44 



CYPERACEAE. 



Heads pale, dense, ovoid; perigynia lanceolate, the 



smooth beak as long as the body. 

 Heads brown, looser, elongate; perigynia ovate, the 



C. douglasii. 

 C. camporum. 



short beak serrulate. 

 Not dioecious, the staminate flowers either at the top 



or the base of the spikelets; heads very dense. 

 Bract exceeding the head. C. athrostachya. 



Bract small or wanting. 



Spikes staminate at top; perigynia dark, nar- 

 rowly margined. C. hoodii. 

 Spikes staminate at base; perigynia pale, rather 



broadly margined. 



Heads pyramidal-ovate, very dense. C. pachystachya. 



Heads looser, some of the lower spikes 



separate. C. multimoda. 



Perigynia not margined. 



Staminate flowers at base of spikelets; head bractless; 



beak of the perigynium serrulate. C. arcta. 



Staminate flowers at the top of spikelets; bract 



present; beak of perigynium not serrulate. 

 Inflorescence dense, oblong or pyramidal; perigynia 



pale, spongy at base, 4-5 mm. long. C. stipata. 



Inflorescence branched at base, rather loose; peri- 

 gynia brown, not spongy at base, 3 mm. long. C. diandra. 



SECTION 2. Spikes of two sorts, except when solitary, the lower wholly 

 pistillate, sessile or stalked, the upper one or two slender and wholly staminate, 

 or sometimes bearing pistillate flowers at base or apex; stigmas 3 and akenes 

 3-angled, or if stigmas 2 and akenes lenticular the lower spikes are stalked. 



Subgenus EUCAREX. 

 Spike solitary and terminal. 



Leaves filiform; bract scale-like. C. filifolia. 



Leaves flat; bract foliaceous. C. geyeri. 



Spikes several, distinct. 



Stigmas 2; akenes lenticular. 



Perigynia subglobose, almost beakless. C. aurea. 



Perigynia flattened, short-beaked. 



Scales acute; perigynia strongly nerved. C. nebrascensis. 



Scales obtuse; perigynia faintly nerved. 



Perigynia stipitate; scales partly green; sheaths 



green. C. kelloggii. 



Perigynia not stipitate; scales wholly purple; 



sheaths purple. C. prionophylla. 



Stigmas 3; akenes 3-angled. 



Beak of perigynium short, entire or merely emarginate. 

 Perigynia pubescent. 



Scales acuminate. C. rossii. 



Scales obtuse. C. concinnoides. 



Perigynia glabrous. 



Leaves broad; spikes 6-10 cm. long. C. amplifolia. 



Leaves rather narrow; spikes 1-3 cm. long. C. aperta. 

 Beak of perigynium rather long, bidentate. 



Perigynia hairy, firm. C. lanuginosa. 



Perigynia glabrous. 



Perigynia not inflated, strongly nerved, the 



teeth 2 mm. long, recurved. 



Sheaths pubescent; spikes ascending. C. atherodes. 



Sheaths glabrous; spikes nodding. C. comosa. 



Perigynia inflated, thin. 



