144. Eustachys Desvaux, Nouv. Bull. Sci. Soc. Philom. Paris. 2: 188. 1810.
真穗草属 zhen sui cao shu
Authors: Bi-xing Sun & Sylvia M. Phillips
Annuals or perennials. Leaf sheaths strongly keeled; leaf blades linear, flat or folded, apex often obtuse; ligule a ciliate rim. Inflorescence digitate; racemes unilateral, slender; spikelets sessile, tightly pectinate-imbricate, biseriate. Spikelets laterally compressed, florets 2, lower floret fertile, upper floret reduced to a small empty lemma, disarticulating above glumes; glumes about as long as florets, broad, membranous, 1-veined; lower glume awnless; upper glume with an oblique, stout, subapical awn; callus pubescent; lemma of fertile floret dark brown, keeled, broad, cartilaginous to leathery, 3-veined, hairy on veins, apex acute to emarginate, awnless or with a fine, subapical awn-point; palea nearly as long as lemma, keels scabrous or ciliolate; upper floret cuneate or obovate, glabrous. Caryopsis ellipsoid, trigonous, pericarp reluctantly free.
Eleven species: tropics and subtropics, mainly in the New World; one species in China.
Eustachys is closely related to Chloris. The chief difference is the broad, subapically awned upper glume. The racemes of brown, very tightly packed spikelets, lacking conspicuous awns, impart a distinctive appearance different from Chloris.