Description from Flora of China
Athyrium frangulum Tagawa; A. iseanum Rosenstock var. fragile Tagawa.
Rhizomes short, erect, apex densely clothed with blackish brown, narrowly lanceolate scales. Fronds caespitose; fertile fronds 60-90 cm; stipe greenish stramineous, 28-36 cm, 2-3 mm in diam., base sparsely scaly, upward glabrescent; lamina 2-pinnate-pinnatipartite, broadly ovate or oblong, 35-50 × 15-35 cm, base cuneate, not narrowed, apex acuminate; pinnae ca. 12 pairs, alternate, markedly oblique, approximate, stalked (stalk 5-6 mm), lanceolate; basal 1 or 2 pairs of pinnae larger, 14-22 × 4-5 cm, base broadly cuneate, parallel to rachis on acroscopic side, pinnate, apex acuminate; pinnules ca. 20 pairs, alternate, oblique, approximate, narrowly deltoid-lanceolate, 2-2.8 cm × 8-12 mm, base inequilateral (but basal pinnule subequilateral), truncate, parallel to costae on acroscopic side, cuneate on basiscopic side, pinnatipartite nearly to costule, apex acute; pinnule segments 8-10 pairs, oblique, approximate, oblong, with long teeth at margin; third and upper pinnae gradually smaller, pinnatifid; veins visible abaxially, pinnate in segments, lateral veins 2-4 pairs, oblique, simple (occasionally forked). Lamina papery when dried, grass-green, glabrate; rachis and costae pale red-purple, with pale or pale brown needlelike spines on adaxial side at base of costa, costule, or midrib bases. Sori narrowly elliptic, biseriate on both sides of costules or midribs, usually inframedial; indusia yellow-brown, narrowly elliptic, membranous, erose at margin, persistent. Perispore surface without folds, with granular ornamentation. 2n = 80*.
Evergreen broad-leaved forests in valleys; 800-1800 m. Chongqing, Guizhou, Sichuan [Japan].