174 



CYPERACEAE (SEDGE FAMILY) 



r. Culms scabrous, at least above. 



Heads cylindric or subcylinduie 26. 



Heads obovoid, conspicuously contracted at base . . 27. 



q. Splkelets spreading, or only the basal refracted in age, in glo- 

 bose or densely short-cylindric heads s. 

 8. Scales appressed, each distinctly overlapping the next above ; 

 spikelets l-4-do\vered t. 

 t. Heads mostly on distinct rays ; achenes linear-oblong, 0.5 

 mm. broad u. 

 u. Spikelets very densely crowded and overlapping. 



Heads globose or broadly obovoid 28. 



Heads cyliudric 29. 



u. Spikelets slightly crowded, the tips mostly divergent . 30. 

 t. Heads all sessile in a glomerule ; achenes ellipsoid or ovoid, 



1 mm. broad 



8. Scales not appressed ; spikelets 5 (rarely 4)-15-flowered v. 



v. Achenes narrowlv obovoid or oblong, about half as broad as 



long. 



Spikelets in dense heads ; each successive scale reaching 



the middle of the one above on the same side . . 



Spikelets in loose heads ; each successive scale reaching 



only the bases of the ones above on the same side , 32. 

 r. Achenes trigunous-ovoid, two thirds as broad as long . . 33. 



D. dipaaciformis. 

 C. retrqfractus. 



C. ocularis. 

 C. cylindricus. 

 C. echinatus. 



31. C. flavus. 



34. C. filiculmia. 



C. Grarjii. 



C. Houghtonii. 



high; 



involucre 

 cm. long, 





200 C. tiavescens. 



201. C. diandrus. 



1. C. flavescens L. Cuhiis 0.5-4 dm 

 3-leaved, very unequal ; spikelets 0.5-1.5 

 1.5-2.5 mm. broad, becoming 

 linear, obtuse, clustered on the 

 2—4 very short rays ; scales ob- 

 tuse, straw-yellow ; stamens 3; 

 achene shining, orbicular, its 

 superficial cells oblong. — Low 

 grounds, N. Y. to Mich., 111., 

 and south w. (Eurasia, Afr., 

 Trop. Am.) Fig. 200. 



2. C. diandrus Torr. Simi- 

 lar ; spikelets lance-oblong, 



0.5-1 cm. long, 2-3 mm. broad, rather loosely flowered, 

 scattered or clustered on the 2-5 very short or unequal 

 rays ; scales rather obtuse, with a narroio purple-brown 



margin or merely broivn-flecked. thin and membranous ; achene 

 dull, oblong-obovate, the superficial cells more or less quadrate ; 

 otherwise much like the last. — Low grounds, N. B. to Ont., 

 Neb., and southw. Fig. 201. 



3. C. rivularis Kunth. Similar; the 

 densely flowered spikelets mostly 1-2 

 cm. long; scales firmer, subcoriaceous, 

 slightly lucid, with broad broicn mar- 

 gins, or brovni all over, or rarely pale; 

 style-branches slightly or not at all 

 exserted. (0. diandrus, var. castaneus 

 Torr.) — Low ground, with the last or 

 by itself. Fig. 202. 



4. C. Nuttallii Eddy. Culms 0.5-3 dm. high ; spikelets lance-linear, acute 

 and very flat, 1-3 cm. long, 2-3 mm. broad, crowded on 

 the few usually very short (or some of them obvious) simple 

 rays; scales oblong, yelloivish-brown, rather loose ; stamens 

 2 ; achene oblong to oblong-obovate (0.6-0.8 mm. broad), 

 bluntly pointed, minutely bullate and more or less reticu- 

 lated, dull. — Mostly in brackish marshes, along the coast, 

 from Me. to Fla. Fig. 203. 



5. C. microd6ntus Torr. Culms .slender, 1-7 dm. high ; 



leaves and .somewhat spreading elongated bracts of involucre 



1-4 mm. wide ; spikelets few to many on the 4-8 rays, linear, 



acute, 0.8-3 cm. long. 1.5-2 mm. thick, the fhachis often 



microdontus. branched ; scales thin, ovate or oblong, acute, closely imbri- 



202 C. rivularis. 



Nuttallii. 



