i 7 8 



CYPERACEAE 



Perigynia beak smooth; scales acuminate, deciduous. 



Perigynia beak minutely roughened; scales obtuse 



or acutish, persistent. 



Perigynia not corky thickened at base, spreading or 



ascending. 



Scales tinged with reddish-purple; perigynia more 



than 4 mm. long. 

 Scales not tinged with reddish purple; perigynia 4 

 mm. or less long. 

 Head 15-30 mm. long, the lower spikes distinct. 

 Head 8-20 mm. long, the spikes densely capitate. 

 Perigynia elliptic-ovate or narrower; leaves 



2.5-4 mm. wide. 

 Perigynia orbicular-ovate; leaves 1-2 mm. 

 wide. 

 Sheaths loose and membranous, easily breaking, conspicu- 

 ously septate-nodulose. 

 Culms sharply triangular, not winged, or flattened; 

 perigynia not ribbed dorsally. 

 Perigynia flat on inner face; sheaths rarely trans- 

 versely rugulose; spikes approximate. 

 Scales less than half length of perigynia body; 

 sheaths truncate at throat, not thickened, and 

 not reddish brown tinged. 

 Scales about length of perigynia body, strongly 

 cuspidate; sheaths rounded at throat, thick- 

 ened and reddish brown tinged. 

 Perigynia with raised border on inner face; sheaths 

 usually conspicuously transversely rugulose; lower 

 spikes usually separate. 

 Culms narrowly-winged, triangular, much flattened in 

 drying. 

 Perigynia strongly nerved on outer face. 

 Perigynia faintly nerved on outer face. 



3. MULTIFLORAE. 



Leaves exceeding culms; perigynia beak equalling body. 

 Culms exceeding leaves; perigynia beak shorter than body. 



Perigynia ovate to suborbicular. 



Perigynia lanceolate to ovate lanceolate. 



4. Paniculatae. 



Spikes approximate or little separate, the lower simple or 

 nearly so; sheaths not copper color at mouth. 



Spikes strongly separate, the lower compound; sheaths 

 strongly copper color at mouth. 



5. Stenorhynchae. 



Sheaths transversely rugulose; not thickened at mouth. 

 Sheath not transversely rugulose; thickened at mouth. 



6. Tenellae, represented only by 



7. Canescentes. 



Lowest bract bristle-form, much prolonged, many times 

 exceeding its 1-5-flowered spike; spikes widely separated. 



2. C. retroflexa. 



3. C. rosea. 



4. C. muricata. 



5. C. Muhlenbergii. 



6. C. cephalophora. 



7. C. Leavenworlhii. 



8. C. cephaloidea. 



9. C. aggregata. 



10. C. sparganioides. 



11. C. conjuncta. 



12. C. alopccoidea. 



13. C. vul pinoidca. 



14. C. annectens. 



15. C. setacea. 



16. C. diandra. 



17. C. prairca. 



18. C. stipata. 



19. C. laevivaginata. 



20. C. disperma. 



21. C. trisperma. 



