The Biology of Polyporus Pargamenus Fries 47 
violaceous pores, thus indicating the close relationship of 
these forms. The point of attachment of the poroid forms 
usually is much broader than that usually seen in P. parga- 
menus and the sporophores frequently spread out over the 
bark to a considerable extent before shelving out. The sporo- 
phores of these poroid forms are also much thicker than 
those of the usual form of P. pargamenus, often being tri- 
quetrous in sectional outline. Specimens of the eastern 
poroid form submitted to Dr. W. A. Murrill were declared 
to correspond closely with the type of Polyporus Sartwellii 
Berk. and Curt. described from New York, which he studied 
carefully while at Kew. 
In one collection made in Pennsylvania from a dead sap- 
ling of Populus grandidentata Michx., the majority of the 
sporophores were exceptionally thick. A close examination 
showed that the growth of the sporophores had been checked 
by dessication early in their life, and that they had revived 
and developed a new hymenial layer which overspread the 
old one. In most of the sporophores the new growth appar- 
ently commenced at the margin of the old pileus and spread 
over it in all directions, often completely enveloping the old 
gray pileus in a new mycelial growth (Plate VI). The sec- 
tions made through these revived pilei presented two definite 
layers of growth (Plate XII, Fig. 2). The appearance of this 
section, in view of the two distinct layers of pores, would seem 
to indicate that this was a perennial sporophore. The two 
hymenial layers occurred not only in the larger pilei but 
also in many of the smaller ones, some of which measured 
less than a quarter of an inch across. While the sectional 
view of any one of these pilei would seem to indicate that 
they were perennial, the macroscopic observations on their 
size, form, color, and rate of growth do not uphold this 
inference but testify that the occurrence of two hymenial 
layers in the pilei were merely the result of periodic or sea- 
sonal growth. It is therefore evident that the presence of 
more than one hymenial layer within a pileus does not neces- 
sarily indicate that the pileus is perennial, since the two 
hymenial layers may have been caused by a revival and 
