Annual or perennial, herbaceous, erect, unarmed; stem 4-angled; leaves opposite, subsessile, glabrous, mid vein with white hairs, elliptic, entire, obtuse at apex; flowers bluish purple, sessile in axillary whorls at the nodes; bract foliaceous elliptic; bracteoles oblong, obtuse, strigose, shorter than calyx, hairy on margin, calyx lobes-5, equal, tubular, linear, acuminate, hispid; corolla bilabiate, nearly glabrous, dilated above, lobes subequal, twisted to left in bud, upper lip 3 lobed, lower lip 2 lobed, dark violet, spotted with yellow on throat, sometimes hairy; stamens 4, didynamous, exserted, adnate to the throat, posterior pair sometimes smaller or rudimentery, filament glabrous, anthers cells 2, equal, oblong, basifixed; ovary oblong, much exceeding the calyx tip hairy; style slender, filiform, hairy; stigma simple linear; capsule narrow, oblong, bearing the seeds throughout; seeds usually many, white, ovoid, compressed.