Leptatherum Nees, Proc. Linn. Soc. London 1: 92 (1841).
Derivation:. From Greek leptos (narrow) and ather (barb or spine), alluding to the long attenuate lemma of the upper floret.
Key references (keys and floras):. J.W.Vickery, Flora of New South Wales, Gramineae 19: 27–28 (1961) as Microstegium; E.E.Henty, Manual Grasses New Guinea 125 (1969) as Microstegium; M.Lazarides, Tropical Grasses S.E.Asia 56–58 (1980) as Microstegium; B.K.Simon, Key to Australian Grasses 132 (1993) as Microstegium; S.W.L.Jacobs and C.A.Wall, Flora of New South Wales 4: 434 (1993) as Microstegium; D.Sharp and B.K.Simon, AusGrass (2002) as Microstegium; S.W.L.Jacobs, R.D.B.Whalley & D.J.B.Wheeler, Grasses of New South Wales, 4th ed, 301 (2008) as Microstegium.
W.D.Clayton & S.A.Renvoize, Genera Graminum (1986), genus (578).
Native. 3 species, from tropical and subtropical Asia. 1 species in Australia, Qld and NSW. Also New Guinea and Malesia.
Habit. Creeping or rambling annual or perennial, decumbent. Leaf blades broad or narrow. Ligule an unfringed membrane.
Inflorescence. Inflorescence of spicate main branches (flexuous, fragile racemes, these not villous), an open panicle with branches ending in racemes of paired spikelets (?), digitate or subdigitate (to scattered on a short axis) or non-digitate (sometimes solitary). Spikelet-bearing axes with heteromorphic spikelets to with homomorphic spikelets (the pedicelled member with a less concave lower glume, and sometimes slightly smaller), disarticulating at joints. Internodes disarticulating transversely, densely long-hairy (rarely, villous) or somewhat hairy or glabrous.
Spikelets. Spikelets dorsally compressed, 2 flowered, with 1 fertile floret, paired, sessile and pedicelled, in pedicelled/sessile combinations; with lower incomplete floret (often very reduced). Fertile spikelets falling with glumes (the pedicelled spikelet falling from its pedicel, the sessile falling with the adjacent internode and pedicel).
Glumes. Glumes more or less equal, long relative to adjacent lemmas, awned (the upper, sometimes) or awnless, dissimilar (the lower bicarinate and chanelled, the upper laterally compressed, naviculate). Lower glume two-keeled (via sharply inflexed margins, the keels not winged), sulcate on back (with a deep groove or broadly concave median channel), relatively smooth, 4–6 nerved. Upper glume 3 nerved.
Florets. Lower incomplete floret(s) sterile. Lemmas exceeded by fertile lemmas to exceeding fertile lemmas, similar in texture to fertile lemmas (hyaline), not becoming indurated. Fertile florets 1. Lemmas less firm than glumes (hyaline or membranous), not becoming indurated, incised, deeply cleft to not deeply cleft (usually bidentate to bifid, often minute), awned (nearly always) or muticous (rarely), glabrous. Awns 1, usually from a sinus, geniculate, hairless (glabrous), much longer than body of lemma. Palea present or absent, relatively long or conspicuous and relatively short to very reduced (always small, but sometimes exceeding the body of the upper lemma), nerveless. Callus short. Lodicules 2. Stamens (2–)3. Hilum short. Embryo large. Pedicels free of rachis. Pedicelled spikelets present, similar in shape to sessile spikelet, bisexual.
2n = 20 and 40, commonly adventive.
Habitat. Mesophytic. Shade species.
Classification. Panicoideae; Andropogoneae.
Notes. Separated from Microstegium by Chen et al in Blumea 54: 175-180 (2009)