68 CYPERACEAE. 



Margins of perigynia thin or winged. 



Perigynia spongy at base, spreading when mature. C. stellulata. 

 Perigynia not spongy at base, ascending or ap- 



pressed. 

 Spikes crowded into a dense head, rarely one or 



two of the lower ones separate. 



Bract leaf-like, longer than the head. C. athrostachya. 



Bract not leaf-like, shorter than the head. 

 Perigynia brown, the margins very nar- 

 row and smooth. C. illota. 

 Perigynia straw-colored, the margins 



winged and serrulate. 



Head ovoid-pyramidal, very dense. C. pachystachya. 

 Head looser, some of the lower spikes 



often separate. C. preslii. 



Spikes distinct, scattered or approximate, mostly 



oblong or ovoid. 



Spikes scattered, silvery green. C. feta. 



Spikes approximate, straw-colored or brown. 

 Leaves involute or folded; heads often 



nodding; perigynia lanceolate. C. phaeocephala. 



Leaves flat; heads erect. 



Heads straw-colored or pale-brown- 

 ish; perigynia lanceolate. C. scoparia. 

 Heads darker. 



Scales ferruginous, dull; perigynia 

 4-4.5 mm. long, reddish at the 

 tip, the orifice not conspicuously 

 white-hyaline. C. leporina. 



Scales chestnut, shiny; perigynia 

 6 mm. long, chestnut at the tip, 

 the orifice conspicuously white- 

 hyaline. C. piperi. 



Section III. EUCAREX. 



Spikes of two sorts, 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 stalked. 



Perigynia pubescent, the beak bidentate. 



Cauline leaves present; bracts sheathing at base; peri- 

 gynia ovoid, not stipitate; spikes dense, many- 

 flowered. 

 Spikes loosely-flowered, approximate; stem not tall 



and slender. C. oregonensis. 



Spikes densely-flowered, scattered; stem tall and 



slender. 



Leaves flat, 2-5 mm. broad. C. lanuginosa. 



Leaves involute, less than 2 mm. broad. C. filiformis. 



Cauline leaves none, the radical numerous; bracts sheath- 

 less; perigynia 3-angled or subglobose, stipitate; 

 spikes few-flowered. 

 I Ma nt tufted; some of the flowering stems short and 



and hidden among the leaves; spikes pale. 

 Stems shorter than the leaves; lowest bract reddish 



.uul auricled at base; perigynia 1-4. C. brevicaulis. 



