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.

Distribution

Introduced; North America, Central America, South America, Eurasia, Africa, Australia.

Discussion

Species 1.

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.

Lower Taxa

Hydrilla verticillata