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Keyed in multiple places:

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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 of 2-13 digitate (whorled) racemes borne at the summit of a peduncle, the peduncle subtended by a raceme sheath
............ ............ ..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 with awns 4-5.2 mm long

Key to Poaceae, Key D: rattail or cob grasses

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1 All spikelets unisexual, the pistillate and staminate spikelets either in separate inflorescences, or the pistillate spikelets below the staminate spikelets in the same inflorescence; leaves 9-120 mm wide; [tribe Andropogoneae].
..2 Pistillate spikelets below the staminate in the same inflorescence
..2 Pistillate and staminate spikelets in separate inflorescences, the pistillate inflorescences axillary, staminate inflorescences terminal
 Zea
1 Some spikelets bisexual; leaves 1-25 mm wide.
....3 Spikelets with 2-7 florets, the lower bisexual and fertile, the upper sometimes sterile; [tribe Triticeae]
....3 Spikelets with at most 2 florets, the lower staminate or sterile, the upper bisexual, staminate, or sterile.
......4 Culms 2-45 cm tall; leaves 1-6 mm wide; plants annual (perennial in Eremochloa and Stenotaphrum).
........5 Plants obviously and prominently rhizomatous (Eremochloa) or stoloniferous (Stenotaphrum); lower glume with pectinate margins (Eremochloa) or irregularly toothed (Stenotaphrum)
..........6 Plant rhizomatous; lower glume with pectinate margins; [commonly naturalized turf grass and roadside weed]; [tribe Andropogoneae]
..........6 Plant stoloniferous; lower glume irregularly toothed; [naturalized turf grass and allegedly also native]; [tribe Paniceae]
........5 Plants annual; lower glume with smooth and cartilaginous margins (or absent); [rare waifs]; [tribe Poeae].
............ 7 Spikelets with 1(-2) glume
............ 7 Spikelets with 2 glumes
......4 Culms 30-400 cm tall; leaves 2-25 mm wide; plants annual or perennial; [tribe Andropogoneae].
............ ..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
............ ......10 Sheaths mostly glabrous (sparsely ciliate towards the base); plants perennial
............ ......10 Sheaths with stiff, papillose-based hairs 1-3 mm long; plants annual
............ ....9 Pedicels appressed, but not fused, to the rame axes.
............ ........11 Pedicellate spikelets 4-8 mm long
............ ........11 Pedicellate spikelets 1-3 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 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
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