The Biology of Polyporus Pargamenus Fries 159 
new material, the active life in a perennial plant is linked 
only with structural portions. In a forest tree, for example, 
the leaves are these active agents; the tissues of the trunk, 
on the other hand, are largely depleted of the organic nitro- 
genous matter (protoplasm) upon which the vital activity 
depends. They have ceased to live in the strict sense of the 
term, but, on the other hand, they are known by casual 
observation to live in the sense opposed to decay. While 
there are various phases of life in the plant recognized by 
ordinary observation, and more exactly defined by the physi- 
ologist, these phases pass by insensible gradations to the 
point where decay and chemical disintegration arepres 
dominant. ‘The most striking general feature of the cellu- 
losic group is that its members are non-nitrogenous. It might 
be reasoned, therefore, that from the very first they are 
excreta and never live in the strict sense of the wood. We 
may conclude that, from the moment of origin, the history 
of the cellulose group is one of progressive withdrawal from 
the realm of the main vital processes, and that to re-enter 
that realm they must undergo a process of proximate reso- 
lution as a result of external action. This reabsorption of 
cellulosic tissues is a frequent phenomenon. The process by 
which the tissues become broken down is of the character of 
an ordinary hydrolysis, that is, it is determined by enzymes. 
The writer has endeavored to trace the changes and modi- 
fications which these substances undergo in the normal life 
of the plant, and evidence has been given showing them to be 
highly reactive and susceptible of modification in various 
directions. Ie now wishes to follow the fate of these sub- 
stances in the ordinary processes of the natural world. Under 
these processes ‘“‘ death” is succeeded by a variety of pro- 
cesses of decay and disintegration. They are in part intrin- 
sic and in part determined by external agencies. They are 
__of two kinds — processes of resolution and processes of com- 
bination or condensation — which usually are concurrent. 
The former are attended with evolution of gaseous products ; 
the latter are defined by an extended series of their products, 
through all stages from “ humus” to the coals. The chief 
