Plants perennials, terrestrial or epiphytic. Roots lacking root hairs, unbranched or with a few narrow lateral branches, in 1 species dichotomously branched. Stems simple, unbranched, upright, with eustelic vascular tissue. Leaf bases dilated, clasping, forming sheath, open or fused, surrounding successive leaf primordia; primordia glabrous or with long, uniseriate hairs. Leaves 1(--2) per stem, with common stalk divided into sterile, laminate, photosynthetic portion (trophophore) and fertile, spore-bearing portion (sporophore). Trophophore blades compound to simple, rarely absent, veins anastomosing or free, pinnate, or arranged like ribs of fan. Indument absent or of widely scattered, long, uniseriate hairs, especially on petioles and rachises. Sporophores pinnately branched or simple. Sporangia exposed or embedded, 0.5--1.5 mm diam., thick-walled, with thousands of spores. Spores all 1 kind, trilete, thick-walled, surface rugate, tuberculate, baculate (with projecting rods usually higher than wide), sometimes joined in delicate network, mostly with ± warty surface. Gametophytes not green, usually fleshy, round or linear, subterranean, mycorrhizal.
Genera 5, species ca. 70--80 (3 genera, 38 species in the flora): nearly worldwide.
Ophioglossaceae comprise two clearly defined subfamilies, Botrychioideae and Ophioglossoideae, which are sometimes recognized as distinct families. Ophioglossaceae may be only distantly related to the ferns and more closely related to Marattiales and certain seedplants, especially Cycadales, in such characteristics as stelar type, cork cambium, dilated leaf bases, conduplicate vernation, intercalary leaf growth, collateral leaf traces, circular-bordered pits, eusporangia, massive gametophytes, sunken archegonia, and presence in some species of endoscopic embryos.
(Key to genera of Ophioglossaceae )