234 



193. 



in the cypress wood are much larger, however, and the structural 

 character of the affected wood is quite different. In the case of 

 the cypress trunks affected with this disease known as ' ' pecki- 

 ness," it is believed that the fungus, while developing at the 

 centres, excretes an enzyme or "ferment," which permeates 

 the surrounding wood and acts as an antiseptic which prevents 

 the further disintegration. It is possible that this is to some 

 extent the case in the formation of the 

 pockets in the spruce timber, that is, that 

 the wood intervening between the centers 

 of rapid disintegration, becomes permeated 

 with an enzyme excreted by the mycelium 

 which renders it immune for a time, or at 

 least retards the disintegration of the wood. 

 But if this is the case, the effect of the 

 antiseptic is not lasting. In the case of 

 fallen logs affected by the Trametes abietis 

 the decay continues until all parts of the 

 wood are in a much decayed condition. 

 Still, in such logs, it is quite evident that 

 the progress of the disintegration has been 

 intermittent, certain centres having first 

 decayed, and in time spreading from these 

 pockets to surrounding areas until all the 

 wood is brought under complete contribu- 

 tion to the mycelium. In such decayed 

 spruce wood, there are further evidences 

 that the decay has spread from numer- 

 ous centers which have been extended until 

 they finally met. This is shown in the 

 varying coloration of the wood, and especi- 

 ally by black boundary or limiting lines. 

 (Fig. 90.) 



It is evident from these and similar studies 

 that there is no cure for the diseases caused by wound parasites 

 after once the fungus has entered through the wound into the 

 interior of the tree. For a few years there may be no apparent 

 injury but with the lapse of time the tree becomes badly injured 



94. Shade tree used as a 

 hitching post. 



