Perennial monoecious aquatic herb. Stems 0.3–2 m long, much-branched. Leaves in whorls of 3–5; submerged leaves ovate, pectinate, with 16–20 pinnae, the lamina 1.2–2 cm long; emergent leaves alternate towards apex, oblong to ovate, entire, glaucous, sometimes red-purple, the lamina 6.5–8 mm long. Bracteoles linear, 0.7–0.9 mm long. Flowers 4-merous, sessile, solitary. Male flowers: sepals deltoid, 0.15 mm long; petals 2.1–2.6 mm long, caducous, yellow to reddish; stamens 8. Female flowers: sepals absent; 4-locular; petals vestigial; styles clavate; stigmas red. Fruit shortly cylindrical, olive-brown; mericarps cylindrical to subfusiform, 1.4–1.5 mm long, rounded and densely spinulose, with a short erect oblique collar at apex.
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