is a small floating fern housing blue-green algae in its leaves. These
algae are capable of absorbing nitrogen from the air, which can then be
used by the plant. A. caroliniana has become a menace all over
the tropics, because it covers lakes and deprives the original aquatic
plants of light. Used as nitrogen fertiliser in rice paddies, and as
animal feed. There are several related varieties on the market, with
similar appearance. A decorative plant for open aquariums.