Acropelta Nakai; Cyrtomidictyum Ching; Hemesteum H. Léveillé (1915), not Newman (1851); Plecosorus Fée.

Plants perennial, terrestrial, evergreen or summer-green. Rhizome short, erect or ascending, together with basal stipe often covered with scales; scales linear to ovate, rarely with hairs. Fronds caespitose, monomorphic or rarely nearly dimorphic; stipe stramineous to purplish brown, canaliculate adaxially, scaly; distal stipe scales sparser, similar to but smaller than basal stipe scales. Lamina linear-lanceolate, lanceolate, ovate-lanceolate, lorate, or oblong, pinnate, bipinnatifid, or bipinnate, rarely finely divided and tripinnatifid or tetrapinnatifid; frond texture thinly papery, papery, or leathery, with lanceolate, subulate, linear, or ovate microscales abaxially and sometimes also adaxially, acroscopic base often auriculate, rarely auricles indistinct; rachis sulcate adaxially, with or without proliferous bulbils, rarely proliferous bulbils borne terminally on a prolonged flagelliform rachis; venation pinnate, free or rarely anastomosing to form 1 or 2 rows of areoles. Sori orbicular, terminal on veins of pinnae, sometimes abaxial or nearly terminal on veins, indusiate or rarely exindusiate; indusia orbicular, peltate, membranous, entire, erose, or irregularly toothed.

Chinese species can be classified into two subgenera and 23 sections.

The following taxa are excluded from the present treatment, pending further research: Aspidium aculeatum (Linnaeus) Swarz var. veitchii Christ (Bull. Herb. Boissier, sér. 2, 3: 513. 1903), described from W Hubei, A. aculeatum var. yunnanense Christ (Bull. Herb. Boissier 6: 964. 1898), described from Yunnan, and A. braunii Spenner var. clarkei Christ (Bull. Herb. Boissier 7: 15. 1899 ["Clarkii"]), described from Yunnan.

About 500 species: common in the temperate regions and subtropical lowlands and montane to alpine areas in the N Hemisphere, mostly in S and SW China, Himalaya, Japan, and Vietnam; a rich diversity of Polystichum also found in Central and South America; ca. 15 species in North America north of Mexico, 16 in Africa, eight in Madagascar and the Mascarenes, three in Macronesia, four in Europe, 12 in Australasia, and a few in New Guinea and the Pacific islands; 208 species (139 endemic) in two subgenera in China.

(Authors: Zhang Libing (张丽兵); David S. Barrington)