ments and pressing gently upon the cover glass
with a needle. In this way it can be easily forced out of the
archegonium, and then by thoroughly washing away the potash,
neutralizing if necessary with a little acetic acid, very beautiful
preparations may be made. If desired, these may be mounted
permanently in glycerine which, however, must be added very
gradually to avoid shrinking the cells.

[Illustration: FIG. 63.--_A_, protonema of _Funaria_, with a bud
(_k_), x 50. _B_, outline of a leaf, showing also the thickened
midrib, x 12. _C_, cells of the leaf, x 300. _n_, nucleus. _D_,
chlorophyll granules undergoing division, x 300. _E_, cross-section of
the stem, x 50.]

For some time the embryo has a nearly cylindrical form, but as it
approaches maturity the differentiation into stalk and capsule
becomes apparent. The latter increases rapidly in diameter, assuming
gradually the oval shape of the full-grown capsule. A longitudinal
section of the nearly ripe capsule (Fig. 58, _G_) shows two distinct
portions; an outer wall of two layers of cells, and an inner mass of
cells in some of which the spores are produced. This inner mass of
cells is continuous with the upper part of the capsule, but
connected with the side walls and bottom by means of slender,
branching filaments of chlorophyll-bearing cells.

The spores arise from a single layer of cells near the outside of
the inner mass of cells (_G_, _sp._). These cells (_H_, _sp._) are
filled with glistening, granular protoplasm; have a large and
distinct nucleus, and no chlorophyll. They finally become entirely
separated and each one gives rise to four spores which closely
resemble those of the liverworts but are smaller.

Near the base of the capsule, on the outside, are formed breathing
pores (Fig. 58, _F_) quite similar to those of the higher plants.

If the spores are kept in water for a few days they will germinate,
bursting the outer brown coat, and the contents protruding through
the opening surrounded by the colorless inner spore membrane. The
protuberance grows rapidly in length and soon becomes separated from
the body of the spore by a wall, and lengthening, more and more,
gives rise to a green filament like those we found attached to the
base of the full-grown plant, and like those giving rise to buds
that develop into leafy plants.

CLASSIFICATION OF THE MOSSES.

The mosses may be divide