Stems short-creeping or ascending. Petiole straw-colored distally, 7--60 cm, base dark red-brown or black, swollen, with 2 rows of teeth; scales light to dark brown, linear- to ovate-lanceolate, 7--20 × 1--5 mm. Blade elliptic, lanceolate to oblanceolate, 2-pinnate to 2-pinnate-pinnatifid, 18--30 × 5--50 cm, herbaceous but with cartilaginous margin, narrowed to base, apex acuminate. Pinnae sessile to short-stalked, linear-oblong to lanceolate, apex acuminate. Pinnules pinnatifid, segments oblong-linear to narrowly deltate, margins serrate. Rachis , costae, and costules glabrous or with glands or hairs. Veins pinnate. Sori straight, hooked at distal end, or horseshoe-shaped; indusia dentate or ciliate.
Athyrium filix-femina is circumboreal, and this or closely related species extend into Mexico, Central America, and South America. The delimitation and infraspecific classification of A . filix-femina need detailed study.
Rhizome short-creeping to suberect, the lvs clustered near its tip, 4-10 dm; blade 10-35 cm wide, acuminate, slightly reduced below, sparsely scaly, otherwise glabrous or minutely glandular, mostly bipinnate or bipinnate-pinnatifid; pinnae 20-30 pairs below the pinnatifid tip, lance-linear, subsessile, attenuate-acuminate, the pinnules mostly serrate to deeply parted, obtuse to acuminate; veins forking, directed into the teeth; indusia dark brown, thin, ciliate (at least when young) mostly short and ±curved or hooked, commonly crossing the veins; 2n=80. Moist woods, meadows, and streambanks; cosmopolitan and highly variable, two vars. in our area:
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.