The Biology of Polyporus Pargamenus Fries 59 
of the hght. Sporophores of Polyporus versicolor grown by 
her in the diffused light of the laboratory, under constant 
conditions of temperature and moisture, were a uniform pale 
buff color; only rarely was a zone emphasized by a slight 
deepening of color. The writer has observed frequently that 
sporophores of Polyporus pargamenus, as well as its near 
relative, Polyporus versicolor, that develop out-of-doors on 
the lower shaded side of a large log for example, or when 
shaded by other means, invariably have pale buff upper sur- 
faces. In such a case, however, the zonation of the pileus 
usually is well marked since the variable atmospheric condi- 
tions are responded to by variations in the growth of the 
hairs. The same sporophores, when they are exposed to a 
greater intensity of light, develop quite normally and the 
butt color soon ch: anges to a darker brown shade. If growth 
is checked rather quickly the margin of the last zone of 
growth, owing to a deficiency in the formation of pigment, 
is marked by a lighter band. Therefore the pilei formed 
in summer, when periods of drought are more frequent and 
growth is arrested suddenly, generally have many brown 
bands marking these periods. It is only the fairly young 
zones of a pileus that show these conspicuous colored bands, 
for ultimately the whole surface assumes the same dark color, 
thereby obscuring the bands of color. The zonate appear- 
ance visible then is due mainly to the differences in texture 
presented by the velvety ridges and satiny furrows which 
become even more conspicuous when the pileus, on becoming 
quite dry, has the well-known gray appearance.. A pale buff- 
colored pileus, when once detached from its host and allowed 
to dry for some time is incapable of developing the darker 
pigment when exposed again to ordinary atmospheric 
conditions. 
The Elements of the Hymenitum.— The hymenium of 
Polyporus pargamenus apparently consists of but three dis- 
tinct structures (Plate VII), viz.: (a) colorless basidia, 
usually with four sterigmata and spores, (b) blunt eystidia 
capitate at the apex with an incrustation of mineral matter, 
and (c) a basidium-lke element which is asterigmate, usu- 
