t first, soon
exposed; spores naked, mostly quaternate, on distinct spicules_ =
HYMENOMYCETES.

[Illustration: FIG. 37.--_Agaricus nudus._]

In this family some mycologists believe that fungi attain the highest
form of development of which they are capable, whilst others contend
that the fructification of the _Ascomycetes_ is more perfect, and that
some of the noblest species, such as the pileate forms, are entitled
to the first rank. The morel is a familiar example. Whatever may be
said on this point, it is incontrovertible that the noblest and most
attractive, as well as the largest, forms are classed under the
_Hymenomycetes_.

In _Gasteromycetes_, the second family, a true hymenium is also
present, but instead of being exposed it is for a long time enclosed
in an outer peridium or sac, until the spores are fully matured, or
the fungus is beginning to decay. The common puff-ball (_Lycoperdon_)
is well known, and will illustrate the principal feature of the
family. Externally there is a tough coat or peridium, which is at
first pale, but ultimately becomes brown. Internally is at first a
cream-coloured, then greenish, cellular mass, consisting of the
sinuated hymenium and young spores, which at length, and when the
spores are fully matured become brownish and dusty, the hymenium
being broken up into threads, and the spores become free. In earlier
stages, and before the hymenium is ruptured, the spores have been
found to harmonize with those of _Hymenomycetes_ in their mode of
production, since basidia are present surmounted each by four
spicules, and each spicule normally surmounted by a spore.[D] Here is,
therefore, a cellular hymenium bearing quaternary spores, but,
instead of being exposed, this hymenium is wholly enclosed within
an external sac or peridium, which is not ruptured until the
spores are fully matured, and the hymenium is resolved into
threads, together forming a pulverulent mass. It must, however, be
borne in mind, that in only some of the orders composing this
family is the hymenium thus evanescent, in others being more or less
permanent, and this has led naturally enough to the recognition of
two sub-families, in one of which the hymenium is more or less
permanent, thus following the Hymenomycetous type; and in the
other, the hymenium is evanescent, and the dusty mass of spores tends
more towards the _Coniomycetes_, this being characterized as the
coniospermous (or dusty-spored) sub-family.