ntry of Europe, and even the hottest
countries (and those under the equator) are not destitute of
representatives of this wide-spread genus.

The _Lactarii_, which are so abundant in the forests of Europe and
North America, appear to grow more and more scarce towards both the
south and north. The same may be stated in regard to _Russula_.

The genus _Marasmius_ is dispersed throughout the globe, and
everywhere presents numerous species. In inter-tropical countries they
are still more abundant, and exhibit peculiarities in growth which
probably might justify their collection into a distinct group.

The genera _Lentinus_ and _Lenzites_ are found in every region of the
world; their principal centre, however, is in hot countries, where
they attain a splendid development. On the contrary, towards the north
they rapidly decrease in number.

The _Polypori_ constitute a group which, unlike that of the Agarics,
especially belongs to hot countries. The _Boleti_ constitute the only
exception to this rule, since they select the temperate and frigid
zones for their special abode, and some of them at times find their
way to the higher regions of the Alps. No one can describe the
luxuriance of the torrid zone in _Polypori_ and _Trametes_, genera of
_Hymenomycetes_, which flourish beneath the shade of the virgin
forests, where perpetual moisture and heat promote their vegetation
and give rise to an infinite variety of forms. But though the genus
_Polyporus_, which rivals _Agaricus_ in the number of its species,
inhabits, in preference, warm climates at large, it nevertheless
exhibits species peculiar to each country. This arises from the
circumstance that the _Polypori_, for the most part, live upon trees,
and are dependent on this or that particular tree for a suitable
habitat; and the tropical flora being prolific in trees of all kinds,
a multitude of the most varied forms of these fungi is a necessary
consequence. _Hexagona_, _Favolus_, and _Laschia_ are common in
inter-tropical countries, but they are either entirely absent or
extremely rare in temperate climes.

When the majority of the species of a genus are of a fleshy
consistence, it may generally be concluded that that genus belongs to
a Northern region, even if it should have some representatives in
lands which enjoy more sunshine. Thus the _Hydna_ are the principal
ornaments of Northern forests, where they attain so luxuriant a growth
and beauty that every other countr