ON A NEW CANKER-DISEASE OF PRUNUS YEDOENSIS, etc. 
found penetrating and ramifying among those tissues. The lignification of 
the cell-walls occurs also more or less, and is rather rare as in the case of the 
primary cortex. 
No change of importance were noticed in the sclerenchyma. A partial 
process of lignification takes place also in the medullary ray cells when they 
are approached by the mycelium. In the case of the chestnut canker, Keefek 1V) 
reported that the cells of the medullary rays are not individually affected or 
broken, but there is an increase in the number of medullary ray cells, due 
probably to a stimulating action by the fungus. In our case also, the medul- 
lary rays seem to remain for a long time without being injured by the fungus, 
but at laSt they also are destroyed. I did not, however, find an increase in 
the number of the medullary ray cells, as Keeper 13) observed. 
The cambium. The cambium is easily killed by the fungus attack, and 
a partial lignification takes place in the wall of the cambium upon the invasion 
of the fungus. No hyphae were seen penetrating the cell-walls or going 
between them as reported by Keefek m . 
The woody portion. As already stated, in the woody portion, the em- 
bryonic tissue and the gum pockets are formed as the result of the disease. 
Although the mycelium is seen even in the deeper portion, the walls of the 
other woody elements apparently show no change. According to my studies, 
the mycelium of this fungus is commonly seen in the wood vessels, medullary 
ray cells, and occasionally in the wood parenchyma, but it is not so numerous 
as to plug up those cells (PI. X, Fig. 10-12.). An experiment was made to 
determine to what depth the fungus really does penetrate into the wood. 
New diseased logs were selected and cut into moderate sizes. The exposed 
surface was passed through the flame of an alcohol lamp to guard against 
contamination. They were at once placed in moist sterilized Petri-dishes. 
After one or two days, the white mycelium grew out even from a deep 
portion of the wood, and occasionally from the central portion of the branch 
of about five centimeters in diameter. The mycelium gradually turned to the 
proper yellowish-brown color, and in the course of a few weeks even stromata 
