e second or asexual generation. The peculiarity of this
asexual or spore-bearing plant is that it is parasitic on the sexual
plant; the two generations, although not organically connected, yet
remain in close contact, and the spore-bearing generation is at all
events for a time nourished by the leafy sexual generation.

The spore-bearing generation consists of a long stalk, closely held
below by the cells of the base of the archegonium; this supports a
broadened portion which contains the spores, and the top is covered with
the remains of the neck of the archegonium forming the calyptra.

The spores arise from special or mother-cells by a process of division,
or it may be even termed free-cell formation, the protoplasm of each
mother-cell dividing into four parts, each of which contracts, secretes
a wall, and thus by rejuvenescence becomes a spore, and by the
absorption of the mother-cells the spores lie loose in the spore sac.
The spores are set free by the bursting of their chamber, and each
germinates, putting out a branched thread of cells called a protonema,
which may perhaps properly be termed a third generation in the cycle of
the plant; for it is only from buds developed on this protonema that the
leafy sexual plant arises.

The characteristics, then, of the mosses are, that the sexual generation
is leafy, the one or two asexual generations are thalloid, and that the
spore-bearing generation is in parasitic connection with the sexual
generation.

In the case of the fern, these conditions are very different.

The sexual generation is a small green thalloid structure called a
prothallium, which bears antheridia and archegonia, each archegonium
having a neck-canal and oosphere, which is fertilized just as in the
moss.

But the asexual generation derived from the oospore only for a short
while remains in connection with the prothallium, which, of course,
answers to the leafy portion of the moss. What is generally known as the
fern is this asexual generation, a great contrast to the small leafless
moss fruit or sporogonium as it is called, to which it is
morphologically equivalent. On the leaves of this generation arise the
sporangia which contain the spores. The spores are formed in a manner
very similar to those of the mosses, and are set free by rupture of the
sporangium.

The spore produces the small green prothallium by cell-division in the
usual way, and this completes the cycle of fern life.

The alt