"Petiole stramineous, stout, with 2 bundles at the base, these uniting upwardly into a single trough-shaped bundle; blade pinnate to tripinnate, sparingly scaly, otherwise glabrous or sparsely hairy; veins free, simple or forked, reaching the margin; indusia borne on the anterior side of the vein, often recurved and crossing the vein and thus hooked or horseshoe-shaped, rarely back to back, subentire or toothed, often ciliate; large wood-ferns with thick, creeping to suberect rhizomes and thin, light green, deciduous lvs, the rhizome and often also the petioles with conspicuous, entire, fibrous scales; rhizome in our spp. beset with old swollen, starch-filled petiole-bases. 150+, cosmop."
Johnson, D. M. 1986b. Trophopods in North American species of Athyrium (Aspleniaceae). Syst. Bot. 11: 26--31. Kato, M. 1977. Classification of Athyrium and allied genera of Japan. Bot. Mag. (Tokyo) 90: 23--40. Liew, F. S. 1972. Numerical taxonomic studies on North American lady ferns and their allies. Taiwania 17: 190--221.