Stamens 5, ± equal or unequal, often the uppermost shorter than the other 4 or didynamous, sometimes 4 stamens and 1 staminode, inserted in the corolla tube usually in the distal part, sometimes on the throat, exserted; filaments ± connate at the base forming a tube surrounding the style, free upwards, slender but somewhat expanded towards the base, curved at the apex, ± glabrous or puberulous, sometimes glandular; anthers all fertile or elsewhere one of them occasionally sterile, variously sized, almost circular, elliptic or ovate in outline, straight or slightly curved, embraced by the stigma in bud, attached on the lower part of the back, extrorse, the thecae separated from each other one-third or more of their length at the lower end, dehiscing by longitudinal slits.
Corolla white with a yellow or purple centre, or variously coloured from pink to purple or violet, sometimes bluish, infundibuliform or salviform; tube ± long, slender, nearly or quite straight, the mouth narrow; limb abruptly expanded, broadly campanulate, saucer-shaped or funnel-shaped, often plicate, spreading, slightly unequally 5-lobed; lobes short, broad, obtuse or rounded, with cochlear aestivation.
Ovary stalked to sessile, 2-locular; ovules numerous in each locule on an enlarged placenta adnate to the dorsal line of the dissepiment, anatropous; style slender; stigma reniform, usually enlarged into a laminar, 2-lamellate or crescent-shaped process between or surmounting and usually surrounding the anthers, exserted.
Disk usually fleshy, cupular or annular, adnate to and surrounding the basal part of the ovary, entire or crenulate, occasionally lacking.
Inflorescences consisting of one or occasionally several flowers in terminal or lateral, subpaniculiform, racemiform or subspiciform cymes; pedicels slender, articulated at the base; bracts single, foliaceous.
Leaves solitary, alternate, occasionally in pairs and appearing opposite, sessile to long-petiolate, entire; minor leaves absent.
Calyx tubular to campanulate, ± curved, 10-ribbed, ± deeply 5-lobed; lobes slightly unequal, narrow, ± linear or lanceolate, acuminate, spreading, with valvate aestivation; in fruit somewhat enlarged, enclosing it or not.
Flowers often showy, actinomorphic or slightly zygomorphic.
Herbs or sometimes small shrubs, prostrate to erect, occasionally forming mats, ± glabrous to densely clothed with eglandular and also glandular, sometimes viscid hairs; rhizomatous structures sometimes present.
Fruit capsular, ovoid, membranous, 2-locular, with a central placenta ultimately detaching at the top, apically dehiscing by 2 septicidal slits, the 2 dry valves often 2-fid.
Seeds numerous, minute, scarcely compressed, 3-gonous, ovate or ± elliptic in outline; testa somewhat leathery; embryo subterete, straight or slightly curved, in the dorsal part of the fleshy endosperm; cotyledons usually broad, subcompressed.