Herbs, annual, viscid-pubescent, from long, narrow taproots. Stems trailing, unarmed, without glutinous bands on internodes. Leaves petiolate, of unequal size in each pair; blade thin to somewhat fleshy, base ± asymmetric. Inflorescences in axils of smaller leaf of pair, 1-flowered, peduncles short in flower, peduncles greatly elongating, pushing into ground in fruit; bracts deciduous, 3 at base of flower, distinct, lanceolate, thin, translucent. Flowers bisexual, chasmogamous; perianth radially symmetric, funnelform but strongly oblique, constricted beyond ovary, gradually flared to 5-lobed limb; stamens 5-18, included or slightly exserted; styles slightly exserted; stigmas peltate. Fruit geocarpous, ± oblong, unribbed, corky, glabrate, smooth or rugose.