282 M.E. P. Fries on the Geographical 
“humus” contributes to the beauty and abundance of fungaceous 
vegetation. An essential difference among the various Fungi 
must, however, be noticed; for whilst certain of them, such as 
Cortinarius and Hydnum, avoid all cultivated ground, for the 
reason that it is too much impregnated with animal matters, 
others, on the contrary, as Pratellus, Paneolus, and, above all, 
the Coprini, are never found to flourish elsewhere. Sandy plains 
are always very poor in Fungi; but the rare species which do 
grow in such localities are peculiar to them: as instances of 
this may be cited Agaricus (Inocybe) maritimus and Peziza 
arenaria. No Fungi grow in water; still, im connexion with 
species of Sphagnum, in marshes, several species are met with, 
the pilei of which alone show themselves above these submerged 
mosses. 
The epiphytous Fungi are not parasites properly so called 
(as many Fungi belonging to the lowest families or the lowest 
ranks in the class are) ; for they never grow except on those parts 
of plants that are in a state of decay or of decomposition. For 
though it often happens that Fungi are seen growing on trees 
still living, yet, if a closer examination be made, it will always 
be found that they have their nidus in an altered or decayed 
portion of the wood, even when the superposed bark itself ap- 
pears to be sound. 
Certain Fungi are peculiar to certain trees, and are found on 
no others—a circumstance which particularly arrests the atten- 
tion when the Fungi proper to coniferous trees are compared 
with those that live on trees with large and deciduous leaves. 
But, further, among the latter forms of Fungi there are species 
which exclusively belong to certain species of trees. The 
following are examples of some such :—Agaricus (Pleurotus) 
ulnarius and A. ostreatus, together with Polyporus squamosus, 
grow upon most of our deciduous-leaved trees; Agaricus (Ar- 
millaria) mucidus finds a fitting habitat only on the beech- 
tree, Fistula hepatica only on the oak, and Polyporus salignus 
and Trametes suaveolens only on willows; Agaricus (Omphalea) 
campanella and Hydnum auriscalpium grow on the leaves and 
cones of pines, Trametes pint on the trunk of the same trees ; 
whilst Polyporus abietinus and Trametes oddrata grow ouly on 
the fir. The Hymenomycetes which lead a parasitic existence 
upon other Hymenomycetes—for instance, Agaricus (Mycena) 
pilipes, Ag. (Collybia) tuberosus, Boletus parasiticus, Nyctalis 
parasitica—are all meteoric, and are among the most singular of 
the Fungi. 
It would be superfluous to follow out these general observa- 
tions on the stations of Fungi in detail, and we will content 
ourselves by referrmg the reader to the work of M. Nicolas 
