or on stolons from the rhizome. Most species, however, persist by perennial creeping rhizomes. In some cases the turions are the only means to differentiate species.

The leaves are alternate, which contrasts with the closely related genus Groenlandia, where the leaves are opposite or whorled. In many species, all the leaves are submerged, and in these cases, they are typically thin and translucent. Some species, especially in ponds and