151 
more in diameter have been found infected, apparently irrespec- 
tive of their size or position. So far as field observations show, 
the fungus might enter wherever a spore happened to find a rest- 
ing place. All of my experiments, however, have failed to intro- 
duce the fungus into a branch while the thin brown layer of 
cortex remained intact ; though it readily entered when this was 
scraped off or punctured. As the fungus does not attack the 
leaves, I was not surprised when repeated attempts failed to 
introduce the disease into green twigs, where, although no cortex 
is present, the quality of the food and the character of the bark 
Fic. 18. A nearer view is here given of the dead branch mentioned under Fig. 17. The fungus was 
introduced by scraping off the cortex and applying active mycelium grown on bean stems. 
is evidently not suited to its development. The present suppo- 
sition is, therefore, that infection takes place only through wounds ; 
or, possibly, through the lenticels. 
Wounds are, unfortunately, only too frequent, especially in the 
case of a tender, rapidly-growing tree like the chestnut, which 
