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Key to Eragrostis

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1 Plants cespitose or rhizomatous perennials, with innovations near the base, and with or without buds in the basal sheaths.
  2 Palea with a broadened wing or tooth on each side near its base that often projects beyond the lemma
  2 Palea lacking a broadened wing or tooth near its base.
    3 Plants with short, knotty, thick rhizomes; florets articulating whole
    3 Plants without short or thick rhizomes; florets usually disarticulating.
      4 Caryopsis with a deep to shallow groove along the adaxial surface.
        5 Caryopsis dorsoventrally compressed, flattened parallel to the side of the embryo, translucent, light brownish
        5 Caryopsis laterally compressed, flattened on the side perpendicular to the embryo, or cylindric, opaque (rarely translucent), usually reddish brown.
          6 Lateral veins of the lemmas conspicuous, often greenish, the lemmas strongly keeled
          6 Lateral veins of the lemmas inconspicuous and hardly evident, the lemmas sometimes weakly keeled.
             7 Lemmas 1.2-1.8 mm long; culms 30-70 cm tall
             7 Lemmas 1.6-3.0 mm long; culms (30-) 40-110 (-120) cm tall.
               8 Spikelets 2-6-flowered, greenish with purple tinges; leaf blades 3-8 (-11) mm wide, 25-60 cm long; sheaths often densely papillose-hirsute
               8 Spikelets (3-) 5-12-flowered, olive green to lead gray; leaf blades 1-3.8 mm wide, (4-) 10-35 cm long; sheaths never papillose-hirsute
      4 Caryopsis not grooved on the adaxial surface.
                   10 Spikelets 4-10 (-19) mm long.
                     11 Spikelets appressed to the panicle branches, with 10-22 florets each
                     11 Spikelets erect on panicle branches, with 3-10 florets each
                   10 Spikelets 2-4.5 (-5) mm long.
                       12 Leaf blades 25-60 cm long, 3-8 (-11) mm wide; lemmas 1.6-2.4 mm long; spikelets 1.0-1.7 mm wide
                       12 Leaf blades (4-) 8-22 cm long, 1-3.5 mm wide; lemmas 1.2-1.8 mm long; spikelets 0.5-1.0 (-1.3) mm wide
                          13 Panicle 15-45 cm wide, open, diffuse, broadly ovate to obovate in outline, the panicle branches capillary; pedicels 0.5-35 (-50) mm long, longer than or shorter than the spikelets.
                            14 Spikelets with widely spreading pedicels, the lower pedicels all generally longer than the spikelets; disarticulation of the lemmas only, the paleas persistent
                            14 Spikelets with appressed pedicels, lower pedicels of each branch shorter than the spikelets; disarticulation usually of the whole floret
                          13 Panicle (1-) 2-17 (-20) cm wide, contracted to open, narrowly ovate to oblong in outline, the panicle branches stiffly spreading (appressed to stiffly spreading in E. scaligera); pedicels (0-) 0.3-6 mm long, always shorter than the spikelets.
                              15 Spikelets 2.4-5 mm wide; upper glumes 2.2-4 mm long; [native and introduced]
                              15 Spikelets (0.7-) 1.3-2.4 mm wide; upper glumes 1.4-2.2 mm long; [non-native].
                                16 Panicles 15-30 cm long; leaf blades (8-) 12-40 cm long, 2-5 mm wide; [SC s. to FL and w. to LA]
                                16 Panicles 2-12 cm long; leaf blades 4-8 (-18) cm long, 1-2 mm wide; [primarily s. FL]
1 Plants cespitose, geniculate or mat-forming annuals, lacking innovations or buds in the lower sheaths.
                                  17 Paleas prominently ciliate-pectinate on the keels, the hairs 0.1-0.8 mm long.
                                       19 Spikelets (1.0-) 1.5-3.5 mm long, 0.9-1.4 mm wide, 4-12-flowered; lemmas 0.7-1.1 mm long, membranous, the apex truncate to obtuse
                                       19 Spikelets 5-12 (-18) mm long, 1.4-2.4 mm wide, 12-42-flowered; lemmas (1.3-) 1.5-2.0 mm long, chartaceous, the apex acute
                                  17 Paleas smooth to scaberulous on the keels, the hairs (if present) <0.1 mm long.
                                         20 Plants extensively stoloniferous, creeping and forming flat mats; inflorescences 1-3.5 cm long; culms (2-) 5-12 (-20) cm tall on the erect portions.
                                         20 Plants not stoloniferous (sometimes creeping and forming flat mats); inflorescences 3-55 cm long; culms (2-) 6-130 cm tall.
                                                 24 Spikelets (4-) 5-10 (-11) mm long, 5-11 (-15)-flowered; pedicels ascending, somewhat appressed along the branches.
                                                 24 Spikelets (1.4-) 2-5 mm long, 2-6 (-7)-flowered; pedicels erect, spreading along the branches.
                                                      26 Panicle 10-45 (-55) cm long, 2/3 or more the height of the plant; pedicels (4-) 5-25 mm long; glandular pits absent below the nodes, branches, and rachis
                                                      26 Panicle 4-20 cm long, < ½ the height of the plant; pedicels 1.5-5 mm long; glandular pits often present below the nodes, branches, and rachis
                                                        27 Plants with glandular pits or bands on the culm below the nodes, on the veins of the sheath, on the margins and veins of the blade, on the rachis, on the inflorescence branches and pedicels, and/or on the midveins of the lemma and palea.
                                                            29 Spikelets 1.1-4 mm wide; pedicels 0.2-4 mm long, straight and rigid, mostly spreading.
                                                              30 Spikelets 6-20 mm long, 2-4 mm wide, 10-40-flowered; lemmas 2-2.8 mm long, with 1-3 crateriform glands along the keel; disarticulation of the entire florets from the persistent rachilla; anthers yellow
                                                              30 Spikelets 4-7 (-11) mm long, 1.1-2.2 mm wide, 7-12 (-20)-flowered; lemmas 1.4-1.8 mm long, rarely with 1-2 crateriform glands along the keel; disarticulation of the lemmas only, the palea and rachilla usually persistent; anthers reddish-brown.
                                                                 31 Inflorescence with glandular areas of spots or rings on the rachis below the panicle branch bases, the glands often shiny or yellowish; stamens 3; blade margins lacking crateriform glands
                                                                 31 Inflorescence sometimes with glandular areas of spots or crateriform pits on the rachis below the panicle branch bases, the glands usually dull and greenish-gray to straw-colored; stamens 2; blade margins sometimes with crateriform glands
                                                        27 Plants lacking glandular pits or bands on the culm below the nodes, on the veins of the sheath, on the margins and veins of the blade, on the rachis, on the inflorescence branches and pedicels, and/or on the midveins of the lemma and palea.
                                                                   32 Spikelets 0.6-2.5 mm wide, 3-22-flowered; disarticulation of the lemmas only, the paleas usually persistent (or deciduous), the rachilla persistent.
                                                                         35 Spikelets 5-12 (-18) mm long, with 12-42 florets; primary branches 6-10 per culm; lemmas 1.3-2.0 mm long; anthers 3
                                                                         35 Spikelets 2-4.6 mm long, with 5-15 florets; primary branches (12-) 15-20 per culm; lemmas 1.0-1.3 mm long; anthers 2
                                                                       34 Lemmas with inconspicuous or moderately conspicuous lateral veins, these usually not greenish; grains 0.5-1.1 mm long, pear-shaped, obovoid, or prism-shaped.
                                                                           36 First glume 0.5-1.5 mm long, >0.5× as long as the lowest lemma; spikelets 1.2-2.5 mm wide; panicle branches solitary or paired at the 2 lowest nodes.
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