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in the Agarics. For we must not forget that the pileus, etc., is not a 
sexually developed organ; it is subject to all the so-called somatic 
influences that affect any vegetative structure. 
It should not be overlooked, however, that conditions of growth 
may affect even such points as the shape of the hymenophore, as 
shown by Massee in Stereum hirsutum, in Pleurotus, etc. Patouillard 
has described a specimen of Psalliota campestris with cross-connected 
gills resembling one of the polyporei, and similar anomalies have been 
described in Amanita, Pleurotus, Coprinus, etc., and are normal 
in Favolus, Lentodium, Marasmius, etc. These cases are, of 
course, not to be confounded with those caused by parasites—e.g., 
Lactarius. ; 
Nor are spores exempt. Horrell has shown that the number of 
basidiospores in Mushrooms vary from two to four, and Brefeld and 
Klebs find that if the chlamydospores (macro-conidia) of Hypomyces 
chrysospermus develope in air they are covered with spike-like as- 
perities, but if formed in a liquid they are smooth, and Biffen observed 
similar effects of the environment on the spores of Acrospeira in my 
laboratory. I showed long ago that Dzdymzum, which has white cal- 
cified spore-cases if growing in air, loses the lime and forms black 
sporangia in water, and Klebs has confirmed this and shown that 
differences in the capillitum and stalk also result. 
I do not propose to insist on these cases, however, further than to 
point out that it is evident we must be cautious in assuming that any 
characters such as those under discussion are sacred from the all- 
pervading influence of conditions. It has been estimated that while 
30 °/o or so of the Agaricini grow on wood, the vast majority—about 
64 °/o of the British species—are developed in the ground, a vague 
term, since it includes old charcoal beds, decaying sawdust, humus, 
etc., and observation shows that peculiar conditions are associated 
with many species. Everyone knows that the Agarics of a Beech- 
wood differ from those of a Pine-forest, and that many species found 
in pastures are not gathered in shaded situations. But more curious 
points arise. Why is Amanita muscaria so partial to the neighbour- 
hood of Birches and Conifers; and why is Marasmius oreades only 
found among grass ? I once traced the mycelium of the latter to the 
roots of the herbage among which it grew, and I have lately had 
Stropharia aeruginosa, a form not uncommon in pastures and woods, 
parasitic on the roots and rhizomes of an Asparagus, a point of some 
interest since Brefeld failed to cultivate this fungus from its spores. 
These cases are not without interest in connection with the 
numerous instances of Mycorhiza which are now known. As you are 
no doubt aware, many trees, shrubs and herbaceous plants are found 
to have their roots either invaded by or enveloped in fungus hyphe, 
and we know that some of these Fungi belong to such generaas/Vectrza, 
Elaphomyces, Polysaccum, Geaster, Agaricus, Lactarius, Cortinarius, 
etc., though for the vast majority of them the fructifications—and 
therefore the systematic position—are quite unknown. We have also 
good grounds for believing that the fungus collects mineral salts and 


