| 1 |
Spikelets with a marginal ciliate fringe of silky hairs; hairs 1–2 mm |
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(2) |
| + |
Spikelets glabrous or pubescent, without a marginal fringe of silky hairs |
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(5) |
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| 2 (1) |
Racemes 2, paired; stoloniferous perennial. |
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1 P. conjugatum |
| + |
Racemes usually more than 2, spread along an axis |
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(3) |
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| 3 (2) |
Spikelets 3–4 mm; upper floret equal to 2/3 length of spikelet. |
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2 P. dilatatum |
| + |
Spikelets 2–3 mm; upper floret equal to or only slightly shorter than spikelet |
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(4) |
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| 4 (3) |
Spikelets light green or purplish, ovate; upper glume pubescent, fringed along whole length. |
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3 P. urvillei |
| + |
Spikelets brown, obovate; upper glume puberulous, fringed only above middle. |
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4 P. virgatum |
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| 5 (1) |
Upper glume and lower lemma broadly winged along margins. |
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5 P. fimbriatum |
| + |
Upper glume and lower lemma not winged |
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(6) |
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| 6 (5) |
Both glumes absent; upper lemma papery, with conspicuous riblike veins. |
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6 P. malacophyllum |
| + |
Upper glume present; upper lemma cartilaginous or coriaceous, with obscure veins |
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(7) |
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| 7 (6) |
Plants with long stolons and/or rhizomes; racemes 2(–3), paired, the spikelets borne singly; spikelets lanceolate to ovate or obovate |
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(8) |
| + |
Plants tufted; racemes up to 20 along a common axis, the spikelets single or paired; spikelets broadly elliptic, obovate or suborbicular |
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(10) |
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| 8 (7) |
Plant with robust woody rhizomes; upper glume and lower lemma cartilaginous and shiny, obtuse. |
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7 P. notatum |
| + |
Plant with slender stolons; upper glume and lower lemma papery, acute |
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(9) |
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| 9 (8) |
Upper glume pubescent; spikelets plano-convex, obovate-oblong. |
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8 P. distichum |
| + |
Upper glume glabrous; spikelets strongly flattened, lanceolate-oblong. |
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9 P. vaginatum |
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| 10 (7) |
Fertile floret dark glossy brown at maturity; spikelets usually glabrous |
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(11) |
| + |
Fertile floret yellowish green to pale brown at maturity; spikelets pubescent or glabrous |
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(13) |
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| 11 (10) |
Lower lemma conspicuously rugose inside margins; spikelets paired. |
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10 P. plicatulum |
| + |
Lower lemma usually smooth, occasionally slightly rugose; spikelets usually single, occasionally paired |
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(12) |
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| 12 (11) |
Pedicels glabrous; nodes, culm apex and leaf blades often glabrous. |
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11 P. scrobiculatum |
| + |
Pedicels pilose; nodes, culm apex and leaf blades densely hairy. |
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12 P. hirsutum |
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| 13 (10) |
Spikelets 1–1.5 mm. |
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13 P. paniculatum |
| + |
Spikelets 2–3 mm |
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(14) |
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| 14 (13) |
Rachis 2–4 mm wide; spikelets 2–2.5 mm, paired, pubescent. |
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14 P. longifolium |
| + |
Rachis 1–1.5 mm wide; spikelets 2.5–3 mm, single or loosely paired |
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(15) |
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| 15 (14) |
Upper glume pubescent especially along the margins; leaf blades hirsute, 5–8 mm wide. |
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15 P. thunbergii |
| + |
Upper glume glabrous; leaf blades glabrous, 3–4 mm wide. |
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16 P. delavayi |
