HEMLOCK DISEASES 185 



of brown charcoal-like rotted wood are formed in the heart- 

 wood. The fruiting-bodies of the causal fungus vary from small 

 thin shelves to larger hoof-shaped bodies. The upper surface 

 is black in the older fruiting-bodies, while the new layer of 

 tubes on the under surface is rose-colored. For further details 

 concerning this heartwood-rot, see under juniper diseases, 

 page 204. The fungus continues to grow in fallen trees and 

 the fruiting-bodies are more commonly found on dead wood 

 than on living individuals. The sapwood is also decayed in 

 dead trees and logs. 



CuBoiDAL Wood-Rot 



Caused by Polyporus borealis Fries 



This heartwood-rot does not seem to occur abundantly, 

 since but little mention of it is found in literature. It is re- 

 ported in New York but no definite statements on its importance 

 and range are available. Red spruce is also known to be 

 affected by this wood-rot. 



Symptoms. 



In the early stages of tke decay, long parallel strands or cords 

 of white mycelium, lying close together, push their way through 

 the wood in the radial and tangential directions. The white 

 strands then disappear, leaving channels in the wood. Because 

 of these perforations and the shrinkage of the wood, it breaks 

 into minute cubes. On the border of the affected wood, the 

 mycelium reaches out into the normal wood in very fine strands. 

 These then develop into the thicker white cords described 

 above (Fig. 28). 



The fruiting-bodies are formed on the trunk or at the base 

 of the tree. Usually several shelf-like bodies one above the 

 other occur together, forming a cluster. The upper surfaces 

 of the shelves are white and shaggy. The under surfaces are 



