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211. Cymbopogon Sprengel, Pl. Min. Cogn. Pug. 2: 14. 1815.
香茅属 xiang mao shu
Authors: Shou-liang Chen & Sylvia M. Phillips
Perennial, rarely annual. Culms often tall, robust. Leaf blades aromatic, filiform to broadly linear; ligule scarious. Inflorescence a dense spathate compound panicle, each ultimate spatheole subtending a pair of short racemes on a short peduncle; spatheoles boat-shaped; each raceme borne on a short, flattened raceme base, often deflexed at maturity, lower raceme with one basal pair of homogamous spikelets below the fertile pairs; rachis internodes and pedicels linear, white-ciliate on margins, sometimes pedicel of homogamous pair swollen and fused to adjacent internode. Sessile spikelet dorsally compressed; callus obtuse, shortly bearded, inserted into internode apex; lower glume papery, flat or concave, sometimes grooved or wrinkled, 2-keeled, keels lateral, often winged above middle, with or without intercarinal veins; upper glume boat-shaped, awnless; lower floret reduced to a hyaline lemma; upper lemma narrowly oblong, usually 2-lobed to near middle, lobes slender, ciliate, awned from sinus, occasionally subentire and awnless; awn geniculate, sometimes weakly, short, glabrous. Pedicelled spikelet male or sterile, narrowly lanceolate, awnless. x = 10, 20, 40, 60.
About 70 species: tropics and subtropics of Africa, Asia, and Australia, predominantly in Asia; introduced in tropical America; 24 species (seven endemic, up to five introduced) in China.
Cymbopogon, with its inserted callus but frequently deflexed raceme bases, provides a link between Andropogon and Hyparrhenia, although its aromatic leaves distinguish it from both these genera. Many of the species are both variable and intergrading, based on inconstant characters, leading to much taxonomic difficulty. Specimens showing intermediate or extreme characteristics are common. Several species are cultivated commercially for the aromatic oils that are distilled from their leaves. The oils are often lemon scented and are used as perfume. Some species are also used medicinally and in cooking. Oil of citronella is used as an insect repellant.
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| 1 |
Rachis internodes and pedicels villous on margins and back with long silky hairs surrounding and obscuring spikelets. |
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1 C. jwarancusa |
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Rachis internodes and pedicels ciliate on margins, back glabrous or pubescent, hairs shorter than spikelets |
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(2) |
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| 2 (1) |
Lower glume of sessile spikelet flat with a slitlike median groove below middle (appearing as a line or keel on inside) |
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(3) |
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Lower glume of sessile spikelet almost flat to deeply concave, the depression uniformly rounded |
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(5) |
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| 3 (2) |
Pedicel of homogamous spikelet pair linear to slightly cuneate, not fused to adjacent rachis internode. |
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2 C. mekongensis |
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Pedicel of homogamous spikelet pair swollen, barrel-shaped, fused to adjacent rachis internode at base |
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(4) |
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| 4 (3) |
Culms up to 1 m; leaf blades 0.5–1 cm wide, base rounded. |
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3 C. annamensis |
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Culms up to 3 m; leaf blades 1–3 cm wide, base cordate, often amplexicaul. |
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4 C. martini |
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| 5 (2) |
Homogamous spikelet pair reduced or absent; pedicelled spikelet small, reduced to barren glumes |
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(6) |
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Homogamous spikelet pair well developed; pedicelled spikelet well developed, often staminate |
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(7) |
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| 6 (5) |
Racemes not deflexing at maturity; spatheoles narrowly lanceolate, 2–2.5 cm. |
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5 C. liangshanensis |
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Racemes deflexing at maturity; spatheoles linear, 1.2–1.5 cm. |
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6 C. minor |
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| 7 (5) |
Lower glume of sessile spikelet with keels rounded in lower half, wingless or almost so |
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(8) |
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Lower glume of sessile spikelet with keels sharp throughout, narrowly to broadly winged |
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(10) |
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| 8 (7) |
Raceme bases slender, unequal; racemes often more than 2 per spatheole. |
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Andropogon munroi (see p. 623) |
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Raceme bases flat, subequal; racemes always paired |
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(9) |
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| 9 (8) |
Lower glume of sessile spikelet deeply concave, depression with a prominent swelling at base. |
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7 C. gidarba var. burmanicus |
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Lower glume of sessile spikelet shallowly concave to almost flat, without a swelling at base. |
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8 C. pospischilii |
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| 10 (7) |
Sessile spikelet awnless or with short awn included within spikelet; cultivated plants |
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(11) |
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Sessile spikelet with exserted geniculate awn; wild plants (C. flexuosus also cultivated) |
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(13) |
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| 11 (10) |
Sessile spikelet 5–6 mm; lower glume linear-lanceolate, ca. 0.7 mm wide. |
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9 C. citratus |
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Sessile spikelet 3–5 mm; lower glume elliptic-oblong, 1–1.2 mm wide |
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(12) |
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| 12 (11) |
Inflorescence densely congested; leaf blades tough, scabrid, drooping for 1/3 of their length |
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10 C. nardus |
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Inflorescence lax, branches spreading; leaf blades softer, smooth, drooping for 2/3 of their length. |
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11 C. winterianus |
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| 13 (10) |
Culms slender to moderately robust, up to 1.5 m tall, 2–5 mm in diam.; spathate panicle 1–3-times branched |
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(14) |
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Culms robust, up to 3 m tall, 5–10 mm in diam.; spathate panicle repeatedly branched |
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(19) |
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| 14 (13) |
Sessile spikelet (6–)7–8 mm; leaf blades filiform, 1.5–3 mm wide. |
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12 C. distans |
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Sessile spikelet 3.5–6.3 mm; leaf blades linear, 2–7 mm wide |
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(15) |
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| 15 (14) |
Lower glume of sessile spikelet 5–7-veined between keels, obviously transversely wrinkled. |
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13 C. nervosus |
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Lower glume of sessile spikelet 2–5-veined between keels; smooth or slightly wrinkled |
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(16) |
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| 16 (15) |
Old basal leaf sheaths curling, reddish brown or orange inside; racemes 1–2 cm |
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(17) |
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Old basal leaf sheaths neither noticeably curling nor reddish inside; racemes 1.7–3 cm |
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(18) |
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| 17 (16) |
Racemes 1–1.5 cm; sessile spikelet narrowly lanceolate-oblong, 3.5–4.5 mm, wings on keels 0.15–0.25 mm; awn 7–10 mm. |
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14 C. tortilis |
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Racemes 1.5–2 cm; sessile spikelet narrowly obovate, 4.5–6 mm, wings on keels 0.25–0.45 mm wide; awn 10–12 mm. |
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15 C. goeringii |
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| 18 (16) |
Racemes 2–3 cm; sessile spikelet ca. 6 × 1.3 mm. |
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16 C. tungmaiensis |
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Racemes 1.7–2 cm; sessile spikelet ca. 5 × 1 mm. |
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17 C. fibrosus |
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| 19 (13) |
Sessile spikelet 5–9 mm (if less than 5.5 mm, lower glume clearly concave) |
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(20) |
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Sessile spikelet 3.5–5.5 mm |
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(22) |
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| 20 (19) |
Sessile spikelet 5–6 mm; lower glume clearly concave in lower 2/3, not wrinkled; wings on keels 0.15–0.35 mm. |
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18 C. pendulus |
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Sessile spikelet 5.5–9 mm; lower glume flat or slightly concave, transversely wrinkled; wings on keels 0.3–0.5 mm |
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(21) |
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| 21 (20) |
Compound panicle very large, open, drooping; racemes 3–4 cm, yellow-green; sessile spikelet 7–9 mm. |
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19 C. xichangensis |
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Compound panicle narrow, erect, subdense; racemes 2–2.5 cm, purple; sessile spikelet 5.5–7 mm. |
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20 C. traninhensis |
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| 22 (19) |
Racemes 1–1.3 cm; sessile spikelet 3.5–4 mm; lower glume 0–2-veined between keels; awn 6–8 mm. |
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21 C. microstachys |
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Racemes 1–2.5 cm; sessile spikelet 4–5 mm; lower glume 3–7-veined between keels; awn 8–12 mm |
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(23) |
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| 23 (22) |
Panicle effuse, grayish green, branches with raceme clusters long, lax, drooping; lower glume of sessile spikelet obscurely 3-veined between keels, narrowly winged (wings 0.1 mm or less). |
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22 C. flexuosus |
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Panicle not effuse, often purplish, branches with raceme clusters dense, erect; lower glume of sessile spikelet distinctly 5(–7)-veined between keels, winged (wings more than 0.1 mm) |
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(24) |
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| 24 (23) |
Leaf blades 0.7–1 cm wide; leaf sheath auricles up to 0.6 mm. |
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23 C. khasianus |
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Leaf blades ca. 1.6 cm wide; leaf sheath auricles ca. 10 mm. |
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24 C. auritus |
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List of lower taxa
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