Shade Trek and Timber Destroying Fungi. 



257 



which the process of clishitegratioii is localized, or where it proceeds 

 much more rapidly than in the surrounding 

 wood. These isolated centres are quite evenly 

 distril)uted. The wood is broken down com- 

 pletely, and largely consumed, leaving a partial 

 skeleton, or nearly all of it having disappeared. 

 The renmant, as well as a thin layer of the 

 bordering tissue, is bleached and white. It is 

 thus in strong contrast with the reddish color 

 of the surroundino; wood where the decav has 

 been checked or has proceeded more slowly. 

 This rapid local disintegration, then, forms 

 numerons small "pockets" distributed through 

 the affected w^ood at a certain stage in the prog- 

 ress of the disease. They are plainly visible 

 because of the bleached tissue. 



These pockets are a characteristic feature in 

 one stage of the heart rot of the spruce from 

 the mycelium of Tixmietes aljietis. If they 

 are found in the heart wood of the trunk of 

 this individual spruce it would be quite con- 

 clusive evidence that the heart rot here was 

 caused by this fungus, and that the infection 

 having occurred at the broken trunk in the 

 top of the tree many years ago had gradually 

 spread down the trunk to the base and out into 

 numerous branches, some of which have been 

 killed as a result. Sections of the trunk of 

 this tree were cut out at different places and 

 shipped to Ithaca for study. 



On splitting sections of the trunk cut from ^1.— Badly pruned oak 

 the discarded logs, these characteristic pockets ^^"^^* 



w^ere found to be present, and Fig. 88 is from a photograph of a 

 small block. These occur in the portions of the trunk where decay 

 has made considerable progress, the entire heart being invaded, and 

 the fungus encroaching on the " sap " wood. When cut with the 

 cross-cut saw, or even with a finer saw, the ends of the blocks do 

 17 



^^. 



