Plants perennial, mostly terrestrial, rarely epiphytic, usually small and fleshy, lacking sclerenchyma. Roots lacking root hairs, unbranched or with a few narrow lateral branches [rarely dichotomously branched], fibrous or fleshy, sometimes producing vegetative buds. Rhizome mostly erect, less often horizontal, rarely branched, eustelic, glabrous or hairy. Fronds 1 to few per plant, monomorphic, vernation nodding (not circinate), erect or folded, stipe base dilated, clasping, forming open or fused sheath surrounding successive leaf buds; buds glabrous or with long, uniseriate hairs; common stipe usually dividing into sterile, laminate, photosynthetic portion (trophophore) and fertile, spore-bearing portion (sporophore); sterile lamina ternately or pinnately compound to simple, rarely absent, glabrous or with scattered, long, uniseriate hairs, especially on stipe and rachis; veins anastomosing or free, pinnate, or palmate. Sporophores 1 per frond [rarely more], spikelike or pinnately branched; sporangia exposed or embedded, sometimes clustered on very short lateral branches, wall 2 cells thick, annulus absent; spores many (> 1000) per sporangium, globose-tetrahedral, trilete, thick-walled, surface rugate, tuberculate, baculate (with projecting rods usually higher than wide), sometimes joined in delicate network, mostly with ± warty surface. Gametophytes subterranean, usually fleshy, mycorrhizal, non-photosynthetic, orbicular or linear. x = 30, (44), 45, (46), 94.
Four(-nine) genera and ca. 80 species: nearly worldwide; three genera and 22 species (two endemic) in China.
Ching Ren-chang, Fu Shu-hsia, Wang Chu-hao & Shing Gung-hsia. 1959. Ophioglossaceae, Botrychiaceae, and Helminthostachyaceae. In: Ching Ren-chang, ed., Fl. Reipubl. Popularis Sin. 2: 6-26, 329-330.