Flora of the Southeastern United States
2022 Edition

Colors

Data mode

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]

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 one-half as long to equaling achene.
............................15 Achene 1.3-1.8 mm long, 0.9-1.2 mm wide, the faces flat with 10-12 transverse ridges
............................15 Achene 0.8-1.4 mm long, 0.7-1.2 mm wide, the faces slightly biconvex with 6-12 transverse ridges.
..............................16 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
..............................16 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.
................................17 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].
..................................18 Achene lenticular and transversely ridge, ±1.4 mm long, ±1.2 mm wide
..................................18 Achene tumid, lightly pitted or cancellate in a honeycomb pattern, 1.5-4.2 mm long, 1.4-3.6 mm wide.
....................................19 Leaves 4-8 mm wide; achene 3.0-4.2 mm long, 3.0-3.6 mm wide
....................................19 Leaves 2-4 mm wide; achene < 2.7 mm long and < 2.5 mm wide.
......................................20 Achene 2.0-2.7 mm long, 2.0-2.5 mm wide
......................................20 Achene 1.5-1.9 mm long, 1.4-1.7 mm wide
................................17 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).
........................................21 Bristles absent; achene 0.7-1.0 mm long; [section Psilocarya].
..........................................22 Tubercle triangular-lanceolate, as long as broad or longer; achene weakly transversely ridged
..........................................22 Tubercle depressed, broader than long; style not persistent; achene strongly transversely ridged
............................................23 Spikelets (5-) 6-10 mm long, tan or brown, with an acuminate tip; tubercle ends upturned away from the achene
............................................23 Spikelets 4-6 (-8) mm long, dark brown to black, with an acute tip; tubercle ends accrescent to the achene
........................................21 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.
..............................................24 Bristles not exceeding the achene body.
................................................25 Cluster branches flexuous; bristles one-half as long to equaling the achene (or longer in R. microcarpa); achene slightly biconvex, 0.8-1.4 mm long, 0.7-1.0 (-1.2) mm wide; [section Mixtae].
..................................................26 Clusters elongate; 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
..................................................26 Clusters usually compact; achene 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
................................................25 Cluster branches stiff; bristles < 1/3 to ¾ (-1) as long as the achene; achene tumid above, often somewhat compressed below, 1.0-1.9 mm long, 1.0-1.7 mm wide; [section Globulares].
....................................................27 Achenes 1.5-1.9 mm long, 1.4-1.7 mm wide, the transverse ridging faint to absent; tubercle grayish-tan to bony white, and buttressed at the base by a thick bony-white rim; leaves to 3 mm wide
....................................................27 Achenes 1.0-1.9 mm long, 1.0-1.7 mm wide, the transverse ridging evident; tubercle grayish to dark brown, without a bony-white buttress; leaves to 3 or 5 mm wide.
......................................................28 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
......................................................28 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).
........................................................29 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
........................................................29 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
..............................................24 Bristles equaling or longer than the tubercle.
..........................................................30 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]
..........................................................30 Primary branches of the inflorescence ascending.
............................................................31 Spikelets 6-9 mm long; [section Mixtae]
............................................................31 Spikelets < 5 mm long.
..............................................................32 Tubercle 0.4-0.8 mm long, the edges setose or uneven with waxy or crusty irregular protuberances; [section Mixtae].
................................................................33 Achene obovate to suborbicular, 1.2-1.6 mm wide, latitudinal alveoli walls strongly raised into transverse ridges
................................................................33 Achene slenderly obovoid, 0.8-1.0 mm wide, latitudinal alveoli walls weakly or not at all raised into transverse ridges
..............................................................32 Tubercle 0.2-0.5 mm long, the edges smooth.
..................................................................34 Spikelets 3.5-4 mm long; bristles exceeding the tubercle; achene 1.3-1.5 mm long, 1.2-1.3 mm wide; [section Globulares]
..................................................................34 Spikelets 2.5-3 mm long; longer bristles about equaling the tubercle; achene 0.8-1.2 mm long, 0.7-1.2 mm wide; [section Mixtae].
....................................................................35 Inflorescence occupying the upper ¼-½ of the culm, the lowest 2-4 nodes barren
....................................................................35 Inflorescence occupying ⅔-¾ of the length of the culm, the lowest lateral panicle at the first or second node above the base