_Polýstichum_
These have been grouped with the wood ferns, but are now usually placed
under the genus _Polýstichum_, which has the sori round and covered with
a circular indusium fixed to the frond by its depressed center. The wood
ferns, on the other hand, have a kidney-shaped indusium attached to the
fronds by the sinus. (_Polýstichum_ is the Greek for many rows, the sori of
some species being in many ranks.)
(1) THE CHRISTMAS FERN
_Polýstichum acrostichòides. Aspídium acrostichòides_
Stipes clothed with pale, brown scales. Frond rigid and evergreen, one to
two feet long, lanceolate, pinnate. Pinnæ linear-lanceolate, scythe-shaped,
auricled on the upper side, and with bristly teeth; fertile pinnæ
contracted toward the top, bearing two rows of sori, which soon become
confluent and cover the entire surface. Indusium orbicular, fixed by its
depressed center.
_F. incìsum_ is a form in which the pinnæ are much incised.
_F. críspum_ has the edges of its pinnæ crisped and ruffled. The name
Christmas fern, due to John Robinson, of Salem, Mass., suggests its fitness
for winter decoration. Its deep green and glossy fronds insure it a welcome
at Christmas time. "Its mission is to cheer the winter months and enhance
the beauty of the other ferns by contrast." In transplanting, a generous
mass of earth should be included and its roots should not be disturbed.
[Illustration: Christmas Fern. _Polystichum acrostichoides_]
[Illustration: Christmas Fern. _Polystichum acrostichoides_]
[Illustration: Christmas Fern. _Polystichum acrostichoides_ Top, Forked
Form; Bottom, Incised Form (Maine)]
(2) BRAUN'S HOLLY FERN
_Polystichum Bráunii. Aspídium aculeàtum Bráunii_
Fronds thick, rigid, one to two feet long, spreading, lanceolate,
tapering both ways, bipinnate. Pinnules ovate or oblong, truncate, nearly
rectangular at the base, sharply toothed and covered beneath with chaff and
hairs. Fruit-dots small and near the mid veins. Indusium orbicular, entire.
Stipes chaffy with brown scales.
[Illustration: Braun's Holly Fern. _Polystichum Braunii_ (Willoughby
Mountain, Vt.) (Herbarium of G.H.T.)]
This handsome fern is rather common in northern New England. We have
collected it in the Willoughby Lake region, Vt., and it is found at Mt.
Mansfield, Randolph, and elsewhere in that state; also at Gorham, N.H.,
and Fernald reports it as common in northern Maine. It also grows in the
mountains of New York and Pennsylvania, and westward. It was formerly
thought to be a variety of the prickly shield fern (_P. aculeàtum_), which
has a very wide range and numerous varieties. The fronds remain green
through the winter but the stipes weaken and fall over.
(3) HOLLY FERN. _Polystichum Lonchìtis_
Fronds linear-lanceolate, short-stalked and rigid, eight to fifteen inches
long. Pinnæ broadly lanceolate-falcate or the lowest triangular, strongly
auricled on the upper side, densely spinulose-toothed. Sori midway between
the margin and midrib.
[Illustration: Holly Fern. Polystichum Lonchitis (Nottawasaga, Canada,
West, Right, Alaska, Left) (Herbarium of C.E. Davenport)]
The name holly fern suggests its resemblance to holly leaves with their
bristle-tipped teeth. The specific name lonchìtis (like a spear) refers to
its sharp teeth. A northern species growing in rocky woods from Labrador
to Alaska, and south to Niagara Falls, Lake Superior and westward. Its
southern limits nearly coincide with the northern limits of the Christmas
fern.