Description from Flora of China
Vines herbaceous, branched. Leaves sessile or petiolate, slightly fleshy. Racemes axillary, rarely branched. Flowers pedicellate; pedicel persistent, articulated below the perianth, apex with 2 pairs of decussate bracteoles adnate to the perianth; lower bracteoles small, connate and persistent or free and caducous; upper bracteoles tepaloid, convex or boat-shaped, often keeled abaxially, sometimes narrowly winged, rarely broadly winged. Perianth segments membranous, spreading rotate at anthesis. Petals connate at base, segments thin, patent in anthesis. Filaments filiform, broadened toward base, reflexed in bud. Styles 3; stigmas globular or club-shaped, papillose. Fruit ovoid to globose, enclosed by perianth, pericarp fleshy or parchmentlike. Seed lens-shaped.
Between five and ten species: warmer parts of the Americas, from the West Indies to Argentina, Galápagos Islands; two species (introduced) in China.