CHESTNUT DISEASES 149 



slightly tan-colored mycelium are exposed. No indications 

 of mycelial fans are found as in the Endothia canker. The 

 cankers soon girdle the trunk and the parts above die. Large 

 elliptical conspicuous cankers with depressed centers surrounded 

 by concentric calluses are also formed on chestnut but not so 

 commonly as on the red and black oak. These cankers and 

 the fungus causing them are described on page 245. 



Brown Checked Wood-Rot 



Caused by Polyporus sulphureus Fries 



The heartwood and sapwood of chestnut are often decayed 

 by the sulfur fungus. The same rot is common in oak, maple, 

 walnut, butternut, locust, alder and other trees. The wood 

 is reduced to a red-brown, powdery mass which separates into 

 cubes. The sporophores are conspicuous, annual, orange and 

 sulfiu'-yellow colored bodies which form at wounds or oh the 

 bark where the fungus has decayed the sapwood. The tops 

 of the trees or large limbs may be killed by the girdling action 

 of the mycelium in destroying the sapwood and bark. A fuller 

 description of the symptoms and cause of brown checked wood- 

 rot which are similar for all the trees affected is given under oak 

 diseases, page 247. 



Straw-Colored Heartwood-Rot 



Caused by Polyporus frondosus Fries 



This heartwood-rot may be found in the base of the trunks 

 of chestnut. The trees do not become hollow. The advancing 

 decay first shows as long, slender, white streaks. Later the 

 wood becomes tan- or straw-colored and is held together by 

 the less affected medullary-rays. The sporophores of the causal 

 fungus arise from the ground around the affected tree. They 

 are large, fleshy, globose structures with many overlapping 

 if 



