298 CONTRIBUTIONS FROM THE NATIONAL. HERBARIUM. 



BB. Lateral spikes elongate, more or less peduncled; terminal spike or spikes nor- 

 mally staminate. 



Culms 3 to 40 cm. high; pistillate spikes 4 to 20-flowered; perigynia golden-yellow 



and translucent at maturity 32. C. aurea. 



Culms 20 to 140 cm. high; pistillate spikes many-flowered; perigynia not golden- 

 yellow and not translucent at maturity. 

 Perigynia green or straw-colored, dull; style jointed with achene. 

 Perigynia with beak not bidentate. 



Perigynia conspicuously nerved; leaf blades 1 to 3 mm. wide; stolons absent. 



45, C. kelloggii. 

 Perigynia nerveless ventrally or nearly so; leaf blades 4 to 8 mm. wide; long 



horizontal stolons present 46. C. substricta. 



Perigynia with beak markedly bidentate and with body strongly ribbed. 



47. C. nebraskensis. 

 Perigynia tinged with yellowish brown, shining; style continuous with achene. 



52. C. miliaris. 

 AA. Stigmas 3; achenes triangular. 

 Perigynia hairy. 



Culms 5 to 25 cm. high; pistillate spikes few-flowered; perigynia 2-ribbed, other- 

 wise nerveless 31. C. rossii. 



Culms 60 to 90 cm. high; pistillate spikes many-flowered; perigynia many-nerved. 



Leaf blades flat, more than 2 mm. wide 48. C. lanuginosa. 



Leaf blades involute, 2 mm. wide or less 49. C. lasiocarpa. 



Perigynia not hairy. 



Bract of lowest pistillate spike sheatliing. 

 Pistillate spikes drooping, on capillary peduncles, 2 to 12-flowered ; perigynia not 



bidentate 33. C. capillaris. 



Pistillate spikes erect, many-flowered; perigynia bidentate. 



Perigynia 2 to 3 mm. long, the beak scarcely half as long as the body. 



50. C. viridula. 

 Perigynia 4 to 6 mm. long, the beak about as long as the body ... 51. C. flava. 

 Bract of lowest pistillate spike not sheathing. 

 D. Perigynia with beak entire or shallowly bidentate with very short teeth, 

 Perigynia glaucous-green. 



Pistillate spikes drooping; plants loosely long-stoloniferous; terminal spike 



staminate 34. C. limosa. 



Spikes erect, the terminal pistillate at top; culms densely tufted, sending 



forth long horizontal stolons 35. C. buxbaumii, 



Perigynia not glaucous-green. 

 Terminal spike in some plants pistillate and linear-cylindric or staminate 



only at apex, in others staminate 36. C, parryana. 



Terminal spike staminate or pistillate at top and staminate below; not 

 pistillate and linear-cylindric. 

 Terminal spike staminate. 

 Culms few-leaved, purplish-tinged at base, the lower leaves reduced to 



bladeless sheaths 37. C. podocarpa. 



Culms many-leaved, clothed at base with dried -up leaves of previous 

 year, not purplish- tinged at base. 



Perigynia flat 38. C. tolmiei. 



Perigynia round in cross section, many-nerved . . 39. C. raynoldsii. 

 Terminal spike pistillate at top and staminate below. 



Perigynia small, 2.5 mm. long or less, triangular in cross section. 



40. C. halleri. 



