118 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Spikes with about 10 perigyuia, 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. (Multiflorae.) 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 6. C. occidentals . 



Scales at most faintly tinged with reddish 

 brown. 

 Perigynia obliquely cut or shallowly 



bid entate, weakly serrulate 9. C.rmbyi. 



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. 



Perigynia coriaceous, glabrous; rootstocks long-creeping. 



(Nitidae.) 22. C. obtusata. 



Perigynia not coriaceous, puberulent; 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. ft 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. 



