Description from Flora of China
Didactylon Zollinger & Moritzi; Haplachne Presl; Psilostachys Steudel; Pterygostachyum Nees ex Steudel.
Annual or perennial. Culms often delicate, erect to decumbent, nodes bearded, the hairs directed upward. Leaf blades linear; ligule short, membranous. Inflorescence terminal, composed of solitary or subdigitate racemes. Racemes 1-sided, spikelets single, shortly pedicelled, usually overlapping in 2 rows; rachis tough, triquetrous or flattened, spikelets disarticulating from pedicels at maturity; pedicels very short, broad, apex concave, margin truncate. Spikelets lanceolate or narrowly oblong, strongly laterally compressed; callus truncate, shortly bearded; glumes herbaceous or thinly papery, folded with a median keel, keel often winged, lower glume narrower and slightly shorter than upper glume; lower floret reduced to a narrow hyaline lemma; upper floret bisexual, lemma hyaline, a little shorter than upper glume, apex shortly 2-toothed, awned from sinus; awn geniculate, sometimes weakly or almost straight, glabrous; upper palea normally absent. Stamens 2. Caryopsis narrowly oblong, laterally compressed.
About 40 species: India, China, and Japan to Indonesia, the Philippines, and Australia; six species (three endemic) in China.
(Authors: Chen Shouliang (陈守良); Sylvia M. Phillips)