The Biology of Polyporus Pargamenus Fries 125 
In this wood the contrast between early and late wood is 
very decided. Consequently it is only natural that the decay 
should start between the annual rings where the soft spring 
wood adjoins the hard summer wood. Therefore, as the 
decay progresses we should expect to find the soft spring 
wood decaying far more rapidly than the harder summer 
wood. It is characteristic of the decay that the early wood, 
especially the innermost portion, becomes badly disintegrated 
and full of large pockets, while only the outermost surface 
of the late wood is attacked, and then only very superficial 
pockets appear. Thus we have an explanation of one of the 
most conspicuous features of the decay of hemlock wood by 
Polyporus pargamenus — the separation of the annual layers 
of growth in the early stages of the decay. Owing to the 
peculiar structure of this wood and the manner in which it 
is decayed by the fungus, it is only natural that it should 
separate along the line of the growth rings when subjected 
to any stress. 
In the later stages of decay the wood becomes almost uni- 
formly pith-like and full of conspicuous pockets of varying 
size. (Plate XXVI.) Within local areas of the wood dis- 
integration often becomes so complete that a mere shell of 
wood of quite uniform thickness is all that separates the 
pockets from one another. The pockets are very variable 
in size, depending upon the extent to which they have united. 
The largest of the pockets rarely exceed 10x2x2 mm. 
extending in the wood in a direction parallel to the axis of 
growth. At this stage of the decay most of the pockets are 
entirely empty and free of any partially decomposed woody 
fibers and present a clean-cut appearance. Closely appressed 
to the inner walls of the pockets are numerous fine white 
strands of mycelium, which can be seen to best advantage 
in a longitudinal section of the wood. In addition larger 
white strands of mycelium frequently transverse the pockets 
at right angles (Plate X XVI), the same strand frequently 
extending through several pockets. At this stage of the 
decay the finer grained wood and wood of uniform and regu- 
lar growth at least has a regular honeycombed appearance, 
