The Misconstrued and Rare Species of Commelina (Commelinaceae) in the Eastern United States

Five species of Commelina (Commelinaceae), all introduced in the eastern United States, are reviewed and discussed. The widespread but overlooked C. caroliniana is contrasted with the more common C. diffusa, and the species are found to be distinguished best by their seeds. Commelina gigas is determined to be a polyploid of C. diffusa, and the new combination C. diffusa var. gigas is made. Variety gigas is considered likely to have been separately introduced. Commelina benghalensis probably became naturalized in Florida early this century. Of the two recently discovered species, C. forskaolii is known from a single Florida population that may have been eradicated, and C. nigritana var. gambiae is becoming well established along roadsides in Florida