5. Athyrium Roth, Tent. Fl. Germ. 3(1,1): 31, 58. 1799.
Lady fern [Greek athyros, doorless; the sporangia only tardily push back the outer edge of the indusium]
Plants generally terrestrial. Stems short-creeping or ascending, stolons absent. Leaves monomorphic, usually dying back in winter. Petiole ± 0.5 times length of blade or less, base swollen and dentate, persisting as trophopod over winter or not; vascular bundles 2, lateral, lunate in cross section. Blade lanceolate to elliptic or oblanceolate, 1--3-pinnate-pinnatifid, gradually reduced distally to confluent, pinnatifid apex, herbaceous. Pinnae not articulate to rachis, segment margins serrulate or crenate; proximal pinnae often reduced, sessile to short-petiolulate, ± equilateral; costae adaxially grooved, grooves continuous from rachis to costae to costules; indument absent or of linear to lanceolate scales or 1-celled glands abaxially. Veins free, simple or forked. Sori in 1 row between midrib and margin, round to elongate, straight or hooked at distal end, or horseshoe-shaped; indusia shaped like sori, persistent, attached laterally or with narrow sinus, or indusia absent. Spores brownish, rugose. x = 40.
Species about 180 (2 in the flora): worldwide.
In species outside the flora stems are sometimes long-creeping to erect, with leaves radially or dorsiventrally arranged.
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.