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205. Ischaemum Linnaeus, Sp. Pl. 2: 1049. 1753.
鸭嘴草属 ya zui cao shu
Authors: Bi-xing Sun & Sylvia M. Phillips
Perennial, or sometimes annual. Culms often decumbent and much branched. Leaf blades linear to lanceolate, narrowed to ligule, sometimes pseudopetiolate; ligule membranous; sheath auricles often present. Inflorescence of paired racemes, or occasionally subdigitate, terminal and axillary, exserted or sometimes supported by a spatheole; racemes 1-sided, when paired often locked back to back and appearing as a single cylindrical raceme, spikelets of a pair similar or not; rachis internodes and pedicels stoutly linear to thickly clavate, U-shaped or triquetrous in cross section. Sessile spikelet dorsally compressed; callus truncate or obtuse, inserted into hollowed internode apex; lower glume papery to leathery, shallowly convex or almost flat, 2-keeled or rounded on flanks, sometimes winged, often rugose; upper glume boat-shaped, awnless or with straight awn from apex; lower floret male, well developed with palea; upper lemma usually deeply 2-lobed, awned from sinus, rarely awnless; awn geniculate, glabrous. Pedicelled spikelet as large as sessile or much smaller, upper lemma sometimes geniculately awned.
About 70 species: throughout the tropics but mainly in Asia, especially India; 12 species (one endemic) in China.
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| 1 |
Margins of lower glume of sessile spikelet broadly rounded in lower part, narrowly inflexed and keeled above, not coarsely rugose or knobbly |
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(2) |
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Margins of lower glume of sessile spikelet narrowly and evenly inflexed and keeled along entire length, often coarsely rugose or knobbly |
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(8) |
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| 2 (1) |
Spikelets of a pair without obvious awns, or only sessile spikelet awned |
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(3) |
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Spikelets of a pair both clearly awned |
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(5) |
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| 3 (2) |
Inflorescence base enclosed in uppermost sheath; plant strongly rhizomatous. |
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1 I. muticum |
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Inflorescence long exserted from uppermost sheath; plant loosely tufted |
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(4) |
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| 4 (3) |
Racemes villous; sessile spikelet 8–10 mm. |
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2 I. anthephoroides |
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Racemes glabrous; sessile spikelet 5.5–8 mm. |
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3 I. aristatum |
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| 5 (2) |
Lower glume of sessile spikelet winged on keels, apex rounded, emarginate |
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(6) |
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Lower glume of sessile spikelet not winged on keels, apex sharply bicuspidate |
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(7) |
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| 6 (5) |
Racemes paired; rhizomes absent; culms less than 60 cm. |
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4 I. ciliare |
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Racemes (2–)3–6; rhizomes present; culms 60–100 cm. |
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5 I. polystachyum |
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| 7 (5) |
Spikelets ± glabrous; upper glume of sessile spikelet not winged on keel; callus hairs less than 1 mm. |
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6 I. timorense |
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Spikelets hispid; upper glume of sessile spikelet winged on keel; callus hairs ca. 2 mm. |
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7I I. thomsonianum |
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| 8 (1) |
Lower glume of sessile spikelet not transversely rugose or knobbly |
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(9) |
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Lower glume of sessile spikelet transversely rugose or knobbly on flanks |
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(10) |
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| 9 (8) |
Lower glume of sessile spikelet wingless, keels pilose; awn 1.8–2.5 cm. |
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8 I. aureum |
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Lower glume of sessile spikelet winged, glabrous; awn 1–1.2 cm. |
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9 I. setaceum |
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| 10 (8) |
Plant annual; lower glume of sessile spikelet coarsely rugose with 4–7 sharp transverse ridges across back. |
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10 I. rugosum |
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Plant perennial; lower glume of sessile spikelet with rounded knobs on keels in lower part, sometimes also with 2–4 weak ridges across back |
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(11) |
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| 11 (10) |
Culms up to 1 m tall; sessile spikelet 5–7 mm, awned, awn 1–1.5 mm. |
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11 I. barbatum |
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Culms 1–2 m tall; sessile spikelet 6.5–8 mm, awnless or awn less than 1 mm. |
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12 I. magnum |
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List of lower taxa
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Treatments in Other Floras @ www.efloras.org
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