Heteranthera callifolia Rchb. ex Kunth

Somewhat fleshy, creeping aquatic herbs up to c. 0.3 m tall, rooting at nodes, roots densely covered with short rootlets; exposed parts dying back in dry season, rhizomes probably perennial. Leaves with erect, hollow petioles up to c. 200 mm long, and cordate, floating blades c. 50 mm long; old leaf-sheaths purple-tinged. Spikes up to 10-flowered, minutely glandular-pubescent, just raised above water. Normal flowers subregular; perianth-tube c. 10 mm long, lobes 6, more or less equal, narrowly ovate, 5 mm long, white, blue, mauve or violet. Stamens exserted from tube placed on anterior side; filaments inserted on tube, white or blue; anthers yellow, reflexed, dorsifixed near base. Ovary ovoid; style deflected to one side, short; stigma small. Capsule cylindrical, apiculate, c. 10 mm long, ensheathed by accrescent perianth-tube; walls disintegrating at maturity; seeds typical. Cleistogamous flower solitary, hidden inside spathe of spike, which in turn is subtended by leaf-sheath. Capsule c. 15 mm long, larger and with more seeds than in that of normal flowers. Buds in lower leaf-axils occasionally forming vegetative shoots.