Amer. Fern J. 20: 118. 1930.
Leaves monomorphic, dying back in winter, 25–90 × 15–30 cm. Petiole 1/3 length of leaf, scaly at least at base; scales scattered, brown, sometimes with darker patch at base. Blade light green, deltate-ovate, 3-pinnate-pinnatifid, herbaceous, not glandular. Pinnae in plane of blade, lanceolate; basal pinnae deltate to broadly lanceolate, not reduced, basal pinnules equal to adjacent pinnules, basal basiscopic pinnule much longer and 2 times width of basal acroscopic pinnule (only in this species); pinnule margins toothed, teeth spine-tipped. Sori midway between midvein and margin of segments. Indusia usually lacking glands. 2n = 164.
Habitat: Cool, moist woods at increasing elevation southward, frequently only at summits of mountains
Elevation: 0–1500 m
N.B., Nfld. and Labr. (Nfld.), N.S., P.E.I., Que., Conn., Maine, Md., Mass., N.H., N.Y., N.C., R.I., Tenn., Vt., Va., W.Va.