died, quite complex in
their structure. The lowest members of the group are flattened,
creeping plants, or a few of them floating aquatics, without distinct
stem and leaves; but the higher ones have a pretty well-developed
central axis or stem, with simple leaves attached.

There are two classes--I. Liverworts (_Hepaticae_), and II. Mosses
(_Musci_).

CLASS I.--THE LIVERWORTS.

One of the commonest of this class, and to be had at any time, is
named _Madotheca_. It is one of the highest of the class, having
distinct stem and leaves. It grows most commonly on the shady side of
tree trunks, being most luxuriant near the ground, where the supply of
moisture is most constant. It also occurs on stones and rocks in moist
places. It closely resembles a true moss in general appearance, and
from the scale-like arrangement of its leaves is sometimes called
"scale moss."

The leaves (Fig. 52, _A_, _B_) are rounded in outline unequally,
two-lobed, and arranged in two rows on the upper side of the stem, so
closely overlapping as to conceal it entirely. On the under side are
similar but smaller leaves, less regularly disposed. The stems branch
at intervals, the branches spreading out laterally so that the whole
plant is decidedly flattened. On the under side are fine, whitish
hairs, that fasten it to the substratum. If we examine a number of
specimens, especially early in the spring, a difference will be
observed in the plants. Some of them will be found to bear peculiar
structures (Fig. 52, _C_, _D_), in which the spores are produced.
These are called "sporogonia." They are at first globular, but when
ripe open by means of four valves, and discharge a greenish brown mass
of spores. An examination of the younger parts of the same plants will
probably show small buds (Fig. 54, _H_), which contain the female
reproductive organs, from which the sporogonia arise.

[Illustration: FIG. 52.--_A_, part of a plant of a leafy liverwort
(_Madotheca_), x 2. _B_, part of the same, seen from below, x 4. _C_,
a branch with two open sporogonia (_sp._), x 4. _D_, a single
sporogonium, x 8.]

On other plants may be found numerous short side branches (Fig. 53,
_B_), with very closely set leaves. If these are carefully separated,
the antheridia can just be seen as minute whitish globules, barely
visible to the naked eye. Plants that, like this one, have the male
and female reproductive organs on distinct plants, are said to be
"dioecious."