Annual or perennial, viscidly pubescent,
herbs. Leaves alternate or opposite above, entire, softly pubescent. Flowers solitary, axillary, in shades of white, purple or red. Calyx
deeply 5-partite, lobes narrow or often foliaceous. Corolla funnel-shaped or
salver-shaped, tube long, often swollen above, limb normally 5-lobed, lobes
unequal or obscurely 2-lipped. Stamens
attached in corolla tube, one of them being sterile. Ovary 2-locular; stigma indistinctly 2-lobed; ovules numerous.
Fruit a dry, 2-valved capsule.