8. Hydrilla Richard, Memoires de la Classe des Sciences Mathematiques et Physiques de L'Institut National de France. 12(2): 9, 61, 73, plate 2a--k. 1814.
[Greek hydr-, water, and -illa, diminutive]
Plants perennial, of fresh or brackish waters. Rhizomes present, stolons absent. Erect stems rooted in substrate, branched or unbranched, elongate. Leaves cauline, whorled, 3--8 per node, submersed, sessile; blade linear, rarely slightly elliptic, base tapering to stem, apex acute; midvein without lacunae along side(s), blade uniform in color throughout; abaxial surface ly with prickles along midvein, without aerenchyma; intravaginal squamules fringed with orange-brown hairs. Inflorescences 1-flowered, sessile to subsessile; spathe not winged. Flowers unisexual, staminate and pistillate on different plants or on same plants, submersed, sessile; petals whitish to reddish. Staminate flowers: filaments distinct, released under water, rising to surface; anthers oval; pollen in monads; . pPistillate flowers: ovary 1-locular; floral tube long, styles 1, not 2-fid. Fruits linear, cylindric, smooth or with simple spiny processes, indehiscent. Seeds cylindric, glabrous.
Species 1: introduced, North America; Central America, South America, Eurasia, Africa, Australia.
SELECTED REFERENCES
Allen, G. E. 1976. Investigations and current status of insect enemies as biological control agents of aquatic weeds. In: C. K. Varshney and J. Rzóska, eds. 1976. Aquatic Weeds in South East Asia. The Hague. Austin, D. 1978. Exotic plants and their effects in southeastern Florida. Environm. Conserv. 5: 25--34. Blackburn, R. D. and L. W. Weldon. 1970. Control of Hydrilla verticillata. Hyacinth Control J. 8: 4--9. Cook, C. D. K. and R. Lüönd. 1982b. A revision of the genus Hydrilla (Hydrocharitaceae). Aquatic Bot. 13: 485--504. Lakshmanan, C. 1951. A note on the occurrence of turions in Hydrilla verticillata Presl. J. Bombay Nat. Hist. Soc. 49: 802--804. Shireman, J. V. , and M. J. Maceina. 1981. The utilization of grass carp, Ctenopharyngodon idella Val., for Hydrilla control in Lake Baldwin, Florida. J. Fish Biol. 19: 629--636. Tarver, D. P., J. A. Rodgers, M. J. Mahler, and R. L. Lazor. 1978. Aquatic and Wetland Plants of Florida. Tallahassee.
