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H a b . — Discovered by T homas N u t t a l l in crevices of rocks along the
Schuylkill River, near Philadelphia ; also found along the Wissahickon
Creek in the same vicinity. Lancaster County, Pennsylvania, Prof. T homas
C. P o r t e r . On moist cliffs of sandstone in the Cumberland Mountains,
East Tennessee, Prof. F. H. B r a d l e y . Hancock County, Alabama, Hon.
T. M. P e t e r s . Mine-la-Motte, Southern Missouri, on sandstone rocks, Dr.
E n c e lm a n n .
D e s c r i p t io n . — The root-stocks of this little fern are creeping,
branched and often entangled', and chaffy with narrow lance-
acuminate dark-fuscous scales. The cellular structure of these
scales is similar to that of the scales of A . ebeneimi, the cells
being oblong-rectangular, and arranged in straight longitudinal
rows. The stalks are from two to four inches long, and slightly
chaffy when young ; they are brown and shining at the base, but
green higher up, except that a narrow line of brown is continued
up the under side of the stalk nearly or quite to the base of the
frond. A section made near the lower extremity of the stalk is
nearly semicircular, and discloses two roundish fibro-vascular
bundles side by side near the middle, and a minute thread of
sclerenchyma, or hard dark tissue, on the inner side of each
bundle. A section just below the frond shows the two fibro-
vascular bundles united into one, and the angles of the stalk
slightly extended, forming very narrow wing-like borders. The
minute inner filaments of sclerenchyma are never continued far
up the stalk, and are sometimes wanting altogether.
The frond is from three to six inches long, and usually half
an inch to an inch broad at the base, from which the general outline
tapers to a long and slender point, not so long as the prolongation
of the walking-leaf, and very rarely, if ever, rooting at the
apcx.^ The fronds are mostly erect, sub-coriaceous or firmly
membranaceous, smooth above, but with a few minute setulose
scales beneath, deeply pinnatifid in the lower and middle portion,
and sinuatcly lobed above, the long terminal portion undulate on
the margins. The midrib is broad and well defined : it is winged
throughout its length ; the wing narrow at the base of the frond,
but constantly widening ' upwards.
The lobes are irregularly roundish-ovate, sinuate, crenate or
slightly toothed ; the lowest ones occasionally drawn out into an
acuminate point an inch long. Most of the lobes are attached
to the wing of the midrib by a broad base : the lower ones sometimes
have a short stalk.
The veins are everywhere free : in the lower lobes, if these
are acuminate, the veins are pinnately branched from a mid-vein ;
elsewhere they are forked or dichotomous. The sori arc mostly
single, though here and there one will be diplazioid, — most commonly
the lowest one on the superior side of the lobe. The indusia
are very delicate ; and the free edge is directed toward the
middle of the lobe, excepting the indusia of the sori nearest the
midrib, and these open toward the midrib. The sori are usually
very full of sporangia, and, when ripe, nearly cover the back of the
frond : even the narrow acumination bears a sorus at each undulation
of the margin. Spores ovoid-bcan-shaped, with reticulating
ridges and an irregular winged border.
‘ I find one or two instances of a slight enlargement of the apex, as if
there were an attempt to form a proliferous bud.
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