VASCULAR PLANTS OF NORTH DAKOTA 233 
Perigynia ovate, the beak half length of body.......11. C. athrostachya. 
Bracts not leaf-like, shorter than head. 
Scales narrower and shorter than perigynia: the perigynia therefore 
conspicuous in head. 
Perigynia lanceolate, widely spreading; sterile shoots with 
numerous widely spreading leaves.......... 12. C. cristatella. 
Perigynia ovate, not widely spreading; sterile shoots with few 
erect leaves. 
Perigynia less than 4 mm. long. 
Perigynia brownish; spikes closely aggregated, rounded 
ate basesaa-- Biber acs es Gk RS NY, HO Sr 13. C. Bebbit. 
Perigynia green; spikes widely separated, the upper clavate 
FEST Ha OFEIC( ETN tel Hoe rae eT ee I Ee ass AN, MA 14. C. tenera. 
Perigynia moresthan) 4) mm: long... 5... ose 15. C. brevior. 
Seales about as wide and as long as perigynia: the perigynia 
therefore not conspicuous in head. 
neddsrstitt; spikessapproximate. ws oo: a. canes 16. C. xerantica. 
Heads slender; spikes widely separate........... 17. C. praticola. 
Perigynia at most sharp-edged, thick. 
Perigynia widely spreading, less than 3 mm. long........ 18. C. interior. 
Remoyiniaiaporesseds 5 i10tm. long... s+ oc. .4- eee os 19. C. Deweyana. 
TAVE 
Pistillate spikes very many flowered; perigynia green or straw-colored. 
Lower leaves of fertile culms with long blades; perigynia not papillose; 
UUM Gees IMOO LEG oiepasies) ature areas Eisieetse sete 20. C. aquatilis substricta. 
Lower leaves of fertile culms with much reduced blades or bladeless; 
perigynia minutely papillose; culms rough.......... 21 (Gy EMOnyt 
Pistillate spikes few-flowered; perigynia golden yellow at maturity. 
22. C. aurea. 
Ve 
Spikes solitary. 
Spikes androgynous; scales with shining white margins; leaf blades 
SUS ENN Eye hy ma he che or nce Oeste. GLa SIRS Eich a ea Nee ee 23. C. filtfoliea. 
Spikes dioecious; scales with dull white margins; leaf blades 
CHOLES 5B thedel ccpeanie Raite sac beter cae Re cna ate RE dete er ted a 24. C. scirpiformis. 
Spikes several. 
Pistillate spikes suborbicular, few-flowered; perigynia long-tapering 
at base. 
Mature perigynia 2mm. wide or more, the body circular in 
RGSS“ SCCELOME erate tetera Rete micas cts tc ee) eer elove. One 25. C. hehiophila. 
Mature perigynia 1.5 mm. wide, the body round—triangular in 
BEOSSZSCCCIONM pert lors iA ale nt ol Ni eohaewy ote Aes 26. C. pennsylvanica. 
Pistillate spikes oblong, many-flowered perigynia rounded at 
"GZISE Cees qnalokd Get tes Gt en RCN CACORE ae ene hoa 27. C. lanuginosa. 
VI. 
Perigynia with beak entire or obliquely cut at orifice. 
