[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. CONCORDIÀNUM. It has small, elliptical, denticulate pinnules and a glandular-pubescent indusium.
Var. AMERICÀNUM (=dilatàtum, syn.). Fronds broader, ovate or triangular-ovate in outline. A more highly developed form of the typical plant, the lower pinnæ being often very broad, and the fronds tripinnate. Inferior pinnules on the lower pair of pinnæ conspicuously elongated. A variety preferring upland woods; northern New England, Greenland to the mountains of North Carolina, Pennsylvania, Michigan and northward.
[THE BLADDER FERNS. Cystópteris]
"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 cystópteris means bladder fern, so called in allusion to the hood-shaped indusium.)
(1) THE BULBLET BLADDER FERN
Cystópteris bulbífera. Fìlix bulbífera
Fronds lanceolate, elongated, one to three feet long, twice pinnate. Pinnæ lanceolate-oblong, pointed, horizontal, the lowest pair longest. Rachis and pinnæ often bearing bulblets beneath. Pinnules toothed or deeply lobed. Indusium short, truncate on the free side. Stipe short.