WATER HYACINTH (Eichhornia erassipes, or Eichhorniu speciosa), which belongs to the natu ral order Pontideriacem. occurs in tropical and subtropical streams of the American emitinents, being a native of tropical South America, and is widely cultivated in Europe. It is capable of growing on marshy banks. but attains a much larger size when floating on the water, as it usu ally does, without being attached to the bottom. The rosettes formed by its leaves above the sur face of the water are sometimes no less than two feet high. The rapidity with which they multi ply may be seen from the fact that, within a few years after having been introduced for the pur pose of beautifying Saint John's River, in Flor ida, they threatened to render navigation on the river an impogsfibility. Great masses of these plants accumulate along the shores and are often driven by wind and current until they form ob structions extending over the entire breadth of the river, and through which not only small boats, but even paddle-wheel steamers, cannot penetrate. Such obstructions have developed in northern South America, and, as already stated, on Saint John's River and its tributaries in Florida. An agent of the United States De partment of Agriculture, who undertook, in 1897, to investigate the danger thus caused to naviga tion in Florida, came to the conclusion that per haps the best way of exterminating the nuisance is to spread among the water hyacinths their natural enemies, the water weeds, or water pests (Philotria Canadensis); further, to disseminate among them collie virulent disease capable of de stroying theni; and finally, to reconstruct the bridges, so that the mass of obstructing plants may be freely carried out into the ocean.
CoNtmorr ARROWHEAD (Nagillaria sagittifolia, or Sagittaria rariabilis) is a widely distributed, beautiful, white, scentless plant. It is indige nous to North America, where it extends as far south as Xlexico, being found in shallow waters throughout the United States and Canada. The name Arrowlmad, or Sagittaria, is extended not only to the common Amerivan plant, but to an entire genus of aquatic plants belonging to the natural order Alismacem. The generic name of
these plants refers to the shape of their leaves. The plants include natives of both cold and warm climates, and are distinguished by unisex ual flowers having three herbaceous sepals and three colored petals, with numerous stamens and carpels. This species is also a native of Europe and Asia. The Chinese arrowhead, Sagittaria k4inenSiS, has long been cultivated in China and Japan for its edible corms, which abound in starch. It is grown in ditches and in ponds, and has arrow-shaped, acute leaves and a branched polygonal scape (leafless stem). A large num ber of species and varieties of arrowhead are native in American waters, and fossil forms of the genus have been recognized in the Tertiary rocks of northern and middle Europe.
WATER-Lux (Nympha'a odorata), often called the "sweet-scented water-lily," has a large white flower of great beauty and of very sweet smell. Its home is North America. Besides this plant, the name water-lily is commonly applied to other species of Nympluea, or Castalia, as well as to plants of the genera Nuphar and Nelumbo, all of which belong to the natural order Nympluea cem. Great Britain produces three species, viz., Nymplara alba (the white water-lily), Nuphar luteunt, and Nuphar minimum (yellow water lilies) ; all these have heart-shaped leaves float ing on the water, those of the yellow lilies being raised by the stalks a little above the surface. The seeds of these species, as well as those of the water-lily of the Nile (Nymphaw lotus), are farinaceous and are sometimes used as food. The stems of Nuphar lutetun are used by the, Turks in making a refreshing beverage.
Consult: Britton and Brown, Illustrated Flora of the Northern United Stutes, Canada, and the 13ritish Possessions (New York, 1896). The structural characters of aquatic plants are discussed at some length under HYDROPHYTES. See also BENTHOS; HALOPHYTES; MANGROVE SWAMP; PLANKTON; and