62 REPORT OF THE BOTANIST OF THE 
this tree was partly due to the fact that the tree was not making 
a vigorous growth of new shoots. It was an invariable rule that 
the leaves affected were those on the basal portion of the new 
shoots, while those on the middle and terminal portions were 
perfectly normal. In other words, the early formed leaves were 
affected and the later ones not. Consequently, the proportion 
of affected leaves became less as the season advanced and more 
new leaves were formed; and the more vigorous the growth the 
more rapidly the percentage became reduced. 
Most of the affected leaves remained on the trees to the end of 
the season and continued to perform their function of assimila- 
tion apparently in a normal manner, excepting, of course, those 
instances in which dead, brown spots appeared as a result of the 
exposure of the cells by the rupturing of the epidermis. On 
some varieties a majority of the blisters became broken, while on 
others most of the blisters continued unbroken to the close of 
the season. On some varieties the breaking of the blisters usu- 
ally resulted in the formation of dead, brown spots, while on 
others there were very few dead spots, although there were large 
numbers of broken blisters. Likewise individual trees of the 
same variety often manifested noticeable differences in both of 
the respects mentioned. 
Trees on which the dead, brown spots formed freely shed some 
of their leaves from this cause, but it is unlikely that any consid- 
erable damage resulted. While the wrinkling and distortion of 
the leaves disfigured them, little if any real damage was done. 
The dead, brown spots caused by the breaking of the blisters 
need not be confused with dead spots due to any other cause. 
While they are simply irregular, dead brown spots as viewed 
from the upper surface, their unusual nature is at once observed 
by an examination of the under surface. There, unmistakable 
evidence is seen of the rupturing of the epidermis, the shriveled 
remains of which are always plainly visible to the unaided eye. 
Dead spots caused by fungi or spray injury show no such evi- 
dence of the rupturing of the lower epidermis. 
