Microstegium Nat. Syst. ed.2. 447
(1836).
Derivation:.
From Greek mikros (small) and stege (cover), alluding to the small
upper floret.
Key references
(keys and floras):. J.W.Vickery, Flora of New South Wales, Gramineae
19: 27–28 (1961); E.E.Henty, Manual Grasses New Guinea 125
(1969); M.Lazarides, Tropical Grasses S.E.Asia 56–58 (1980); B.K.Simon, Key
to Australian Grasses 132 (1993); S.W.L.Jacobs and C.A.Wall, Flora of
New South Wales 4: 434 (1993); D.Sharp and B.K.Simon, AusGrass (2002);
S.W.L.Jacobs, R.D.B.Whalley & D.J.B.Wheeler, Grasses of New South Wales,
4th ed, 301 (2008).
W.D.Clayton &
S.A.Renvoize, Genera Graminum (1986), genus (578).
Native. About 15
species, from tropical and subtropical Africa and 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.
Kranz Anatomy.
C4, biochemical type NADP-ME (1 species).
2n = 20
and 40, commonly adventive.
Habitat.
Mesophytic. Shade species.
Classification.
Panicoideae; Andropogoneae.
Notes. A
variable genus, recognised by the characteristic, though sometimes rather
obscure, median concavity of the lower glume. Tiny cordate lemmas occur in only
a few genera, and their presence in Microstegium strongly suggests
kinship with Eulalia (Clayton and Renvoize, 1986).
Types Species. M.
willdenowianum Nees = M. vimineum (Trin.) A.Camus.
Biogeographic
Element. Clifford & Simon 1981, Simon & Jacobs 1990: Old World
Tropics.