104 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Perigynia 4 mm. long or more, often strongly nerved on the inner face. 

 Scales obtuse or, at most, acutish. Spikes straw-colored or ferruginous. 



31. C. brevior. 

 Scales long-acuminate or aristate. 

 Inflorescence stiff; spikes green or dull brown; perigynia obovate, abruptly 



narrowed at the base 32. C. alata. 



Inflorescence flexuous; spikes becoming dark brown; perigynia suborbicular, 

 abruptly slender-beaked 33. C. hormathodes. 



9. Acutae Fries. 



Marsh, swamp, or bog plants, common in low grounds and along streams throughout 

 the region. 



Scales long-aristate; achenes strongly constricted at the middle. 



Sheaths glabrous; lower pistillate scales abruptly long-awned 34. C. crinita. 



Sheaths rough-hispid ; lower pistillate scales tapering into the awn . . 36. C. gynandra. 

 Scales obtuse to acuminate; achenes not constricted. 



Beak of mature perigynium twisted when dry 36. C. torta. 



Beak not twisted. 



Culms densely cespitose, forming tufts; stolons inconspicuous; sheaths strongly 



filamentose 37. C. stricta. 



Culms forming loose beds; stolons long and conspicuous; sheaths at most slightly 

 filamentose. 



Mature perigynia straw-colored, few-nerved 38. C. emoryi. 



Mature perigynia green, nerveless 39. C. aquatilis. 



10. Polytrichoideae Tuckerm. 



A characteristic bog plant (placed by Kiikenthal in the subgenus Primocarex) . 

 A single species 40. C. leptalea. 



11. Phyllostachyae Tuckerm. 



Scales bractlike, almost or quite enveloping the perigynia. 



Perigynia somewhat 2-edged, oblong; pistillate flowers usually 3-10; leaves pale 

 green, 1.5-4 mm. wide. 41. C. willdenovii. 



Perigynia globose, with long slender beaks; pistillate flowers usually 1-3; leaves 

 darker, 1-2 mm. wide 42. C. jamesii. 



12. Montanae Fries. 



Low plants with small heads, usually in dry soil of wooded or open banks; in 

 this region the earliest to mature. 



Culms short, many of them hidden among the leaf bases. 



Scales purplish black on each side of the midrib 43. C. nigromarginata. 



Scales green, with lighter or hyaline margins 44. C. tonsa. 



Culms long, none of them hidden among the leaf bases. 



Plants not stoloniferous; leaves 2-4 mm. wide 45. C. communis. 



Plants stoloniferous; leaves 0.5-3 mm. wide. 



Stolons short, tawny -fibrillose ; plants light green 46. C. emmonsii. 



Stolons long, strongly red -fibrillose ; plants dark green 47. C. pennsylvaniea. 



13. Pubescentes Kiikenth. 



Plants pubescent throughout; terminal spike strictly staminate. 

 A single species 48. C. hirtifolia. 



