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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 Poaceae, Key B: robust herbaceous grasses

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1 Inflorescence an array of spikes, the spikelets closely imbricate in 2 rows along the rachis of the spikes, the spikes alternate along the primary inflorescence axis; [tribe Zoysieae; subtribe Sporobolinae]
1 Inflorescence otherwise, either the spikelets embedded or in grooves in an thickened rachis, or the inflorescence a slender or broad panicle.
  2 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). Spikelets unisexual, with male and female spikelets in separate inflorescences or in different parts of the same inflorescence; [tribe Andropogoneae].
    3 Racemes of mixed sex (female below, male above)
    3 Racemes of single sex
 Zea
  2 Spikelets not embedded or fitting into grooves in the rachis, the inflorescence a slender or broad panicle (the spikelets visibly separate and often pedicelled).
      4 Spikelets with a single floret, this unisexual (either pistillate or staminate); plants with aerenchymatous culms, [plants of seasonally or tidally flooded wetlands]; [tribe Oryzeae].
        5 Pistillate spikelets on the upper branches of the panicle, staminate spikelets on the lower branches; lemmas and paleas clasping along their margins; plants annual
        5 Pistillate and staminate spikelets intermingled on the same branches of the inflorescence; lemma margins free; plants perennial
      4 Spikelets with 2 or more florets, at least some of these bisexual; plants without aerenchymatous culms, [plants of uplands or temporarily to seasonally flooded wetlands].
          6 Spikelets with 2-8 florets, these bisexual.
             7 Leaves primarily basal, plants densely cespitose.
               8 ; [tribe Arundineae
               8 Panicles plumose; [tribe Danthonieae]
             7 Leaves cauline; plants short-rhizomatous (somewhat clumped) to long-rhizomatous; [tribe Arundineae].
                 9 Lemmas pilose; rachilla glabrous; plants short-rhizomatous (somewhat clumped); culms to 10 m tall; [plants of uplands or saturated or temporarily flooded wetlands]
                 9 Lemmas glabrous; rachilla sericeous; plants long rhizomatous; culms to 4 m tall; [plants of uplands or saturated, tidally flooded, or seasonally flooded wetlands]
          6 Spikelets almost always with 2 florets, the lower florets sterile or staminate (sometimes reduced to lemmas or completely absent).
                   10 Spikelets falling separately, not attached to rachis segments, stalks, or bristles; spikelets <2× as long as wide; [tribe Paniceae].
                     11 Spikelets (at least the terminal) subtended by 1-many stiff, terete bristles
                     11 Spikelets not subtended by stiff bristles.
                       12 Fertile lemma rugose with cross-venation
                       12 Fertile lemma smooth or hairy, not rugose
                   10 Spikelets falling with attached rachis segments, stalks, or bristles; spikelets >3× as long as wide; [tribe Andropogoneae].
                          13 Pedicelled spikelet differing from the sessile in shape and sex (sometimes represented only by a pedicel).
                            14 Inflorescence a panicle, the branches not subtended by sheaths.
                              15 Pedicelled spikelet represented by pedicel only; apex of sheath bearing 2 auricles 1-10 mm long; [native]
                              15 Pedicelled spikelet present, staminate; apex of sheath truncate; [exotic]
                          13 Pedicelled spikelet similar to the sessile spikelet, both fertile.
                                16 Spikelets falling separately from the persistent rachis
                                16 Spikelets falling in pairs together with sections of the disarticulating rachis
                                  17 Spikelets awned with awns 10-26 mm long; anthers 2; [native, collectively common and widespread]
                                  17 Spikelets unawned or with awns to 5.2 mm long; anthers 3; [exotic, rarely encountered]
                                    18 Spikelets unawned
                                    18 Spikelets with awns 4-5.2 mm long

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

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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 not paired, unaccompanied by a vestige
  2 Leaves tapering to a broadly cuneate base; spikelets paired (one of the pair sometimes vestigial)
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 lacking glands; panicle open, the branches 5-8 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, the branches not subtended by sheaths.
                                       19 Pedicelled spikelet represented by pedicel only; apex of sheath bearing 2 auricles 1-10 mm long; [native]
                                       19 Pedicelled spikelet present, staminate; apex of sheath truncate; [exotic]
                                    18 Inflorescence of 1-13 digitate (whorled) racemes borne at the summit of a peduncle, the peduncle subtended by a raceme sheath.
                                         20 Racemes 1 per peduncle and raceme sheath
                                         20 Racemes 2-13 per peduncle and raceme sheath.
                                           21 Pedicels of the pedicelled (reduced or absent) spikelets terete or slightly flattened and grooved on one side only
                                           21 Pedicels of the pedicelled (reduced or absent) spikelets strongly flattened and with or without grooves on both sides.
                                             22 Rame internodes and pedicels with a translucent medial groove; pedicelled spikelets smaller than the sessile spikelets (or vestigial/absent)
                                             22 Rame internodes and pedicels without a translucent medial groove; pedicelled spikelets ca. the same size as sessile spikelets