33. Perigynia more numerous per spike, ovate, broadly winged, nerved dorsally 



and ventrally; perigynia 2.7-4.8 mm. wide 28. C. Bicknellii. 



34(32). Larger perigynia (including beaks) 5.5-8.5 mm. long 



29. C. Brittoniana. 



34. Larger perigynia (including beaks) 2.8-5.5 mm. long 30. C. reniformis. 



35(2). Bracts long-sheathing; perigynia golden-yellow or whitish-pulverulent at 

 maturity (36) 



35. Bracts nearly or quite sheathless; perigynia not golden-yellow nor pulverulent 



at maturity (37) 



36(35). Mature perigynia whitish-pulverulent, elliptic-obovoid, not fleshy nor 

 translucent, rather obscurely ribbed; scales appressed..31. C. Hassei. 



36. Mature perigynia golden-orange to rich dark-brown, orbicular-obovoid, fleshy, 



translucent, coarsely ribbed; scales spreading 32. C. aurea. 



37(35). Scales aristate, subulate-tipped; equaling or longer than the perigynia 



33. C. crinita. 



37. Scales obtuse to acute, not aristate (38) 



38(37). Flowering culms from the center of a tuft of leaves of the previous year 

 (39) 



38. Flowering culms all or mostly arising laterally, not from the center of a tuft 



of leaves from the previous year (42) 



39(38). Leaf sheaths breaking and becoming filamentose 34. C. senta. 



39. Leaf sheaths not becoming filamentose when breaking (40) 



40(39) . Perigynia conspicuously veined or ribbed ventrally (41 ) 



40. Perigynia nerveless ventrally or with obscure impressed nerves; scales 



appressed 35. C. aquatilis. 



41(40). Perigynia early-deciduous, membranaceous, conspicuously stipitate, the 



apiculate beak entire; lowest bract exceeding the inflorescence 



36. C. Kelloggii. 



41. Perigynia persistent, coriaceous, strongly ribbed, the broad beak bidentate; 



lowest bract equaling the inflorescence 37. C. nebraskensis. 



42(38). Lower sheaths fibrillose; juncture of sheath and blade V-shape 



38. C. stricta. 



42. Lower sheaths not fibrillose; juncture of sheath and blade flat or slightly 



arcuate 39. C. Emoryi. 



43 ( 1 ) . Lower part of style hard, texturally similar to the achene, persistent (44) 



43. Lower part of style jointed to achene, texturally difi'erent, withering and be- 



coming detached from mature achene (59) 



44(43). Perigynia obconic or broadly obovoid, truncate or abruptly rounded to 

 a long subulate beak (45) 



44. Perigynia subulate to ovoid or subglobose, gradually tapering to a beak (48) 



45(44). Spikes elongate, linear-cylindric; achene silvery-black, minutely pitted.... 

 40. C. ultra. 



45. Spikes subglobose to thick-cylindric or ellipsoid; achene yellow to brown, 



granular (46) 



46(45). Terminal spike staminate; pistillate rough-awned scales longer than the 

 perigynia 41. C. Frankii. 



46. Terminal spike gynecandrous; pistillate scales shorter than the bodies of the 



perigynia (47) 



47(46). Pistillate scales obtuse; style straight 42. C. typhina. 



47. Pistillate scales acuminate or awned; style curved 43. C. squarrosa. 



493 



