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of the hyphz impels them to form zygospores ; promote it, and they 
develope sporangia. 
In other words, the nutritive conditions decide not only the mode 
of reproduction, but also whether it shall form reproductive organs 
at all, and this quite apart from any injury to the growth, which is 
often more vigorous if sterile. 
Now, it is clear that although we do not know all the stages of these 
processes—for instance, we are profoundly ignorant of what sub- 
| stances pass from the mycelium into the sporangiophores and 
H zygophores—a great step has been made in establishing, as Klebs has 
i done, that definite conditions of nutrition are concerned in bringing 
about the reproduction processes, and in modifying their characters. 
The mere fact that in Penicillium, for instance, the spores contain, 
according to Kramer’s analyses, 61°13 °/o of dry substance containing 
3°09 °/o of ash, as against 12°36 °/o and 11°34 °/o respectively in the 
mycelium, shows that enormous changes in substance occur when the 
i living protoplasm is impelled to produce’ spores, and the great ac- 
of cumulations of fat, nuclei, etc., in other reproductive bodies tell a 
a similar tale. Whether we shall ever learn exactly what occurs must 
| i be left to the future, but it is obvious that the present steps in the 
enquiry are essential to enable us to set the further questions to be 
answered. 
| | One of these questions is, how far is the development of the pileus, 
ia spores, etc., of a hymenomycete dependent on the nutritive con- 
ditions ? Another is, do the conditions affect the characters of these 
| organs ? The matter is important, because we determine the species 
Ho entirely from these characters. : 
i The question now arises, Can we apply the preceding considera- 
a tions to the higher Fungi, such as the Hymenomycetes ? 
ia In so far that genera and species are still accepted which are merely 
immature or arrested conditions of forms placed in other genera and 
| species when complete, there can be no doubt of it. I propose my- 
1] self to show you that MNaematelia is merely an abortive state of 
ath | Tremella, and other cases of the kind can be adduced. 
In so far, also, that considerable variation occurs in the higher 
agarics, etc., we have grounds for raising the questions I am raising. 
I need only remind you of the well marked varieties of the common 
Mushroom both in cultivation and in the field; and at the risk of an 
uplifting of the eye-brows on the part of you masters of the Friesian 
Mycology, I venture to put to you whether the characters which 
differentiate extreme varieties of Psalliota campestris are not as strik- 
ing as those which distinguish this species as a whole from P. 
cretacea (Fr) P. silvicola (Vitt), P. arvensis Scheff and P. sylvatica 
Scheff) ? 
Plenty of other instances can be selected from among those agarics 
which have been sufficiently studied. Armillaria mellea is a case in 
point. A good authority has said of it, “There is scarcely a plant 
more apt to assume different aspects under different conditions than 
the present one,” a statement we can all confirm; and that exquisitely 
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