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........-..eeee cece eee eee 3. C. camporum. 
Culms cespitose, the rootstocks at most short-creeping. 
Spikes numerous, in a more or less compound 
head. (MULTIFLORAE.).............0.2205. 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.......2-.2..2- 02 eee eee eee eee 6. C. occidentalis, 
Scales at most faintly tinged with reddish 
brown. 
Perigynia obliquely cut or shallowly 
bidentate, weakly serrulate........ 9. C. rusbyt. 
Perigynia deeply bidentate, strongly 
serrulate. 
Spikes with few perigynia; sheaths 
tight, inconspicuously septate- 
nodulose..........--e+e-eeeeeee 7. C. neomexicana. 
Spikes with several to many perigy- 
nia; sheaths soon loose, easily 
breaking, conspicuously septate- 
_nodulose............20--2-2-0-- 8. C. gravida. 
Achenes triangular or lenticular; if lenticular the lower lateral spikes 
elongated and terminal spikes staminate. (EuCcAREX.) 
Spike solitary. 
Perigynia coriaceous, glabrous; rootstocks long-creeping. 
(NITIDAE.)..... 000 e cece cece ee cece eee ween eeeeeee 22. C’. obtusata. 
Perigynia not coriaceous, puberulent; culms densely 
cespitose. (FILIFOLIAE.)..........c0eeeee erence eee 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.)......... 2-2-2 e eee e cece eee eee 27. C. capillaris. 
