CHESTNUT, BARK DISEASE. 437 
41 successful out of a total of 55, or 75 per cent., on the sprouts. 
An attempt to inoculate a young Japanese chestnut six inches 
in diameter failed entirely, although sixteen inoculations were 
made at two different periods. This seems to show that the 
tree had great resistance, if not immunity, to the disease. 
As regards inoculation of chestnut, versus oaks, it was found 
that the former were much more readily infected than the latter, 
which showed only 12 successful infections out of 51, or 23 
per cent. All of these were confined to the sprouts, and did not 
make nearly so vigorous growth as did the inoculations on 
chestnut sprouts. The oak seedlings used were rather small, 
and the inoculations were made comparatively late, using cultures 
obtained originally from both oak and chestnut. 
Source of Cultures. Most of our inoculations were made 
with cultures obtained from chestnut, as at the time we had only 
one culture of var. parasitica from oak, namely Quercus velutina 
from Woodmont, Pa. This was inoculated into both chestnut 
and oak seedlings and sprouts. The inoculations into chestnut 
seedlings showed 4 successful out of 25, or about 15 per cent., 
while the 16 made on the chestnut sprouts all apparently failed, 
for some not very evident reason, possibly because made in July 
with old spores. Of the 20 inoculations on oak seedlings, all 
failed, while of the 12 on oak sprouts, 5, or 42 per cent., took 
more or less vigorously. From the results of the inoculations 
with this single culture, it would seem that the strain from oak 
at least was not quite so active a parasite as that from the 
chestnut itself. 
Whether or not cultures from chestnuts from different regions, 
or from living as compared with dead trees, show any difference 
in virulence, we are not certain. In our experiments we did 
not get any conclusive results along this line. To determine 
these points accurately, however, one would need cultures that 
had only recently been obtained from their hosts, and whose 
spores when used were comparatively young and of the same 
age. 
Age of Cultures. It seems quite probable that the longer the 
variety parasitica is kept in culture the more likely it is to lose, 
at least in part, its virulence. While no direct experiments were 
made to determine this point, it is possibly shown by the cul- 
tures obtained originally from a Japanese chestnut in Westville 
27 
