Rhynchospora
beak-rush, beaksedge, rhynchospore
procumbent to erect, usually trigonous, wiry to stout.
basal and cauline, polystichous, mostly 3-ranked;
sheaths open apically, glabrous;
ligules present or absent;
blades flat, V-shaped in cross section or terete, typically keeled abaxially, margins involute or revolute, usually scabrid or scabridulous.
terminal, rarely pseudolateral, paniculate, corymbose, anthelate, racemose, or capitate;
spikelets 3–100 or more;
involucral bracts 1–6, spreading or rarely the proximal erect, leaflike.
scales spirally or distichously arranged, each subtending flower; 1 or more proximal scales empty.
all bisexual or sometimes distalmost staminate;
perianth absent or of 2–12(–20) bristles, usually persistent in fruit, rarely deciduous, variously barbed or plumed, shorter or longer than achene, seldom smooth;
stamens 2–3;
styles undivided or shallowly 2-fid, or deeply cleft into 2(–3) linear stigmatic branches;
style base persistent as tubercle on fruit, usually articulate to achene apex, distinct, enlarged.
achenes, borne on pedicellar joint, directly distal to compact, dilated receptacle;
body various shades of brown, flattened, lenticular (biconvex), or nearly terete, smooth and lustrous or variously ridged, pitted, alveolate (honeycombed), cancellate (netted, latticed), papillate, or warty;
tubercle mostly conic or variously triangular, terete or flattened and 2-edged, sometimes longitudinally sulcate, widest across base;
base along narrow transverse suture, lunate, 2-lobed, or topping achenial “neck” or buttress, much narrower, as wide as, or wider than achene apex, decurrent down achene margins.
Rhynchospora
Species over 250 (68 in the flora).
The working basis for the classification used here is from G. Kükenthal, the first modern monographer of Rhynchospora worldwide (1949–1951). He divided the genus into two subgenera, Haplostylae (Nees) Bentham and Diplostylae Bentham, based on degree of stylar branching. In subg. Haplostylae the stylar apex is virtually unlobed, surmounted by two tuberclelike stigmas, or shallowly bifid with the stigmatic branches rarely approaching 1 mm. Thus the stigmatic area is small compared to that of plants in subg. Diplostylae, in which the stylar apex is divided into two narrowly linear, elongate stigma branches.
The North American flora has representatives of only two sections of subg. Haplostylae: sect. Longirostres Kunth and sect. Polycephalae C. B. Clarke. Sect. Longirostres, comprising both cespitose and clonal species, contains some of the largest, most robust species in the genus (e.g., Rhynchospora careyana, R. corniculata, R. inundata), with culms often reaching nearly two meters. Section Polycephalae is represented in the flora by only one species, R. tracyi Britton, which forms large clones by slender, stoloniferous rhizomes. Subg. Haplostylae makes up species 1–6 in this treatment; the remaining 62 species all have deeply bifid styles, in most cases with slender stigmas fully half as long as to nearly equaling the undivided slender portion of the style, and therefore belong to subg. Diplostylae. A clear majority of 54 species were very competently evaluated by S. Gale (1944) who referred them to sect. Eurhynchospora, now treated as subg. Rhynchospora. These species sort into several species groups called “series,” “subsections,” “pars,” or “sections,” depending on treatment authors. Two sections of Rhynchospora with the deeply divided styles, Dichromena (4 species in the flora) and Psilocarya (3 species in the flora), both without vestigial perianth, were omitted from Gale’s treatment. Members of the sect. Dichromena, with leafy, often whitened, involucral bracts subtending whitish heads of spikelets, and sect. Psilocarya, with spikelets peduncled in congested to diffuse panicles, were treated as genera until recently.
Most members of Rhynchospora are cespitose. This does not preclude the possibility of some species (e.g., R. caduca, R. mixta) from having welldeveloped scaly rhizomes or others (e.g., R. oligantha, R. breviseta, R. rariflora, R. stenophylla) from forming dense, hard-based tufts from packed, intertwined short rhizomes. Only a few species are strongly clonal by elongate rhizomes; those are mostly in subg. Haplostylae (e.g., R. tracyi, R. careyana, R. inundata) or subg. Diplostylae sect. Dichromena (e.g., R. colorata).
Also in this treatment the term “fruit” is used not just for the achene but for the achene and all structures attached and subsequently shed with it. A total length measure begins at the pedicellar joint (nearly always very contracted) and proceeds through the receptacle and fruit body (achene) to the tubercle tip. Tubercle length is measured from the middle of the achene summit to the tip of the tubercle. For accuracy one must measure completely ripened fruit, particularly to note the very narrow zone at the tubercle tip where the proximal portion of the style disarticulates.
Unless specifically stated, fruit measurements include the tubercle.
Rhynchosporas are often dominant or co-dominant herbaceous graminoids in marshlands and savannas. Many species occuring in marshlands provide food for migratory waterfowl.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Styles simple or 2-fid only at tip; fruit tubercles either stout-conic and 2-sulcate, equaling fruit body or linear to narrowly triangular-subulate, distinctly longer than fruit body; plants usually tall, slender to robust, often 1–1.5+ m. | → 2 |
1. Styles deeply divided into 2 slender stigmatic branches; fruit tubercle compressed, mostly triangular subulate, slightly shorter than, equaling, or slightly longer than fruit body; plants from less than 10 cm with filiform leaves and culms to 1+ m with linear, wandlike culms and linear leaves. | → 7 |
2. Larger spikelet clusters dense, globose or subglobose; tubercle tip barely exserted; mature spikelet less than 10 mm. | → 3 |
2. Larger spikelet clusters dense or open, hemispheric to turbinate; tubercle tip long exserted; mature spikelet well over 10 mm. | → 4 |
3. Plants strongly rhizomatous; fruit body 2.5–3(–4) × 1.5–2 mm, edges not crimped; fruit tubercle narrowly linear, base much narrower than fruit summit. | R. tracyi |
3. Plants not rhizomatous; fruit body 3–4 × 2–2.5 mm, edges crimped; fruit tubercle conic, stout, base capping fruit summit. | R. indianolensis |
4. Plants scaly rhizomatous; some perianth bristles nearly reaching apex of fruit body or beyond. | → 5 |
4. Plants not rhizomatous, mostly in tufts; perianth bristles shorter or longer than fruit body. | → 6 |
5. Perianth bristles ± 2 times as long as fruit body; fruit body broadest near middle, usually less than 3 mm wide; longer leafy bracts extending beyond inflorescence; rhizomal internodes usually less than 2 mm thick. | R. inundata |
5. Perianth bristles slightly longer to slightly shorter than fruit body; fruit body broadest distal to middle, 2.8–3.5 mm wide; longer leafy bracts usually overtopped by inflorescence; rhizomal internodes mostly more than 3 mm thick. | R. careyana |
6. Bristles ± 2 times as long as fruit body; clusters of spikelets compact, distant along culm. | R. macrostachya |
6. Bristles usually 1/2 as long as fruit body; clusters of spikelets open, more diffuse inflorescences. | R. corniculata |
7. Perianth bristles retrorsely barbellate (except in scattered forms of R. capitellata, R. cephalantha, and R. capillacea, in which bristles are either smooth or antrorsely barbellate); base of fruit body narrowed to stipe. | → 8 |
7. Perianth bristles, when present, antrorsely barbellate (shortest ones may be smooth); base of fruit body not stipelike. | → 16 |
8. Spikelets whitish to straw colored, pale dull brown to pale red brown (pallid in living material); perianth bristles 10–20. | → 9 |
8. Spikelets rich red brown (rarely pale brown) to dark brown; perianth bristles 6. | → 10 |
9. Bristles 10–12; fruit body 1.5–1.8(–2) × 0.9–1.2 mm. | R. alba |
9. Bristles 18–20; fruit body (1.7–)2–2.2 × (0.8–)1–1.5 mm. | R. macra |
10. Clusters of spikelets ovoid or ellipsoid; spikelets all ascending or erect; fruit body narrowly ellipsoid. | R. capillacea |
10. Clusters of spikelets turbinate to hemispheric or globose; spikelets spreading to erect; fruit body obovoid or round. | → 11 |
11. Fruiting florets (1–)2–3(–5) per spikelet, if 1, then terminal floret reduced. | → 12 |
11. Fruiting florets 1 per spikelet, terminating rachilla. | → 14 |
12. Spikelets 2–3 mm; fruits 1.5–1.9 mm; tubercle triangular, distinctly shorter than fruit body. | R. knieskernii |
12. Spikelets 3.5–6.5 mm; fruits (2–)2.5–4 mm; tubercle triangular-subulate, slightly shorter to slightly longer than fruit body. | → 13 |
13. Spikelets 3.5–4(–5); fruits (2–)2.5–3 mm. | R. capitellata |
13. Spikelets 4.5–6.5 mm; fruits 3–3.5(–4) mm. | R. glomerata |
14. Spikelets mostly pale red brown, narrowly ellipsoid to lanceoloid, spreading to erect in turbinate to hemispheric clusters; fruit body (2.5–)2.7–3.3(–3.5) mm; tubercle less than 0.5 mm wide at base. | R. chalarocephala |
14. Spikelets dark red brown, more broadly lanceoloid, erect to reflexed in dense, mostly globose clusters; fruit body 2.5–4.5 mm; tubercle at least 0.5 mm wide at base. | → 15 |
15. Clusters of spikelets mostly 1–2 cm thick; fruit 3.5–4(–4.2) mm, body (1–)1.5–2 mm wide. | R. cephalantha |
15. Clusters of spikelets mostly 0.5–1 cm thick; fruit 2.5–3 mm, body 0.9–1.1 mm wide. | R. microcephala |
16. Bristles absent; tubercle of fruit broad based, often decurrent on fruit body (fruit body usually margined). | → 17 |
16. Bristles present or absent, if absent then tubercle base thickened, not decurrent, or tubercle strongly flattened and sharply 2 edged. | → 23 |
17. Spikelets brown to nearly black, stalked, in diffuse cymose or paniculate inflorescences; plants annual. | → 18 |
17. Spikelets whitened, crowded in capitate, leafy involucrate cluster; plants perennial. | → 20 |
18. Style base triangular to subulate, at least 0.5 mm. | R. scirpoides |
18. Style base depressed, crescent-shaped, less than 0.5 mm. | → 19 |
19. Spikelets acuminate, (5–)6–10 mm, dull brown or tan; achene margin with narrow, distinct sulcus; style base ends turned up, hornlike. | R. eximia |
19. Spikelets acute, mostly 4–6(–8) mm, dark brown to nearly black; achene margin without sulcus; style base ends not turned up or hornlike. | R. nitens |
20. Plants solitary or sparsely cespitose, with scaly rhizomes; fruit 1.5–2 mm. | → 21 |
20. Plants densely cespitose, without scaly rhizomes; fruit 0.8–1.2 mm. | → 22 |
21. Longer involucral bracts at least 5 mm wide at base, mostly abruptly narrowed and green at or distal to midbract; fruit widest at midbody; tubercle base lunate, decurrent; rhizomes mostly 2–4 mm thick; in acid, boggy substrates. | R. latifolia |
21. Longer involucral bracts mostly less than 5 mm wide at base, mostly gradually narrowing, green well proximal to midbract; fruit widest at or near apex; tubercle base transverse or slightly lunate, scarcely decurrent; rhizomes mostly 2 mm or less thick; in calcareous or basic substrates. | R. colorata |
22. Fruit body rugose; keels of spikelet scales not ciliolate; sw United States. | R. nivea |
22. Fruit body rugulose; keels of at least proximal spikelet scales ciliolate; peninsular Florida. | R. floridensis |
23. Bases or entire length of perianth bristles densely plumose; fruit tubercle conic. | → 24 |
23. Bases of perianth bristles not densely plumose (may be setose), or perianth absent; tubercle variously shaped. | → 28 |
24. Spikelets on divaricate capillary stalks, 1–5 at common level along filiform culm. | → 25 |
24. Spikelets on shorter, thicker stalks, more densely crowded, in spreading to ascending branched spikelet clusters. | → 26 |
25. Bristles more than 1/2 length of fruit body; fruits 1–3 per spikelet; tubercle base strongly rimmed atop distinctly “necked” fruit body. | R. oligantha |
25. Bristles equal to or less than 1/2 length of fruit body; fruits 3–8 per spikelet; tubercle base weakly rimmed, not “necked”. | R. breviseta |
26. Spikelets light brown, narrowly lanceoloid, 8–10 mm; fertile scales 5–8 mm; perianth bristles more than 2 times as long as fruit, excurved, strongly exserted apically and laterally. | R. megaplumosa |
26. Spikelets light red-brown to dark brown or dark red-brown, broadly fusiform to ovoid or lance-ovoid, 3.5–6 mm; fertile scales no longer than 4 mm; perianth bristles rarely extending past fruit tubercle apex, closely surrounding fruit body, erect, not exposed. | → 27 |
27. Fruit body (1.5–)2–2.2 mm, tubercle conic, 0.5–0.8(–1) mm, prominently 2-lobed at base; leaves linear, (1–)2–3 mm wide, shallowly involute; plant base rich red-brown. | R. pineticola |
27. Fruit body 1.3–1.8(–2) mm, tubercle depressed-conic to conic, 0.3–0.5 mm; leaves linear-filiform, 1–1.5 mm wide, deeply involute; plant base dull brown to straw colored. | R. plumosa |
28. Tubercle of fruit a “button” (as in Bulbostylis), its base not broader than fruit apex; perianth none; densely cespitose; fruit 1 mm or less. | → 29 |
28. Tubercle of fruit not a “button” (except in R. divergens), its base broader than fruit apex; perianth bristles 0–6(–12 in R. megolocarpa, R. alba, R. baldwinii); habit various; fruit mostly more than 1 mm. | → 30 |
29. Fruit body transversely rugulose, not striate-reticulate, glassy. | R. pusilla |
29. Fruit body not transversely rugulose, finely striate-reticulate, glassy. | R. divergens |
30. Fruit body irregularly transversely finely or more often coarsely ridged, ridges separated by rows of isodiametric or vertically oriented alveolae or lattices, these slightly to deeply concave and sharply bordered (shape of alveolae measured at midbody of fruit). | → 31 |
30. Fruit body, if cross ridged, with ridges fine, low, and many, forming narrow border for transverse rows of broadly rectangular to isodiametric lattices, shallow alveolae, or lattices or body smooth to glassy or minutely pitted. | → 52 |
31. Plants forming mats or dense tussocks of filiform leaves and scapes; spikelets few to many per cluster, solitary or paired on capillary secondary or ultimate stalks; perianth present. | → 32 |
31. Plants, if forming mats or tussocks, with broader leaves and culms; spikelets in dense or open clusters; perianth present or absent. | → 34 |
32. Fruit 1 mm, body distinctly margined, cancellate; transverse ridges only slightly stronger than vertical ridges. | R. thornei |
32. Fruit 2–3 mm, body not distinctly margined, narrowly alveolate; transverse ridges much stronger than vertical ridges. | → 33 |
33. Spikelets 5 mm; fruit tubercle narrowly triangular acuminate, (0.8–)1–1.5 mm; bristles mostly reaching to or beyond tubercle base. | R. stenophylla |
33. Spikelets 3–4(–4.5) mm; fruit tubercle short triangular, 0.3–0.6 mm; bristles rarely extending past fruit midbody. | R. rariflora |
34. Fruit (1.8–)2+ mm. | → 35 |
34. Fruit mostly 1.3–1.7 mm (to 1.8 or 2 mm in R. globularis var. saxicola). | → 45 |
35. Perianth bristles reaching tubercle base or beyond. | → 36 |
35. Perianth bristles, if present, not reaching beyond tubercle base (except in R. punctata), usually extending only 2/3 or less length of fruit body. | → 41 |
36. Fruit body strongly compressed, faces nearly level. | → 37 |
36. Fruit body distinctly biconvex (lenticular) or tumid. | → 38 |
37. Spikelets lanceoloid, 5–7 mm; mature culms arching outward, drooping tipped; fruit body narrowly oblong ellipsoid, tubercle narrowly triangular, 1 mm, acute. | R. inexpansa |
37. Spikelets ovoid, 4–5 mm; mature culms ± erect; fruit broadly oblong-obovoid, tubercle broadly triangular, 1 mm, apiculate. | R. punctata |
38. Plants cespitose or solitary, with well-developed rhizomes; clusters of spikelets mostly diffuse; fruit body ellipsoid to obovoid oblong, tubercle triangular-subulate with edges setulose. | R. mixta |
38. Plants cespitose, sometimes with short rhizomes or rhizomes absent; spikelets usually few in ultimate clusters, these close on ascending secondary branches, clusters dense; fruit body pyriform, broadly obovoid or suborbicular, tubercle short triangular with edges setulose or narrowly triangular subulate with edges not setulose. | → 39 |
39. Spikelets 5–7 mm; pedicellar joint 0.3–0.6 mm; tubercle edges setulose. | R. odorata |
39. Spikelets 3–5 mm; pedicellar joint 1.5–3 mm; tubercle edges entire or setulose. | → 40 |
40. Fruit body pyriform, surfaces vertically striate-alveolate between ridges; tubercle subulate-triangular, edges not setulose; California. | R. californica |
40. Fruit body broadly obovoid to suborbicular, surfaces vertically finely striate and rectangular-alveolate; tubercle triangular-acuminate, edges setulose; se United States. | R. caduca |
41. Larger leaf blades 2–3 mm or less wide; fruit body compressed, obovoid, 2 mm; tubercle flat, low triangular, 0.2–0.3(–0.5) mm, lunately curved to fit fruit summit, decurrent along edges. | R. torreyana |
41. Larger leaf blades mostly 3–4 mm wide; fruit body compressed or tumid, mostly 2–2.5(–3) mm, tubercle more narrowly triangular to subulate, compressed or shallowly biconvex, 0.5–1 mm, tubercle base and fruit summit either level or curved. | → 42 |
42. Fruit body distinctly flattened, mostly 2–2.5(–3) mm; plants cespitose, not rhizomatous. | → 43 |
42. Fruit body lenticular or tumidly biconvex, 1.3–1.6(–1.8) mm; plants solitary or cespitose, rhizomatous or not. | → 44 |
43. Perianth bristles extending past tubercle base; alveolae broadly rectangular to nearly isodiametric; tubercle somewhat compressed, directly capping curved fruit summit, triangular. | R. punctata |
43. Perianth bristles extending to midbody of fruit; alveolae narrowly rectangular to oblong-linear; tubercle conic subulate, strongly rimmed at base distal to necklike fruit apex. | R. compressa |
44. Plants cespitose, rhizomes absent; spikelets rich red brown; tubercle base with dilated rim. | R. recognita |
44. Plants solitary or cespitose, rhizomes stoloniferous; spikelets deep dark purple brown, nearly black; tubercle base not rimmed. | R. kunthii |
45. Longer perianth bristles mostly not reaching past midbody of fruit, or vestigial, or absent. | → 46 |
45. Longer perianth bristles reaching at least to, more often beyond, tubercle base. | → 48 |
46. Fruit strongly compressed; perianth absent or vestigial. | R. perplexa |
46. Fruit distinctly biconvex or tumid; perianth vestigial to ± as long as fruit body. | → 47 |
47. Tubercle of fruit conic. | R. globularis |
47. Tubercle of fruit triangular, sharp edged. | R. microcarpa |
48. Fruit body strongly flattened; longer perianth bristles spreading widely. | R. elliottii |
48. Fruit body biconvex or tumid; perianth bristles closely ascending around fruit. | → 49 |
49. Plants cespitose, rhizomatous; culms wandlike, to 1.5 m; inflorescence branches divaricately spreading. | R. miliacea |
49. Plants cespitose, not rhizomatous (except rarely in R. decurrens); culms stiff, or if wandlike scarcely exceeding 1 m; inflorescence branches ascending, not divaricately spreading. | → 50 |
50. Fruit body narrowly obovoid or ellipsoid; branches of inflorescence capillary, clusters elongate, diffuse; tubercle triangular, confluent with narrow, pale, wirelike fruit edge. | R. decurrens |
50. Fruit body broadly obovoid to suborbicular; branches of inflorescence stouter, clusters shorter, compact; tubercle depressed-conic or triangular, confluent or not with fruit edge, edge without pale, wirelike rim. | → 51 |
51. Fruit tubercle depressed-conic or even patelliform, apiculate; rimmed base not confluent with fruit body. | R. globularis |
51. Fruit tubercle broadly triangular, compressed; rimless base more confluent with edges of more shallowly convex fruit body. | R. microcarpa |
52. Fruit body tumid at least apically, not edged; surfaces smooth or with transverse rows of lattices; fruit tubercle subconic. | → 53 |
52. Fruit body distinctly lenticular, narrow edged, surface mostly either smooth, even glassy, or transversely striate with fine pits; fruit tubercle compressed, thin edged. | → 56 |
53. Midbody of fruit with irregular transverse rows of broadly rectangular to subisodiametric lattices; thickened tubercle base and fruit summit not connected by distinct buttress. | R. globularis |
53. Midbody of fruit smooth or with many undulate transverse rows of pits; thickened tubercle base and fruit summit connected by distinct buttress. | → 54 |
54. Spikelets 4–8 mm; fruit body smooth or longitudinally striate; body (3.5–)4–5 mm; larger leaf blades at least 5 mm wide. | R. megalocarpa |
54. Spikelets 2.5–5.5 mm; fruit body pitted between many fine, undulate, transverse ridges; body usually 3 mm or less; no leaf blades as wide as 5 mm. | → 55 |
55. Fruit 2.5–3 mm; spikelets 4–5.5 mm; perianth reaching past fruit midbody. | R. grayi |
55. Fruit 2–2.5 mm; spikelets 2.5–4 mm; perianth not reaching past fruit mid-body. | R. harveyi |
56. Tubercle edges setulose ciliate; perianth bristle bases and/or pedicellar joint often setose. | → 57 |
56. Tubercle edges not setulose ciliate; perianth bristle bases and/or pedicellar joint not setose. | → 62 |
57. Spikelets 3–4 mm. | R. filifolia |
57. Spikelets (4.5–)5–7 mm. | → 58 |
58. Fruit body narrowly oblong ellipsoid; leaf blades filiform. | R. curtissii |
58. Fruit body obovoid; leaf blades filiform or linear. | → 59 |
59. Plants sparsely or densely cespitose, strongly clonal, rhizomes stoloniferous, 1–2 mm thick; pedicellar stipe joint stout, no longer than 0.3 mm; leaf blades filiform. | → 60 |
59. Plants cespitose, not clonal, without rhizomes (except in R. crinipes); pedicellar stipe joint 0.3–0.6 mm, setose; leaf blades linear to filiform. | → 61 |
60. Culms few per clump; longer involucral bracts surpassing subtended fascicle; fruit from base of pedicellar joint to tubercle tip 2.5 mm, joint smooth, tubercle edge setulose only at base. | R. fusca |
60. Culms densely clumped; longer involucral bracts barely if at all surpassing subtended fascicle; fruit from base of pedicellar joint to tubercle tip 2 mm, joint setose, tubercle edges setulose. | R. pleiantha |
61. Principal leaf blades no wider than 2 mm; fruit from stipe base to tubercle tip to 2.5 mm; pedicellar stipe joint sparsely setose, to 0.4 mm; fruit body obovoid, 1–1.1 mm wide; spikelet clusters mostly 1–3; tubercle sides concave. | R. harperi |
61. Principal leaf blades 2–3 mm wide; fruit from stipe base to tubercle tip 2.5–3 mm; pedicellar stipe joint densely curled-setose, 0.6–1 mm; fruit body narrowly obovoid, 0.8–1 mm wide; spikelet clusters (3–)4–7(–10); tubercle sides straight. | R. crinipes |
62. Spikelets 2–3.5 mm. | → 63 |
62. Spikelets (3.5–)4–7 mm. | → 68 |
63. Fruit not over 1.8 mm. | → 64 |
63. Fruit 1.8+ mm. | → 66 |
64. Perianth evident, some bristles reaching or slightly exceeding tip of fruit body. | R. fernaldii |
64. Perianth not evident, vestigial, no bristles exceeding midbody of fruit. | → 65 |
65. Inflorescence compounds solitary, dense, hemispheric, rarely with 2d compound approximate beneath; spikelets light brown; fertile scales attenuate-aristate; fruit body pale green, ends dark brown. | R. chapmanii |
65. Inflorescence compounds rarely solitary, sparse, turbinate or ellipsoid, (1–)2–3, distant; spikelets pale red-brown; fertile scales acute aristulate; fruit body red-brown with pale center. | R. brachychaeta |
66. Fruit tubercle flat, sometimes apiculate; perianth none or more often vestigial, no bristles reaching beyond midbody of fruit. | R. debilis |
66. Fruit tubercle tip subulate or blunt; perianth bristles no shorter than apex of fruit body. | → 67 |
67. Tubercle tip subulate, perianth extending to or slightly beyond it. | R. gracilenta |
67. Tubercle tip blunt, perianth not exceeding it. | R. wrightiana |
68. Basal leaves 3+ mm wide, spreading, coarse; fruit 3–3.5(–3.7) mm. | → 69 |
68. Basal leaves mostly 1–3 mm wide, ascending, not coarse; fruit (1.9–)2–2.5 mm. | → 70 |
69. Culms triquetrous, harsh edged; perianth bristles 12. | R. baldwinii |
69. Culms terete or obscurely trigonous, not triquetrous or harsh-edged; perianth bristles 6, some vestigial. | R. ciliaris |
70. Spikelets ovoid or lance ovoid, 3.5–5 mm, brown or red brown; fruit tubercle acutely or subulately triangular. | → 71 |
70. Spikelets narrowly lance fusiform, 5–7 mm, near white to straw colored or orangish brown; fruit tubercle low-triagular or depressed-triangular. | → 72 |
71. Fruit tubercle abruptly long-subulate; perianth reaching at least to tubercle tip, often beyond. | R. gracilenta |
71. Fruit tubercle no more than triangular or concavely triangular; perianth reaching at most to mid-tubercle, never to tip. | R. fascicularis |
72. Perianth reaching to at least base of tubercle, fruit 2 mm; culm bases not bulbous; spikelets rich orange brown, 6–7 mm. | R. solitaria |
72. Perianth vestigial or absent; fruit 1.5–2 mm; culm bases bulbous; spikelets whitish to tan, (3.5–)4–5 mm. | R. pallida |
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