The Biology of Polyporus Pargamenus Fries 43 
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species often grows much larger than P. abietinus, some- 
times attaining a length of 6-7 cm., and is often fan- 
shaped or cuneate in outline and attached by a narrow, 
attenuate, sometimes stem-like base, so that the form and 
size of the sporophore will usually separate it from P. abie- 
tinus. Other differences may be pointed out as follows: 
P. abietinus lacks the more or less shining, indistinct, 
buff, to dark-brown zones which are so characteristic of 
P. pargamenus. The sporophores of the latter plant are 
sometimes concentrically suleate but rarely prominently so; 
those of P. abietinus, however, are almost invariably concen- 
trically suleate and frequently very conspicuously so (Plate 
IV). The pubescence of the pileus of P. pargamenus varies 
from silky to velvety, while that of P. abietinus varies from 
silky-villous to strigose. The pores of P. abietinus are 
larger, more delicate and shallow than those of P. parga- 
menus. In the latter the mouths of the pores almost always 
become irpiciform at a very early age —in fact almost as 
soon as they are formed ( Plate 1): ; in the former, however, 
the poroid configuration of the hymenium usually is retained 
until maturity (Plate IV). Even then they practically 
never become irpiciform to the same extent that occurs in 
P. pargamenus. The pores of P. abietinus are very thin- 
walled, usually becoming somewhat radiately-lacerate with 
age. Both species often have a violaceous or lavender tint 
to the margin of the hymenium, especially on the margins 
of young pilei. This peculiar coloration is almost always 
present in P. abietinus, occasionally becoming so pronounced 
in young specimens that the hymenium is indigo. This 
coloration may or may not be present in P. pargamenus, but 
when present it 1s rarely so pronounced as that which com- 
monly occurs in P. abictinus. The hymenium of the former 
plant usually is marked by a prominent sterile margin, 
except in very old specimens; that of the latter rarely has 
any sterile margin to speak of. In P. pargamenus the 
freshly growing margin of the pileus is silky at first, while 
in pilei of P. abietinus it is usually more or less strigose 
from the beginning. The microscopic examination of the 
