3o6 
ON A NEW CANKER-DISEASE OF PRUNUS YEDOENSIS, etc. 
e. Pruning. 
It is a very rare practice in Japan to prune Prunus yedoensis and other 
Flowering Cherry trees, while it is quite common to prune Prunus Mume and 
Prunus Persica. The cut surface of the branches is most likely to become 
a place of entrance for the disease. An instance of such infection is shown 
in the photograph in PI. VII, Fig. 3. 
f. Rain and Wind. 
As the pycnospores appear to be sticky, there is no evidence that they 
are transmitted by wind except where they are washed down into the dust 
and blown about with it. But rain dissolves the mucilaginous matrix of the 
spore horns, and the pycnospores may be splashed to other trees that are in 
close proximity to diseased ones ; particularly they are washed down from 
twig infections to the lower parts of the tree where they lodge in wounds 
and produce cankers. But the ascospores can be caught up by the wind and 
carried for considerable distances and may well be responsible for a large part 
of the infection, fur they are forcibly ejected into the air. Also the asco- 
spores, which sometimes ooze out instead of being forcibly ejected, may be 
carried down in the same manner as the pycnospores. 
15. Relation between the Present Disease and Gummosis. 
Gummosis is a disease common to a number of trees, and is specially 
prevalent in the genus Prunus. The name gummosis is applied to a condition 
in which an exudation of the gummy substance takes place through the bark. 
The gummosis of Prunus has been the subject of study by many investigators, 
but it was most thoroughly studied by Butler (191 Dr. S. Kusano 
(191 1) 10 also studied the gummosis at the basal portion of the witches' broom 
in Prunus serrulata. 
It is generally said that such plants are susceptible to gummosis whenever 
conditions are favourable for the active growth of the cambium. It is also said 
that the disease may be produced either autogenously or by external agents. 
