Nasturtium gambellii (syn. Rorippa gambellii) is a rare species of flowering plant in the mustard family known by the common names Gambel's yellowcress and Gambel's watercress. It is known from three or four scattered occurrences in California. It has been reported to exist in central Mexico and Guatemala, but these reports remain unconfirmed and in need of further investigation. Its total U. S. population was last estimated at fewer than 300 individuals. It was federally listed as an endangered species of the United States in 1993. Some sources spell the epithet with a single "l" as "gambelii," others with a double "ll" as "gambellii. " Watson, in the original 1876 publication, spelled it with a double "l" and stated that it was named after "Gambell," collector of the type specimen. The collector was in fact William Gambel. Section 60. 7 of the ICN states that such errors in the spelling of personal names is to be corrected only in the case of the omission of the final letter of the person's name. This is not what happened here. Watson added an extra letter rather than deleting a letter. Hence Watson's error must stand uncorrected in the scientific epithet, though no such rules apply to the common name.