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195. Microstegium Nees in Lindley, Nat. Syst. Bot., ed. 2. 447. 1836.

莠竹属 you zhu shu

Authors: Shou-liang Chen & Sylvia M. Phillips

Ischnochloa J. D. Hooker.

Perennial or annual. Culms slender, creeping or rambling, usually much branched and rooting at lower nodes. Leaf blades broadly linear to lanceolate or elliptic, base narrow, apex acuminate to setaceous; ligule membranous, truncate, back pubescent. Inflorescence terminal, composed of 1 to many subdigitate racemes on a short axis; racemes elongate, sparsely hairy, usually fragile, sessile and pedicelled spikelets of a pair similar, rarely both spikelets unequally pedicelled; rachis internodes filiform to clavate or inflated; pedicels resembling internodes but shorter. Sessile spikelet lanceolate, dorsally compressed; callus shortly bearded; glumes herbaceous to cartilaginous; lower glume deeply grooved on back or with a broad median channel, margins inflexed, 2-keeled at least toward apex; upper glume boat-shaped, acute to shortly awned; lower floret almost always sterile, reduced to a single scale or absent; upper floret bisexual, lemma linear to cordate, deeply 2-lobed, shortly 2-toothed, or rarely entire, usually awned; awn flexuous or geniculate. Stamens 2–3. Pedicelled spikelet resembling the sessile but slightly narrower and less concave, occasionally slightly smaller and staminate.

About 20 species: India to Japan and SE Asia, a few species in Africa; 13 species (three endemic) in China.

The name Microstegium glaberrimum (Honda) Koidzumi (Bot. Mag. (Tokyo) 43: 394. 1929; Pollinia glaberrima Honda, Bot. Mag. (Tokyo) 39: 42. 1925), described from Taiwan, has been misapplied in recent literature to forms of M. ciliatum. The protologue describes a grass with only 2 or 3 short racemes of small (ca. 2 mm), awnless spikelets. The type has not been seen, and it has not proved possible to establish the identity of this taxon.

1 Rachis internodes filiform, glabrous or villous, equaling or longer than spikelets   (2)
+ Rachis internodes linear to clavate, inflated upward, hairy on angles, usually shorter than spikelets   (6)
2 (1) Rhizomatous perennial; raceme solitary; rachis internodes and pedicels long-ciliate.   1 M. batangense
+ Annuals; racemes 2–7; rachis internodes and pedicels glabrous or almost so   (3)
3 (2) Stamens 3; lower lemma reduced or absent.   2 M. fauriei
+ Stamens 2; lower lemma well developed, slightly shorter than glumes   (4)
4 (3) Spikelets of a pair one sessile, the other pedicelled; raceme rachis fragile.   3 M. nudum
+ Spikelets of a pair both pedicelled, one pedicel long, the other short; raceme rachis tough   (5)
5 (4) Spikelets 1-awned (from upper lemma); lower glume smooth, apex subentire; nodes of culm glabrous.   4 M. japonicum
+ Spikelets 3-awned (from upper glume and both lemmas); lower glume scabrid, apex 2-cleft; nodes of culm pubescent.   5 M. somae
6 (1) Upper lemma well developed, 3–4 mm, split to about middle into 2 long, acute lobes   (7)
+ Upper lemma small, 1–2 mm, shortly 2-lobed or entire   (8)
7 (6) Culms rambling, up to 2 m; leaf blades 15–20 cm, pseudopetiolate, at least the lower; racemes 6–20; pedicelled spikelet awned.   6 M. petiolare
+ Culms erect, up to 40 cm; leaf blades 3–8 cm, not pseudopetiolate; racemes 2–3; pedicelled spikelet awnless or almost so.   7 M. lanceolatum
8 (6) Anthers 0.3–0.5 mm; awn often very short, included within spikelet; sessile spikelet 4–5 mm   (9)
+ Anthers 0.8–2.5 mm; awn clearly exserted from spikelet; sessile spikelet 2–4(–5) mm   (10)
9 (8) Lower glume with transverse veinlets below apex; leaf blades 5–8 mm wide.   8 M. vimineum
+ Lower glume with transverse veinlets below apex and down flanks; leaf blades 8–12 mm wide.   9 M. reticulatum
10 (8) Spikelets 2–2.5 mm; lower glume flat on back or almost so, veins obscure.   10 M. delicatulum
+ Spikelets 2.8–5 mm; lower glume grooved on back, veins obvious   (11)
11 (10) Anthers 0.8–1.5 mm; upper glume with 0.3–3 mm awnlet; awn flexuous, column obscure.   11 M. ciliatum
+ Anthers 1.5–3.5 mm; upper glume acute or minutely mucronate; geniculate, column distinct   (12)
12 (11) Sessile spikelet 2.8–4 mm; anthers 1.5–2.5 mm; upper lemma emarginate, glabrous.   12 M. fasciculatum
+ Sessile spikelet 4.5–5 mm; anthers 3–3.5 mm; upper lemma bifid, ciliate.   13 M. multiciliatum

  • List of lower taxa


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