Aquatic Plants

Collier's New Encyclopedia (1921)

plants growing in or belonging to water. The presence of water is not only essential to the active life of all organisms, but is peculiarly necessary for plants which are for the most part dependent for food supply on matter dissolved in water, as well as on the carbonic anhydride mingled with Numerous plants are, moreover, in the strict sense of the word aquatic, having never acquired or having lost all direct connection with the soil. The simplest plants or algæ are almost all aquatic, though many occur in damp situations on land, or on other organisms, while others remain for long periods quiescent in comparative dryness. Many algæ are absolutely isolated in the water, while others are more or less intimately fixed to some solid substratum. such Some rhizocarps, as salvinia, are aquatic, with leaves rising to the surface, while others are land or marsh plants, like the higher horse-tails and club-mosses. Among the flowering plants, or phanerogams, a return to aquatic life is exhibited by numerous, though cases, while a very large number grow exceptional in moist situations, and have a semiaquatic habit. The simple monocotyledons, known as helobieæ, or marsh lilies, are more or less strictly water-plants. The arrowhead (sagittaria), and other alismaceæ; the butomis of the marshes; hydrocharis, with floating kidney-shaped leaves; the water soldier (stratiotes), with narrow submerged leaves; and the Canadian pond weed (anacharis). Among dicotyledons, the white water buttercup (ranunculus aquatilis), with its slightly divided floating, and much dissected submerged leaves; the yellow and white water-lilies (nymphæa); the sacred lotus flower of the Ganges and Nile (nelumbium); the gigantic Victoria regia of tropical South America; and the insectivorous bladderwort or utricularia, are among the most familiar aquatic forms.