The Biology of Polyporus Pargamenus Fries 131 
Tue Decay or OruerR Woops. 
The foregoing five particular woods were selected on the 
basis of their structure as type woods for the study of the 
‘decay produced by Polyporus pargamenus. At the beginning 
of this part of the investigation it was thought that broader 
and more momentous conclusions could be drawn regarding 
the nature of the decay produced by this particular fungus 
if the study was made on a number of representative woods 
of as widely different structure as possible, rather than on a 
number of woods selected more for the convenience with 
which they could be obtained. At the same time the idea 
of working with species of wood of commercial value for 
lumber was not lost sight of. In view of this feeling, type 
woods were selected from each of the three commonly recog- 
nized groups of woods. Among the heterogeneous (dicotyle- 
donous) or porous woods yellow birch and sugar maple were 
selected as representatives of the diffuse-porous group, while 
bitternut hickory and chestnut oak were selected as repre- 
sentatives of the ring-porous group. Among the homogene- 
ous (coniferous) or non-porous class of woods hemlock was 
selected as the representative wood. As a matter of fact, 
the selection of hemlock was a necessity since, with one 
exception, it was the only coniferous wood found to serve 
as a host for this particular fungus. 
The results secured from the study of these five woods 
were further supplemented by macroscopic studies on other 
woods, although only the five type woods were imbedded in 
celloidin and sectioned on the microtome. The macroscopic 
appearance of the decay of the following woods by Polyporus 
pargamenus was examined and found to be essentially the 
same as occurred in the five type woods that were studied 
in full detail: Butternut (Juglans cinerea), pignut hickory 
(Hicoria glabra), glaucous willow (Salix discolor), trem- 
bling aspen (Populus tremuloides), large-tooth aspen (Popu- 
lus grandidentata), white birch (Betula populifolia), paper 
birch (Betula papyrifera), sweet birch (Betula lenta), river 
birch (Betula nigra), blue beech (Carpinus caroliniana), 
