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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 present or absent; if absent, then the achene > 1 mm long or > 0.7 mm wide, and tubercle triangular to subulate. | |
5 Achene including tubercle 1.5-2.9 mm long; tubercle triangular to triangular-acuminate; [section Rariflorae]. | |
4 Culms stouter; leaves wider, not filiform. | |
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 0.8-1.4 mm long, 0.7-1.2 mm wide, the faces slightly biconvex with 6-12 transverse ridges. | |
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 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. | |
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. | |
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. | |
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 | |
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] | |
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 | |
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] |