The Biology of Polyporus Pargamenus Fries 89 
oped the blocks in a luxuriant growth and eventually filled 
the whole dish. At the end of two months the blocks were 
examined and exhibited but little or no evidence of decay. 
The results would indicate that the mycelium of this fungus, 
at least so long as food is readily av: ailable, will take it from 
fee eoarce of least resistance —in other words, the source 
from which the food can be most easily assimilated. 
Regeneration of Lost Parts of Sporophores.—As 1s com- 
monly the case in the less highly organized plants, the lost 
parts of their structures often are replaced — a direct regen- 
eration thus taking place. This procedure is of especially 
common occurrence among the sporophores of the wood- 
destroying fungi but the regeneration is limited to actively 
growing sporophores. The regeneration of lost parts can be 
demonstrated readily in Polyporus pargamenus by cutting 
off carefully a portion of the pileus or even the hymenium 
alone. It is only a matter of a few days, in case conditions 
for favorable growth are present, for the lost part to be 
entirely restored. 
The Destruction of Wood by Polyporus Pargamenus. 
Cremistry anp Piysrcs or rune Decay. 
Wood decay in general consists of a series of chemical and 
physical changes brought about by the action of the mycelium 
of the fungus. As in other wood- destroying fungi, the decay 
caused by Polyporus pargamenus 1s essentially a process otf 
digestion and absorption. The digestion of woody tissues by 
this fungus is due to the excretion of a number of enzymes 
or organized ferments which reduce the woody substance to 
simpler organic compounds capable of being absorbed 
through the walls of the mycelial filaments, and which deter- 
mine the manner of the decay of the woody substance. It 
is by means of their enzyme excretions that the minute and 
delicate, thin-walled fungal hyphze are enabled to dissolve 
their way through the lignified membranes of their host. 
This action is comparable to that of the ferment secreted by 
-yeast cells in breaking down sugar, After the fungal hyphee 
