What is the scientific name for nasturtiums?

Nasturtium is a plant genus of the cabbage family, with five species, known as "Watercress." Nasturtium is not to be confused with Tropaeolum, a genus of perennial flowers that are commonly known by that name (there are about 80 species of Tropaeolum). Nasturtium is also sometimes confused with Rorippa, a similar genus in the cabbage family, that was, for some time, believed to be the same as Nasturtium.