Leaves monomorphic, dying in winter, 15--75 × 10--30 cm. Petiole 1/4--1/3 length of leaf, scaly at least at base; scales scattered, tan. Blade light green, ovate-lanceolate, 2--3-pinnate-pinnatifid, herbaceous, not glandular. Pinnae ± in plane of blade, lance-oblong; basal pinnae lanceolate-deltate, slightly reduced, basal pinnules usually longer than adjacent pinnules, basal basiscopic pinnule longer than basal acroscopic pinnule; pinnule margins serrate, teeth spiny. Sori midway between midvein and margin of segments. Indusia lacking glands. 2 n = 164. Swampy woods, moist wooded slopes, stream banks, and conifer plantations; 0--1200 m; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Ark., Conn., Del., Idaho, Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., Mont., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Pa., R.I., S.C., Tenn., Vt., Va., Wash., W.Va., Wis.; Eurasia.