Seeds longitudinally ribbed. Turions produced or not. S. polyrhiza Spirodela intermedia W. Koch, Ber. S. biperforata W. Koch. Roots to at least 1.5 cm long.
Fronds broadly obovate to subreniform, ca.
Turions not produced. Pan. to Arg. The geographic ranges of the largely South Amer. S. intermedia and the more northern S. polyrhiza overlap in Central Amer. The two spp. are only weakly distinguished.