Glabrous, hermaphroditic, perennial, much-branched leafy climbers or subshrubs up to 5 m tall. Leaves alternate, distichous, with a prominent to obscure midrib, sessile or with a short petiole, sometimes sheathing at the base, lanceolate to ovate or sometimes linear; veins numerous, parallel with few or no cross veins; midrib prominent; spines and stipules lacking; leaves reduced to scales under each branch. Inflorescence an axillary fascicle or a loose terminal cyme or panicle; pedicel articulate immediately under the flower. Flowers small, perfect, actinomorphic, campanulate, hypogynous, often pendulous. Sepals firm, valvate in bud, shortly hood-shaped at apex. Petals flat, obtuse, slightly imbricate, the margins thin and entire. Stamens 6, in two whorls, hypogynous, not exceeding the perianth; filaments free or fused at the base; anthers oblong-linear, bilocular, basifixed, introrse, sagittate at base, erect, yellow, poricidal. Ovary superior, trilocular with axile placentae; ovules few, anatropous or campylotropous, crassinucellate; style filiform; stigma punctate. Fruit a berry or capsule. Seeds several, rounded to angular-crescentic, black, shiny, sometimes strophiolate; endosperm copious, lacking starch; embryo linear.
Dahlgren et al. (1985) placed both genera, plus Luzuriaga, Behnia and Elachanthera, in the Luzuriagaceae, separate from the Philesiaceae, whereas Dahlgren & Clifford (1982) included them in the Philesiaceae. Cronquist (1981) put them in the Smilacaceae. More recent cladistic and phenetic evidence suggests that, while Eustrephus and Geitonople- sium are closely related to each other, they are only distantly related to Luzuriaga and Philesia (Conran 1987a). Their closest relatives appear to be in the Phormiaceae (Con- ran 1989). The two genera are here treated in the separate family Geitonoplesiaceae. Both species are highly variable. Several synonyms and infraspecific taxa have been proposed, although none is here accepted (Schlittler 1951; Conran 1987b; Laferriere 1995).