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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
                   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 unawned
                                    18 Spikelets with awns 4-5.2 mm long

Key to Poaceae, Key F: grasses of tribe Paniceae (also including grasses keyed as well in Keys B, C, D, and H)

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1 Inflorescences spikelike branches, the spikelets partially embedded in the rachises
1 Inflorescences panicles or spikes (if spikes, the spikelets not embedded.
  2 Spikelets (at least the terminal) subtended by 1-many stiff, terete bristles.
    3 Bristles persistent on the inflorescence, each spikelet disarticulating above the bristles
    3 Bristles falling with the spikelets at maturity (the disarticulation at the base of the fascicles)
  2 Spikelets not subtended by stiff bristles.
      4 Inflorescences of spikelike branches 1-3.7 cm long, the branch extending 2.5-4 mm beyond the attachment of the distal spikelets
      4 Inflorescences not as above.
        5 Upper florets laterally compressed
        5 Upper florets dorsally compressed.
          6 Lower glumes or lower lemmas awned.
             7 Leaves > 10× as long as wide; ligules absent or of hairs
             7 Leaves < 8× as long as wide; ligules present, membranous or of hairs.
               8 Lower glumes unawned or very shortly so; upper glumes ciliate-margined; plants erect or basally decumbent
               8 Lower glumes awned; upper glumes not ciliate-margined; culms trailing; plants strongly trailing, rooting at the nodes
          6 Lower glumes and lower lemmas unawned.
                 9 Lemma margins flat, hyaline; lower glumes absent or < ¼ the length of the upper glume.
                   10 Subterranean (cleistogamous) inflorescences present; aerial inflorescences with elongate rachises; spikelets of the aerial inflorescences often sterile; spikelets glabrous; leaves either with a white cartilaginous margin or prominently ciliate; [of the Coastal Plain]
                   10 Subterranean inflorescences absent; aerial inflorescences either with digitate or subdigitate branches and glabrous spikelets, or with elongate rachises and conspicuously pubescent spikelets; spikelets of the aerial inflorescences fertile; spikelets glabrous, ciliate, or pubescent; leaves various (often not as above); [collectively widespread]
                     11 Inflorescence a narrow panicle with the branches strongly ascending to appressed; spikelets ellipsoid to obovoid; [of Coastal Plain pinelands]
                     11 Inflorescence either a panicle with digitate or subdigitate clusters of spikelike branches or a broad panicle with widely divergent branches; [widespread]
                 9 Lemma margins not hyaline, frequently involute; lower glumes various (absent, < ¼ the length, to longer than the upper glume).
                       12 Spikelets subtended by a cuplike callus
                       12 Spikelets not subtended by a cuplike callus.
                          13 Leaves primarily lacking ligules (at least the upper, and often all, leaves without ligules, if vestigial ligules present, these of hairs)
                          13 Leaves with ligules, these either membranous or of hairs.
                            14 Lower (sterile) palea indurate and expanding the spikelet at maturity, as long as the lower (sterile) lemma; lower and upper florets standing apart from one another at maturity; outer surface of the upper (fertile) palea with compound papillae
                            14 Lower (sterile) palea membranous, not expanding the spikelet at maturity, usually shorter than lower (sterile) lemma, or absent; lower and upper florets closely appressed at maturity; outer surface of the upper (fertile) palea lacking compound papillae.
                              15 Inflorescence of 1-sided, spikelike primary branches.
                                16 Spikelets with lower lemmas (and lower glumes, if present) adjacent to the branch axes.
                                  17 Lower glumes absent
                                  17 Lower glumes present on at least most spikelets
                                16 Spikelets with upper lemmas (and upper glumes, if present) adjacent or appressed to the branch axes.
                                    18 Both glumes absent from all or most spikelets
                                    18 Upper or both glumes present on all spikelets.
                                       19 Lower glumes usually absent; upper lemmas smooth to slightly rugose
                                       19 Lower glumes present; upper lemmas rugose and verrucose
                              15 Inflorescence either paniculate with well-developed secondary branchlets or if the primary branches spikelike, then the spikelets not borne in a 1-sided arrangement on the spicate branches.
                                         20 Inflorescences dense, the spikelets obscuring most of the internal branches
                                         20 Inflorescences open panicles, or if narrowed, all or nearly all the panicle branches readily visible.
                                           21 First glume 5-7.5 mm long, nearly as long as sterile lemma; fertile lemma 1/3 length of sterile lemma; rachilla prolonged between the florets
                                           21 First glume shorter, or if this long, then at most 3/4 length of sterile lemma; fertile lemma > ½ the length of the sterile lemma; rachilla not prolonged between the florets.
                                             22 Plant developing a terminal (“spring”) inflorescence usually before mid-summer, followed by lateral (“autumnal”) inflorescences from lower, mid, and/or upper nodes, these often included or hidden among the fascicles of smaller “autumnal” leaves; often developing a rosette of overwintering basal leaves
                                             22 Plant developing a terminal inflorescence usually after mid-summer, the lateral inflorescences, when present, from the upper nodes, usually appearing at the same time as the terminal panicle, and not hidden by dense fascicles of smaller leaves; plants lacking a rosette of overwintering basal leaves.
                                               23 Spikelets tuberculate (or tuberculate-hispid)
                                               23 Spikelets smooth, not tuberculate.
                                                 24 Panicle < 2 cm wide at maturity.
                                                    25 Spikelets > 4.5 mm long; first glume > 2.4 mm long; ligule 4-6 mm long; [of coastal dunes]
                                                    25 Spikelets < 4 mm long; first glume < 2.1 mm long; ligule < 2 mm long; [not of coastal dunes].
                                                      26 Blades involute, 1.5-4 mm wide; culms wiry
                                                      26 Blades flat, the larger 6-20 mm wide; culms stout.
                                                        27 Panicles constricted, 0.3-1.6 cm wide; spikelets subsessile to short-pediceled; summit of fertile palea not enclosed by fertile lemma
                                                        27 Panicles > 1 cm wide; spikelets short to long-pedicelled; summit of fertile palea enclosed by fertile lemma
                                                 24 Panicle > 2 cm wide at maturity.
                                                          28 Fertile lemmas rugose with cross-venation between the main parallel veins
                                                          28 Fertile lemmas not rugose.
                                                            29 Lower primary panicle branches in whorls of 4-7 at the nodes, stiffly spreading, naked on the proximal ½, the axils strongly pilose; lower culm internodes appressed papillose-pubescent; first glume acuminate, ½ as long as spikelet; fertile lemma chestnut brown at maturity
                                                            29 Plants without the above combination of characters.
                                                              30 Plants from a cluster of fibrous roots, without rhizomes or hard knotty crowns, annual
                                                              30 Plants with rhizomes or hard knotty crowns, perennial.
                                                                 31 Plants with hard crowns, lacking rhizomes; fertile lemma 1.2-1.6 mm long
                                                                 31 Plants with rhizomes; fertile lemma 1.6-4 mm long.
                                                                   32 Rhizomes about 1 cm thick with pubescent scale-like leaves; lower portion of culm hard, nearly woody
                                                                   32 Rhizomes less than 1 cm thick with glabrous scale-like leaves; culms not woody.
                                                                     33 First glume truncate apically
                                                                     33 First glume acute to obtuse.
                                                                       34 Culms slightly compressed below; ligules 0.5 mm long or less; spikelet pedicels appressed, the spikelets subsecund, usually some obliquely bent above the first glume; fertile lemma 1.8-2.2 mm long
                                                                       34 Culms terete; ligules 1-6 mm long; at least some spikelet pedicels spreading, spikelets not at all secund, essentially straight; fertile lemma 2-4 mm long