This genus is closely related to Calamagrostis Adans.. Confusion between the two genera in the past was due to the attempt to apply artificial characters in delineating them, e.g. the degree of prolongation of the rhachilla. The unsatisfactory nature of these characters has been emphasized by J. D. Hooker (FI. Br. Ind. 7 : 265. 1896). Miss J. W. Vickery (Contr. N. S. Wales Nat. Herb. /, 2 : 46. 1940) was the first to study the character of the lemma, which is indurate and more or less densely scabrous in Deyeuxia, very thin and hyaline in Calamagrostis. Besides, the species of Calamagrostis have very long, narrow, acuminate glumes with a relatively short lemma and the hairs of the callus usually much exceed the lemma. The species of Deyeuxia have relatively shorter and broader glumes, less clearly exceeding or even distinctly shorter than the lemma; the callus hairs are much shorter than or rarely as long as the lemma. With one exception the species of Calamagrostis occur on the northern hemisphere, while those of Deyeuxia occur in both hemispheres.