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AUosor-us gracilis, P r e s l , Tent. Pterid., p. 15 3 .—T o r r e y , F1. New
York, ii., p. 486.—G r a y , Manual, ed. i., p. 624: ed. ii., p. 591,
t. ix . — P a r r y , in Owen's Geol. Surv. of Wisconsin, etc., p.
621.— M e t t e n iu s , Fil. Hort. Lips., p. 44.
Cheilanthes gracilis, K a u l f u s s , Enum. Fil., p. 2 0 9 .
Pteris Stelleri, G m e lin , “ N o v . Com. Petrop., x i i., p. 5 1 9 , t. 12 , f. i . ”
Allosorus Stelleri, R u p r e c h t , Distr. Crypt. Vase, in Imp. Ross., p.
47. — L e d e b o u r , Fi. Ross., iv., p. 526. — M o o r e . Ind. Fil., p.
46. — L aw s o n , in Canad. Naturalist, i., p. 272.
Allosorus minutus & Pteris minuta, T u r c z a n in o w , fid s Moore.
H a b . — Crevices of damp and shaded calcareous rocks, especially in
deep glens; Labrador, B u t l e r , to British Columbia, and southward to
Iowa, P a r r y , Wisconsin and Pennsylvania. Also in Colorado, near
Breckinridge City, B r a n d e g e e . Siberia, Tibet and the Himalayas. It
is found in Sunderland, Massachusetts; at Trenton Falls, Chlttenango
Falls, and other deep glens in Central New York; in Lycoming and
Sullivan Counties, Pennsylvania, and in other similar places in Vermont,
Michigan, etc., but is by no means a common plant.
D e s c r i p t i o n ; — This is the most delicate of all the
Pellceas, and has fronds a good deal like those of Crypto-
gramme acrostichoides, but tenderer, and with sub-marginal
fructification. The root-stock is very slender, scarcely more
than half a line in thickness, and sometimes two or three
inches long. It is so hidden in the crevices of the rocks
that it is seldom secured by collectors. The scales are minute,
appressed to the root-stock, and almost filmy in their
delicacy.
F E R N S O F NORTH AM E R IC A . 67
The stalks are scattered along the root-stock, and are,
generally about five or six inches long, those of tire fertile
fronds longer, stouter and of a darker color than the others.
They are smooth and somewhat polished, but lighter in color
and far more tender in consistency than in most of our other
species of this genus.
The fertde and the sterile fronds are unlike, though both
aie very delicately membranaceous, and pinnate with once or
twice pinnatifid pinnæ. The rachis is not winged in its lower
half, except in very small fronds, but above the middle it is
narrowly winged, as are also its divisions. The lowest one
or two pairs of pinnæ are twice pinnatifid in the largest
specimens, but more commonly but once pinnatifid. In the
sterile fronds the segments of the pinnæ are very plainly
adnate to tlie secondary midrib, and are roundish or roundish-
obovate in shape. They are from three to six lines long and
about two-thirds as broad. Their margin is more or less
lobed and crenately toothed. In the fertile fronds the segments
are more distinct, longer and narrower, measuring often
SIX to ten lines in length and one or two in width. The terminal
pinna of the frond and the terminal segments of the
pinnæ are considerably longer than the others. The veins
are conspicuous, and distant, much more so than in our
other species of Pellæa. They fork once about midway between
the midvein and tlie margin, and sometimes, especially
in fertile fronds, a second time just within the margin.
The involucre is continuous, broad, and even more del-
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