Annual, diffused or sometime erect herb, 20-30 cm high; branches many, slender, dichotomous; stem 4 angled or winged; leaves opposite, sub-sessile, lanceolate or elliptic, 1-3 cm long, narrowed at both ends, membranous, 3 nerved, upper leaves much smaller than lower ones, transforming into bracts; flowers irregular, in lax, terminal, erect, trichotomous or diffused cymes; pedicels short, slender; calyx 4-toothed, lanceolate, striate, not winged; corolla tube cylindric, lobes-4, asymmetric, as long as the calyx teeth, imbricate in bud; stamens 4, unequal, one longer than other, fertile stamens-3 with ovate or oblong anthers; ovary 1-celled, ovules many; style long, filiform; stigma-2, short, hemispheric, or 2-lobed; capsule cylindric, 2 valved, many seeded, breaking up irregularly; seeds very small, polyhedral, dark brown, reticulated.