192 CYPERACEAE 
Style long, its branches much shorter than the united lower part. 
Spikelets in 14 dense globose heads. . 
Achene truncate, tipped by a subulate tubercle, ciliate. 
Achene obovoid, tipped by a conic tubercle, not ciliate. 
Spikelets in panicled clusters : achene capped by a stout tubercle. 
Mature spikelets about 1 em. long: tubercle slightly longer than the achene. 
Mature spikelets much over 1 cm. long: tubercle several times longer than 
the achene. 
Style short, its branches as long as the united part or longer. 
Perianth-bristles none or very short. 
Achene transversely wrinkled. 
Achene smooth or reticulated. 
Achene reticulated, 0.5-0.7 mm. long: spikelets loosely corymbose. 
Achene smooth, 1.5-2 mm. long: spikelets corymbose-capitate. 
Stem-leaves with blades 0.7 mm. wide or Jess: spikelets 3-4 mm. long. 
Stem-leaves with blades 1.5-2.5 mm. wide: spikelets 4-6 mm. long. 
Perianth-bristles present and usually well developed. 
Bristles plumose: achene wrinkled. 
Spikelets solitary or 2-4 together. 6-8 mm. long. 
Spikelets numerous, clustered, 2.5-4 mm. long. 
Perianth-bristles plumose nearly or quite to the top. 
Stems slender, 1.5-3.5 dm. tall: spikelets small. 
Stems stout, 3-6 dm tall: spikelets large. 
Perianth-bristles plumose below the middle or only near the base. 
Bristles not plumose. 
Bristles retrorsely barbed. 
Scales ra green or white: perianth-bristles 9-24. 
Scales brown: perianth-bristles 6. 
Spikelets few to numerous in rather loose, often panicled clusters. 
Spikelets numerous, in 2-4 dense globose heads. 
Spikelets 5-6 mm. long: achene 2.5 mm. long. 
Spikelets 3-3.5 mm. long: achene 1.5 mm. long. 
Bristles upwardly barbed. 
Achene smooth or cancellate, not transversely wrinkled. 
Achene smooth. 
Tubercle of the achene ciliate to serrulate. 
Leaf-blades fiat. 
Leaf-blades channeled, involute, filiform or nearly so. 
Achene linear-oblong : perianth-bristles much overtopping 
the tubercle. 
Achene obovoid: perianth-bristles not longer than the 
achene and tubercle, or scarcely so. 
Achene 1 mm. long or less, light brown. 
Achene 1.5-2 mm. long, dark brown. 
Tubercle of the achene smooth or merely granular. 
Perianth-bristles as long as the achene or longer. 
Leaf-blades 0.5-2 mm. wide. 
Perianth-bristles about as long as the achene. 
Perianth-bristles much longer than the achene. 
Leaf-blades 2-7 mm. wide. 
Perianth-bristles much shorter than the achene, sometimes 
very short. 
Leaf-blades 0.5-3 mm. wide: spikelets 2-5 mm. long. 
Leaf-blades narrowly linear: spikelets 2-3 mm. Sone. 
Leaf-blades bristle-like, filiform : spikelets 4-5 mm. long. 
Leaf-blades 4-10 mm. wide: spikelets 6-8 mm. long. 
Achene cancellate. 
Leaf-blades broadly linear, blunt or merely acute: achene 1.5 
mm. long. 
Leaf-blades parowy linear, attenuate. 
Achenes 2.5 mm. long, equalling or shorter than the bristles. 
Achenes 1.5 mm. long, much longer than the bristles. 
Achene transversely wrinkled. 
Perianth-bristles shorter than the achene. 
Leaf-blades and stems filiform : spikelets filiform-pedicelled. 
Leaf-blades not filiform, flat or involute: spikelets sessile or 
short-pedicelled. 
Leaf-blades involute. 
Achene flat, 1.5 mm. long, continuous with the tubercle. 
Achene strongly biconvex, 2 mm. long, constricted under 
the tubercle. 
Leaf-blades flat. 
Achene biconvex, not constricted under the tubercle. 
Achene 1mm. long : tubercle depressed, wider than high. 
armed mm. long: tubercle conic, about as high as 
wide. 
Achene compressed, constricted under the tubercle. 
Perianth-bristles as long as the achene or longer. 
A. Spikelets ovoid to globular, 2-4 mm. long. 
a. Achene not stipitate. 
* Tubercle setose. 
+ Spikelets 1-3-flowered. 
Perianth-bristles not longer than the achene and 
tubercle. 
Perianth-bristles longer than the achene and tubercle. 
Achene broadly or orbicular-obovoid. 
Achene narrowly obovoid. 
1. 
2. 
3. 
4. 
EA 
oo 
22. 
R. Tracyi. 
R. solitaria. 
R. Indianolensis. 
R. corniculata. 
. pusilla. 
. divergens. 
. Chagmanii. 
R 
R 
R 
R. pallida. 
E: 
. oligantha. 
. R. plumosa. 
R. intermedia. 
R. semiplumosa. 
. alba. 
R 
. R. glomerata. 
R 
. axillaris. 
. R. microcephala. 
. R. fuscoides. 
. R. Curtissii. 
. R. filifolia. 
. R. leptorhyncha. 
. R. distans. 
R. gracilenta. 
23. R. Baldwinii. 
R. fascicularis. 
R. brachychaeta. 
. R. dodecandra. 
27. R. ciliata. 
32. 
33. 
R. Grai. 
R. Plankii. 
R. rariflora. 
. R. Torreyana. 
R. Earlei. 
R. perplexa. 
. R. cymosa. 
. R. compressa. 
. R. patula. 
. R. caduca. 
. R. mixta. 
