310 MANUAL OF TREE DISEASES 



White Pocket Heaetwood-Rot 

 Caused by Polyporus Rheades Fries ( = Polyporus dryophiXus Berkeley) 



This heartwood-rot is sometimes found in poplar, especially 

 in the Northwest, following the common white wood-rot caused 

 by Forms igniarius (see page 305). In oak this heartwood- 

 rot is common and destructive in the Southwest. The rot is 

 confined to the upper part of older trees and may involve the 

 sapwood. In cross-sections of affected poplars, the spring- 

 wood of the annual rings is whitish while the summer-wood is 

 light brown. The medullary-rays also become white. In 

 longitudinal section these white bands of decayed tissue cause 

 a mottled appearance. Small irregularly shaped brown areas 

 appear here and there. The white areas enlarge until but 

 little brownish wood remains between them. No cavities are 

 formed since the white deligniiied fibers are not entirely de- 

 stroyed. The sporophores of the causal fungus are shelf- or 

 hoof-shaped when they occiu" at branch wounds and are more 

 or less globose when formed directly on the bark. They are 

 brown and have a granular sandstone-like core which reaches 

 back into the sapwood. For further details concerning this 

 heartwood-rot, see imder oak diseases, on page 250. 



White Butt-Rot 



Caused by Fames applanalus Fries 



The fungus which causes this important white butt-rot of 

 many kinds of deciduous trees is the most common bracket- 

 fungus growing everywhere on dead wood. It is the most 

 generally known of the polypores because of the practice 

 of using the under surface of the sporophore for amateur 

 etching. Recently it has been learned that this fungus attacks 

 the wood of the roots and base of many trees, especially poplar, 

 beech, oak, birch and maple. The amount of damage caused 



