Pistia stratiotes L. is a widely distributed free-floating perennial hydrophyte ( Sculthorpe, 1967) and one of the world's most troublesome weeds ( Holm et al., 1977). These rapidly growing plants block streams and canals and produce masses of feathery roots which provide shelter and breeding habitat for disease-carrying mosquitoes. On the positive side, the plant offers some potential as feed for livestock and may also find use in bioremediation and basic biochemical research.