232 



BULLETIN 193. 



in which the process of disintegration is localized, or where it 

 proceeds much more rapidly than in the surrounding wood. 

 These isolated centres are quite evenly 

 distributed. The wood is broken down 

 completely, and largely consumed, leaving 

 a partial skeleton, or nearly all of it hav- 

 ing disappeared. The remnant, 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 sur- 

 rounding wood where the decay has been 

 checked or has proceeded more slowly. 

 This rapid local disintegration, then, forms 

 numerous small ' ' pockets ' ' distributed 

 through the affected wood at a certain stage 

 in the progress of the disease. They are 

 plainly visible because of the bleached 

 tissue. 



These pockets are a characteristic feat- 

 ure in one stage of the heart rot of the 

 spruce from the mycelium of Trametes 

 abietis. If they are found in the heart 

 wood of the trunk of this individual 

 spruce it would be quite conclusive evi- 

 dence 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 gradu- 

 ally spread down the trunk to the base 

 and out into numerous branches, some of 

 which have been killed as 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 the discarded logs, these characteristic 

 pockets were found to be present, and Fig. 

 88 is from a photograph of a small block. 



91. Badly pruned oak 

 tree. 



These occur in the 



