WOOTON AND STANDLEY FLORA OP NEW MEXICO. 117 



KEY TO THE SPECIES. 



Achenes lenticular; stigmas 2; terminal spike partly pistillate or 

 if staminate the lateral spikes short or heads dioecious. 



(ViGNEA.) 



Spikes mostly staminate at the base. 



Perigynia not wing-margined. (Stellulatae.) 



Perigynia with very short beaks, widely spreading at 



maturity 13. C. interior. 



Perigynia with long beaks, appressed 14. C. holanderi. 



Perigynia wing-margined. (Ovales.) 



Beak of the perigynium flattened and margined to the 

 tip. 



Scales strongly tinged with reddish brown 21. C. v>ootoni. 



Scales little if at all tinged with reddish brown. 

 Perigynia thin, lanceolate (at least two and 



one-half times as long as wide) 19. C. scoparia. 



Perigynia thick, ovate 20. C. festucacea. 



Beak of the perigynium slender, nearly terete and 

 scarcely margined at the apex. 

 Several of the bracts conspicuously exceeding the 



head 18. C. tenuirostris. 



Bracts inconspicuous. 



Perigynia 2.5 to 3.5 mm. long; culms smooth 



beneath the head 15. C. suhfusca. 



Perigynia 4.5 to 6 mm. long; culms rough be- 

 neath the head. 



Perigynia about 4.5 mm. long, ovate 16. C.festiva. 



Perigynia 4.5 to 6 mm. long, lanceolate. .17. C. eBenea. 

 Spikes staminate at apex or some spikes wholly staminate. 

 Perigynia little compressed, whitish-puncticulate. 



(Tenellae .) 12. C. disperma. 



Perigynia strongly compressed, not whitish-puncticulate. 

 Culms one to few together, the rootstocks long and 

 creeping. 

 Perigynia wing-margined, the beak bidentate. 



(Arenariae.) 5. C.siccata. 



Perigynia not wing-margined, the beak obliquely 

 cut, or bidentate in age. (Divisae.) 



Culms smooth above; rootstocks slender 1. C. douglasii. 



Culms rough beneath the head; rootstocks 

 stout. 

 Perigynia chestnut, scarcely sharp-edged, 

 the beak about one-fifth the length 



of the body at maturity 4. C. dmulata. 



Perigynia brownish or blackish, sharp- 

 edged, tapering into a beak about 

 half the length of the body. 

 Spikes with one to several perigynia, 

 the heads appearing a mass of 

 straw-colored scales; staminate 

 flowers conspicuous; perigyn- 

 ium body at maturity about 

 2 mm. wide 2. C. latebrosa. 



