Corolla tubular; tube broadly cylindric, wide mouthed, gibbous at base, villous within.
Leaves simple, entire, usually opposite below, becoming alternate above.
Calyx 5-lobed; lobes longer than corolla tube, markedly unequal.
Herbs, annual, simple or branched, glabrous or glandular-pilose.
Flowers zygomorphic in terminal racemes, or solitary-axillary.
Capsule ovoid, gibbous, opening with 2 pores.
Stamens 4, didynamous, included.
Ovary bilocular; ovules many.