AQUATIC PLANTS, or WATER PLANTS, are those plants which live entirely in water, or which require a preponderating quantity of water as the medium of their existence. The families of plants, like the families of animals that live in the water, are found to belong to all classes into which the whole have been divided, although those belonging to the lower classes are by far the moat prevalent Many of the families of plants having the highest organisation have members belonging to them which are inhabitants of the water : of this the Ranunculus aquatilis is an example in the natural order Ran:ince/seem All the species of the orders Nympluracem, Callitrichaceir, Cerato phyllacter, and Podostartarece, belonging to the class Exogens, grow in water. Among Endogens, the orders Butomacete, Naiadacea or Fleerialcs, Pistiacar, Alismacea, fie consist entirely of water-plants ; whilst one of the largest of the few families into which Cryptegarnie Plants are divided, the Alga., consists almost entirely of plants which live in the water.
For the purpose of studying the distribution of the vegetable kingdom, water-plants are distributed into several groups. One of the first division that suggests itself in the study of their forma is derived from the composition of the waters in which they grow. Thus we have those which grow in the saline waters of the ocean, and those which grow in the fresh waters inland. Moat of the plants which grow at the bottom of the ocean or float in its waters belong to the family of Alger. [ALGAL] There are however many plants not belonging to this order which require the influence of salt-water on the soil on which they grow for their production. Thus species of the genera &Isola, Anabasis, Salicornia, and Claux will not grow but where they can feel the influence of saltwater: hence they have been called Planta Salinal. These plants are found not only where the sea washes, but wherever salt-springs find their way to the surface of the earth. There is another group of plants which have their
existence determined by saline waters, but are always found near the sea or on the banks of rivers to which the aea has access. Such are species of Chenopodium, Heliotropism, ritex, Eryngium, &motets, and time Mangrove (Rhizophora). These are called Planta Littorates, sea Aloritimae.
The largest proportion of Fresh-Water Plants belong also to the natural order A ter, although by far the moat conspicuous specimens belong to the tribes of Exogenous and Endogenous plants. Aa the pea claims nearly all the species of the genus Facets and its allies, so the fresh-water claims the majority of the species of the old genus Conferra and its allies.
Aquatic Plants, in Horticulture, are those which naturally grow in deep water, and are carefully distinguished by the cultivator from marsh-plants. The management of them, when they are hardy, is of the simplest kind, nothing being necessary beyond planting them in boxes with holes in time sides, and sinking them 3 or 4 feet below the surface of a pond, so that the boxes lie upon or among the mud at the bottom.
Hut for those which demand the protection of the stove or green house, some additional precautions are requisite. If left to them selves in such situations, the uniformity of temperature is such as to deprive them in some measure of the repose that they naturally receive from the alternation of seasons ; kept constantly in a growing state, their excitability is gradually destroyed, and death ensues as a matter of course. The plants which demand special treatment are chiefly those which belong to the natural order Nympluraceer. [Waren-Lttv.] The most beautiful of these is the rictoria regia. Various methods have been recommended ; but they all depend for their success upon keeping in view the principle of periodical rent and rapid growth under a high temperature, with but little air during the season of vegetation.