Annual or perennial, erect, often tufted, glandular hairy herb; 10-30 cm high, simple or branched, brittle when dry; leaves opposite, coursely membranous, broadly ovate, obtuse, crenate, glandular hairy; lower leaves petiolate, upper one sessile; inflorescence axillary or terminal, 1-many flowered, unilateral, lax racemes; bracts leaf like; bracteoles none; pedicels short; calyx segments 5, ovate, acute, shorter than bract, recurved, glandular hairy; corolla yellow, sparsely hairy, lower lip 3-lobed, spreading, upper lip narrow, base with 2-plaits; stamens-4, didynamous, included; filament filiform; anther cells separate, stipitate, all fertile; ovary 2-celled, ovoid, pubescent, style filiform, stigma simple; capsule ovoid, 2-valved, grooved, loculicidal, separating from the placentiferous axis, hairy above the middle; seeds numerous, minute, ellipsoid.