amous flora; it is probable, however,
that, in the lapse of more or fewer years, this richness will
decrease, in consequence of the extension of cultivation--as is
illustrated, indeed, in what has already taken place in the more
thickly peopled districts, as, for example, in the vicinity of New
York."

Although heat and humidity influence all kinds of vegetation, yet heat
seems to exert a less, and humidity a greater, influence on fungi than
on other plants. It is chiefly during the cool moist autumnal weather
that the fleshy fungi flourish most vigorously in our own country, and
we observe their number to increase with the humidity of the season.
Rain falls copiously in the United States, and this is one of the most
fruitful countries known for the fleshy fungi. Hence it is a
reasonable deduction that moisture is a condition favourable to the
development of these plants. The _Myxogastres_, according to Dr. Henry
Carter, are exceedingly abundant--in individuals, at least, if not in
species--in Bombay, and this would lead to the conclusion that the
members of this group are influenced as much by heat as humidity in
their development, borne out by the more plentiful appearance of the
species in this country in the warmer weather of summer.

In the essay to which we have alluded, Fries only attempts the
recognition of two zones in his estimate of the distribution of fungi,
and these are the temperate and tropical. The frigid zone produces no
peculiar types, and is poor in the number of species, whilst no
essential distinction can be drawn between the tropical and
sub-tropical with our present limited information. Even these two
zones must not be accepted too rigidly, since tropical forms will in
some instances, and under favourable conditions, extend far upwards
into the temperate zone.

"In any region whatever," writes Fries, "it is necessary, in the first
instance, to draw a distinction between its open naked plains and
its wooded tracts. In the level open country there is a more rapid
evaporation of the moisture by the conjoined action of the sun and
wind; whence it happens that such a region is more bare of fungi
than one that is mountainous or covered by woods. On the other hand,
plains possess several species peculiar to themselves; as, for
example, _Agaricus pediades_, certain _Tricholomata_, and, above
all, the family _Coprini_, of which they may be regarded as the
special habitat. The species of this family au