Coelachyrum Hochst. & Nees in Linnaea. 16:221. 1842. Sultan & Stewart, Grasses W. Pak. 2:247. 1959; Bor, Grasses Burma Ceyl. Ind. Pak. 488. 1960; Bor in Rech.f., Fl. Iran. 70: 435. 1970.
Annuals or perennials, usually stoloniferous; leaf-blades linear to lanceolate, flat; ligule membranous, lacerate or ciliate. Inflorescence either an open panicle or composed of several loose to dense racemes or spikes on a central axis. Spikelets several-flowered, broadly elliptic to ovate, subsessile or pedicelled, disarticulating between the florets; glumes 1-several-nerved, rounded or lightly keeled, subequal to unequal, shorter than the lemmas, persistent; lemmas 3-nerved, elliptic to ovate, rounded on the back, membranous, scarious or herbaceous, glabrous or appressed pilose on the back and glabrous or villous along the lower part of the margins, sometimes also villous along the midnerve, the tip obtuse, sometimes mucronate; palea glabrous or villous along the keels, sometimes pilose on the flaps. Grain broadly elliptic to subrotund, concave on the hilar side, rugose, enclosed within a free hyaline pericarp.
A genus of 6 species from Northeast Africa through Arabia to Pakistan; 1 species occurs in Pakistan.
This genus comprises a rather heterogenous assemblage of semi-desert grasses, placed together mainly on account of the broad rugose concavo-convex grain enclosed within a free pericarp, and the rounded backs of the lemmas. However, the species differ considerably in inflorescence structure and the hairiness of the spikelets. Coelachyrum appears to form a link in some respects between the genera Eragrostis and Eleusine. Those species with a paniculate or loosely racemose inflorescence closely resemble Eragrostis, whereas the rugose grain within a free pericarp indicates affinities with Eleusine, a resemblance particularly marked in those species where the inflorescence-branches are reduced to one-sided spikes.
