Stems. - Immersed, one to three feet long. Leaves. - Many-parted, hair-like, bearing numerous bladders. Scape. - Six to twelve inches long. Flowers. - Yellow, five to twelve on each scape. Calyx. - Two-lipped. Corolla. - Two-lipped, spurred at the base. Stamens. - Two. Pistil. - One.

This curious water-plant may or may not have roots; in either case it is not fastened to the ground, but is floated by means of the many bladders which are borne on its finely dissected leaves. It is commonly found in ponds and slow streams, flowering throughout the summer. Thoreau calls it "a dirty-conditioned flower, like a sluttish woman with a gaudy yellow bonnet."

The horned bladderwort, U. cornuta, roots in the peat-bogs and sandy swamps. Its large yellow helmet-shaped flowers are very fragrant, less than half a dozen being borne on each scape.