Ferns are propagated in various ways. A frequent method is by perennial
rootstocks, which often creep beneath the surface, sending up, it may be,
single fronds, as in the common bracken, or graceful leaf-crowns, as in the
cinnamon fern. The bladder fern is propagated in part from its bulblets,
while the walking leaf bends over to the earth and roots at the tip.
[Illustration: MALE SHIELD FERN. Fern Reproduction by the Prothallium]
Ferns are also reproduced by spores, a process mysterious and marvellous as
a fairy tale. Instead of seeds the fern produces spores, which are little
one-celled bodies without an embryo and may be likened to buds. A
spore falls upon damp soil and germinates, producing a small, green,
shield-shaped patch much smaller than a dime, which is called a prothállium
(or prothallus). On its under surface delicate root hairs grow to give it
stability and nutriment; also two sorts of reproductive organs known as
antherídia and archegònia, the male and female growths analogous to the
stamens and pistils in flowers. From the former spring small, active,
spiral bodies called ántherozòids, which lash about in the moisture of
the prothállium until they find the archegònia, the cells of which are so
arranged in each case as to form a tube around the central cell, which is
called the òösphere, or egg-cell, the point to be fertilized. When one
of the entering ántherozòids reaches this point the desired change is
effected, and the canal of the archegònium closes. The empty òösphere
becomes the quickened òösphore whose newly begotten plant germ unfolds
normally by the multiplication of cells that become, in turn, root, stem,
first leaf, etc., while the prothállium no longer needed to sustain its
offspring withers away.[1]
[Footnote 1: In the accompanying illustration, it should be remembered that
the reproductive parts of a fern are microscopic and cannot be seen by the
naked eye.]
Fern plants have been known to spring directly from the prothállus by a
budding process apart from the organs of fertilization, showing that Nature
"fulfills herself in many ways."[2]
[Footnote 2: The scientific term for this method of reproduction is apógamy
(apart from marriage). Sometimes the prothallus itself buds directly from
the frond without spores, for which process the term apóspory is used.
(Meaning, literally, without spores.)]