Northern lady fern

Aspidium angustum Willdenow, Sp. Pl. 5(1): 277. 1810; Athyrium angustum (Willdenow) C. Presl; A. filix-femina subsp. angustum (Willdenow) Clausen; A. filix-femina var. michauxii (Sprengel) Farwell

Petiole (7--)15--55 cm; scales brown to dark brown, linear-lanceolate, 8(--10) × 2 mm. Blade elliptic, 2-pinnatifid to 2-pinnate, (20--)30--75 × (5--)10--35 cm, moderately narrowed proximally, broadest near or just below middle, apex acuminate. Pinnae short-stalked or sessile, oblong-lanceolate. Pinnules decurrent onto costal wing or sessile, linear to oblong, base unequally cuneate, apex obtuse to acute or in larger leaves acuminate, lobed halfway or more to costules. Rachis , costae, and costules glabrous or with pale glands. Sori straight, less frequently hooked at distal end or horseshoe-shaped; sporangial stalks bearing glandular hairs; indusia irregularly dentate, ± ciliate. Spores yellow or brown. 2 n = 80.

Moist woods, swamps, thickets; 0--1100 m; Greenland; Man., N.B., Nfld., N.S., Ont., P.E.I., Que., Sask.; Conn., Del., Ill., Ind., Iowa, Maine, Md., Mass., Mich., Minn., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Pa., R.I., S.Dak., Vt., Va., W.Va., Wis.