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only on the grounds that we are all interested in all that concerfis 
Fungi that I accepted, knowing that while those aspects of Mycology 
which most concern me at present must be of interest to you, you will 
be able to teach me far more than I can pretend to offer in return. 
A fungus spore contains but a minute fraction of the food-materials 
required by the mycelium which developes from it under suitable 
conditions, and we know that additional supplies must be provided 
from outside. Moreover, we can trace the destruction and disappear- 
ance of the constituents of the food supplied as the mycelium grows, 
and analyses show that it is especially organic carbon compounds 
which are accumulated in the growing fungus. 
Experiments prove that in no case does this nutrition consist in a 
mere transference of substances absorbed from the food medium into 
the body of the fungus: on the contrary, profound and complex 
changes must occur before the substance of the food becomes sub- 
stance of the fungus, and these changes are often accompanied by 
great waste of materials. 
The kinds of changes most in evidence are as follows. The food- 
substances must be rendered soluble and in a fit condition to be ab- 
sorbed in solution, and this frequently entails alterations brought 
about by the fungus itself or by some body excreted by it—e.g., the 
inversion of non-assimilable sugars (Yeast), the saccharification of 
starch (Aspergillus), the softening of horn (Onygena) or wood 
(Stereum), and so forth. 
Then we find that when the food-stuffs have been absorbed, still 
more profound chemical decompositions are undergone inside the 
cells of the fungus. The atoms and molecules are re-arranged and 
re-distributed in various ways, and never wholly as they were at first. 
Some of them are temporarily built up into the living structures, only 
to undergo still more turbulent and disturbing redistributions ; some 
combine with oxygen and are burnt off in respiration; some are 
finally brought into a condition of comparative rest in the so-called 
permanent structures of the fungus—e.g., the cell-walls—while others 
are left to wander here and there, inside or outside the arena of 
stormy life-activity, and ultimately attain a condition of rest—again 
only comparative—it may be in union with other vagrant molecules, 
in the form of some substance not wanted by the plant. 
Meanwhile, substances resulting from the various chemical changes 
referred to, pass out of the fungus into the external world, and may 
in their turn produce secondary series of alterations on the food 
medium—may even poison it, in fact—and the now altered food may 
re-act again’on the fungus. 
It is in the province of physiology to describe and explain these 
various phenomena of absorption, conversion, constructive and de- 
structive metabolism and excretion; to show how they are linked 
together in life-actions, and to discover how the living substance of 
the fungus is built up and broken down, and how it is enabled to 
perform those remarkable evolutions we term life. 
