AQUATIC PLANTS. A term ajiplicd to many widely distriljuted plants that live either wholly or partlj' in water. Some aquatic plants .have their inllorescence, and even part of their foliage, above the surface of the water; others are in water entirely; still others are attached by roots to the bottom. The algie, which are e.xclusively aquatic, seem adajjted to perform under water all the functions of their life. Aquatic plants are generally of less compact structure than plants belonging to other classes, and are therefore better adapted for rising in their growth toward the surface of the water. But many of them, including some of the alga;, are also provided with air-bladders of consider- able magnitude, as may be seen in some of the cnnunon seaweeds. Some of the more common a<inatic plants are shown in the accompanying plate and deserve brief descriptions.
CUt-Tail (Typhii latifolia) , sometimes called bulrush, grows to the height of five or six feet. Its root-stocks are astringent and diuretic, and abound in starch. Its young shoots are uuich eaten by the Cossacks of the Don, and arc some- times used in England under the name of "Cos- sack asparagus." Its pollen is intlannnable. and has been used as a substitute for lycopodium. LoXG-LE.WEU Po.XDWEED (PoUimoijctoii luci'iis) is one of some 05 species and a number of varieties, included in the genus Potaniogcton, which belongs to the natural order Naiadaceie. The long-leaved pondweed has thin elliptical leaves that lloat on the surface of ponds or slow- streams. It is indigenous to the United States and is foimd from New Brunswick to Washing- ton, and soutli to Florida and California. American Lotu.s (ydumbium liileum), also known as yellow nelumbo, yields edible tubers and seeds. The seeds are sought after by children, and the farinaceous roots are agreeable when boiled. The plant is found as far north as On- tario.
Water Hyacinth {Eichhoniiti ci-asxipcs. or Eichhnniia spcciosn). which belongs to the natu- ral order Pontideriace*. occurs in tropical and subtropical streams of the American continents, being a native of tropical South America, artd 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 h.aving been introduced for the pur- pose of beautifying Saint .John's River, in Flor- ida, they threatened to render navigation on the river an impossibility. 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, bvit even paddle-wheel steamers, cannot penetrate. Such obstructions have develojied 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 extemiinating the nuisance is to spread among the water hyacinths their natural enemies, the water weeds, or water pests (I'hilotria Vanadeitsis) ; further, to disseminate anmng them some virulent disease capable of de- stroying them; and finally, to reconstruct the bridges, so that the mass of obstructing plants may be freely carried out into the ocean.
(^oMMON Arrowhead (Safiittaria snr/itfifolia, or Kagitfaria rariubilis) is a widely distributed, beautiful, white, scentless plant. It is indige- nous to North America, where it extends as far south as Mexico, being found in shallow waters throughout the United States and Canada. The name Arrowhead, or Sagittaria, is extended not only to the common American plant, but to an entire genus of aquatic plants belonging to the natural order Alismacese. 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 unise.x- luil flowers having thrive 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 Sinensis, 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 polj'gonal 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-Lily {Nymphwa 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 Nyniphcea, or Castalia, as well as to plants of the genera Nuphar and Nelumbo, all of which belong to the natural order Nyniphsea- cea-. CJreat Britain produces three species, viz., Nympluea alba (the white water-lily), Nuphar luteum, and Xuphar minimum (j-ellow water-lilies) ; all these have heart-shaped leaves floating on the water, those of the 3'ellow 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 (i/mpli<ra lotus), are farinaceous and are sometimes used as food. The stems of Nuphar luteum are used by the Turks in making a refreshing beverage.
Consult: Britton and Brown, Illustrated Flora of the Northern United States, Canada, and the British Possessions (New York, 1896). The structural characters of aquatic plants are discussed at some length under Hydrophytes. See also Benthos; H.vi,oi'hyte.s; Mangrove Swa.mp ; Plankton ; and Swamp.
A'QUATINT (It. ncqua, Lat. aqua, water + tinta. dyed). A kind of emrraviui; on copper invented in 1700 by .Jean Baptiste Leprince. The process is not unlike that of mezzotint, but produces more rapid results. After the outline of objects has been tiaced, the plate is covered with a Ijvyer of fine sand or powdered rosin, over which the passing of aqua-fortis produces a fine graining, which renders easy an imitation of aquarelles in sejjia, India ink, or umber. The aquatint has been used successfully in pictures as an element of expression, affecting the physiognomy of things by producing shadows, and deepening and spreading color.
