in Franklin, Narr. Journey Polar Sea 754, 767. 1823.
Stems decumbent to erect, much branched from base, stout, 10–20 mm diam. (including hardened, persistent leaf bases); scales bicolored, dense, broadly lanceolate to linear, to 6 × 2 mm. Leaves densely tufted, green over winter, persistent after withering; sterile leaves spreading, 3–17 cm; fertile leaves erect, 5–25 cm; hairs small, appressed, cylindric, scattered along grooves of petiole and along costae and costules of adaxial blade surface. Petiole green to straw-colored, dark brown on proximal 1/8 or less, 1–2 mm wide, firm and strawlike, not collapsed; scales bicolored or ± concolored, becoming sparse distally. Blade deltate to ovate-lanceolate, all 2–3-pinnate, somewhat leathery, opaque; hydathodes sunken below leaf surface. Segments of sterile leaves oblong to ovate-lanceolate, bases cuneate, distal 2/3–1/2 of segments crenate to dentate, often somewhat more deeply incised every 2d tooth; segments of fertile leaves horizontal to ascending, strongly differentiated from those of sterile leaves, linear, 3–12 × 1–2 mm; margins of fertile segments revolute, covering sporangia. Sporangia in sori that coalesce at maturity. 2n = 60.
Habitat: New growth produced in spring, spores maturing in summer, sterile leaves green over winter, senescing 2d spring. Noncalcareous cliff crevices, rock outcrops, and talus, often in relatively dry habitats, typically montane but occurring in lowland to alpine habitats
Elevation: 0–3700 m
Alta., B.C., Man., N.W.T., Ont., Sask., Yukon, Alaska, Ariz., Calif., Colo., Idaho, Mich., Mont., Minn., Nev., N.Mex., Oreg., Utah, Wash., Wyo., reported from Mexico in Baja California, Asia.
Cryptogramma acrostichoides has often been treated as a variety or subspecies of the strictly European Cryptogramma crispa (Linneaus) R. Brown, which has a chromosome number of 2n = 120.