Description from Flora of China
Plants terrestrial or epilithic, medium-sized or small; outlines highly variable. Rhizomes short and erect, or long and creeping, with siphonostele, covered with scales; scales brown or black, lanceolate, thick in texture, usually entire. Fronds monomorphic, whorled and clustered, scattered in 2 rows or compact, not articulate; stipe black or reddish brown, glossy, fine and rounded, hard, with 1 or 2 vascular bundles and combined into 1 upward; lamina mostly 1-3- or more pinnate or 1-3-dichotomous with pedate branches, rarely reduced to solitary entire and orbicular-flabellate pinnule, herbaceous or papery, less often leathery or membranous; rachises, costae, and stalks same color as stipe; pinnules sometimes with articulate stalk, ovate, flabellate, orbicular-flabellate, or dimidiate, margins serrate, lobed, or entire, usually deciduous when dried; veins free, reaching margins, simple or dichotomously forked, often radiate [rarely anastomosing (Hewardia)], usually visible on both surfaces of lamina. Sori borne on veins of recurved, membranous margins (false indusium); false indusium orbicular, reniform, lunate, ± rectangular, or oblong, free or continuous, upper margins forming deep sinus, retuse or truncate. Sporangia globose, long stalked, annuli erect; mostly consisting of 18-28 incrassate cells. Spores yellowish, tetrahedral, trilete, transparent, smooth. x = 15(30), 29.
The following species could not be treated here because no material was seen by the present authors: Adiantum menglianense Y. Y. Qian (Acta Bot. Austro Sin. 8: 37. 1992) and A. ornatum Ching (Bull. Fan Mem. Inst. Biol., Bot. 11: 55. 1941).
More than 200 species: from cold temperate zone to tropics, most in South America; 34 species (16 endemic) in China.
(Authors: Lin Youxing (林尤兴); Jefferson Prado, Michael G. Gilbert)