Description from Flora of China
Plants terrestrial, medium-sized. Rhizomes short, mostly erect, occasionally creeping or ascending, rarely long creeping; fronds caespitose, rarely approximate or distant. Stipe grooved abaxially, terete adaxially, often shortly glandular hairy in groove, base often swollen, with uniseriate tuberculate pneumathodes on lateral sides, narrowed toward very base, sometimes without pneumathodes, not narrowed to base, with vascular bundles 2, upward connected abaxially into U-shaped single bundle in section, scaly at base; scales red-brown, brown, or blackish brown, ovate-lanceolate, linear-subulate, or linear-lanceolate, entire, membranous, basifixed; lamina ovate, oblong, or broadly lanceolate, 1-3-pinnate; lamina segments inequilateral at base; groove of rachis and costae continuous to grooves of costae and costules, respectively; spines at base of costae, costules, and midribs on adaxial side present or absent, spines continuous from ridges on both sides of groove. Veins free, forked or pinnate, extending to tooth tips at lamina margin. Lamina usually herbaceous when dried, in a few cases papery or leathery, usually glabrate, rarely scaly or hairy, or shortly glandular hairy adaxially. Sori orbicular, orbicular-reniform, horseshoe-shaped, J-shaped, oblong, or shortly linear, abaxial, lateral to or crossing over veins; indusia brown, orbicular-reniform, horseshoe-shaped, J-shaped, lunate, oblong, or shortly linear, membranous, erose or ciliate, rarely entire at margin, usually persistent, rarely exindusiate or indusia undeveloped. Spores bilateral, elliptic in polar view, bean-shaped in equatorial view, and perispore surface with or without folds. x = 40.
The distribution center is located in the mountainous areas of SE China.
Athyrium is one of the largest genera of the pteridophytes and one of the taxonomically most difficult genera. Molecular data shows Athyrium as defined here is not monophyletic; Athyrium niponicum is transferred to Anisocampium, while Pseudocystopteris is nested within Athyrium. Hybridization makes the taxonomy of this genus more difficult. More than 60 hybrids have been known in Japan, and many additional hybrids are possible in China, requiring further analysis.
The following species, distributed in Taiwan, could not be treated here because no material was seen by the present authors: Athyrium puncticaule (Blume) T. Moore (Index Fil. 186. 1860; Aspidium puncticaule Blume, Enum. Pl. Javae 2: 159. 1828), Athyrium leiopodum (Hayata) Tagawa (Acta Phytotax. Geobot. 2(3): 195. 1933; Diplazium leiopodum Hayata, Icon. Pl. Formosan. 4: 217. 1914), and A. tenuicaule (Hayata) Tagawa (Acta. Phytotax. Geobot. 2(3): 195. 1933; Diplazium tenuicaule Hayata, Icon. Pl. Formosan. 4: 220. 1914), treated by Knapp as a synonym of A. leiopodum (Ferns Fern Allies Taiwan, 980. 2011). For more information, see Liu and Fraser-Jenkins (Taiwania 51: 293-297. 2006), Liu et al. (Fern Fl. Taiwan Athyrium, 26, 42. 2009), and Knapp (loc. cit.: 129-130, 439).
In addition, eleven uncertain taxa, not included in the following key, are listed at the end of the account.
Athyrium dulongicola W. M. Chu (Acta Bot. Yunnan., Suppl. 5: 41. 1992 [“dulongicolum”]), described from Yunnan.
Athyrium excelsium Ching (Acta Bot. Boreal.-Occid. Sin. 6(1): 20. 1986), described from Yunnan.
Athyrium fargesii Christ (Bull. Soc. Bot. France 52(Mém. 1): 49. 1905), described from Yunnan.
Athyrium filix-femina (Linnaeus) Roth subvar. brevidens Christ (Bull. Soc. Bot. France 52(Mém.
1): 46. 1905), described from Yunnan.
Athyrium filix-femina (Linnaeus) Roth var. duclouxii Christ (Bull. Soc. Bot. France 52(Mém. 1): 46. 1905), described from Yunnan.
Athyrium filix-femina (Linnaeus) Roth var. paleosum Christ (Notul. Syst. (Paris) 1: 48. 1909), described from Yunnan.
Athyrium ×heterosporum Y. T. Hsieh & Z. R. Wang (Acta Phytotax. Sin. 27: 156. 1989), described from Yunnan and treated in FRPS (3(2): 266. 1999).
Athyrium nemotum Ching (Acta Bot. Boreal.-Occid. Sin. 6(3):149-150. 1986), described from Guangxi.
Athyrium nigripes (Blume) T. Moore var. elongatum Christ (Bull. Herb. Boissier 7(1): 13. 1899), described from Yunnan.
Athyrium rotundifolium Ching (Fl. Fujian. 1: 597. Apr 1982), described from Fujian.
Athyrium silvestrii Christ (Nuovo Giorn. Bot. Ital. n.s., 17. 226. 1910), described from Hubei.
About 220 species: distributed mainly in the temperate zone and subtropical mountain forests; 123 species (probably more plus a number of hybrids) (69 endemic) in China.
(Authors: Wang Zhongren (王中仁); Masahiro Kato)