Some of the rock-loving ferns in dry places are known as "resurrection"
ferns, reviving after their leaves have turned sere and brown. A touch of
rain, and lo! they are green and flourishing.

Ferns vary in height from the diminutive filmy fern of less than an inch
to the vast tree ferns of the tropics, reaching a height of sixty feet or
more.

REPRODUCTION

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 prothallium
(or prothallus). On its under surface delicate root hairs grow to give it
stability and nutriment; also two sorts of reproductive organs known as
antheridia and archegonia, the male and female growths analogous to the
stamens and pistils in flowers. From the former spring small, active,
spiral bodies called antherozoids, which lash about in the moisture of
the prothallium until they find the archegonia, the cells of which are so
arranged in each case as to form a tube around the central cell, which is
called the ooesphere, or egg-cell, the point to be fertilized. When one
of the entering antherozoids reaches this point the desired change is
effected, and the canal of the archegonium closes. The empty ooesphere
becomes the quickened ooesphore whose newly begotten plant germ unfolds
normally by the multiplication of cells that become, in turn, root, stem,
first leaf, etc., while the prothallium 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 prothallus by a
budding process apart from the organs of fertilization, showing that Nature
"fulfills hersel