigs, and also the cankers upon the trunks and limbs. In the Rhine-district, 
from about the year 1899, * ne cherry trees have been so severely affected by 
the fungus as to arouse the attention of many phytopathologists. Frank 
(1899) 1 " studied the disease and ascribed it to Cytospora riibesccns Fk. On 
the other hand, Goethe (1899) n) , Zapfe (iSgg)^^, Sokauer (*90o) 27) Raschen* 
(1900) 20 and Labonte (1900) !3) considered the disease to be due to some un- 
favorable climatic conditions or to other physiological derangements. It was 
by Adekhold ( 1903) 1 ' that this disease was most thoroughly investigated ; and 
he proved it to be caused by Valsa leucostoma, the generally ascrived climatic 
causes to be merely its promoting agencies, and Cytospora rubescens, which 
was observed by Frank. (1899)'", to be the pycnosporous stage of this fungus. 
