FERNS OF NORTH AMERICA.
Polypodium obtusum, S p r e n g e l , Aiileituiig, p. 92; Engl, version, p. 102.—
Sw.\RTZ, Syn. Fil., p. 39.—S c h k u h r , Krypt. Gew., p. 18, t. 21.
Aspidmm obtusum, W il ld en o w , Sp. PL, v., p. 254 .— S c h k u h r , Krypt.
Gew., p. 197, t. 43^. — P u r sh , FL Am. Sept., ii., p. 662.
Hypopeltis obtusa, T o r r e y , Compendium, p. 380.
Cystopteris obtusa, P r e s l , T e n t . P te r id ., p. 9 3 .
Pkysematium obtusum. H o o k e r , FL Am. Bor., ii., p. 2 59 ,
Woodsia Perriniana, H o o k e r & G r e v il l e , I c. FiL, t. Ix v iii.
Alsophila Perriniana, S p r e n g e l , Syst. Veg., iv.. p. 125.
Pliysematium Perrinianum, P r e s l , Tent. Pterid., p. 6 6 .— K u n z e , Analecta
Pteridogr., p. 4 3 .— L in k , Fil. Hort. Berol., p. 44.
Cystopteris Perriniana, L in k , “ Hort. BeroL, ii., p. 1 3 1 . ”
H a b .—On rocks and stony hillsides, not rare ; from New England
to Wisconsin, and southward to Georgia, central Alabama, Arkansas and
Indian Territory. It reappears in British Columbia, where Dr. L y a l l
found it on the Galton Mountains, but is not known in the eastern
provinces of Canada. In Synopsis Filicum several South American
varieties are indicated, the W. incisa, Peruviana, and crenata of authors,
but I have not examined them, and have no opinion of my own to
offer concerning them. The species does not occur in the eastern
hemisphere.
D e s c r ip t io n . — This species of Woodsia forms tufts or
patches, though of less extent than some of the others.
The root-stock is one or two inches long, creeping, covered
with the remains of old stalks, and moderately chaffy. The
chaffiness consists of little ovate-acuminate nearly entire
scales, most of them thin in texture and pale in color. As
FERNS OF NORTH AMERICA.
in W. Oregana some of the median cells are often dark-
colored, and even so densely as to form a midnerve. The
stalks are several to each root-stock: they are commonly
four or five inches long, roundish, but flattened or even
slightly furrowed in front, green with a dark-brown or blackish
base in the living plant, but bright brownish-straw-color
when dry. There are two oblique strap-shaped ñbro-vascular
bundles in the base of the stalk, which unite higher up and
form one which has something the shape of the two fore-
wings of a butterfly. The stalk is chaffy when young, and
a little of the chaff remains till the fronds wither, which
they do at the earliest frost of autumn.
The fronds are commonly six or eight inches long and
two or three inches broad, but occasionally measure full fifteen
inches in length by four in the greatest breadth, which
is near the middle. They are rather delicately herbaceous in
texture, and minutely glandular, particularly on the lower
surface and along the rachis. The pinnæ are rather distant
and very short-stalked, triangular-ovate or triangular-lanceolate,
and usually obtuse. They are pinnatifid into oblong-oval
obtuse segments, the larger ones of which are contracted at
the base and often pinnatifid, and the smaller ones adnate
to the midrib of the pinna and crenate or crenately toothed.
The veins are pinnately arranged on the midveins, and are
either simple or forked. They are always free, but not very
conspicuous.
The sori are placed on the veins, mostly just below the
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