The Biology of Polyporus Pargamenus Fries 127 
earlier remained in the pockets and gave them a whitish 
appearance. The remaining woody tissue is now very soft 
and sponge-like when wet; when dry it becomes somewhat 
stiffer and more brittle, but still retains much of the spongy 
texture. 
The bark of the hemlock, on the other hand, is very 
resistant to decay and remains entirely sound, even though 
all of the sapwood immediately underlying it be reduced to 
pith-like consistency. Its extreme durability is due, in a 
large measure, to the high tannin content. 
Comparison of the Decay of Hemlock Wood by Polyporus 
pargamenus and P. abietinus.— Earler in this paper an 
effort was made to distinguish between the sporophores of 
P. pargamenus and its near relative, P. abietinus. The 
resemblance of the decay produced in hemlock by these 
respective fungi, however, is even more confusing than the 
resemblance between their sporophores. In hemlock wood of 
a more nearly uniform structure it has been noticed that 
P. abietinus sometimes begins to decay the late wood first. 
Whether this ever occurs in the decay caused by P. parga- 
menus the writer is unable to say. In other cases P. abietinus 
decays the early wood just as rapidly as the late wood, and 
in hemlock wood of a decidedly uneven texture the early 
wood is considerably decayed before the late wood of the 
annual ring is attacked appreciably. Hemlock wood decayed 
by P. pargamenus had numerous prominent white strands of 
mycelium running radially in the wood. In that decayed by 
P. abietinus the radially running white mycelial strands 
were even more abundant and conspicuous. Aside from these 
minor differences no other difference in the manner of the 
decay of hemlock wood by these two closely related fungi 
could be observed macroscopically. 
Microscopic Appearance of the Decayed Wood.— From 
the microscopic appearance of the decayed wood it 1s evident 
that extensive chemical changes must have occurred to pro- 
duce such great structural alterations of the woody substance. 
A comparison of cross sections of both normal and decayed 
