Shade Tr?:e and Timber Destroying Fungi. 



259 



disintegration. It is possible that this is to some extent the case in 

 tiie formation of the pockets in the spruce timber, that is, that the 

 wood intervening between tlie centres of rapid disintegration, 

 becomes permeated with an enzynie excreted by the myceham 

 which renders it immune, for a time, or at least retards the disin- 

 teo^ration 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 ahietis 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 

 disinteo-ration 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 com- 

 plete contribution to the mycelium. In such 

 decayed spruce wood, there are further evi- 

 dences that the decay has spread from numer- 

 ous centres which have been extended until 

 they finally met. This is shown in the vary- 

 ing coloration of the wood, and especially 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 bv 

 wound parasites after once the fungus has 

 entered thi-ough 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 if not destroyed. 

 The trees may live for years, or even a century 

 or more with the fungus inside still growing. 

 They may be so weakened that they are broken down or uprooted 

 during strong winds. Shade trees may be rendered unsightly, and 

 lacking in density of foliage. Fruit trees may be rendered less 

 fruitful if not ultimately killed. Timber trees in a very few years 

 may be so injured as to be worthless for the market. 



In their relation to forestry these studies emphasize the desira- 



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V"-< 



94. — Shade tree used as 

 a Mulling -post. 



