The Biology of Polyporus Pargamenus Fries 187 
Acknowledgments 
These studies were carried on in the Botanical Laboratory 
of the The New York State College of Forestry under the 
supervision of Dr. L. H. Pennington, to whom the writer is 
indebted for advice and kindly criticism. The writer also 
wishes to express his gratitude to Dr. H. P. Brown, whose 
advice and interest in that portion of the work dealing with 
ee microtechnique and anatomy of woody tissues have been 
source of constant help and guidance. 
a conclusion the writer also wishes’ to express his grati- 
tude to Dr. W. A. Murrill, Dr. J. R. Weir, Mr. C. G. Lloy d, 
Dr. E. A. Burt, Dr. L. O. Overholts, Mrs. Flora W. Patter- 
son and others, for counsel given and courtesies shown when 
examining specimens in their charge, or by having compiled 
for his use lists of specimens in their charge. 
Summary 
Polyporus pargamenus is one of the most common wood- 
destroying fungi causing a sap-rot of most of the species of 
dicotyledonous trees occurring throughout its nearly cosmo- 
politan range. It is essentially a saprophytic organism, and 
as such is especially notorious for attacking dead wood, espe- 
cially felled wood from which the bark has not been removed. 
Ii frequently becomes a wound-parasite, and as such is 
especially prevalent on fire-searred trees throughout the hard- 
wood forests of the eastern half of the United States. 
The sporophores of Polyporus pargamenus are subject to 
wide variation in their morphological characters, and the 
various diverse forms are to be regarded as ecological adapta- 
tions of the fructification in response to varied environmental 
factors, particularly the moisture content of the substratum 
and the humidity of the air. 
As a species Polyporus pargamenus consists of a number 
of more or less intergrading forms which often become suf- 
ficiently distinct as io constitute varietal forms or subspecies. 
It is advocated that these varietal forms be recognized for 
