8 
Mycologia 
apparently as ever.' Logs, limbs an inch or more in diameter, 
rail fences, chestnut posts and structural chestnut timber may 
be attacked. The infection at the start is a local one, and the 
diseased areas first occur in the last few rings. In such cases they 
are next to the ground, or with large logs on the lateral side most 
protected from drought. Only in an advanced stage is the whole 
cross section attacked, and before this condition is reached the in- 
roads of the fungus are usually arrested through lack of moisture. 
Chestnut is very durable in contact with the soil, and it is not un- 
common to find fallen decorticated limbs and branches showing 
the decay described above on the lower side, while they are as 
sound at the core and on the upper side as normally. Only where 
sufficient moisture is available is the center of the log attacked. 
Cracks due to checking and frost action greatly facilitate the ac- 
tion of the fungus, since they permit the ready ingress of water 
into the deeper-lying tissues (Fig. 28). 
All parts of the annual ring are susceptible to the attacks of 
the fungus (Fig. 14). The white areas of varying extent and 
irregular outline may include within their boundaries one or more 
vessels in the spring wood, or be entirely confined to the outer 
portion of the ring. The last is usually most severely attacked, 
however. Occasionally infected spots coalesce and form large 
areas, although they usually remain free from the start. 
At first there is no disintegration in the wood other than the 
formation of the irregular white areas. The elements retain 
their original size, thickness, and continuity with one another. 
Subsequently near the center of the white areas a small cavity 
appears (Fig. 6). This is bounded at first by white tissue on all 
sides and includes but a small portion of the diseased area. The 
white tissue at the margin remains undisturbed. 
Within the cavity itself, disintegration is not complete. It is 
filled with long, white, fibrous elements which remain loosely at- 
tached or entirely free from one another. These are thick-walled 
and offer great resistance to the dissolving action of the fungus. 
The cavities gradually enlarge as the disintegration goes on until 
finally all that remains of the original white area is a narrow 
r The whole mass of tissue is never affected as in the case of some forms 
12, 18 , and the wood never loses completely its firmness and elasticity. 
