570 BULLETIN 347 
in the bark, but wounds form the usual means of entrance.”” Anderson 
and Babcock (1913) were unable to produce the disease by inoculating 
with spores without making wounds. 
At Napanoch, New York, glass rings were affixed to healthy, smooth 
bark, which was then sprayed with a suspension of ascospores. The 
rings were then closed in order to secure moisture conditions favorable 
for germination. The purpose of the experiment was to see whether 
infection could take place through lenticels. Forty-nine inoculations 
made in this way gave negative results. In another set of experiments 
the rings were placed over natural cracks — which are abundant on heavy- 
bark trees in spring and early summer, due to the rapid growth of the 
trees — and these were inoculated as above. The fourteen inoculations 
made in this way gave negative results. In.a supplementary set of experi- 
ments, ascospores were sprayed on one hundred and ninety of these cracks 
and were not protected in any way. All but four gave negative results. 
In still another set, twenty pieces of bark containing perithecia were 
placed so that the ascospores would be ejected during rains into these 
natural cracks. No infection resulted. 
As is indicated later under another head, the fungus appears to be 
incapable of effecting any change in the cork tissue. It should be kept 
in mind, also, that even when the bark appears sound it may contain 
small punctures or abrasions which could easily escape notice; and that, 
unless the point of inoculation is well protected, wounds may be produced 
subsequent to inoculation which are not taken into account by the experi- 
menter. It is evident, then, that at most the cases in which the fungus 
enters without an abrasion must be so rare as to be negligible. 
Agents that produce the wounds.— When the disease was first brought to 
notice, Murrill (1906 a:151~-152) suggested a number of agents that 
might be responsible for the wounds that give entrance to the parasite — 
such as lumbermen, nut-gatherers, winter injury, the green fly, the twig- 
borer, squirrels, birds, insects, mice, moles, and rabbits. Later (1906 b) 
he suggests dead twigs as a channel of entrance, since he often finds these 
at the cénter of young cankers. 
Metcalf and Collins (1911:10) believe that insects are responsible for 
most of the wounds: ‘When the spores have once been carried to a 
healthy tree, they may develop in any sort of hole in the bark which is 
reasonably moist. These may be wounds or mechanical injuries, but by 
far the most common place of infection is a tunnel made by a borer. 
In many parts of the country where the disease is prevalent there is very 
direct evidence that bark borers, and particularly the two-lined chestnut 
borer (Agrilus bilineatus), are directly associated in this way with ninety 
per cent or more of all cases of this disease.” Ruggles (1913) points out 
