118 



CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Spikes with about 10 perigynia, con- 

 cealed by inconspicuous scales, 

 these tinged with green or 

 brown; staminate flowers in- 

 conspicuous; perigynium body 

 at maturity less than 1.5 mm. 



long 3. C, camporum. 



Culms cespitose, the rootstocks at most short-creeping. 

 Spikes numerous, in a more or less compound 



head. (Multiplorae.) 11. C.agrostoides. 



Spikes less than 10, in a simple head. 



Perigynia strongly nerved, the beak exceed- 

 ing the body. (Stenorhynchae.) . . .10. C. stipata. 

 Perigynia weakly nerved, the beak not ex- 

 ceeding the body. (Muhlenber- 



GIANAE.) 



Scales conspicuously tinged with reddish 



brown G. C. occidentalis. 



Scales at most faintly tinged with reddish 

 brown. 

 Perigynia obliquely cut or shallowly 



bidentate, weakly serrulate 9. C. rushyi. 



Perigynia deeply bidentate, strongly 

 serrulate. 

 Spikes with few perigynia; sheaths 

 tight, inconspicuously septate- 

 nodulose 7. C. neomexicana. 



Spikes with several to many perigy- 

 nia; sheaths soon loose, _ easily 

 breaking, conspicuously septate- 

 nodulose 8. C. gravida. 



Achenes triangular or lenticular; if lenticular the lower lateral spikes 

 elongated and terminal spikes staminate. (Eucarex.) 

 Spike solitary. 



Per^nia coriaceous, glabrous; rootstocks long-creeping. 



(NiTiDAE.) 22. C. obttisata. 



Perigynia not coriaceous, iDuberulent; culms densely 



cespitose. (Filifoliae.) 23. C. filifolia. 



Spikes more than one. 



Perigynia puberulent, triangular or suborbicular in cross 

 section, long-stipitate, 2-ribbed. (Montanae.) 



Basal spikes absent 24. C heliophila. 



Basal spikes numerous. 



Perigynium body suborbicular; staminate spike 

 2.5 mm. wide; bract shorter than the culm; 



blades 1.5 to 2.5 mm. wide 25. C. geophila. 



Perigynium body oval; staminate spike 1.5 mm. 

 wide; bract normally exceeding the culm; 



blades 0.75 to 1.5 mm. wide 26. C. pityophila. 



Perigynia differing from the above section in one or more 

 particulars. 

 Pistillate spikes drooping on slender penduncles; 

 perigynia strongly beaked, not bidentate. 

 (Capillares.) 27. C. capillaris. 



