Hydrocera triflora (L.) Wight. & Arn.

Plants perennial, hydrophytic, glabrous. Stem erect, to 1 m tall, fleshy, many branched; underwater part white, ca. 4 mm in diam., with fibrous roots; above water part green, often pink-tinged. Leaves alternate, sessile or shortly petiolate, with 1 pair of sessile basal glands; leaf blade pale green abaxially, dark green adaxially, linear or linear-lanceolate, 10-20 × 0.6-1.5 cm, lateral veins 10-17 pairs, base cuneate, margin serrate, apex acute or acuminate. Racemes 3-5-flowered; peduncles 0.7-1.6 cm. Pedicel 1.2-3 cm, slender, bracteate at base; bracts caducous, lanceolate, 6-9 mm, apex acute or acuminate. Flowers pink or yellowish. Lateral sepals 4; outer 2: 1.2-1.5 × ca. 0.8 cm, apex slightly acute or obtuse; inner 2: 1-1.5 × ca. 1.2 cm,
apex obtuse. Lower sepal navicular, 1.5-2 cm deep, mouth vertical, abruptly constricted into an incurved spur; spur 6-8 mm. Upper petal subcucullate, obovate, 1.5-1.9 × 1.2-1.5 cm, apex mucronulate; lateral petals 4, all free; upper 2 elliptic to elliptic-obovate, 1.3-1.5 cm × 7-9 mm; lower 2 narrowly oblong, 2-2.5 cm × 6-8 mm, apex slightly obtuse. Stamens 5, 0.9-1.1 cm; anthers obtuse. Ovary glabrous. Fruit purple-red at maturity, globose, 0.8-1 cm. Seeds 1 per locule, rugose. Fl. and fr. Sep-Nov. 2n = 16.

S Hainan (Lingshui, Sanya) [Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, Sri Lanka, Thailand, Vietnam].

Lakesides, swamps, wetlands, rice fields; ca. 100 m.

Impatiens triflora Linnaeus, Sp. Pl. 2: 938. 1753; Hydrocera angustifolia (Blume) Blume; I. angustifolia Blume; I. natans Willdenow; Tytonia natans (Willdenow) G. Don; T. triflora (Linnaeus) C. E. Wood.