Abstract
1) The present paper deals with the brown shot hole disease of cherry leaves caused by Mycosphaerella cerasella Aderh., which is known as the ascigeuous stage of Cercospora cerasella Sacc.
2) Investigations on the causal organism were carried out chiefly on the morphological characters of its conidiophore, conidium, perithecium, ascus and ascospore by the writer under the directions of Mr. Y. Nisikado, Plant Pathologist of the Ohara Institute.
3) This disease is not only common in Prunus cerasus, but also in Prunus Yamasakura var. typica, Prunus. Yamasakura var. spontanea subvar. hortensis P. Itosakura and P. Itosakura var. subhirtella in the western parts of Japan.'
4) The genetic relation of Cercospora cerasolla Sacc. and Mycosphaerella ferasella Aderh. has been demonstrated by comparative cultural studies of the isolations secured from both ascigenous and conidial stages.
5) The parasitic nature of the present fungus has been ascertaind by successful inoculations carried out on above described five varieties of the cherry (Prunus spp.)
