Annual or perennial, unarmed or spinous, bitter herbs or undershrubs, often glandular-hairy. Stem terete, farctate, with a peripheral whorl of air-vessels. Leaves spread, simple, entire, exstipulate. Flowers ♀, actinomorphic, solitary, opposite or between the leaves, or by stunting of the leaves, more or less arranged in a racemiform or paniculiform inflorescence, distinctly pedicelled, lilac blue. Calyx persistent, 5-partite to near the base, segments lanceolate, imbricate in bud, after anthesis not or hardly accrescent. Corolla gamopetalous, deeply 5-partite; limb rotate; segments imbricate in bud, oval, obtuse. Stamens 5, free, inserted in the throat of the corolla, alternating with the segments; filaments filiform from a broadened base,...