Roegneria: its generic limits and justification for its recognition

We document diagnostic characteristics of Roegneria by which it differs from genera with which it has often been confused. Characteristics of Roegneria are the absence of underground runners; slightly curved and elongated rachis with long internodes, each rachis node bearing one spikelet only and often adhering to the internode, and inflorescence appearing more or less one sided because of the disposition of the spikelets; spikelet functionally disarticulating below the glumes; glume symmetric with nerves tapering in the apex; lemma with nerves tapering in the apex; and palea generally shorter than the lemma, and if equal to the lemma then the tip obtuse, truncate, or retuse. Genera difficult to separate from Roegneria are Agropyron, Elymus, and Elytrigia; these share one or more characteristics but none have them in the same combination. We also stress the merit of recognizing Roegneria for germ-plasm utilization.