190 College of Forestry 
The enzymatic digestion and consequent decay of wood by 
Polyporus pargamenus is accomplished mainly by the exceed- 
ingly minute fungal hyphe, which are the ultimate branches 
of the mycelial system. Upon the completion of the decay 
within any given area of the wood the older mycelium, which 
has fulfilled its purpose, causes to function in the enzymatic 
reduction of the woody substance, although it still may prove 
useful in the translocation of the elaborated food materials. 
When the final stage of the decay is reached the mycelium 
itself apparently is dissolved together with the woody sub- 
stance in areas of the wood w here the decay is most intense. 
The decay of wood by Polyporus pargamenus is character- 
ized by its habitual tendency to produce a minute pocket type 
of decay, which, while not very pronounced in the early stages 
of the decay, becomes a conspicuous feature of the later 
stages. As a result of the intensity of the decay in these 
innumerable pockets the destruction of the woody elements 
becomes completed in these initial centers of the decay before 
the wood lying between these areas is materially destroyed. 
Within the individual pockets the decay progresses mainly 
in a direction parallel to that of the woody elements, the 
central elements becoming reduced rapidly to pith-like con- 
sistency. In the late stages two or more adjoining pockets 
may coalesce into one, ie resulting pockets becoming quite 
empty of contents and separated by almost membranous 
layers of less decayed wood. The largest pockets observed 
were in yellow birch wood, where they attained a maximum 
diameter of three mm. in diameter and three em. in length. 
The first chemical change brought about by the action of 
this fungus is that of delignific ation. The decay begins at 
the interior of the cell-wall and destroys it progressively from 
the internal or last-formed layer to the middle or primary 
lamella between two adjoining cells, first removing the lignin 
constituents and then the remaining cellulose. The tertiary 
and secondary layers are entirely dissolved before the delig- 
nification of the middle lamellee commences. 
The results obtained from the study of the decay by Poly- 
porus pargamenus establish the fact that the minor variations 
