Microstegium Nees in Lindl., Nat. Syst., ed. 2:447. 1836. Bor, Fl. Assam 5:327. 1940; Bor in Kew Bull. 7:209. 1952; Sultan & Stewart, Grasses W: Pak. 1:81. 1958; Bor, Grasses Burma Ceyl. Ind. Pak. 192. 1960; Bor in Rech. f., Fl. Iran. 70:520. 1970; Tzvelev, Poaceae URSS 694. 1976.
Rambling perennials, or sometimes annuals. Leaf-blades linear to lanceolate, narrowed at the base and often with a short false petiole; ligule short, scarious. Inflorescence terminal, comprising up to 25 subdigitate racemes, these rarely solitary or with a short common axis; racemes fragile (very rarely tough), seldom conspicuously hairy, bearing paired similar spikelets; internodes and pedicels linear or rarely inflated. Spikelets dorsally comprssed, the callus obtuse; lower glume herbaceous to cartilaginous, the back flat with a median groove and the margins sharply inflexed, acute or notched at the tip; upper glume acute or with a short awn-point; lower floret male, reduced to a hyaline. scale, or suppressed, these variants often mixed in the same panicle; upper lemma hyaline, linear to cordate, often minute, bidentate to bifid, with a glabrous awn from the sinus; palea small or absent; stamens 3, rarely 2; caryopsis narrowly ellipsoid to lanceolate, dorsally flattened.
A genus of about 15 species mainly in tropical Asia; 2 species occur in Pakistan.
The lower floret is very variable, being well-developed and male, or reduced. Some species of Microstegium (e.g. Microstegium petiolare (Trin.) Bor) illustrate the “orthodox” mode of reduction in Andropogoneae, whereby the lower lemma enfolds the upper floret, the lower palea is suppressed, and the upper palea survives as a tiny scale. Other species (e.g. Microstegium eucnemis (Steud.) A. Camus) display an alternative mode, apparently peculiar to the genus, in which the lower lemma is suppressed, but the lower palea is well-developed, convex towards the upper floret, and may subtend adaxial lodicules and stamens. When the lower floret is consistently reduced (as in Microstegium nudum), the homology of its single scale is impossible to establish.