THE CHESTNUT BARK DISEASE. 365 
are girdled the fungus continues to grow extensively through the 
dead bark, sometimes covering the entire surface with reddish brown 
pustules. These pustules produce mostly the type of spores called 
ascospores, although occasionally long strings of conidia are also 
produced, even on bark that has been dead at least a year. If the 
proper conditions of moisture are present the fungus will continue 
to grow on the bark of chestnut logs and even upon bare wood. 
When a branch or trunk is girdled the leaves above change color 
and sooner or later wither. (Pl. XXXVII.) These prematurely 
killed leaves often remain on the branches, forming, together with the 
persistent burs, the most conspicuous winter symptom of the disease. 
The most conspicuous symptom at all times of the year is the occur- 
rence of sprouts at the base of the tree, on the trunk, or on the branches. 
(Pl. XXXV; PL XXXVI, figs. 1 and 2; also Pl. XXXVII.) 
Sprouts may appear below every canker on a tree, and there are often 
many such cankers. These sprouts are usually very luxuriant and 
quick growing, but rarely survive their second or third year, as they 
in turn are killed by the fungus. The age of the oldest living sprout, 
as determined by the number of its annual rings, is an indication of 
the minimum age of the canker immediately above. The annual de- 
velopment of sprouts from the base of a tree sometimes continues 
vigorously for at least six years after the tree is dead, which fact 
affords clear evidence of the healthy condition of the roots. If 
infection of these basal sprouts could be prevented, they would de- 
velop into a much better type of coppice than is usually seen, since 
they are rooted in the ground. After the tree is dead the dead 
sprouts, together with the scars left by cankers on the outer layers 
of wood, serve to show what killed the tree long after the bark has 
completely decayed and fallen away. 
The fungus apparently does not penetrate to any considerable dis- 
tance below the ground; nor does it attack the green leaves or the 
greenest of the young wood. Late in the season it will readily attack 
wood of the current year. This is observed, however, most com- 
monly on sprouts. 
Regarding the virulent parasitism of Endothia parasitica there is 
no possible question. It is easy to demonstrate this by making arti- 
ficial inoculations in healthy trees. Plate XX XVII shows such an 
inoculated tree. The conidia, or so-called summer spores of the 
fungus, were put into a slit in the bark near the base of this little 
potted chestnut tree and a canker promptly developed. The typi- 
cal symptoms of the bark disease, as they occur in large trees, fol- 
lowed—girdling of the trunk, withering of the leaves above, and 
prompt development of sprouts from below the canker. Some weeks 
after the photograph (Pl. XX XVIT) was taken the sprouts were all 
killed by the downward growth of the canker. 
