Annual, semiaquatic herb; stem, upright, hardly reaching 50 cm, sticky-hairs; leaves shortly petioled, opposite, simple, ovate-lanceolate, about 4-6 cm long, pointed at the tip, more or less rounded at the base, entire, covered with sticky hairs; flowers bisexual, actinomorphic, pentamerous, shortly stalked,1-2 in axil of the leaves; calyx tube short, free, persistent, sepals 4-6, united at the base, glandular hairy; petals 4-6, free, unequal, purple, inserted near the top of calyx tube; stamens usually twice as many as the petals, inserted on the calyx tube; ovary 2-6 celled, superior with a curved gland at its base, ovules many, placenta axile; fruit dehiscent capsules, globose to oblong, many seeded; seeds flattened, brown seeds.