Athyrium thelypterioides (Michx.) Desv.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Rhizome short-creeping, the lvs at the front end, 3.5–11 dm, the blade longer than the petiole, 13–22 cm wide, sharply acuminate, slightly reduced below, pinnate-pinnatifid, the rachis septate-hairy and sparsely scaly, pinnae 15–20 pairs below the pinnatifid tip, deeply pinnatifid, the costal wing 0.5–1 mm wide, the segments oblong, barely to strongly toothed, 6–13 × 3–6 mm; veins simple or forked, directed into the teeth; indusia 3–7 pairs per segment, light brown, firm, elongate, mostly 1.5–2 mm, straight or nearly so, seldom crossing the veins; 2n=80. Rich moist woods; N.S. and N.B. to Ont., and Minn., s. to Ga., La., and Okla. (Asplenium acrostichoides; Diplazium t.)