Plant 30-60 cm. Petioles of emergent leaves to 50 cm; middle lobe of lamina to 12 cm, ± narrowly sagittate, lobes shorter or only somewhat longer than rest of lamina, apex and lobes acute; ovate floating leaves and linear submerged leaves, 1-1.5 cm broad, may occur in deep water. Pedicels usually c. 2 cm in male flowers, less than 1 cm in female flowers. Sepals 5-7 mm. Petals white, usually with a purple spot at base, c. 10 mm, obtuse at apex. Anthers elliptic, 1-1.5 mm, purple. Achenes c. 5 mm, beak c. 1 mm. Fl. 6-9. Lake and river shores, marshes, usually in water, s.I.-1700 m.