M. It has small, elliptical,
denticulate pinnules and a glandular-pubescent indusium.

Var. AMERICANUM (=_dilatatum_, syn.). Fronds broader, ovate or
triangular-ovate in outline. A more highly developed form of the typical
plant, the lower pinnae being often very broad, and the fronds tripinnate.
Inferior pinnules on the lower pair of pinnae conspicuously elongated. A
variety preferring upland woods; northern New England, Greenland to the
mountains of North Carolina, Pennsylvania, Michigan and northward.

THE BLADDER FERNS. _Cystopteris_

"Mark ye the ferns that clothe these dripping rocks,
Their hair-like stalks, though trembling 'neath the shock
Of falling spraydrops, rooted firmly there."

The bladder ferns are a dainty, rock-loving family partial to a limestone
soil. (The Greek name _cystopteris_ means bladder fern, so called in
allusion to the hood-shaped indusium.)

(1) THE BULBLET BLADDER FERN

_Cystopteris bulbifera. Filix bulbifera_

Fronds lanceolate, elongated, one to three feet long, twice pinnate. Pinnae
lanceolate-oblong, pointed, horizontal, the lowest pair longest. Rachis and
pinnae often bearing bulblets beneath. Pinnules toothed or deeply lobed.
Indusium short, truncate on the free side. Stipe short.

[Illustration: Bulblet Bladder Fern. _Cystopteris bulbifera_ (Willoughby,
Vt., 1904, G.H.T.)]

[Illustration: Bulblet Bladder Fern. _Cystopteris bulbifera_]

One of the most graceful and attractive of our native ferns; an object of
beauty, whether standing alone or massed with other growths. It is very
easily cultivated and one of the best for draping. "We may drape our homes
by the yard," says Woolson, "with the most graceful and filmy of our common
ferns, the bladder fern." This fern and the maidenhair were introduced into
Europe in 1628 by John Tradescant, the first from America.

It delights in shaded ravines and dripping hillsides in limestone
districts. While producing spores freely it seems to propagate its species
mainly by bulblets, which, falling into a moist soil, at once send out a
pair of growing roots, while a tiny frond starts to uncoil from the heart
of the bulb. Mt. Toby, Mass., Willoughby Mountain, Vt., calcareous regions
in Maine, and west of the Connecticut River, Newfoundland to Manitoba,
Wisconsin and Iowa; south to northern Georgia, Alabama and Arkansas.

(2) THE COMMON BLADDER FERN

_Cystopteris fragilis. Filix fragilis_

Stipe long and brittle. Fronds