Nomenclatural notes on Cyperus retrorsus Chapm. and 'Cyperus retroversus Chapm.' (Cyperaceae), including a lectotypification

Cyperus retrorsus Chapm. is common and widespread in the southeastern United States. Although authors have indicated the existence of types at NY and US, none has ever been specifically designated as such. A lectotype at US and an isolectotype at NY are herein designated, and ambiguity resulting from A.W. Chapman's use of both C. retrorsus and “C. retroversus” for the same species is discussed.