U. vulgaris: aquatic; root-like, floating branches, 1/2-1 foot long or more; leaves numerous, capillary, much divided, more or less interspersed with little green vesicles; flower-stems 6-8 inches high, bearing a few rather large yellow flowers, the corolla with a short, conical, more or less curved spur, and a broad convex palate. - Deep pools and water-channels. Fl. June, July.

U. minor differs chiefly in the small size of its parts, the floating branches being very slender, the leaves small, fine, with few forked lobes and few bladders, and the flowers half the size, pale yellow, with a very short spur.