174 



CYPERACEAE (SEDGE FAMILY) 



r. Culms scabrous, at least above. 



Heads cylindric or subcylindric 



Heads obovoid, conspicuously contracted at base 

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

 bose or densely short-cylindric heads s. 

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

 spikelets l-4-flo\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 



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. 

 •». Achenes narrowly obovoid or oblong, about half as broad as 

 long. 

 Spikelets in dense heads; eacb 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 

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



26. C. dip9aciform48i 



27. C. retrqfractus. 



29. 



C. ovularU. 

 C. cylindricvit. 

 C. echinatus. 



81. C. flatus. 



84. CflliculmU. 



32. C. Grayii, 



33. C. Houghtonii. 



200. C. liavescens. 



C. diandrus. 



1. C. flavlscens 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 south w. (Eurasia, Afr., 

 Trop. Am.) Fig. 200. 



2. C. diandrus Torr. Simi- 

 lar ; pikelets lance-oblong, 



0.5-1 cm. lo7ig, 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 brovm-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 Kninth. 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. 203. C. Nuttaliii. 



4. C. Nuttaliii 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 ; 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. ^03. 



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 rhachis often 



<04. c. microdontus. branched ; scales thin, ovate or oblong, acute^ closely imbri- 



rivularis. 



