Undescribed Timber Decay of Pitch Pine 269 



its growth produces both types of enzymes but that in the young 

 mycelium more of the cellulose destroying enzyme is produced 

 while in later stages the lignin destroying enzyme is produced in 

 larger quantities. 



Eventually the tracheids in the spring wood are entirely de- 

 stroyed and long narrow cavities are formed in the space it 

 formerly occupied. The summer wood is attacked before the 

 spring wood is destroyed and it may even be possible that 

 mycelium enters it as early as it does the spring wood. But the 

 more compact structure of the former makes it able to withstand 

 the attacks of the fungus for a much longer time. Even after 

 the spring wood is entirely destroyed the summer wood is quite 

 firm, although it has changed to the cinnamon-buff color and has 

 become quite brittle. Because its destruction is such a long 

 drawn out process it may even be doubted whether in a state of 

 nature it is ever entirely destroyed by this fungus. Longer 

 periods of exposure might result in the entrance of other organ- 

 isms through which the decay would be hastened and eventually 

 completed. 



Summary 



Polyporus amorphus cannot yet be said to be a common fungus 

 in this country since only a few collections are known. It is 

 probable, however, that it is more common than these collections 

 would indicate. Indications are that its range will be southern 

 Canada, New England, and the states bordering on the Canadian 

 line. 



The fungus causes a characteristic decay of the sapwood of 

 Pinus rigida, and has been collected also on wood of P. Strobus, 

 P. pungens, and Tsuga canadensis. 



In external appearance the decayed wood is darker in color 

 than sound wood and is of a cinnamon-buff color (Ridgway). 

 The spring wood is completely decayed long before the summer 

 wood disappears. This results in the formation of concentric 

 cavities alternating with the bands of firmer summer wood, and 

 has suggested the name " stringy rot." 



Microscopic examination and microchemical tests establish the 

 fact that the fungus first dissolves out the cellulose of medullary 



