10 THe JOURNAL OF HEREDITY 
AMERICAN CHESTNUT ATTACKED. 
This and the four following figures, showing stages in the progress of the bark disease, were 
taken by Professor J. F. Collins at various points on Long Island. This photograph 
shows where the disease has secured a foothold on some of the smaller limbs, which are 
quickly killed. 
may survive for several years. 
parasite have been considered as pos- 
sible retarding agents, but as these 
same insects appear to also distribute 
the spores, their controlling influence 
is not likely to prove important. 
MANNER OF INFECTION 
When, in the Chinese chestnut, any 
spores of the parasitic fungus gain 
entrance into a wound on any part of 
the trunk or limbs, they give rise to a 
canker which persists on the tree, be- 
coming deeper year by year as healthy 
wood is formed around it. In the 
American chestnut, however, the canker 
rapidly enlarges until it girdles the tree. 
If the part attacked happens to be the 
trunk, the whole tree is killed, some- 
times in as short a time as a single 
season. If the smaller branches are 
When the infection is on the smaller limbs, however, the rest of the tree 
(Figure 2.) 
attacked, only those portions beyond 
the point of attack are killed, and the 
remainder of the tree may survive for 
several years. Ultimately, however, all 
American chestnut trees that are at- 
tacked, die completely (fig. 5). Figures 
2, 3, and 4 show the typically ragged 
appearance of such trees, due to the 
fact that some branches are not yet 
girdled and still have normal foliage, 
while others are dead. 
Limbs and trunks with smooth bark 
soon show cankers in the form of dead, 
discolored, sunken areas, which con- 
tinue to enlarge and become covered 
more or less thickly with the yellow, 
orange, or reddish brown pustules of 
the fruiting fungus (figs. 6 and 7). 
From these pustules masses of minute 
spores (conidia) are commonly extruded 
