Erect herbs, sometimes woody at base. Leaves sessile to petiolate, blade 0.8-17 cm long; 3-veined. Inflorescences terminal, either diffuse panicles or cymes, dichasial; bracts and bracteoles leaf-like or scale-like (bracts leaf-like, floral bracteoles scale-like). Flowers pedicellate, 4-5-merous, actinomorphic; calyx fused for 1/2-3/4 of total length, coriaceous, campanulate, lobes elliptic to triangular, with a low dorsal keel, thickened, apex abruptly acute to acuminate; corolla bud apex tapering; corolla fused for 1/2-2/3 of total length, thin, narrowly funnel-shaped, 30-65 mm long; androecium zygomorphic with stamens and style bent towards bottom of corolla mouth; stamens inserted in lower half of corolla tube, of unequal length, anthers linear to oblong, without sterile appendages; pollen in polyads; pistil without(?) a disk (C. bella), stigma bilamellate. Fruit a capsule, with persistent calyx and corolla; seeds irregular to rounded, sometimes flattened, testa pattern cupuliform and concave (C. imthurniana).