BLADDER-WORT, the name given to a submerged water plant, Utricularia vulgaris, with finely divided leaves upon which are borne small bladders provided with trap-door entrances which open only inwards. Small crustaceans and other aquatic animals push their way into the bladders and are unable to escape. The products of the decay of the organisms thus captured are absorbed into the plant by star-shaped hairs which line the interior of the bladder. In this way the plant is supplied with nitrogenous food from the animal kingdom. Bladder-wort bears small, yellow, two-lipped flowers on a stem which rises above the surface of the water. It is found in pools and ditches in the British Isles, and is widely distributed in the north temperate zone. The genus contains about two hundred species in tropical and temperate regions.
A, Bladder of Utricularia neglecta (after Darwin), enlarged.
B, stellate hairs from interior of bladder of U. vulgaris.