Pellæa gracilis:—Root-stock slender, creeping, cord-like, scantily furnished with little ovate appressed scales; stalks scattered, slender, a span long or less, brownish-stramineous, somewhat shining, darker and slightly chaffy at the base; fronds two to four inches long, thin and tender, smooth, ovate or ovate-oblong, pinnate; pinnæ few, the lower two to four pairs once or twice pinnatifid, the uppermost simple; segments of the sterile fronds adnate-decurrent, roundish-obovate, crenately lobed and toothed; those of the taller fertile fronds lanceolate or linear-oblong, and more distinct, entire or auricled, terminal ones longest; veins rather distant, mostly once forked; involucre broad and continuous, delicately membranaceous.
Pellæa gracilis, Hooker, Sp. Fil., ii., p. 138, t. cxxxiii, B.—Eaton, in Gray’s Manual, ed. v., p. 659; Ferns of the South-West, p. 319.—Hooker & Baker, Syn. Fil., p. 145.—Porter & Coulter, Syn. Fl. Colorado, p. 153.
Pteris gracilis, Michaux, Fl. Bor.-Am., ii., p. 262.—Swartz, Syn. Fil., p. 99.—Willdenow, Sp. Pl., v., p. 376.—Pursh, Fl. Am. Sept., ii., p. 668.—Hooker, Fl. Bor.-Am., ii., p. 264.
Allosorus gracilis, Presl, Tent. Pterid., p. 153.—Torrey, Fl. New York, ii., p. 486.—Gray, Manual, ed. i., p. 624; ed. ii., p. 591, t. ix.—Parry, in Owen’s Geol. Surv. of Wisconsin, etc., p. 621.—Mettenius, Fil. Hort. Lips., p. 44.
Cheilanthes gracilis, Kaulfuss, Enum. Fil., p. 209.
Pteris Stelleri, Gmelin, “Nov. Com. Petrop., xii., p. 519, t. 12, f. 1.”
Allosorus Stelleri, Ruprecht, Distr. Crypt. Vasc. in Imp. Ross., p. 47.—Ledebour, Fl. Ross., iv., p. 526.—Moore, Ind. Fil., p. 46.—Lawson, in Canad. Naturalist, i., p. 272.
Allosorus minutus & Pteris minuta, Turczaninow, fide Moore.
Hab.—Crevices of damp and shaded calcareous rocks, especially in deep glens; Labrador, Butler, to British Columbia, and southward to Iowa, Parry, Wisconsin and Pennsylvania. Also in Colorado, near Breckinridge City, Brandegee. Siberia, Tibet and the Himalayas. It is found in Sunderland, Massachusetts; at Trenton Falls, Chittenango Falls, and other deep glens in Central New York; in Lycoming and Sullivan Counties, Pennsylvania, and in other similar places in Vermont, Michigan, etc., but is by no means a common plant.
Description:—This is the most delicate of all the Pellæas, and has fronds a good deal like those of Cryptogramme acrostichoides, but tenderer, and with sub-marginal fructification. The root-stock is very slender, scarcely more than half a line in thickness, and sometimes two or three inches long. It is so hidden in the crevices of the rocks that it is seldom secured by collectors. The scales are minute, appressed to the root-stock, and almost filmy in their delicacy.