ENDOTHIA CANKER OF CHESTNUT 589 
place, one can well imagine their being blown for miles in a strong wind 
from tall trees and from the tops of the mountain ridges where the disease 
is frequently found. Heald, Gardner, and Studhalter (1914) were able 
to catch the spores over three hundred and eighty feet from the nearest tree. 
Having proved that the spores are ejected all through the summer 
and that they are carried about in great numbers by the wind, only one 
link of a solid chain of evidence was missing: that was to prove that such 
wind-blown spores produce cankers when they fall into wounds. In the 
first series of experiments in order to determine this point, bark con- 
taining active perithecia was supported within a few inches of sterile 
wounds in healthy trees for a short time and then the wounds were 
wrapped with cotton in order to exclude later inoculation. Of the 1395 
wounds treated in this way, seventy-eight per cent developed cankers. 
In the next set of experiments, the distance was increased to one to four 
feet and a wind was artificially produced by bellows. Seventy-four per 
cent of the 185 wounds treated in this way had cankers about them later. 
Wounds treated in the same way but not exposed to shooting perithecia 
remained uninfected. 
In another experiment, groups of trees were selected in which some had 
cankers on them while others were free from disease. Sterile wounds 
were made in the healthy trees and protected by fine-meshed wire screen 
and cotton bands, so that it was believed that spores could not be intro- 
duced in any way except by the wind. The cankers on the diseased 
trees were frequently drenched in order to induce spore ejection. Of 
the 559 wounds treated in this way, 114 developed cankers. 
The results of the above experiments lead the writers to believe that 
. wind is an important factor in the spread of the disease. 
Other animate agents 
It is easy to believe that the sticky pycnospores remain attached to 
the feet of animals, such as squirrels, mice, and numerous others which 
run over the cankers. But after the spores are isolated from them, as 
undoubtedly they could be, it would still be necessary to prove that 
such spores are deposited in wounds where they produce infection. State- 
ments made with respect to the agency of animals in dissemination should 
be supported by more complete chains of experimental data than have 
been commonly adduced. 
It can be said at present only that it is possible that the fungus is spread 
by such means. 
PATHOLOGICAL HISTOLOGY 
Keefer (1914) reports detailed microchemic and histologic studies 
of the effect of the fungus in the bark and the wood of the tree. He 
