114 CYPERACEAE 



7. DlVISAE. 



Rootstocks slender, light brownish; culms obtusely triangular, normally smooth; leaf- 

 blades narrowly involute. 



Perigynia long-beaked; heads dioecious or nearly so. 10. C. Douglasii. 



Perigynia short-beaked; heads androgynous. 11. C. stenophylla. 



Rootstocks stout; culms acutely triangular, normally rough above. 

 Perigynia not strongly nerved ventrally; leaf-sheaths hyaline. 



Perigynia chestnut, thick, the beak about one-fifth as long as the body. 



12. C. simulata. 

 Perigynia blackish in age, plano-convex, the beak one-third to one-half as long as 



the body. 13. C. praegracilis. 



Perigynia strongly nerved ventrally; upper leaf-sheaths green-striate opposite the 

 blades. 14. C. Sartwellii. 



8. CHORDORRHIZAE. 



Represented by one species in our range. 15. C. chordorrhiza. 



9. ARENARIAE. 

 Represented by one species in our range. 16. C. siccata. 



10. MUHLENBERGIANAE. 



Sheaths tight, inconspicuously, if at all, septate-nodulose. 



Densely cespitose; head ovoid, capitate; perigynia serrulate to the middle. 



17. C. Hoodii. 

 Rootstocks elongate; head linear, interrupted; perigynia serrulate at the apex only. 



Scales obtuse to short-cuspidate, not concealing the spreading perigynia. 



Spikes with conspicuous staminate flowers; scales half as long as the perigynia. 



18. C. vallicola. 



Spikes with inconspicuous staminate flowers; scales about as long as the peri- 

 gynia. 19. C. occidentalis. 



Scales strongly cuspidate, concealing the appressed perigynia. 



20. C. Hookeriana. 

 Sheaths loose and membranous, easily breaking, conspicuously septate-nodulose. 



21. C. gravida. 



11. MULTIFLORAE. 



Represented by one species in our range. 22. C. vulpinoidea. 



12. PANICTJLATAE. 



Culms loosely cespitose; sheaths not copper-tinged at the mouth; head little interrupted; 

 perigynia 2-2.75 mm. long, shining, not concealed by the scales. 



23. C. diandra. 



Culms densely cespitose; sheaths copper-tinged at the mouth; head interrupted; peri- 

 gynia 2.5-4 mm. long, dull, concealed by the scales. 



Leaves 1-2.5 mm. wide; perigynia 2.53 mm. long; scales tinged with reddish brown. 



24. C. prairea. 

 Leaves 2.5-6 mm. wide; perigynia 3-4 mm. long; scales chestnut-tinged. 



25. C. Cusickii. 

 13. STENORHYNCHAE. 



Perigynia 3-4 mm. long, the beak much shorter than the body; scales strongly dark- 

 tinged. 

 Leaves clustered at base; sheaths not cross-rugiilose ventrally; culms slender. 



26. C. Jonesii. 

 Leaves not clustered at base; sheaths cross-rugulose ventrally; culms stout. 



27. C. nervina. 

 Perigynia 4-6 mm. long, the beak longer than the body; scales not dark-tinged. 



28. C. stipala. 



14. STELLULATAE. 



Spikes in a small (6-10 mm. long) densely capitate brownish black head. 



29. C. illota. 

 Spikes more or less widely separate, not brownish black. 



Perigynia broadest in middle, the beak sparingly serrulate; culms weak. 



30. C. laeviculmis. 

 Perigynia broadest near base, the beak strongly serrulate; culms stiff. 



Beak of the perigynia one-fourth as long as the body, the teeth short, and ventral 



suture inconspicuous. 31. C. interior. 



Beak of the perigynia longer, strongly bidentate, the ventral suture conspicuous. 



32. C. angustior. 



15. DEWEYANAE. 



Culms densely cespitose; perigynia tapering at base, 4-5 mm. long, the upper part of 

 the body covered by translucent scale. 33. C. Deweyana. 



Rootstocks slender, elongate; perigynia substipitate, 3.5-4.5 mm. long. 



Perigynia shallowly bidentate. the upper part of body not covered by the scale. 



34. C. leptopoda. 

 Perigynia deeply bidentate, the body covered by the scale. 35. C. Bolanderi. 



16. O VALES. 



Lower bract or bracts conspicuous, several-many times the length of the head. 



Perigynia subulate, the beak much longer than body; lower bracts more than 1 dm. 

 long, without yellowish brown margins at base. 36. C. sychnocephala. 



