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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 I: rice grasses, of tribe Oryzeae (also including grasses keyed as well in Key B)

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1 Lemma margins free; plants perennial.
..2 Plants either < 1 m tall or a floating aquatic with lax stems to 1.5 m long
..2 Plants 1-4 m tall, emergent, the stems stout, not lax
1 Lemmas and paleas clasping along their margins; plants annual or perennial.
....3 Spikelets either pistillate or staminate, the upper branches of the panicle with pistillate spikelets, the lower branches with staminate spikelets; grains terete
....3 Spikelets bisexual; grains laterally flattened.
......4 Glumes absent and also lacking glume-like sterile florets subtending the floret; lemmas and paleas pectinately ciliate-hispid on the margins; [native]
......4 Glumes absent or greatly reduced, glume-like sterile florets subtending the fertile floret; lemmas and paleas glabrous or pubescent, but not pectinately ciliate hispid on the margins; [introduced]
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