Erect to spreading, perennial herbs, shrubs or perennial twining (counterclockwise) vines, without cystoliths. Branches ± terete to quadrangular, occasionally longitudinally grooved. Leaves opposite, petiolate, blades often cordate to hastate at base, margins entire to lobed or dentate. Inflorescences of solitary or clustered flowers in leaf axils or in a terminal thyrse of alternate or opposite, 1-flowered, pedunculate dichasia; bracteoles (previously called “bracts” by this and other authors) green, spathaceous, enclosing most or all of corolla tube, usually persistent in fruit, free or fused along one side. Flowers homostylous, sessile; calyx persistent, reduced, annular, entire or ± irregularly 5-20-lobed; corollas white, yellow, orange, blue or purple, tube funnelform or salverform, expanded distally into a distinct throat, throat sometimes very wide and open, limb 5-lobed, subregular to 2-lipped with upper lip 2-lobed, lower lip 3-lobed, lobes subequal, contorted in bud, spreading or reflexed; stamens 4, often didynamous, inserted near base of throat, included; anthers 2-thecous, thecae equal to unequal in size, parallel to subparallel, equally to subequally inserted, often awned or appendaged basally, variously pubescent, staminodes 0; disk annular, enclosing ovary at base; ovary fleshy with 2 collateral ovules in each locule, stigma funnelform or 2-lobed, lobes equally inserted or superposed. Capsules estipitate, with expanded seed-bearing portion at base, apically prominently rostrate, retinacula lacking; seeds 4, 2 in each locule, semiglobose to ovoid, with a prominent pore or flattened (ventral) side, verrucose or smooth.
Africa present, Asia present, Guianas cultivated, tropical and subtropical regions of America cultivated
A paleotropical genus of approximately 90 species found in Asia and Africa. Five species are commonly cultivated in the tropical and subtropical regions of America, some of them existing as escapes; 4 species in the Guianas.