Deyeuxia Clar. ex P. Beauv.
Tufted perennials. Leaf-blades flat or convolute. Panicle usually rather narrow and dense. Spikelets linear to lanceolate, acuminate; rhachilla disarticulating above the glumes, prolonged or not; glumes persistent, sub-equal or unequal, linear-lanceolate to lanceolate, firmly membranous, keeled above, acute, the lower 1-nerved, the upper 1-3-nerved; lemma lanceolate to oblong, shorter than the glumes, hyaline or firmly membranous, smooth or scabrid, 3-5-nerved, truncate-denticulate or ± bifid with the lobes acute or toothed, awned from the back or from the sinus of the lobes or from the tip; awn short, fine, straight or twisted below; callus bearded with white hairs shorter than to much longer than the floret; palea as long as the lemma or shorter.
A genus of ± 280 species in temperate regions throughout the world; 8 species occur in Pakistan.
The traditional characters for separating Calamagrostis and Deyeuxia (the latter is said to have a scabrid lemma and penicillate rhachilla extension) are unreliable in Eurasia, and the modern view (Tzvelev 1976, Clarke 1980) is that they are insufficient to warrant the recognition of more than one genus (but see Vickery in Contr. N.S.W. natn. Herb. 1(2): 43-45. 1940 for an alternative view).
The taxonomic value of the rhachilla extension is over-rated in Calamagrostis since it can be present or absent in several species. Calamagrostis garhwalensis Hubbard & Bor was distinguished from species 1-3 in this account on the basis of its prolonged rhachilla. In fact each of the other species shows a prolongation to some degree in some specimens, and all Pakistani material named by Bor as Calamagrostis garhwalensis can be comfortably accommodated in one or another of these species. The type specimen, however, has not yet been seen, so the name does not appear in synonymy.
Calamagrostis munroi Boiss., with a dense narrow panicle, occurs in Afghanistan in the Kurram Valley, but it does not appear to have penetrated into Pakistan.