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Keyed in multiple places:

Click the number at the start of a key lead to highlight both that lead and its corresponding lead. Click again to show only the two highlighted leads. Click a third time to return to the full key with the selected leads still highlighted.

Key to Muhlenbergia

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1 Panicle open and diffuse, > 4 cm broad, ultimately appearing broad and not spikelike; the spikelets borne separately on slender or capillary pedicels longer than the lemmas or borne tightly and appressed on diverging spikelike branches.
  2 Spikelets mostly sessile, not borne on capillary pedicels, tightly appressed to the panicle branches; panicle branches strongly divergent; [subgenus Pseudosporobolus]
  2 Spikelets borne on slender or capillary pedicels (pedicellate), not appressed tightly to panicle branches, individual panicle branches not spikelike; branches primarily ascending (sometimes weakly divergent).
    3 Spikelets 1.1-2.2 mm long; spikelets with 1 floret, occasionally 2 or 3.
      4 Plants without rhizomes, instead tufted with erect culms (bunched); Spikelets 1.5-2 mm long; lemmas awnless; [subgenus Pseudosporobolus]
      4 Plants not cespitose, rhizomatous, the rhizomes prominent, creeping, and covered with imbricate scales; awns of the lemma 1.1-2.2 mm long.
        5 Culms compressed-keeled, ascending; blades conduplicate (folded lengthwise), 6-20 cm long; panicles cylindrical, 10-28 cm long, 4-8 cm wide; [subgenus “incertae sedis”]
        5 Culms terete to somewhat compressed-keeled near the base, decumbent-ascending; blades usually flat, occasionally conduplicate, 2-7(-11) cm long; panicles ovoid, 6-21 cm long, 4-16 cm wide; [subgenus Pseudosporobolus]
    3 Spikelets 2.5-5 mm long (excluding awns); spikelets with 1 floret [subgenus Trichochloa].
          6 Lemma awn 0-1.5 (-4) mm long; glume bodies (1.1-) 2.0-3.3 (-3.6) mm long, < ½ as long as the lemma bodies, acuminate, not awned (rarely the second with a short awn < 0.6 mm long); spikelets usually brown or bronze (when fresh); basal sheaths usually very fibrous
          6 Lemma awn (2-) 3-35 mm long; glume bodies (0.3-) 0.7-1.7 (-2.4) mm long, > ½ as long as the lemma body, one or both glumes sometimes awned; spikelets usually purple (when fresh); basal sheaths rarely strongly fibrous.
             7 Lemma awn (2-) 3-13 (-18) mm long, first glume awnless (or rarely with an awn to 3.2 mm long), second glume awnless (or rarely with an awn up to 5.0 mm long), palea awnless; lemma lacking setaceous teeth flanking the awn; flowering late Aug-Oct; [widespread in our area, particularly in rocky, clayey, or sandy glades, barrens, and woodlands with prairie affinities]
             7 Lemma awn (8-) 12-26 (-35) mm long, first glume awn (0.5-) 1-7 (-10) mm long, second glume awn (1-) 5-19 (-25) mm long, palea awn-tipped; lemma with two setaceous teeth flanking the awn, the teeth 0.5-2.5 (-4.7) mm long; flowering Oct-Nov; [sandy maritime situations on barrier islands of the outer Coastal Plain]
1 Panicle slender, dense, < 2.5 cm broad, ultimately appearing spikelike, the spikelets sessile or on non-capillary pedicels shorter than the lemmas; [subgenus Muhlenbergia].
               8 Glumes minute, 0-0.5 mm long; plant lacking rhizomes; culms weak, decumbent and cespitosely branching in their lower portions, rooting at the nodes, the upper portions erect and sparsely branched
               8 Glumes well-developed, 1-8 mm long; plant with scaly rhizomes (except for M. cuspidata); culms firm (rarely sprawling), few or solitary (rarely forming dense colonies).
                 9 Glumes 3-8 mm long (tapered to arched or straight awns), 1.3-2x the length of the lemma (excluding its awn); panicle dense and spike-like, 0.8-16 cm long and 0.3-10 mm broad.
                   10 Culms with little to no branching above the base; internodes dull and puberulent, strigose directly below the nodes; awns of the glumes to 5 mm long; ligules 0.2-0.6 mm long
                   10 Culms much-branched above the base; internodes smooth, polished, and mostly glabrous (sometimes puberulent directly below the nodes); awns of the glumes to 1 mm long; ligules 0.6-1.7 mm long
                 9 Glumes 1.2-3 mm long, shorter than to barely exceeding the lemma; panicle usually slender, arching, generally less dense and not spike-like, often with some elongated (though appressed) branches, 4-50 cm long, 2-15 mm broad.
                     11 Callus glabrous; plant lacking scaly rhizomes (with slender stolons and a hard, knotty crown); leaves 0.5-2 mm wide; [calcareous cliffs]
                     11 Callus bearded (sometimes only slightly so) (glabrous in M. glabriflora); plant with scaly rhizomes (except for M. tenuifolia); leaves (1-) 2-14 mm wide; [various habitats].
                       12 Awns of the lemma 10-30 mm long; [e. TX westward]
                       12 Awns of the lemma 0.1-12 (-13) mm long; [collectively widespread]
                          13 Panicle linear, loosely flowered, much exceeding the leaves; culm erect, simple or sparingly branched; glumes relatively broad, the body ovate, 1.2-2.5 mm long, abruptly narrowed to the acuminate tip; ligule obsolete or shorter than the elongate cartilaginous summit of the leaf sheath.
                            14 Lemmas awnless or awn < 0.5 mm long; spikelets 1.5-2.5 mm long; leaf blades usually (1-) 2-6 mm wide
                            14 Lemma awn 1-11 mm long (rarely awnless); spikelets 3-5 mm long; leaf blades (2) 6-10 (-13) mm wide (often > 8 mm wide)
                          13 Panicle lanceolate, densely (rarely loosely) flowered, leaves often extending conspicuously into the inflorescence; culm geniculate, freely branched; glumes relatively narrow, the body lanceolate, 2-3 mm long, tapering from base to apex; ligule usually obvious above the short cartilaginous summit of the leaf sheath.
                              15 Culm glabrous throughout (including below the nodes).
                                16 Glumes 1.4-2.0 mm long; ligule 0.2-0.5 mm long
                                16 Glumes 2-4 (-5) mm long; ligule 0.8-1.5 mm long
                              15 Culm pubescent, at least below the nodes.
                                  17 Lemma awn 7-12 mm long; spikelets loosely clustered, on pedicels 2-4 mm long
                                  17 Lemma awnless or with a short awn tip (rarely to 9 mm long); spikelets densely clustered, on pedicels < 1 mm long.
                                    18 Lemma glabrous below, or with short basal bearding; ligule 0.5-1.5 mm long
                                    18 Lemma pilose basally; ligule 0.5-1 mm long

Key to Poaceae, Key L: grasses with 1 floret and awned lemmas

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1 Lemma awn 3-branched (the lateral 2 sometimes very reduced compared to the central); [tribe Aristideae]
1 Lemma awned with a simple awn.
  2 Upper glumes present, 1-veined; lower glumes absent or much shorter than the upper glumes and veinless; [tribe Brachyelytreae]
  2 Both glumes present, 1-many-veined.
    3 Lemma hardened, distinctly different than the glumes in texture when mature; [tribe Stipeae].
      4 Rhizomatous perennials; primary leaves cauline (the basal leaves < 2 cm long or merely represented by sheaths), 8-16 mm wide
      4 Cespitose perennials; primary leaves basally disposed, 0.2-10 mm wide.
        5 Leaves > 4 mm wide.
          6 Florets 2.5-3.5 mm long; awns 3.4 mm long; [exotic, rarely naturalized]
          6 Florets 5-13 mm long; awns either 7-15 or 30-120 mm long; [exotics or natives].
             7 Leaves 2-8 mm wide, not twisted at the base; awns 30-120 mm long
             7 Leaves 4-10 mm wide, the base twisted so that the abaxial surface is uppermost; awns 7-15 mm long
        5 Leaves < 4 mm wide.
               8 Florets 7-25 mm long; awns 30-225 mm long.
                 9 Palea grooved, longer than the lemma; lemma margins involute, fitting into the paleal groove; [native species, collectively widespread in our area]
                 9 Palea flat, shorter than or equal to the lemma; lemma margin convolute or not overlapping; [exotic species, rare in our area]
                   10 Lemma margins not or only slightly overlapping at maturity; awns 60-190 mm long
                   10 Lemma margins strongly overlapping for their entire length at maturity; awns 40-120 mm long
               8 Florets 1.5-4.5 mm long; awns 1-35 mm long
                     11 Leaves 0.2-0.6 mm wide; florets 1.5-2.5 mm long; awns 15-35 mm long
                     11 Leaves 0.5-10 mm wide; florets 2.2-4.5 mm long; awns 1-15 mm long.
                       12 Leaves 0.5-1.8 mm wide; central vein of the lemma not prominent; [native species]
                       12 Leaves 2-10 mm wide; [rare exotic species]
    3 Lemma neither hardened nor distinctly different than the glumes in texture when mature.
                          13 Spikelets 18-32 mm long; [tribe Poeae]
                          13 Spikelets 1.1-8 mm long.
                            14 All spikelets sessile or subsessile and arrayed along inflorescence axes (racemes) divergent from the central axis (but not both overlapping one another and clearly ranked on one side of the axis, so as to be keyed under Key H).
                              15 Inflorescences with disarticulating branches; Lower glumes 0.9-4 mm long; spikelets disarticulating below the glumes, the spikelet falling as a whole; spikelets appressed to divergent from the raceme axes; sheaths not strongly overlapping; [tribe Cynodonteae; subtribe Eleusininae]
                              15 Inflorescences without disarticulating branches; lower glumes 1.5-3 mm long (Muhlenbergia paniculata) or (2-) 3.5-7 mm long (Gymnopogon); spikelets disarticulating above the glumes (which often remain on the inflorescence); spikelets strongly appressed to the raceme axes; sheaths strongly overlapping or not , if so then at least on the upper culm, therefore hiding the culm; [tribe Cynodonteae; subtribe “incertae sedis”]
                                16 Blades with thick, white margins and well-developed midrib; inflorescence branches strongly divergent; glumes unequal, usually shorter (sometimes only slightly so) than the solitary floret
                                16 Blades lacking both thick, white margins and well-developed midribs; glumes subequal, usually exceeding the 1-2(4) floret(s)
                            14 Spikelets pedicellate and arrayed in a more complex and open panicle.
                                  17 Lemma surrounded by a tuft of callus hairs; [tribe Poeae]
                                  17 Lemma not surrounded by callus hairs.
                                    18 Spikelets articulated below the glumes, the spikelet falling intact, leaving a naked pedicel; [tribe Poeae]
                                    18 Spikelets articulated above the glumes, the floret falling, leaving the glumes attached to the pedicels.
                                       19 Lemmas faintly 5-veined; awn from the back of the lemma; lower glume longer than the lemma; palea much shorter than the lemma (or absent); [tribe Poeae]
                                       19 Lemmas strongly 3-veined; awn from the tip of the lemma; lower glume shorter than (rarely equaling) the lemma; palea about equaling the lemma; [tribe Cynodonteae; subtribe Muhlenbergiinae]
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