Distribution of Fungi. 281 
The stations of species are determined by the physical con- 
ditions presented by different localities. In relation to this sub- 
ject, a distinction must be made between Fungi which grow 
from the soil (Fungi geogenet) and those which grow on dead 
plants (Fungi epiphyti). The most highly developed and per- 
fect species of each series all grow on the ground, as Amanita, 
Boletus, &c.; they are epigeous, though the mycelium of most 
of them vegetates beneath the soil upon decayed wood or the 
worn-out bark of trees. The species lowest in the scale of or- 
ganization are, on the contrary, epiphytes. Among those Fungi 
whose existence is most independent of the influence of light, 
there are several species, and even entire orders, such as the 
Tuberi, which are ‘hypogeous, or, in other words, which live 
entirely beneath the surface of the ground. The most evident 
proof attainable as to how far the development of Hymenomycetes 
requires the action of light is, that such as have not been exposed 
to its influence (those, for example, which have lived in the gal- 
leries of mines, in caverns, or in hollow trees) assume strangely 
anomalous forms. The metamorphosis of such individuals re- 
mains incomplete, or, in other words, every Fungus preserves its 
mycelium-nature, its abnormal growth being limited to a mon- 
strous modification of this mycelium. 
The ‘ coprogenous’ Fungi (those growing on manure and those 
which flourish on decayed wood) occupy an intermediate position 
between geogenous and epiphytic Fungi. These coprogenous 
forms acquire their complete proportions in a very brief period, 
and are decomposed with similar rapidity, in consequence, with- 
out doubt, of the great quantity of nitrogen they imbibe in their 
ordinary matrix. On the contrary, the Fungi which live upon 
trees grow very slowly, on account of the hardness of the sub- 
stratum; many species of them, which live at the expense of the 
hard wood or of the bark, are perennial, and annually form new 
layers overlying those of older date. These perennial species 
abound in tropical climates, and decrease in number gradually 
as we approach the poles. It might, @ priori, be supposed that 
these Fungi would, on account of their solid texture, suffer less 
from the effects of cold, and that, for this reason, they would 
advance further rth in their distribution: such, however, is 
not the case; for it is those Fungi which most speedily attain 
their full and complete development which are found to exist at 
the greatest altitudes on the Alps; and this so happens because 
their development may be frequently accomplished within the 
space of twenty-four hours. 
The influence of the chemical constitution of the soil on the 
production of Fungi is not at present understood ; but it is per- 
fectly well known how materially the richness of the soil in 
