176 



CYPERACEAE (SEDGE FAMILY) 



212. C. fuscus. 



3-nerved. (C. calcaratus Nees.) Wet places, Del. to Fla. and Tex. ; north w. 

 in the flat country to Mo. and Kan. FIG. 211. 



13. C. FUSCUS L. Low (1-3 dm. high) ; spikelets linear, 3-8 mm. long, the 



thin brown scales (greenish 



only on the keel) very faintly 



nerved ; stamens 2 ; achenes 



equaling the scales. Locally 



on ballast, Mass, to N. J. 



(Adv. from Eu.) FIG. 212. 

 14. C. hdspan L. Culms 



sharply angled (2-8 dm. 



high) ; leaves linear, often 



reduced to membranous 



sheaths ; umbel spreading, the filiform rays mostly longer 

 than the 2-leaved involucre ; spikelets narrowly linear ; 

 scales light reddish-brown, oblong, mucronate, 3-nerved ; 213 c h 

 wings of rhachilla persistently attached ; achenes round- 

 obovoid. Ponds and ditches, Va. to Fla. and Tex. FIG. 213. 



15. C. dentatus Torr. Perennial by slender rootstocks 

 and tuber-bearing stolons; culms slender (1-6 dm. high) ; 

 leaves rigid and keeled ; umbel erect, shorter than the 3-4- 

 leaved involucre ; spikelets 5-13-flowered ; scales reddish- 

 brown, with green keel, ovate, acute, 7 -nerved, 



the mucronate tips prominent. Sandy shores, 

 Me. to N. Y., and southw. Spikelets often 

 abortive and changed into leafy tufts. FIG. 

 214. 



Var. cten6stachys Fernald. Spikelets 15- 



40-flowered ; scale-tips less prominent. Mass. 

 , -vr T T? 01 c 



? n + ' * T /AT o A TD 



16. C. rotundus L. (NUT GRASS.) Peren- 



nial by tuber-bearing stolons; culm slender (1-6 dm. high), longer than the 

 leaves ; umbel simple or slightly compound, about 

 equaling the involucre ; the few 

 rays each bearing 4-9 dark chest- 

 nut-purple 12-40-flowered acute 

 spikelets (0.8-2.5 cm. long) ; scales 

 ovate, closely appressed, nerveless 

 except on the keel ; achenes linear- 

 oblong. Sandy fields, Va. to 

 Fla. and Tex. ; also adv. near 

 Phila. and N. Y. City. (Trop. and 

 subtrop. regions.) FIG. 216. 



17. C. HalliiBritton. Similar; 

 culm stout, 4-9 dm. high, scarcely 

 exceeding the broad (0.5-1 cm.) 

 leaves ; umbel compound, the 

 numerous rays much exceeded by 2n - c - escuientus. 

 the involucral bracts; spikelets chestnut-purple, 1-1.5 cm. long; the acutish 

 scales distinctly nerved. Kan. to Tex. 



18. C. escu!6ntus L. Similar ; culms (3-9 dm. high) equaling the leaves ; 

 umbel often compound, 4-7 -rayed, much shorter than the long involucre ; spike- 

 lets numerous, light chestnut or straw-color, acutish, 0.5-1.5 

 cm. long; scales ovate or ovate-oblong, narrowly various- 

 margined, nerved, the acutish tips rather loose ; achene 

 oblong-obovoid. Low grounds, along rivers, etc. ; spreading 

 extensively by its small nut-like tubers and sometimes 

 becoming a pest in cultivated grounds. (Eurasia.) FIG. 217. 

 Var. LEPTOSTA.CHYUS Boeckl., with spikelets 1.8-3.5 cm. long, is less frequent. 

 FIG. 218. 



214. C. dentatus. 



, 

 . aentaius, 



v. ctenostachys. 



216. C. rotundus. 



218. C. escuientus, 

 v. leptostachyus. 



