They are herbaceous plants, or shrubs. It has an erect, branched stem, without scaly rhizomes. The leaves are arranged in the opposite way. The inflorescences are axillary, in
cymes or solitary flowers. The
corolla is red, orange or yellow, in the form of a long tube, which is broader in the centre. With the base of the extremities and narrow throat. The fruit (or seed capsule) is a dry, ovoid or ellipsoidal bivalve capsule. ==Taxonomy==