Herbs annual, biennial [or perennial]. Roots slender, fibrous. Stems subquadrangular. Flowers terminal, solitary, 4-merous; flower bud slightly flattened, 4-angled. Calyx tubular-campanulate, with triangular discontinuous intracalycular membranes, 2 outer calyx lobes narrower than and basally overlapping 2 inner lobes. Corolla tubular-campanulate to funnelform, lobes frequently toothed to fringed, plicae absent. Nectaries on corolla tube. Stamens inserted on corolla tube; anthers yellow. Capsules 2-valved, many seeded. Seeds angular-papillate.