Cenchrus longispinus (Poaceae), a new record from coastal sands of Caspian Sea (N Iran)

In the framework of collection and determination of coastal sand dune plants of S Caspian Sea in Gilan and Mazandaran provinces (N Iran), a new species of the family Poaceae, Cenchrus longispinus (Hack.) Fernald, was determined in coastline of Babolsar, Mazandaran. Cenchrus longispinus is closely resembles C. spinifex and C. echinatus. From the latter it is best distinguished by the absence of a basal ring of numerous flexible, retrorsely barbellate bristles. However, most problematic is the distinction of C. longispinus and C. spinifex. Cenchrus longispinus always has more spines, the inner being terete to slightly flattened and the outer (lowermost) often bristle-like and relatively slender.