The Biology of Polyporus Pargamenus Fries a 
adjacent hyphze and extend downward at right angles to 
those of the surface. These rapidly growing hyphz extend 
over the lower surface of the young pileus in the form of a 
net, the regions in which the hy phee do not grow correspond- 
ing to the meshes and forming the future pores. Basidia 
begin to appear when the pore cavities are quite shallow. 
They are formed by some of the hyphe growing outward 
at right angles and englarging at the free ends. Conse- 
quently the pores at the margin are often immature when 
those at the rear of the pileus are fully developed. 
Examination of sections of the sporophores shows that the 
bases of the pores all lie in the same plane. 
Relation of the Hymenophore to the Pileus.— In Poly- 
porus pargamenus the hyphze of the context extend parallel 
to the surface. When the pores are formed some of the 
hyphee or their branches extend obliquely downward, and, 
turning gradually, soon grow at right angles to the hyphz 
of the context. Thus the course taken by the hyphe of the 
context extends at right angles to that taken by the hyphee 
of the hymenophore. ‘The trama of the pores is no denser 
than that of the pileus. The hyphe are slightly finer but 
then they are not so old as those in the context of the pileus. 
The arrangement of the hyphe in the context of the 
pileus must determine to a large extent their arrangement 
in the hymenophore. At least a certain number of the 
hyphz must extend in the direction of growth. If, there- 
fore, the hyphee in the context of the pileus are parallel to 
the surface as they descend into the hymenophore, they must 
change their direction to that of the pores which are verti- 
cally opposed to the pileus. 
The Pore Walls.— Associated with the thickness of the 
pore partitions or clissepiments are modifications of the edges 
of the pore openings such as dentations and lacerations. 
In Polyporus pargamenus the pore-walls are very thin. At 
an early age they become irregularly lacerated and when the 
slits progress to the base of the cavities the segments appear 
as hydnoid processes, Such plants can be mistaken easily 
