Undescribed Timber Decay of Pitch Pine 265 



shell made up of wood that is apparently nearly sound. This is 

 probably because these layers have too low a water content for 

 the growth of the fungus. That this surmise is correct is borne 

 out by the fact that where the thick bark of the pitch pine remains 

 as a protective covering on the trunk the outer layers of sapwood 

 are decayed to a considerable extent. The bark falls off rather 

 readily in the pitch pine, especially if the tree stands for several 

 months after it dies. Consequently, in cases where the decay is 

 well advanced the bark is generally lacking and the more sound 

 shell of sapwood is present. 



The sound dried sapwood of Pinus rigida is of a very light 

 color and contrasts strongly with the. brownish red color of the 

 less extensive heartwood. One of the conspicuous character- 

 istics of the decay is the change in color of the diseased sapwood 

 from the normal light color to a shade that matches exactly the 

 " cinnamon buff " of Ridgway's color manual. Since those 

 decays in which delignification of the woody elements takes 

 place result in a whitening of the diseased wood, it can be 

 conjectured at once that the action in this case is at least in 

 part not one of delignification but one in which cellulose is one 

 of the chief elements dissolved. 



The most conspicuous feature of the decay is now to be de- 

 scribed. When a mass of the decayed wood is examined and 

 attention directed to a lateral view of a rough radial section one 

 sees very narrow bands of fairly firm wood between which the 

 woody elements have been almost entirely removed. In other 

 words, narrow bands of sounder wood alternate with long 

 narrow cavities, neither band nor cavity with a thickness of more 

 than one millimeter. Into these cavities or furrows project 

 small bits of wood, often triangular in outline. The frequency 

 of their occurrence and their form suggest that they are medullary 

 rays. Under the microscope they are seen to be composed mostly 

 of vertical tracheids bound together by the remains of the ray 

 tracheids. The parenchyma cells of the rays have disappeared 

 and the vertical tracheids are well filled with mycelium and are 

 seen to be in a state verging on collapse. 



The alternating elongated cavities and bands of wood are the 

 characteristic marks of the decay and have suggested the name 



