Distribution
Netherlands, Ukraine

Native to: Algeria, Altay, Austria, Baltic States, Belarus, Belgium, Bulgaria, Central European Rus, Czechoslovakia, Denmark, East European Russia, Finland, France, Germany, Great Britain, Greece, Hungary, Ireland, Irkutsk, Italy, Kazakhstan, Krasnoyarsk, Krym, Morocco, Netherlands, North Caucasus, North European Russi, Northwest European R, Norway, Palestine, Poland, Portugal, Romania, South European Russi, Spain, Sweden, Switzerland, Transcaucasus, Turkey, Turkey-in-Europe, Ukraine, West Siberia, Yugoslavia.
Introduced into: Michigan, New Jersey, New York, Ontario, Québec, Vermont, West Himalaya.

Herbs, to 20 cm. Rhizomes absent; stolon buds with 1 root. Leaves floating or, in dense vegetation, emergent; blade 1.2-6 x 1.3-6.3 cm; primary veins forming 75-90° angle with midvein, broadly curving, aerenchyma confined to midvein region (not margin to margin as in Limnobium), individual aerenchyma space (located ca. 1 mm from either side of midvein) 0.1-0.5 mm across its longest axis, 0.1-0.5 mm wide, 1 mm from midvein. Flowers: staminate flowers 1-5 in each spathe; pedicel to 4 cm; stamens 9-12 in 4 whorls; filaments basally not obviously connate; pistillate flowers solitary; pedicels to 9 cm; styles 2-fid for less than ½ length. Seeds 1-1.3 mm. 2n = 28 (Netherlands).
Flowering spring-fall. Ponds, bays of rivers; 10-50 m.