174 



CYPERACEAE (SEDGE FAMILY) 



r. Culms scabrous, at least above. 



Heads cylindric or subcylindric 



Heads obovoid, conspicuously contracted at base 

 . Spikelets spreading, or only the'basal refracted in age, in glo- 

 bose or densely short-cylindric heads . 

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



spikelets 1-4-flowered 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 



Heads cylindric 



u. Spikelets slightly crowded, the tips mostly divergent 

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



1 mm. broad 



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

 v. Achenes narrowly 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 

 . Achenes trigonous-ovoid, two thirds as broad as long . 



26. C. dipsacfformis. 



27. C. retrofractua. 



28. C. orulari*. 



29. C. cylindricus. 



30. C. echinatue. 



31. C. flavus. 



84. C.filiculmis. 



:;.'. C. (irai/ii. 

 33. C. HougMowti. 



200. C. tiavescens. 



201. 0. diandrus. 



1. C. flavescens L. Culms 0.5-4 dm. high ; involucre 

 3-leaved, very unequal ; spikelets 0.5-1.5 cm. long, 

 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 southw. (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 narrow purple-brown 



margin or merely brown-flecked, thin and membranous ; achene 

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

 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 brown mar- 

 gins, or brown all over, or rarely pale ; 

 style-branches slightly or not at all 

 exserted. (C. 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, yellowish-brown, rather loose ; xt<mn * 

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

 bluntly pointed, minutely bullate and more or less ivtiru- 

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

 fr<>m Me. to Fla. FIG. 203. 



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

 leaves and somewhat spreading elongated bracts of involucre 

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

 acute, 0.8-3 cm. Ion-. l.f>-2 mm. thick, the rhachis often 

 jot. ( mki.xiontus. branched ; scales thin, ovate or oblong, acute, closely 



202 C. rivularis. 



0. Nuttallii. 



