Type species: Cipoia inserta C.T.Philbrick, Novelo & Irgang.
Herbae perennae aquaticae parvae; folia petiolata, disticha, monomorpha, erecta, simplicia (haec rara, tantum in base caulium juvenium) vel composita, dichotome divisa, stipulata; stipula constata ex extension baseos folii cymbiformis, apice integro vel emarginato,indurato, in caulibus longioribus vetustioribusque persistenti. Flores 1-aliquot per caulem, axillares, hermaphroditi, zygomorphi, brevipedicellati vel sessiles, spathella saccata obtecti; tepala 2, squamiformia; stamen 1; anthera basifixa, introrse longitudinaliterque dehiscens; pollinis grana in dyadibus, tricolpata; ovarium 2-carpellatum, 2-loculare, per anthesin intus spathella remanens, in gynophoro portatum, gynophoro per anthesin elonganti, plerumque tandem quam pedicello longiore; pedicellus brevissimus vel absens; stigmata 2, libera; fructus capsularis, 2-locularis, intus spathella rumpenti maturans, duabus valvis aequalibus, persistentibus, quoque 3-costata; semina ignota.
Small aquatic perennial herbs, attached to rocks in river-rapids and waterfalls. Roots prostrate, elongate, dorsiventrally flattened to elliptical in cross-section, sometimes intertwined, green and photosynthetic, branched, with asymmetric root cap, attached to rocks via holdfasts (haptera) and adhesive hairs. Stems arising opposite or subopposite along the flanks of roots, unbranched, erect, elliptical to terete in cross-section at base, monomorphic. Leaves petiolate, distichous, monomorphic, upright, monothecous or dithecous, simple (rare, basal on young stems only) to compound, dichotomously divided, stipulate; ultimate leaf segments linear to spathulate, lacking a vein; petiole elliptical in cross-section; stipule composed of an extension of the amplexicaul, boat-shaped leaf base; apex entire to emarginate, hardened and persistent on older stems. Flowers 1 to several per stem, axillary, chlamydeous, hermaphroditic, zygomorphic, short pedicellate or sessile, covered by a sac-like spathella; spathella clavate, punticulate, rupturing apically into several small and irregularly shaped segments; tepals 2, scale-like, linear, one on either side of the stamen filament, apex acute; stamen 1, deciduous, filaments elongating during anthesis and projecting from the ruptured spathella; anthers basifixed, triangular, tapering outward toward the base; thecae acute, joined at the top, of equal height, dehiscing introrsely and longitudinally; pollen in dyads, tricolpate; ovary 2-carpellate, 2-locular, elliptical, with 6 longitudinal dark lines, remaining inside the spathella during anthesis, borne on a gynophore which elongates during anthesis and usually becomes longer than pedicel; ovules numerous, placentation axile; stigmas 2, free, linear, upright prior to rupture of the spathella, during anthesis elongating, upright or divergent, projecting from the ruptured spathella, longer than ovary; pedicel very short or lacking; fruit a capsule, 2-locular, elliptical, maturing within the ruptured spathella, with two equal valves (isolobous); valves persistent, each 3-ribbed, suture margins appearing thickened and rib-like; seeds unknown.