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gradually accustomed to new food-substances. It is interesting to 
note in this connection an observation of Brefeld’s, which I have also 
confirmed, viz., that spores of coprophilous agarics which can only be 
got to germinate in dung-decoctions, will, when a vigorous mycelium 
is once started, go on growing in other food media, and other examples 
of the same kind are not uncommon. ‘Thus we may have Fungi in- 
capable of parasitism until the spores have been. germinated in dead 
media, as 1 showed to be the case in the Lily Disease due to a 
Botrytis. ' =e 
It appears to me that the foregoing evidence—which can be largely 
extended—leads to the following argument. Since the principal 
destiny of all the essential food-materials is to build up the protoplasm 
of the fungus, and since the whole of the structural peculiarities of 
the fungus result from the activity of the protoplasm, we must con- 
clude that if two individual mycelia of the same species are being fed 
in different ways, from different sources which supply the essential 
constituents in different combinations, the working of the protoplasm 
must vary in each case, and if the protoplasm varies, the results of its 
activity must vary also. It does not follow that the resulting varia- 
tions will be visible to us, though it can be shown that they often are 
visible; nor does it follow that we can predict what the variations 
will be, though the purely experimental enquiry, which alone can de- 
cide such matters, shows that even this can now be done to some 
extent, as we shall see. 
The point to be emphasized for the moment is merely that if we 
vary the nutrition of the protoplasm—and we see this can be done 
within certain limits—then we vary its activities, and among such 
activities are results of the highest importance to the present argu 
ment, some of which may be such as our senses take cognisance of, 
though others will be too subtle or too transient to be noted by us. 
If to variations of food-supply we add variations in the other con- 
ditions of life-activities—e.g., temperature, moisture, concentration of 
food-materials, illumination, aeration, etc.—all of which are known to 
induce changes of importance, we see dimly down long vistas of possi- 
bilities, and the wonder is not that Fungi vary, but that any species is 
able to maintain its average standard of peculiarities and properties. 
Here, however, we open up questions into which there is not time tO 
enter, and I must pass on. 
If I now cast a glance at some of the curious cases of habitat and. 
food-supply known, it must necessarily be brief and only serve to re- 
mind us of examples. 
Mycophthorous Fungi are by no means uncommon. Polyporus 
agaricinicola (Ludw) on Amanita, Boletus parasiticus (Bull) on 
Scleroderma, Volvaria Loveiana on Clitocybe nebularis and the well- 
known cases of Nyctalis, Hypomyces, Hypocrea, Cordyceps, Barya, etc. 
etc., are cases in point. 
Carbonicolous species are also abundant, as exemplified by Flam- 
mula carbonaria, Cantharellus carbonarius, Ascobolus carbonarms 
and other pezizinez ; the well-known Peztza omphalodes (P. confiuens) 

