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the attack so vigorous that young trees often succumb in one or 
two years, and older ones soon lose branches of such size that 
the vigor of the entire tree is materially impaired and its beauty 
and usefulness practically destroyed. It is not the primary effect 
of the fungus on the living tissues of the tree, widespread as this 
effect often is, that causes the greatest damage ; but the secondary 
effect of this injury on the remaining portions of the trunk or 
branch affected ; for it is the habit of the entering mycelium to 
proceed in a circle about.the affected portion until it is completely 
girdled. This girdling habit is due to the stoppage of the circula- 
tion up and down the stem at the infected point and the growth of 
the mycelium toward the current of water and food supply, which 
is more and more deflected by the invading fungus until finally 
cut off altogether. 
This is well shown in Fig. 19, which represents a portion of a 
young tree being girdled by the fungus, viewed from three 
different directions. The fungus entered in 1905 through an 
undressed pruning wound, and grew nearly half-way around the 
trunk during last season. The first week in May, 1906, when 
the weather was warm and moist and the inner bark full of food, 
the mycelium began to grow again, and by May 11 it had cov- 
ered that part of the trunk indicated by the light area in the figure. 
On May 15 the two growing borders had united and the girdling 
was apparently complete ; though death did not ensue for several 
days, on account of tissues lying next to the sapwood that still 
remained uninjured. At this time the leaves of the opening buds 
were scarcely an inch in length; too young to have made use of 
much of the nutriment stored in the stem. 
When the tips of branches are affected, the progress of the 
disease is of necessity slow, since the affected area is small and 
the food supply scanty. On the other hand, the base of the 
young tree is a point of special danger, since the abundance of 
moisture and food it supplies facilitates the speedy growth of the 
fungus and thus endangers the life of the entire tree. 
The way in which the fungus in question first enters a chestnut 
tree is at present largely a matter of conjecture. Twigs, sprouts, 
nursery trees, branches of various sizes, and trunks a foot or 
