Description:—The ostrich-fern is one of our finest ferns, being surpassed
in grandeur only by _Acrostichum aureum_, _Woodwardia radicans_, and
perhaps _Osmunda regalis_. The plant is propagated chiefly by long and
slender stolons, bearing appressed rudimentary stalk-bases. These stolons
are said by Sachs to originate from buds formed on the stalks near the
base: they run underground for several inches or a foot, and at the end
rise to the surface and there thicken into a short erect caudex, covered
by imbricating stalk-bases, and throwing up from the apex a grand
vase-like circle of foliage, which is often higher than a man’s head, and
sometimes extends above his utmost reach.
The stalks are seldom over a foot long: they are flattened, blackish, and
chaffy at the base, but above ground they are green, drying dull-brown,
somewhat four-sided, and deeply channelled in front, when dried furrowed
on the sides also. They contain two flattened fibro-vascular bundles. The
stalks of the sterile fronds are rather longer than the others, but more
rigid, and remain erect till the second year.
The sterile fronds are oblong-lanceolate in outline, gradually narrowed
to the base from near the middle and abruptly short acuminate. The pinnæ
are usually of nearly equal breadth from the base to beyond the middle.
They are pinnatifid to within a line of the midrib into numerous oblong
and obtuse segments, the veins of which are free, simple and pinnately
arranged on a midvein.
The fertile fronds are produced late in the summer, and are contracted,
much shorter than the others, and very rigid. The pinnæ are sometimes
nearly entire, and in other examples pinnately lobed. The margins are
very much recurved, so that the pinnæ are pod-like, and either
sub-cylindrical or somewhat moniliform. The venation is free, and the
sori are dorsal on the veins. Mr. Faxon writes: “The indusium can be
detected only when the fertile frond is very young, and appears as a very
delicate, lacerate membrane, attached at the base of the receptacle, and
serving to separate the sorus from its neighbors. I have not found it in
any case hood-like as in _O. sensibilis_. The sori are quickly confluent,
and all trace of the indusium is soon lost. The membranaceous edge of the
transformed fertile pinna is attached near the bases of the inferior sori
and a fold is usually found pressed against the sori as seen in the
drawing (Fig. 3). This is usually ruptured, so as to leave a portion
attached at the base of the sorus, and must not be mistaken for the true
indusium, which is within.”
The sporangia have twenty-six or twenty-eight articulations of the ring.
The spores are dark-colored and ovoid.
Imperfectly fertile fronds are often found, which are analogous to the
“_obtusilobata_” condition of _O. sensibilis_.
ALPINE BEECH-FERN.
FRAGRANT WOOD-FERN.
[Illustration: ]
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