Perennial herbs, or shrubby trailing or climbing vines; stems slender, or stout and succulent, glabrous; rhizomes sometimes with fleshy tubers. Leaves alternate, sometimes succulent, mucilaginous, simple, entire; sessile or petiolate; stipules absent. Inflorescence of axillary or terminal spikes, racemes or panicles; peduncles nearly absent to present; pedicel subtended by a thin bract; flower always subtended by 2 or 4 deciduous or persistent, sometimes connate bracteoles. Flowers bisexual, actinomorphic, sessile or pedicellate; tepals (4-)5(-13), green, sometimes white to purple, entire, forming a calyx-like perianth; stamens 5, opposite tepals, anthers 4-locular, dehiscent by lateral slits; ovary superior or half-inferior, 3-carpellate, 1-locular, ovule solitary, basal, erect, campylotropous to orthoamphitropous, styles 3, stigmas 1 or 3. Fruit a dry utricle or nutlet, sometimes baccate and fleshy, enclosed by accrescent, sometimes winged perianth; seed 1, embryo annular, cochleate or spiral, perisperm sparse.