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(Last Modified On 10/22/2012)
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(Last Modified On 10/22/2012)
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Genus
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ANDROPOGON L.
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PlaceOfPublication
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Sp. P1. 1045. 1753.
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Synonym
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Schizachyriu-m Nees, Agrost. Bras. 331. 1829. Bothriochloa Kuntze, Rev. Gen. P1. 2:767. 1891. Amphilophis Nash in Britton, Man. 71. 1901.
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Description
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Spikelets arranged in pairs at each node of a disarticulating rachis, one sessile and perfect, the other pedicellate and staminate, neuter, or sterile, often very much reduced, the rachis and sterile pedicels sparsely to usually densely ciliate or villous; glumes of sessile spikelet indurate, the first flat or rounded on the back, several- nerved, the median nerve obscure or wanting, the margins keeled toward the summit; sterile lemma hyaline; fertile lemma hyaline, narrow, much shorter than the glumes, awnless or usually awned from the apex or from between minute lobes, the awns straight, or geniculate and twisted below; pedicellate spikelets as large as the sessile, or more or less reduced, sometimes only the pedicel present, the glumes not indurate.
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Note
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Annuals or perennials with solid culms, the spikelets arranged in racemes, these sessile and crowded on a common axis, paniculate, or usually solitary or paired, sometimes in 3's or 5's, the common peduncle enclosed or exserted from a spathe- like sheath, these sheaths aggregate in a loose or dense, often silky, compound inflorescence.
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Key
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a. Racemes solitary on each peduncle. b. Plants annual; culms slender, widely spreading - 1. A. BREVIFOLIUS bb. Plants perennial; culms coarser, erect, densely cespitose. c. Spikelets awnless; racemes 1 cm. long, nearly glabrous; inflo- rescence dense -_ _. - 5. A. VIRGATUS cc. Spikelets awned; racemes 2-8 cm. long; inflorescences loose, the racemes scattered, or if dense, plume-like. d. Racemes very flexuous, conspicuously villous, crowded in a dense plume-like inflorescence _ -- -- 6. A. CONDENSATUS dd. Racemes straight, not conspicuously villous, the spikelets ap- pressed. e. First glume of sessile spikelet usually densely villous- - 2. A. HIRTIFLORUS ee. First glume of sessile spikelet glabrous. f. Rachis joints 4-5 mm. long; spikelets not crowded, the sessile one commonly 5-6 mm. long; blades 2-5 mm. wide 3. A. SEMIBERBIS ff. Rachis joints 2-3 mm. long; spikelets rather crowded, the sessile one about 4 mm. long; blades usually not more than 1.5 mm. wide-- -- _ 4. A. TENER aa. Racemes 2 or more, digitate, paniculate, or crowded along a common axis. b. Racemes numerous, sessile, crowded along a common axis in a dense, white, or silvery inflorescence. Culms erect -14. A. SACCHAROIDES bb. Racemes few to several, paniculate, the panicles terminal on the main culm and short branches. Culms decumbent or straggling, rooting at the nodes - 13. A. CONDYLOTRICHUS bbb. Racemes 2-5, sessile, paired or digitate at the ends of the peduncles. c. Spikelets awnless. d. Plants slender, usually less than 1 m. high; spathes not aggre- gate. e. Ligule 1-2 mm. long; tips of blades acute, not boat-shaped; spikelets 3 mm. long - --0. A. LEUCOSTACHYUS ee. Ligule less than 1 mm. long; tips of blades boat-shaped; spikelets about 4 mm. long- 11. A. SELLOANUS dd. Plants robust, 1-2.5 m. high; spathes aggregate in a usually dense inflorescence - -- 7. A. BICORNIS cc. Spikelets awned. d. Awns geniculate, twisted below; spikelets of the lower pairs alike; second glume with a slender divergent awn- 12. A. ANGUSTATUS dd. Awns slender, straight; spikelets of the lower pairs unlike. e. Racemes aggregate in a dense compound inflorescence, the spathes inconspicuous, rarely equaling the racemes; ultimate branchlets densely villous below the spathes -8. A. GLOMERATUS ee. Racemes scattered in a long loose inflorescence, the spathes conspicuous, exceeding the racemes; ultimate branchlets gla- brous or nearly so below the spathes -- 9. A. VIRGINICUS
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