Herbs, to 70 cm. Leaves emersed, petiolate; blade lanceolate, 6--23 ´ 1--4.5 cm. Inflorescences to 70 cm. Flowers chasmogamous; sepals 1.6--3 mm; petals purplish pink, 4.4--6.5 mm, margins ± erose, apex acuminate; anthers ellipsoid, 0.6--1.1 mm; style ± curved, 0.4--0.6 mm, equaling ovary length. Fruiting heads 4--8 mm diam; achenes obovoid, 2--2.9 mm, with 1--2 abaxial grooves, beak erect. 2n = 26, 28 (Eurasian material). Flowering and fruiting summer--fall. Streams and marshes; 0--500 m; introduced; Calif., Oreg. OTHER REFERENCES Baldwin, J. T. and B. M. Speese. 1955. Chromosomes of taxa of the Alismataceae in the range of Gray´s Manual. Amer. J. Bot. 42: 406--411. Brown, W. V. 1946. Cytological studies in the Alismaceae. Bot. Gaz. 108: 262--267. should that be Alismataceae-----ed. Heiser, C. B. and T. W. Whitaker. 1948. Chromosome number, polyploidy and growth habit in California weeds. Amer. J. Bot. 35: 179--186. Löve, Á. and D. Löve. 1981. In: IOPB chromosome number reports LXXII. Taxon 30: 694--708.