Plants epiphytic, petrophilous, or terrestrial, small to medium-sized. Rhizome sometimes short and erect, but usually slender and long creeping, often covered with hairs when young, simple or sometimes irregularly branching. Lamina simple to pinnately decompound, or flabellate, digitate, dichotomous, or even irregularly divided. Segments with a single veinlet, cells in one layer, or rarely with 2-4 cell layers without intercellular spaces and stomata. Sori terminal on veins, solitary, at apex of ultimate segments, or marginal on simple to pinnatifid fronds; involucres cup-shaped to deeply 2-cleft nearly to base; receptacles terminating a vein, short, capitate or clavate, or long and projecting; sporangia shortly stalked to (sub)sessile, maturing basipetally; annulus oblique, not interrupted; dehiscence irregular; spores globose-trilete, tetrahedral, containing chloroplasts, usually short-lived. x = 8, 11, 12, 13, 17, 21, 22, 26, 28, 36, 54 (base numbers x = 8, 54 are doubtful).

Traditionally, only two genera-Hymenophyllum with bivalved involucres and Trichomanes Linnaeus with tubular involucres-have been recognized in this family. This scheme was expanded by Morton (Contr. U.S. Natl. Herb. 29: 139-202. 1968) who hierarchically placed many subgenera, sections, and subsections under two larger genera, Hymenophyllum and Trichomanes, and recognized four monotypic genera, Cardiomanes Morton, Serpyllopsis Morton, Hymenoglossum Morton, and Rosenstockia Morton, all of which have specialized fronds. Conversely, Copeland (Gen. Fil. 31-44. 1947) split the family into 34 genera, basing his work on herbarium specimens as well as his field observations of Asian material. Taking into account these past studies plus recent investigations including molecular data, Ebihara et al. (Blumea 51: 221-280. 2006) proposed a modern scheme of classification on which the system of this treatise is based.

Ching Ren-chang, Fu Shu-hsia, Wang Chu-hao & Shing Gung-hsia. 1959. Hymenophyllaceae. In: Ching Ren-chang, ed., Fl. Reipubl. Popularis Sin. 2: 132-196, 350-357, 379.

Nine genera and ca. 600 species: tropical, subtropical, and temperate regions of both the Old and New Worlds; seven genera and 50 species (six endemic) in China.

(Authors: Liu Jiaxi (刘家熙), Zhang Qiaoyan (张巧艳); Atsushi Ebihara, Kunio Iwatsuki)