Armed or unarmed herbs or shrubs. Leaves petiolate to almost sessile, simple, entire, cystoliths present on both sides. Flowers often large and showy yellow, blue-purple or white, in axillary or terminal spikes; bracts entire or serrate, often spinescent or ciliate rarely absent; bracteoles linear or absent. Calyx deeply 4-lobed; lobes imbricate, unequal, narrow, occasionally spit tipped. Corolla infundibuliform or salver-shaped; tube slender, straight incurved; limb subequally 5-lobed or obscurely 2-lipped, upper lip 4-lobe lobes patent, imbricate, rounded or ovate. Stamens 4, all fertile and ± exserted, or 2 posterior ones staminodial and partly sterile or absent, anthers dithecous, oblong, muticous, emucronate. Ovary oblong-conical, 2 or 4-ovuled; style thickened at apex; stigma minutely 2-id or entire. Capsule ovoid-oblong elliptic-obovoid, flattened, ± stipitate, pointed above, seminiferous below the middle, 2 or 4-seeded. Seeds flat, ovate or orbiculate, covered with hygroscopic hairs, rarely glabrous, on hooked funicles.