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Key to Poaceae, Key E: grasses of tribe Andropogoneae (also including grasses also keyed in Keys B, C, and D)

Poaceae

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1 Leaves ovate-lanceolate, 2-10 cm long, 2.5-7× as long as wide; plants weak-stemmed annuals, branching, decumbent, rooting at the lower nodes; [exotic weeds].
  2 Leaves cordate-clasping at base; spikelets awned, not paired, unaccompanied by a vestige; each panicle with 12-20 rames
  2 Leaves tapering to a broadly cuneate base; spikelets unawned, paired (one of the pair sometimes vestigial); each panicle with 1-few rames
1 Leaves lanceolate to linear, either longer or proportionately narrower; plants either perennial or coarse annuals with erect and mostly unbranched culms.
    3 Spikelets embedded in the thickened rachis (the inflorescence thus like an ear of corn), or fitting into grooves in the thickened rachis (the inflorescence thus cylindrical and resembling a rat's tail), or the pistillate inflorescences enclosed in a hard, bead-like, pearly-white, modified bract.
      4 Spikelets unisexual, with male and female spikelets in separate inflorescences or in different parts of the same inflorescence.
        5 Internode narrower than and more-or-less enclosed by the female spikelet
        5 Internode broader than and more-or-less enclosing the female spikelet.
          6 Racemes of mixed sex, female flowers below, and male above
          6 Racemes of single sex, the female inflorescences (“ears”) borne on axillary branches, the male inflorescences (“tassels”) terminal on the culm
 Zea
      4 Spikelets, or at least one of each pair, bisexual.
             7 Culms 2-45 cm tall; leaves 1-5 mm wide; plants perennial, obviously and prominently rhizomatous; lower glume with pectinate margins; [commonly naturalized turf grass and roadside weed]
             7 Culms 30-400 cm tall; leaves 2-25 mm wide; plants annual or perennial, cespitose or short-rhizomatous; lower glume winged or not, but not pectinate.
               8 Lower glumes of the sessile spikelets rough, rugose, pitted, tuberculate or alveolate between the keels
               8 Lower glumes of the sessile spikelets smooth or scabrous.
                 9 Pedicels at least partially fused to the rame axes
                 9 Pedicels appressed, but not fused, to the rame axes
                   10 Pedicellate spikelets 4-8 mm long
                   10 Pedicellate spikelets 1-3 mm long
    3 Spikelets not embedded or fitting into grooves in the rachis, the rachis slender (the spikelets visibly separate and often pedicelled).
                     11 Pedicelled spikelet similar to the sessile spikelet, both fertile.
                       12 Spikelets falling separately from the persistent rachis.
                          13 Panicle contracted, spikelike; glumes membranous
                          13 Panicle loose; glumes cartilaginous or coriaceous
                       12 Spikelets falling in pairs together with sections of the disarticulating rachis.
                            14 Spikelets awned with awns 10-26 mm long; anthers 2; [native, collectively common and widespread]
                            14 Spikelets unawned or with awns to 5.2 mm long; anthers 3; [exotic, rarely encountered]
                              15 Spikelets unawned
                              15 Spikelets with awns 4-5.2 mm long
                     11 Pedicelled spikelet differing from the sessile in shape and sex (sometimes represented only by a pedicel).
                                16 Spikelets awned, the awn 10-20 cm long.
                                  17 First glume with a row of punctate, concave glands; panicle contracted, spikelike
                                16 Spikelets with or without awns, if awned the awns < 5 cm long.
                                    18 Inflorescence a panicle (false panicles in Hyparrhenia), the branches not subtended by sheaths.
                                       19 Inflorescence a false panicle with numerous inflorescence units; peduncles with 2 rames in digitate clusters (1 almost sessile, the other rame stalked and both bearing 7-14 heterogamous spikelet pairs), disarticulation in the rames beneath the bisexual spikelets; spikelets a mix of heterogamous and homogamous pairs; awns of the lemma 1-3.5 cm long; [non-natives]
                                       19 Inflorescences true panicles (with evident rachises); disarticulation beneath the sessile spikelets (or not occurring at all); spikelets only heterogamous; awns of the lemma (5-) 10-40 mm long (when present); [native and non-natives].
                                         20 Pedicelled spikelet represented by pedicel only; apex of sheath bearing 2 auricles 1-10 mm long; awns of the lemmas once or twice-geniculate; [native]
                                         20 Pedicelled spikelet present, staminate; apex of sheath truncate; lemmas unawned or awned and once geniculate; [non-native]
                                    18 Inflorescence of 1-13 digitate (whorled) racemes borne at the summit of a peduncle, the peduncle subtended by a raceme sheath.
                                           21 Racemes 1 per peduncle and raceme sheath
                                           21 Racemes 2-13 per peduncle and raceme sheath.
                                             22 Pedicels of the pedicelled (reduced or absent) spikelets terete or slightly flattened and grooved on one side only.
                                               23 Pedicellate spikelet sterile, vestigial or absent; sessile spikelets < 7 mm long
                                               23 Pedicellate spikelet staminate, as large as the sessile, fertile spikelet; sessile spikelets > 7 mm long
                                             22 Pedicels of the pedicelled (reduced or absent) spikelets strongly flattened and with or without grooves on both sides.
                                                 24 Rame internodes and pedicels with a translucent medial groove; pedicelled spikelets smaller than the sessile spikelets (or vestigial/absent)
                                                 24 Rame internodes and pedicels without a translucent medial groove; pedicelled spikelets ca. the same size as sessile spikelets