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112 F E R N S O F NORTH AM E R IC A .
Woodsia hyperborea, var. rtifidula, Koci-i, Syn. FI. Germ, et Helvet.,
ed. iii., p. 7 3 1. — M i l d e , Fil. Eur. et Atlant., p. 164.
Woodsia hyperborea, PuRsi-i, certainly as to the original specimens preserved
at Kew.
AcrosticJmm Ilvense, L i isnæ u s , Sp. PL, p. 1 5 2 8 .
Polypodium Ilvense, S w a r t z , Syn. Fil., p. 39. — S c h k u h r , Krypt. Gew.,
p. 16, t. 19 .— W I l ld en ow , Sp. PL, V., p. 198.
Nephrodmm rufidulum, M ic h a u x , FL Bor.-Am., ii., p. 269.
Aspidium rzfduhcm, S w a r t z , Syn. Fil., p. 58. — W il ld en o w , Sp. PL,
V., p. 282.— P u r sh , FL Am. Sept., ii., p. 665.
Some additional synonymy may be found in Moore’s Nature-
Printed British Ferns, and in Milde’s work above referred to.
H a b . — On high exposed rocks and in their crevices, in the
mountainous regions of the Northern United States, and throughout
British America as far as the Rocky Mountains, D rummo n d , and Norway
House, Mr. G e o r g e B a rn sto n . In New England it is sometimes
found at low elevations near the sea, as on Mount Desert Island,
Maine. It is particularly fine and abundant on the tops of the mountains
above West Point, on the Hudson River; and along the Saguenay
river, in Canada, Mr. W a t t . It occurs as far north as Disco Head, in
Greenland, and is common in the northern and alpine parts of Europe
and Asia, extending as far east as Hakodadi, in Japan.
D e s c r i p t i o n : — Though the individual root-stocks of this
fern are slender and ascending, and only one or two inches
long, yet by their branching they form large tufts of the
plant, the patches being not infrequently two or three feet in
extent. The stalks are continuous with the root-stock, and
those that support living fronds grow from the apex of it: —
T
F E R N S OF NORTH AM E R IC A . 1 13
they are from one to four inches long, and about three-fourths
of a line in diameter. They are rounded at the back, furrowed
in front, and usually very chaffy. The -chaff near the
base of the stalks consists of thin ferruginous ovate-acuminate
scales, composed of straight rhomboid-oblong or oblong-linear
cells, and scantily denticulate with slender and often recurved
teeth. Higher up the scales become narrower, and are intermixed
with paleaceous hairs. The same scales and hairs beset
the rachis and the lower surface of the frond, but the
upper surface bears only a few short hairs. The stalks are
articulated about half an inch from the base, as in IV. hyperborea,
and have a similar fibro-vascular bundle.
The fronds are commonly a little larger than in that
species, and have a broader outline. They are also a little
thicker in texture, and more rigid. When young they are
whitish, from the color of the scales, but turn to a rusty-
brown in maturity. The pinnæ are oblong-ovate, rather acute,
and pinnatifid into about seven to ten oblong obtuse lobes
on each side. The margin is commonly somewhat recurved.
The sori are abundant, and set near the margin of the lobes.
When ripe the sporangia are more or less confluent.
The indusium does not differ from that of W. hyperborea,
and when examined by a lens of moderate power is very
beautiful, the long white ciliiform processes being curled over
the sporangia, as if trying to protect what they cannot fully
cover. The spores are bean-shaped, marked with a single
vitta, and slightly roughened on the surface.
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