A rather small family, widely distributed, growing in fresh-water swamps and streams. The leaves are all from the root, with long sheathing leaf-stalks, and the flowers are regular and perfect, or with only pistils or only stamens; the sepals three; the petals three; the stamens six or more; the ovaries numerous, superior, developing into dry, one-seeded nutlets.

There are a good many kinds of Sagittaria, with fibrous roots and milky juice; the leaves are usually arrow-shaped; the lower flowers usually pistillate and the upper ones usually staminate; the stamens are numerous and the numerous ovaries are closely crowded and form roundish heads. The name is from the Latin for "arrow," referring to the shape of the leaves.