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Key to Rhynchospora, Key E: beaksedges with bristles smooth, or antrorsely barbed and filiform,
or absent, the achene surface smooth, minutely pitted, or finely striate
[subgenus Diplostylae; sections Chapmaniae, Fasciculares, and Fuscae]

Cyperaceae

Rhynchospora

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1 Bristles 12; [section Fasciculares]
1 Bristles 6 or fewer.
  2 Leaves with a short taper at the tip, blunt to acute, but not long-acuminate; achene surface minutely pitted near the margin; [section Chapmaniae].
    3 Basal leaves 4-6 mm wide, ciliate, rosulate; scales acuminate, the midrib ciliate; bristles 6, < ½ the length of the achene; achenes 1.6-2 mm long; [widespread in mesic to wet pinelands from VA s. to FL, w. to e. LA]
    3 Largest basal leaves 2.5-3 mm wide, eciliate, not rosulate; scales aristate, the midrib eciliate; bristles 3-4, 1 or more equaling or exceeding the tubercle; achenes (1.4-) 1.5-1.7 (-1.9) mm long; [rare, s. GA, disjunct in se. SC]
  2 Leaves long-acuminate at the tip; achene surface smooth or finely striate.
      4 Bristles absent or 1-3 rudimentary; scales white to pale tan (or pale reddish-brown in R. brachychaeta); [section Chapmaniae].
        5 Inflorescence composed of (1-) 2-3 turbinate to ellipsoid clusters; spikelets pale reddish-brown, (2.7-) 3-3.5 mm long; achenes usually 2 per spikelet
        5 Inflorescence composed of 1 (-2) hemispheric to broadly turbinate cluster(s); spikelets white to pale brown, either 2-2.5 (-3) mm or (3.5-) 4-5.5 mm long; achenes 1 per spikelet.
          6 Base of plant not bulb-like, not enclosed in bladeless sheaths; spikelets 2-2.5 (-3) mm long; achene 1.0-1.2 mm long, 0.8-1.0 mm wide
          6 Base of plant bulb-like, enclosed in bladeless sheaths; spikelets (3.5-) 4-5.5 mm long; achene 1.4-1.8 mm long, 1.2-1.5 mm wide
      4 Bristles present (if rudimentary, then 4-6); scales tan, pinkish-tan, rufous, or brown.
             7 Achene 0.6-1.1 mm wide, pyriform, obovoid, or narrowly elliptic, pale to dark brown but not blackish; tubercle margin setose (except R. setosa).
               8 Inflorescence of 1 cluster; tubercle 0.3-0.4 mm long, the margin smooth; [s. MS Coastal Plain; section Chapmaniae]
               8 Inflorescence of (1-) 2-4 (-10) clusters; tubercle 0.4-1.4 mm long, the margin setose; [widespread; section Fuscae].
                 9 Achene narrowly elliptic or narrowly obovoid, 1.2-1.5 mm long by 0.6-0.7 mm wide, twice as long as wide; tubercle 0.8-1.2 mm long
                 9 Achene broadly elliptic to obovoid or pyriform, < 2× as long as wide; tubercle 0.4-1.5 mm long.
                   10 Leaves 2-4 (-5) mm wide; stipe subtending achene 0.5-1.0 mm long
                   10 Leaves 0.2-1.5 (-2) mm wide; stipe subtending achene < 0.4 mm long.
                     11 Leaves to 1.5 (-2) mm wide; achene 1.0-1.7 mm long, 0.9-1.1 mm wide; tubercle 0.5-1.5 mm long, triangular-subulate, the margins typically conspicuously concave.
                       12 Culms solitary to loosely cespitose by slender rhizomes; terminal internode straight; clusters turbinate to ovoid; achene 1.0-1.3 mm long, uniformly medium to dark brown; tubercle 0.7-1.5 mm long; bristles usually of two lengths, some equaling the tubercle, and some equaling or shorter than the achene
                       12 Culms solitary to cespitose, without slender rhizomes; terminal internode often arched; clusters corymbose to hemispheric; achene 1.3-1.7 mm long, pale to reddish-brown, often translucent centrally, with a distinctly thickened wire-like margin; tubercle 0.5-1.0 mm long; all bristles more-or-less equaling the tubercle
                     11 Leaves filiform, < 1 mm wide; achene 0.8-1.3 mm long, 0.6-0.9 mm wide; tubercle 0.4-0.8 mm long, deltoid to triangular-subulate, the margins flat to concave.
                          13 Plants with delicate, long-creeping rhizomes; spikelets 5-7 mm long; achene uniformly opaque; tubercle 0.6-0.8 mm long
                          13 Plants without rhizomes; spikelets 2.5-5 mm long; achene translucent centrally; tubercle 0.4-0.7 mm long.
                            14 Achenes 1.5-1.9 mm long, 0.5-0.8 mm wide; stipes 0.2-0.3 mm long; tubercles 0.4-0.6 mm long
                            14 Achenes 2.1-2.3 mm long, 0.8-0.9 mm long; stipes 0.3-0.4 mm long; tubercles 0.6-0.7 mm long
             7 Achene > 1 mm wide (except 0.8 mm wide in R. fernaldii with a blackish surface), suborbicular or broadly ellipsoid; tubercle margin smooth or roughened but not setose; [section Fasciculares].
                              15 Achene 0.9-1.0 mm long, 0.8 mm wide, blackish
                              15 Achene 1.3-4.2 mm long, 1.1-3.6 mm wide, brown to dark brown.
                                16 Achene 2.0-4.2 mm long, 2.0-3.6 mm wide.
                                  17 Leaves 2-4 mm wide; achene light to dark brown, usually at least somewhat rugulose in texture, 2.0-2.7 mm long, 2.0-2.5 mm wide, the tubercle base often somewhat rimmed
                                  17 Leaves 4-8 mm wide; achene blackened (when fully ripe), shiny and smooth in texture, 3.0-4.2 mm long, 3.0-3.6 mm wide, the tubercle base usually not rimmed (grading more smoothly between the dark achene body and lighter-colored tubercle
                                16 Achene 1.3-2.0 mm long, 1.1-1.7 mm wide.
                                    18 Tubercle 1.0-2.6 mm long, long-attenuate to subulate
                                    18 Tubercle 0.2-0.8 mm long, triangular to triangular-attenuate or with a strap-like beak.
                                       19 Bristles rudimentary to ½ as long as the achene body.
                                         20 Larger leaves to 1 mm wide; mature culms to 4.5 dm long; floral fascicles 1 (-2); tubercle 0.2-0.5 mm long
                                         20 Larger leaves 2-4 mm wide; mature culms to 13 dm long; floral fascicles (1-) 2-4; tubercle 0.4-0.7 mm long
                                       19 Bristles > ½ as long to exceeding the achene body.
                                           21 Basal leaves filiform to (rarely)1.3 mm wide, the longer approaching length of culm; tubercle narrowed above the base into a strap-like beak
                                           21 Basal leaves 1.3-4 mm wide, all much shorter than the culm; tubercle triangular to triangular-attenuate.
                                             22 Longer bristles equaling to exceeding the achene body; achene body elliptic, 1.1-1.3 mm wide; tubercle triangular-attenuate; larger basal leaves 1.3-2.5 mm wide
                                             22 Longer bristles < ½ as long to exceeding achene body; achene suborbicular, 1.2-1.5 mm wide; tubercle triangular; larger basal leaves 2-4 mm wide

Key to Rhynchospora, Key F: beaksedges with bristles smooth, or antrorsely barbed and filiform, or absent,
the achene surface transversely ridged, rugose, or honeycombed-reticulate
[subgenus Diplostylae; sections Globulares, Harveyae, Mixtae, Psilocarya, Pusillae, Rariflorae]

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1 Bristles absent (or apparently so at 10×); achene 0.5-0.7 mm wide; tubercle 0.1-0.2 mm long, skull-cap like; [section Pusillae].
  2 Achene including tubercle 1.0-1.2 mm long, the achene surface evidently reticulate and obscurely transversely ridged, the body ellipsoid; bristles present, white, barely visible at 20×, the longest shorter than the achene body
  2 Achene including tubercle 0.6-0.9 mm long, the body obovoid; bristles absent.
    3 Achene surface smooth, faintly reticulate, not transversely ridged
    3 Achene surface rough, distinctly transversely ridge
1 Bristles present or absent; if absent, then the achene > 1 mm long or > 0.7 mm wide, and tubercle triangular to subulate.
      4 Culms and leaves filiform.
        5 Achene including tubercle 1.0-1.2 mm long; tubercle minute, skullcap-like; [section Pusillae]
        5 Achene including tubercle 1.5-2.9 mm long; tubercle triangular to triangular-acuminate; [section Rariflorae].
          6 Bristles subequaling to exceeding the tubercle; tubercle 0.75-1.4 mm long
          6 Bristles shorter than the achene body; tubercle 0.3-1.0 mm long.
             7 Achene 1.3-1.6 mm long, 0.9-1.4 mm wide; tubercle 0.3-0.6 (-0.75) mm long; bristles 1/3-1/2(-4/5) as long as achene body
             7 Achene 1.6-1.8 mm long, 1.35-1.5 mm wide; tubercle 0.6-1.0 mm long; bristles 2/3 to nearly as long as achene body
      4 Culms stouter; leaves wider, not filiform.
               8 Achene faces flat or concave; when one face is concave, the opposite face is sometimes slightly convex (slightly biconvex R. decurrens and R. microcarpa are keyed here for convenience).
                 9 Achene at least twice as long as wide, elliptic-oblong; tubercle subulate, 0.8-1.2 mm long; [section Mixtae]
                 9 Achene < twice as long as wide, obovate; tubercle triangular, 0.2-0.9 mm long.
                   10 Longer bristles exceeding the achene body.
                     11 Achene ±2.2 mm long, ±1.8 mm wide; tubercle ±0.9 mm long; [section Globulares]
                     11 Achene 0.8-1.2 mm long, 0.7-1.2 mm wide; tubercle 0.2-0.5 mm long; [section Mixtae].
                       12 Larger leaves (3-) 4-6 mm wide; bristles exceeding tubercle; achene faces flattened
                       12 Larger leaves 1-3 (-4) mm wide, bristles half as long as achene to equaling tubercle; achene faces slightly convex
                   10 Longer bristles shorter than to equaling achene body, or absent.
                          13 Larger leaves 3-5 mm wide; achene 1.4-1.6 mm wide; tubercle 0.6-0.8 mm long, abruptly rising from a flaring basal collar; [section Globulares]
                          13 Larger leaves 1-3 (-4) mm wide; achene 0.7-1.3 mm wide; tubercle 0.15-0.5 mm long, without a flaring basal collar; [section Mixtae].
                            14 Bristles rudimentary or absent
                            14 Bristles evident, at least 1/4 as long to exceeding achene.
                              15 Culms 20-50 cm long; leaves 1-2 mm wide; bristles ½ or less as long as achene body
                              15 Culms 50-110 cm long; leaves (1-) 2-4.5 mm wide; longer bristles more than ½ as long to exceeding achene body.
                                16 Achene 1.3-1.8 mm long, 0.9-1.2 mm wide, the faces flat with 10-12 transverse ridges
                                16 Achene 0.8-1.4 mm long, 0.7-1.2 mm wide, the faces slightly biconvex with 6-12 transverse ridges.
                                  17 Clusters elongate; achene 1.0-1.4 mm long, 0.8-1.0 mm wide, narrowly obovate to elliptic, averaging 8-12 transverse ridges; most tubercle bases convexly seated on the achene summit and somewhat decurrent along the achene margins, the tubercle surface often whitish-waxy
                                  17 Clusters usually compact; achene 0.8-1.2 mm long, 0.7-1.2 mm wide, suborbicular to elliptic, averaging 6-7 transverse ridges; most tubercle bases flat across the achene summit, not decurrent, the tubercle surface usually dark, not waxy
               8 Achenes biconvex or tumid.
                                    18 Achene 1.4-4.2 mm long, 1.2-3.6 mm wide, the summit with a thickened bony to crustaceous rim surrounding the base of the tubercle; [section Harveyae].
                                       19 Achene lenticular and transversely ridge, ±1.4 mm long, ±1.2 mm wide
                                       19 Achene tumid, lightly pitted or cancellate in a honeycomb pattern, 1.5-4.2 mm long, 1.4-3.6 mm wide.
                                         20 Leaves 2-4 mm wide; achene < 2.7 mm long and < 2.5 mm wide.
                                           21 Achene 2.0-2.7 mm long, 2.0-2.5 mm wide
                                           21 Achene 1.5-1.9 mm long, 1.4-1.7 mm wide
                                    18 Achene 0.7-1.8 mm long, 0.7-1.5 mm wide, the summit without a textured rim surrounding the base of the tubercle (if the base of the tubercle is rim-like, then it is distinguished from the summit of the achene by a constriction or articulation).
                                             22 Bristles absent; achene 0.7-1.0 mm long; [section Psilocarya].
                                               23 Tubercle triangular-lanceolate, as long as broad or longer; achene weakly transversely ridged
                                               23 Tubercle depressed, broader than long; style not persistent; achene strongly transversely ridged
                                                 24 Spikelets (5-) 6-10 mm long, tan or brown, with an acuminate tip; tubercle ends upturned away from the achene at about a 90 degree angle
                                                 24 Spikelets 4-6 (-8) mm long, dark brown to black, with an acute tip; tubercle ends accrescent to the achene
                                             22 Bristles present (occasionally detached in R. decurrens and R. miliacea with achenes 1.0-1.4 mm long); achene 0.8-1.9 mm long.
                                                    25 Bristles not exceeding the achene body.
                                                      26 Cluster branches flexuous (the branches curved), not uniformly erect and stiff; bristles one-half as long to equaling the achene (or longer in R. microcarpa); [section Mixtae].
                                                        27 Clusters elongate; spikelets 2.5-3.5 mm long; achene narrowly obovate to elliptic, averaging 8-12 transverse ridges; most tubercle bases convexly seated on the achene summit and somewhat decurrent along the achene margins, the tubercle surface often whitish-waxy
                                                        27 Clusters usually compact, branches ascending to spreading (sometimes widely so in R. vernalis); spikelets 1.5-3.0 mm long; achene suborbicular to elliptic, averaging 5-8 (-9) transverse ridges, most tubercle bases flat across the achene summit, not or only slightly decurrent, the tubercle surface usually dark, not waxy.
                                                          28 Inflorescence occupying the upper 2/3-3/4 of the length of the culm, the lowest lateral panicle at the first or second node above the base; spikelets 1.5-2.25 mm long, broadly ovoid to suborbicular, apically rounded; achene body averaging 5-6 (-7) horizontal ridges; tubercle 0.2-0.4 mm long
                                                          28 Inflorescence occupying the upper ¼-½ of the culm, the lowest 2-4 nodes barren; spikelets 2.0-3.0 mm long, ovoid, acute; achene body averaging 6-9 horizontal ridges; tubercle 0.25-0.85 mm long.
                                                            29 Inflorescence cluster branches ascending, the clusters mostly tightly congested; achene 1.0–1.7 times as long as wide, dark brown, shallowly nearly horizontally ridged or with nearly isodiametric alveolae, ridges 7–9; bristles of each achene nearly equal in length, from 0.5 to 1.5 times as long as the achene body; plants slender, mostly less than 1 meter tall, with leaves typically less than 40 cm long and 3 mm wide; [NC s. to s. FL, w. to s. MO and s. TX]
                                                            29 Inflorescence cluster branches widely spreading in flower, spreading to ascending in fruit, the clusters rather open, not congested; achene 1.0–1.2 times as long as wide, light brown, strongly transversely ridged with 6–8 irregular ridges and narrow rectangular alveolae; bristles unequal in length, from 0.9–1.5 times as long as the achene body; plants robust, typically more than 1.2 meters tall, with leaves often over 50 cm long and 4 mm wide; [FL]
                                                      26 Cluster branches stiff, erect, bristles < 1/3 to ¾ (-1) × as long as achene body; [section Globulares].
                                                              30 Leaves to 2 mm wide; longer bristles no more than ½ as long as achene; achene body lenticular, one side often flattened
                                                              30 Leaves to 5 mm wide; longer bristles > ½ as long to equaling achene; achene biconvex.
                                                                 31 Larger culm leaves to 5 mm wide; achenes (1.2-) 1.4-1.6 (-1.9) mm long, (1.1-) avg. 1.4 (-1.75) mm wide; achene surface alveoli longitudinally narrow; tubercle 0.3-0.7 mm long, base 0.6-1.0 mm wide
                                                                 31 Larger culm leaves to 3 mm wide; achenes (1.0-) avg. 1.3 (-1.5) mm long and wide; if achene surface alveoli longitudinally narrow, then tubercle 0.2-0.4 mm long and base 0.5-0.7 mm wide (R. globularis).
                                                                   32 Longer bristles ⅓-½ (-¾)× the length of the achene; achene surface alveoli longitudinally narrow (typically 0.02-0.05 mm wide between the longitudinal walls), the latitudinal walls raised into horizontal ridges; tubercle 0.2-0.4 mm long, the base 0.5-0.7 mm wide
                                                                   32 Longer bristles ⅔-1× the length of the achene; achene surface alveoli nearly as wide as long (typically 0.05-0.1 mm wide between the longitudinal walls), the latitudinal walls obscurely or not at all raised into horizontal ridges; tubercle 0.35-0.7 mm long, the base 0.7-0.9 mm wide
                                                    25 Bristles equaling or longer than the tubercle.
                                                                     33 Primary branches of the inflorescence spreading at right angles from the culm, each spikelet or small cluster on slender spreading or reflexed stalks; [section Mixtae]
                                                                     33 Primary branches of the inflorescence ascending.
                                                                       34 Spikelets (4-) 6-9 mm long; achene (body) 1.4-1.7 mm long (including a stipe 0.3-0.6 mm in length); [section Mixtae]
                                                                       34 Spikelets < 5 mm long; achene (body) 1.0-1.5 (-1.6) mm long (if ≥ 1.4 mm long, then the achene stipe either absent (R. saxicola) or the stipe ≤ 0.3 mm (R. caduca); [section Mixtae, except R. saxicola in section Globulares].
                                                                         35 Tubercle 0.4-0.8 mm long, the edges setose or uneven with waxy or crusty irregular protuberances; [section Mixtae].
                                                                           36 Achene obovate to suborbicular, 1.2-1.6 mm wide, latitudinal alveoli walls strongly raised into transverse ridges; achene base with a stipe to 3 mm long
                                                                           36 Achene slenderly obovoid, 0.8-1.0 mm wide, latitudinal alveoli walls weakly or not at all raised into transverse ridges; achene stipe diminuitive or virtually absent
                                                                         35 Tubercle 0.2-0.5 (-0.85) mm long, the edges smooth.
                                                                              37 Spikelets 3.5-4 mm long; bristles (usually) exceeding the tubercle; achene 1.3-1.5 (-1.6) mm long, 1.2-1.3 mm wide; [section Globulares]
                                                                              37 Spikelets 1.5-3 mm long; longer bristles nearly equaling the tubercle; achene 0.8-1.2 mm long, 0.7-1.2 mm wide; [section Mixtae].
                                                                                38 Inflorescence occupying the upper 2/3-3/4 of the length of the culm, the lowest lateral panicle at the first or second node above the base; spikelets 1.5-2.25 mm long, broadly ovoid to suborbicular, apically rounded; achene body averaging 5-6 (-7) horizontal ridges; tubercle 0.2-0.4 mm long
                                                                                38 Inflorescence occupying the upper ¼-½ of the culm, the lowest 2-4 nodes barren; spikelets 2.0-3.0 mm long, ovoid, acute; achene body averaging 6-9 horizontal ridges; tubercle 0.25-0.85 mm long.
                                                                                  39 Inflorescence cluster branches ascending, the clusters mostly tightly congested; achene 1.0–1.7 times as long as wide, dark brown, shallowly nearly horizontally ridged or with nearly isodiametric alveolae, ridges 7–9; bristles of each achene nearly equal in length, from 0.5 to 1.5 times as long as the achene body; plants slender, mostly less than 1 meter tall, with leaves typically less than 40 cm long and 3 mm wide; [NC s. to s. FL, w. to s. MO and s. TX]
                                                                                  39 Inflorescence cluster branches widely spreading in flower, spreading to ascending in fruit, the clusters rather open, not congested; achene 1.0–1.2 times as long as wide, light brown, strongly transversely ridged with 6–8 irregular ridges and narrow rectangular alveolae; bristles unequal in length, from 0.9–1.5 times as long as the achene body; plants robust, typically more than 1.2 meters tall, with leaves often over 50 cm long and 4 mm wide; [FL]