BLADDER-WORT, a submerged water plant, Utricularia vulgaris, with finely divided leaves upon which are small bladders provided with trap-doors which open only inwards. When small crustaceans and other aquatic animals touch the front of the bladder it alters its shape and they are sucked in and are unable to escape. The products of the decay of the organisms thus cap tured are absorbed by star-shaped hairs which line the interior of the bladder. In this way the plant is supplied with additional nitrog enous food. 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 200 species in tropical and temperate regions, some 20 of which occur in North America. (See INSECTIVOROUS PLANTS.)