Herb, erect about 1 m high; stem and branches 4-6 angled, glabrous or pubescent; leaves opposite or 3-nately whorled, lanceolate or elliptic, width variable, apex obtuse, margins serrate; shortly petiolate; flowers small, white, yellow or blue, solitary or few in axillary clusters; pedicels long, slender; bract minute; bracteoles absent; sepals 4, narrow, oblong, acute or subacute, entire, 3-5 nerved; corolla white, rotate, pilose, tube very short, lobes subequal, obtuse, throat densely bearded; stamens 4, subequal, filaments filiform; anthers sagitate, cells distinct, parallel or divergent; ovary 2-celled; style slightly clavate towards apex; stigma truncate or notched, ovules many; capsules subglobose, globose or ovoid, septicidal, valves entire, membranous, margins inflexed, separating from the placentiferous axis; seeds many, obovoid, angled.