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108 FERNS OF NORTH AMERICA.
Asplermcm murorunt, L am a r c k , Flore Française, i., p . 28.
Asplenium micrale, B e r n i ia r d i, in Schraders Journal für die Botanik, i 8 o i ,
i., p. 19.
Scolopendrium Rula-muraria, R o t i i, F 1. Germ., iü ., p. 52-
Tarachia Ricta-muraria, P r e s l , Epimel. Bot., p . 8 1 .
I I a b . — Clefts of calcareous rocks, from Vermont to North Carolina,
and westward to Indiana and Tennessee, but not seen on walls in America.
It is common throughout Europe on walls and on rocks, especially calcareous
rocks. It has been noticed in Algeria, and in Asia as far east as
Cashmere.
D e s c r i p t io n . — Root-stocks short, creeping, entangled ; covered,
like the base of the young stalks, with narrow slender-
pointed blackish scales. These scales are composed of irregular
oblong cells, with the dissepiments very heavy and black. The
slender tips are composed of two series of cells ; and it is only
the wall between the adjacent cells that is thickened, the walls
along the edges of the scale being thin and transparent. The
analogy to the structure of a tooth of a moss-peristome is noticeable.
The stalks are of variable length, according to the size of the
plant and its place of growth. In bare, sunny spots, the whole
plant will be scarcely an inch high ; while, on damp and shaded
rocks, specimens fully six inches long have been collected. The
stalks are green and herbaceous except at the very base, where
they are deep-brown and more rigid, and, as Dr. Milde has especially
noticed, furnished with globose unicellular glandules of a
grayish color, “ so large that you might take them for unicellular
FERNS OF NORTH AMERICA. 109
alg^. The fibro-vascular bundle seems in the living plant to be
flattened-cylindrical in shape, and at the very base of the stalk to
have a blackish mass of sclerenchyma in front of it. Near the
base the surrounding tissue is semi-transparent, with an exterior
layer of dark cells ; but higher up the surrounding tissue is filled
with chlorophyll, and the outside layer is colorless. A more careful
study of the stalk would probably discover other peculiarities
which have escaped my observation.
The frond is generally a little shorter than the stalk, and is
triangular-ovate or deltoid in outline. It is simply pinnate near
the apex, but twice pinnate, or even three times pinnate, near the
base. It is, when mature, perfectly smooth, and of a sub-coriaceous
texture. The rachis and its divisions are quite slender, and
green like the segments. These are extremely variable in form,
so that from their shape no less than nine varieties have been
distinguished by Heufler, In small plants, grown in dry exposed
places, the segments are roundish-obovate, with a cuneate base,
and the outer edge merely crenate. More frequently the form is
cuneate-rhomboid with the outer edges toothed ; and specimens,
either large or small, with narrower and deeply-incised segments,
are by no means rare. These forms all occur indiscriminately;
and it seems better to simply record the great variability of the
form of the segments than to split up the species into nine varieties,
with Heufler, or ten, with iMilde.
The sori are long or short, and variable in number, according
to the size and shape of the segment. When fully ripe, the sporangia
nearly cover the under surface, so that the fern has been
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