Athyrium

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.

In species outside the flora stems are sometimes long-creeping to erect, with leaves radially or dorsiventrally arranged.

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.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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