12. A. aculeàtum, Swartz, var. Braùnii, Koch. Fronds spreading (1½–2° long), oblong-lanceolate in outline, with a tapering base, the lower of the many pairs of oblong-lanceolate pinnæ gradually reduced in size and obtuse; pinnules ovate or oblong, obtuse, truncate and almost rectangular at base, short-stalked, or the upper confluent, sharply toothed, beset with long and soft as well as chaffy hairs.—Deep woods, mountains of New Eng., N. Y., and Penn., and northward. (Eu.)
14. CYSTÓPTERIS, Bernhardi. Bladder Fern. ([Pl. 19.])
Fruit-dots roundish, borne on the back of a straight fork of the free veins; the delicate indusium hood-like or arched, attached by a broad base on the inner side (toward the midrib) partly under the fruit-dot, early opening free at the other side, which looks toward the apex of the lobe, and is somewhat jagged, soon thrown back or withering away.—Tufted ferns with slender and delicate 2–3-pinnate fronds; the lobes cut-toothed. (Name composed of κύστις, a bladder, and πτερίς, fern, from the inflated indusium.)
1. C. bulbífera, Bernh. ([Pl. 19], fig. 1–3.) Frond lanceolate, elongated (1–2° long), 2-pinnate; the pinnæ lanceolate-oblong, pointed, horizontal (1–2´ long); the rhachis and pinnæ often bearing bulblets underneath, wingless; pinnules crowded, oblong, obtuse, toothed or pinnatifid; indusium short, truncate on the free side.—Shaded ravines, not rare from N. Eng. to Ark., commoner on calcareous rocks. July.—Specimens from Tenn. and Ark. have sometimes shorter fronds and few or no bulblets, indicating an approach to the next species.
2. C. frágilis, Bernh. Frond oblong-lanceolate (4–8´ long, besides the brittle stalk which is fully as long), 2–3-pinnate; the pinnæ and pinnules ovate or lanceolate in outline, irregularly pinnatifid or cut-toothed, mostly acute, decurrent on the margined or winged rhachis; indusium tapering or acute at the free end.—Shaded cliffs and rocky woods; common and greatly varying in the shape and cutting of the pinnules. July. (Eu.)
15. ONOCLÈA, L. ([Pl. 16] and 19.)
Sporangia borne on elevated receptacles, forming roundish sori imperfectly covered by very delicate hood-shaped indusia attached to the base of the receptacles. Fertile fronds erect, rigid, with contracted pod-like or berry-like divisions at first completely concealing the sporangia, and at last, when dry and indurated, cracking open and allowing the spores to escape. Sterile fronds foliaceous. Rootstocks creeping and constantly forming new plants. (Name apparently from ὄνος, a vessel, and κλείω, to close, from the singularly rolled up fructification.)
§ 1. ONOCLEA proper. Sterile frond with anastomosing veins.
1. O. sensíbilis, L. (Sensitive Fern.) ([Pl. 19], fig. 1, 2.) Fronds scattered; the sterile ones long-stalked (2–15´ long), triangular-ovate, pinnatifid into a few oblong-lanceolate sinuately lobed or nearly entire segments; veins reticulated with fine meshes; fertile fronds contracted, closely bipinnate, the pinnules rolled up into berry-like bodies.—Moist meadows and thickets, very common and variable. July.—Imperfectly fertile fronds sometimes occur, with the still foliaceous pinnæ cut into obovate segments with free veins and abortive sori; the so-called var. obtusilobàta.
§ 2. STRUTHIÓPTERIS. Sterile frond with free veins.