Stems creeping, few branched, slender, 1--1.5 mm diam., succulent, brittle; scales colorless, sparse, transparent-reticulate, ovate, 0.4 × 0.3 mm; stems shriveling in 2d year following emergence of leaves. Leaves scattered along stems, ephemeral (dying by late summer), soon shed; sterile leaves erect, 3--15 cm; fertile leaves erect, 5--20 cm; petioles, costae, and costules glabrous. Petiole dark brown in proximal 1/2 or less, becoming greenish distally, ca. 1 mm wide when dry, only slightly furrowed, glabrous. Blade broadly lanceolate to ovate-lanceolate, all pinnate-pinnatifid to 2-pinnate, herbaceous to membranous, thin; hydathodes superficial, often poorly developed or absent. Segments of sterile leaves ovate-lanceolate to fan-shaped, distal 1/2--1/3 shallowly lobed; segments of fertile leaves horizontal to ascending, often only partially differentiated from sterile leaves, lanceolate to linear, 8--25 × 2--4 mm; margins reflexed, forming continuous false indusia. Sporangia often in discrete sori. 2 n = 60. New growth produced in spring, dying by late summer. Sheltered calcareous cliff crevices and rock ledges, typically in coniferous forest or other boreal habitats; 0--3000 m; Alta., B.C., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Yukon; Alaska, Colo., Conn., Ill., Iowa, Maine, Mass., Mich., Minn., Mont., Nev., N.H., N.J., N.Y., Oreg., Pa., Utah, Vt., Wash., W.Va., Wis., Wyo.; Europe in ne former Soviet republics; Asia.
Rhizomes slender, soft, creeping, pilose and scaly, the pale brown, hyaline-reticulate scales not over 2 נ0.5 mm; lvs scattered, thin and soft, deciduous; petioles castaneous or dark purple basally, usually greenish or stramineous distally, 2.5-15 cm, the fertile ones commonly longer than the sterile; sterile blades 3-8 נ2-5 cm, 2-3 times pinnate with confluent, flabellate to ovate, distally toothed pinnules 5-15 נ3-10 mm; fertile blades with longer and narrower, sometimes linear pinnules to 2 cm נ3(-5) mm, the rather narrowly reflexed, evidently hyaline-scarious indusial margin more strongly modified than in C. crispa; 2n=60. Calcareous rocks and moist shady slopes, circumboreal, in Amer. from Nf. to Alas., s. to n. N.J. (formerly), n. Pa., W.Va., Ill., Io., Utah, and Wash.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.