Herbaceous or shrubby, pubescent or glabrous climbers, rarely erect. Leaves petiolate, simple, opposite, ovate to lanceolate, cordate or hastate, acute to acuminate. Flowers pedicellate, mostly large and showy, blue, yellow, or white, solitary-axillary or in terminal racemes; bracts 2, large, foliaceous, ovate or lanceolate; bracteoles 2, spathe-like, enveloping calyx, mostly persistent. Calyx cup-like, with 10-16 subulate teeth or reduced to a rim. Corolla infundibuliform, tube incurved or oblique, widened above, limb patent, 5-lobed, lobes subequal, obtuse or truncate, contorted in bud. Stamens 4, all fertile, didynamous, inserted near the base of corolla tube; anthers bithecous, thecae oblong or ovoid, parallel, ± unequal, connective apiculate, pollen spheroidal, spirotreme. Ovary fleshy, globose, bilocular, each locule with 2 collateral ovules; style long, stout; stigma bifid, entire or fringed; Disc shortly annular or pulvinate. Capsule globose below, abruptly beaked in upper part, 4-seeded, loculicidally dehiscent. Seeds semiglobose to ovoid, glabrous, funicle papilla-like, retinacula absent.