[Illustration:  Spinulose Shield Fern. Aspidium spinulosum (Maine, 1877, Herbarium of Geo. E. Davenport)]

[Illustration:  Aspidium spinulosum, var. intermedium]

[Illustration:  Aspidium spinulosum, var.  AMERICANUM]

A tripinnate form of this variety discovered at Concord, Mass., by Henry Purdie, has been named var.  CONCORDIANUM.  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