s_ are all the large
and common forms; but they differ much in the position of the
spore-bearing tissue, as well as in the form and size of the whole
spore fruit. They are sometimes divided, according to the position of
the spores, into three orders: the closed-fruited (_Angiocarpous_)
forms, the half-closed (_Hemi-angiocarpous_), and the open or
naked-fruited forms (_Gymnocarpous_).

[Illustration: FIG. 49.--_Basidiomycetes_. _A_, common puff-ball
(_Lycoperdon_). _B_, earth star (_Geaster_). _A_, x 1/4. _B_, one-half
natural size.]

Of the first, the puff-balls (Fig. 49) are common examples. One
species, the giant puff-ball (_Lycoperdon giganteum_), often reaches a
diameter of thirty to forty centimetres. The earth stars (_Geaster_)
have a double covering to the spore fruit, the outer one splitting at
maturity into strips (Fig. 49, _B_). Another pretty and common form is
the little birds'-nest fungus (_Cyathus_), growing on rotten wood or
soil containing much decaying vegetable matter (Fig. 50).

[Illustration: FIG. 50.--Birds'-nest fungus (_Cyathus_). _A_, young.
_B_, full grown. _C_, section through _B_, showing the "sporangia"
(_sp._). All twice the natural size.]

In the second order the spores are at first protected, as we have seen
in _Coprinus_, which belongs to this order, but finally become
exposed. Here belong the toadstools and mushrooms (Fig. 51, _B_), the
large shelf-shaped fungi (_Polyporus_), so common on tree trunks and
rotten logs (Fig. 51, _C_, _D_, _E_), and the prickly fungus
(_Hydnum_) (Fig. 51, _G_).

[Illustration: FIG. 51.--Forms of _Basidiomycetes_. _A_, _Tremella_,
one-half natural size. _B_, _Agaricus_, natural size. _C_, _E_,
_Polyporus_: _C_, x 1/2; _E_, x 1/4. _D_, part of the under surface of
_D_, natural size. _F_, _Clavaria_, a small piece, natural size. _G_,
_Hydnum_, a piece of the natural size.]

Of the last, or naked-fruited forms, the commonest belong to the
genus _Clavaria_ (Fig. 51, _F_), smooth-branching forms, usually of a
brownish color, bearing the spores directly upon the surface of the
branches.

CHAPTER XI.

SUB-KINGDOM IV.

BRYOPHYTA.

The Bryophytes, or mosses, are for the most part land plants, though a
few are aquatic, and with very few exceptions are richly supplied with
chlorophyll. They are for the most part small plants, few of them
being over a few centimetres in height; but, nevertheless, compared
with the plants that we have heretofore stu