A large family, mainly of herbs and undershrubs in the tropics and subtropics, and particularly prominent in West Africa in forest undergrowth. Members of the family have opposite exstipulate leaves and lack latex. The leaves are generally shortly petiolate or sessile, and long-cuneate. The inflorescences are often conspicuous; either dense cone-like spikes with prominent overlapping, sometimes forked (or papery – Rungia), bracts from between which the flowers appear (Sell, 1969b), or lax and panicle like. The flowers are zygomorphic, with two or four stamens and a two-celled ovary developing into a characteristic capsule.

Introduced species occur as a rule only in gardens. The most prominent are the Indian Thunbergia grandiflora and T. laurifolia, with blue flowers (the former sometimes with white flowers), and T. alata, with winged petioles and yellow-to-reddish flowers with a dark ‘eye’. Two Barleria spp. have also been introduced.

Several genera contain only, or at least some, prickly species, the prickles often needle like. Crossandra, with prickle-edged bracts and pale flowers, and Acanthus, with prickly leaves as well, occur in forest, while Diclipera verticillata (also in Gambia) is a red-flowered savanna herb, the only one in the genus with a spine at the tip of each bracteole.

Lepidagathis collina is a yellow-flowered savanna herb which can grow as a pyrophyte. When it does so, its globular inflorescences resemble burrs, up to 4 cm Ø, the needle-like tips of the bracts (there are no bracteoles) sticking out all round.