The Biology of Polyporus Pargamenus Fries 53 
Consistency of the Sporophore.— In the growing margin 
of the pileus the hyphe, whatever may have been their ear- 
ler arrangement, usually are parallel to one another, little 
interwoven, and extend in the direction of growth. As the 
pileus matures they become variously interwoven and modi- 
fied. In this as well as other coriaceous species the pileus 
is quite thin and usually fibrous and flexible. Microscopic 
examination of a pileus of Polyporus pargamenus showed 
that it consists of a mass of branching, sparingly septate 
hyphe extending singly or in loose strands parallel to the 
surface. These hyphee or strands of hyphz are but little 
interwoven and form a tissue homogeneous throughout the 
pileus. At the upper horizontal surface many hyphee grow 
upward and terminate as the hairs of the pileus. Other 
hyphe grow vertically downwards and form the trama of 
the tubes. At maturity the ends of these hyphee bend out- 
ward at right angles and form the elements of the hymenium 
(Plate VII). 
Size of the Ilyphw.— Measurements were made of hyphie 
in different portions of the pileus. In different plants of this 
species the size of the hyphe is fairly constant, although 
there may be a slight difference between their size in the 
different portions of the same pileus. The hyphe are 
stouter in the context of the pileus and become smaller in 
the trama of the pores. Even within the context of the pileus 
the size of the hyphe is extremely variable, but they average 
from 3-4 y in thickness. The larger hyphee are very thick- 
walled and have small lumina. Clamp connections and 
eross-walls occur but rarely, especially in the larger hyphee, 
and then usually are indistinct. In general the size of the 
hyphe is of little diagnostic value since there is so small a 
range of variation in the different species. 
Surface Modifications— The upper surface of the pileus 
of Polyporus pargamenus not only remains incapable of 
further growth but has a completely undifferentiated sur- 
face. The upper surface is composed only of the unmodi- 
fied terminations of the hyphz of the context, which end at 
