Sinistrorsely twining herbs with white milky juice. Leaves spirally arranged, simple or lobed to varying degrees, cordate, palmatinerved, long-petioled, glabrous as is the stem, exstipulate. Flowers bisexual, or polygamous (andromonoecious), small, subsessile, in unilateral repeatedly forked cincinni, composed of loose axillary panicles, ebracteate. Calyx deeply (4-)5-partite, lobes imbricate in bud, whether or not slightly accrescent in fruit, persistent. Petals (4-)5, caducous, lower half forming a widely funnel-shaped corolla, lobes imbricate in bud. Stamens (4-)5 inserted on the upper part of the corolla tube, alternate with its lobes; filaments very short, glabrous; anthers medifixed, introrse; pollen grains oblate, triangular in polar view, tricolporate. Disk absent. Ovary oblong-ovoid, subquadrangular (rudimentary in ♂), 1-celled; styles 2, one with a deep longitudinal groove, and two inequal ovate rather obtuse distal divisions, accrescent in fruit and becoming linear and succulent then, the other short-curved, capitate at apex, deciduous; ovules 2 (often one of them aborted), pendent from apex of cavity, anatropous, with dorsal raphe. Fruit indehiscent, compressed, with 2 longitudinal broad and transversely striate stramineous wings, obovate-elliptic to orbicular in outline, apex emarginate, crowned by the columnar accrescent soft and green stigma, base very shortly or hardly (Mal.), sometimes elongately contracted into a kind of stipe. Seed 1, linear, sulcate; testa thin; embryo minute, conical, in top of granular fleshy albumen.
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Lianas herbaceous, glabrous. Leaves long petiolate; leaf blade cordate or cordate-hastate, thin, membranous, lobed or not, palmately 3-7-veined. Panicles sparse, scorpioid at apex; bracts early deciduous, ovate, small, apex acuminate. Flowers bisexual or polygamous, sessile. Calyx deeply (4 or)5-lobed; lobes persistent, imbricate. Petals deciduous, imbricate, coherent at base. Stamens alternate with petals, inserted at throat of corolla; filaments very short; anthers introrse, 2-celled, longitudinally dehiscent. Ovary ovoid-oblong, slightly 4-ribbed, rudimentary in staminate flowers; styles short, stout; stigmas 2-lobed, 1 capitate and early deciduous, 1 elongate in fruit, apex 2-lobed, deciduous. Fruit broad, orbicular or obcordate, wings membranous, horizontally veined. Seeds longitudinally grooved; endosperm densely granular, fleshy.
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