2. Limnobium Richard, Memoires de la Classe des Sciences Mathematiques et Physiques de L'Institut National de France. 12(2): 66. 1814.
American frog-bit [Greek limnobios, living in pools]
Plants perennial, of fresh waters. Rhizomes absent; stolons floating on or suspended in water, rooted or not, unbranched, short. Leaves basal, emergent or floating, petiolate; blade elliptic to orbiculate, base reniform or cordate, apex obtuse to acuminate; midvein without rows of lacunae along sides, blade uniform in color throughout, abaxially surface without prickles, smooth on emergent leaves or with aerenchymous tissue on floating leaves; intravaginal squamules entire. Inflorescences cymose, sessile or short-pedunculate; spathe not winged. Flowers unisexual, staminate and pistillate on same plants, emersed, pedicellate; petals greenish white to yellowish. Staminate flowers: filaments connate at least ½ their length; anthers elongate; pollen in monads. Pistillate flowers: ovary 1-locular, falsely 6--9-locular; styles 3--9, 2-fid nearly to base. Fruits ellipsoid to spheric, smooth to ridged, dehiscing irregularly. Seeds ellipsoid, echinate, covered with blunt cylindric hairs.
Species 2 (1 in the flora): North America, Central America, South America.
SELECTED REFERENCES
Cook, C. D. K. , and K. Urmi-König. 1983. A revision of the genus Limnobium including Hydromystria (Hydrocharitaceae). Aquatic Bot. 17: 1--27. Díaz-Miranda, D., D. Philcox, and P. Denny. 1981. Taxonomic clarification of Limnobium Rich. and Hydromystria G. W. F. Meyer (Hydrocharitaceae). Bot. J. Linn. Soc. 83: 311--323. Hunziker, A. T. 1981. Hydromystria laevigata (Hydrocharitaceae) en el centro de Argentina. Lorentzia 4: 5--8. Hunziker, A. T. 1982. Observaciones biológicas y taxonómicas sobre Hydromystria laevigata (Hydrocharitaceae). Taxon 31: 472--477. Wilder, G. J. 1974. Symmetry and development of Limnobium spongia (Hydrocharitaceae). Amer. J. Bot. 61: 624--642.
