_Chara_. They are found in
groups, contained in little bud-like branches (54, _H_). In order to
study them, a plant should be chosen that has numbers of such buds,
and the smallest that can be found should be used. Those containing
the young archegonia are very small; but after one has been
fertilized, the leaves enclosing it grow much larger, and the bud
becomes quite conspicuous, being surrounded by two or three
comparatively large leaves. By dissecting the young buds, archegonia
in all stages of growth may be found.

[Illustration: FIG. 54.--_A-D_, development of the archegonium of
_Madotheca_. _B_, surface view, the others in optical section. _o_,
egg cell, x 150. _E_, base of a fertilized archegonium, containing a
young embryo (_em._), x 150. _F_, margin of one of the leaves
surrounding the archegonia. _G_, young sporogonium still surrounded by
the much enlarged base of the archegonium. _h_, neck of the
archegonium. _ar._ abortive archegonia, x 12. _H_, short branch
containing the young sporogonium, x 4.]

When very young the archegonium is composed of an axial row of three
cells, surrounded by a single outer layer of cells, the upper ones
forming five or six regular rows, which are somewhat twisted
(Fig. 54, _A_, _B_). As it becomes older, the lower part enlarges
slightly, the whole looking something like a long-necked flask (_C_,
_D_). The centre of the neck is occupied by a single row of cells
(canal cells), with more granular contents than the outer cells, the
lowest cell of the row being somewhat larger than the others
(Fig. 54, _C_, _o_). When nearly ripe, the division walls of the
canal cells are absorbed, and the protoplasm of the lowest cell
contracts and forms a globular naked cell, the egg cell (_D_, _o_).
If a ripe archegonium is placed in water, it soon opens at the top,
and the contents of the canal cells are forced out, leaving a clear
channel down to the egg cell. If the latter is not fertilized, the
inner walls of the neck cells turn brown, and the egg cell dies; but
if a spermatozoid penetrates to the egg cell, the latter develops a
wall and begins to grow, forming the embryo or young sporogonium.

[Illustration: FIG. 55.--Longitudinal section of a nearly full-grown
sporogonium of _Madotheca_, which has not, however, broken through the
overlying cells, x 25. _sp._ cavity in which the spores are formed.
_ar._ abortive archegonium.]

The firs