46 CYPEEACEAE. 



nut-brown, acute: achenes ovoid, about 2 mm. long, acute, longitudinally striate. 

 — M. Bare, mostly in the Dillerville swamp. — Sum. — Twig-rush. 



9. RYNCHOSPORA Vahl. Caulescent herbs, mostly perennial by root- 

 stocks. Leaves few: blades narrow, flat or involute. Spikelets ovoid, oblong, 

 or fusiform, variously clustered. Scales thin, 1-nerved, imbricate, usually mucro- 

 nate by the excurrent midvein, the lower empty. Upper flowers imperfect. 

 Perianth of 1-24 (mostly 6) barbed or scabrous bristles, or wanting. Stamens 

 commonly 3. Stigmas 2. Achene lenticular, often turgid, smooth, cancellate 

 or transversely wrinkled, crowned with the base of the style (tubercle), or in 

 some species with the whole style. — Beak-rush. 



Perianth-bristles retrorsely barbed. 



Spikelet-scales white or pale: perianth-bristles 9-15. 1. R. alba. 



Spikelet-scales brown : perianth-bristles 6. 



Achene oblong or obloiag-ovoid : leaves with filiform 



blades. 2. R. capillacea. 



Achene obovoid : leaves with flat linear blades. 3. R. glomerata. 



Perianth-bristles upwardly barbed. 4. R. cymosa. 



1. R. alba (L.) Vahl. Pale-green: stems slender, 1.5-6 dm. tall: leaves much 

 shorter than the stem; blades very slender: spikelets whitish or pale-green, nar- 

 rowly oblong or lanceolate, in 1-4 dense clusters, 4-6 mm. long: scales acute: 

 perianth-bristles 9-15, about as long as the achene and tubercle: achenes obo- 

 void-oblong, fully 1.5 mm. long, smooth, pale-brown; tubercle lanceolate, fully 

 i as long as the achene-body. — Rather common, in swamps. — Sum. and fall. 



2. R. capillacea Torr. Deep-green: stems slender, 1-4.5 dm. tall: leaves much 

 shorter than the stems; blades filiform: spikelets few, chestnut-brown, oblong 

 or oblong-lanceolate, in 1-3 lax clusters, 4—6 mm. long: scales mucronate: peri- 

 anth-bristles 6, or rarely 12, stout: achenes oblong to oblong-ovoid, 1.5-2 mm. 

 long, minutely wrinkled, brown, short-stipitate ; tubercle lanceolate, about A the 

 length of the achene-body. — M. Rare, in the Dillerville swamp. — Sum. 



3. R. glomerata (L.) Vahl. Deep-green: stems 3-10- dm. tall: leaf -blades flat, 

 rough-margined : spikelets oblong, narrow at both ends, 3-4 mm. long, in 3-7 

 corymbose-capitate axillary clusters: scales lanceolate, dark-brown: achenes 

 obovoid, above the slender base, about 1.5 mm. long, smooth, dark -brown; 

 tubercle subulate, nearly as long as the achene. — Rather rare, in swamps. — 

 Sum. and fall. 



4. R. cymosa Ell. Light-green: stems tufted, 3-11 dm. tall: leaf -blades flat, 

 smooth: spikelets ovoid-oblong, acute, 3 mm. long, sessile or nearly so, capitate 

 in 2's-7's on the ultimate axillary and terminal branches: scales dark-brown, 

 broadly ovate: achenes broadly obovoid or orbicular-obovoid, 1.5 mm. long, 

 transversely wrinkled; tubercle conic, about as high as wide, ^-i as long as 

 the achene. — ^S. R-ather rare, in swamps. — Schists, serpentine. — Sum. and fall. 



10. SCLERIA Berg. Perennial or rarely annual, caulescent herbs. Spike- 

 lets small, in terminal, or terminal and axillary fascicles, or rarely inter- 

 ruptedly glomerate-spicate. Flowers monoecious, the fertile spikelets 1-flowered, 

 the staminate many-flowered. Scales loosely imbricate, the 1-3 lower ones, and 

 sometimes also the upper ones of the pistillate spikelets empty. Perianth want- 

 ing. Stamens 1-3. Stigmas 3. Ovary often supported by a disk (hypogy- 

 nium) . Achenes globose or ovoid, crustaceous, enamel-like, or bony, white. — 

 Nut-rush. 



Inflorescence of a single terminal cluster, or of several terminal and lateral clusters. 

 Achene smooth. 1. S. triglomerata. 



Achene ridged, reticulate, or papillose. 

 Achene irregularly ridged or reticulate. 



