44 CYPERACEAE 



10. MUHLENBERGIANAE. 



Sheatbs 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 sernilate 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. Pantculatae. 



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— i mm. long, dull, concealed by the scales. 



Leaves 1-2.5 mm. wide; perigynia 2.5-3 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. Stenorhykchae. 



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

 tinged. 

 Leaves clustered at bEise; sheaths not cross-rugulose ventrally; culms slender. 



26. C JonesU. 

 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. stipata. 



14. Stelltjlatae. 



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 inierioT. 



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



32. C. angusHor. 



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. leplopoda. 

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



16. OVALES. 



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. 



Perigynia lance-ovate, the beak shorter than the body; longer bracts less than 1 dm. 

 long, with yellowish brown margins at base. 

 Perigynia nerveless ventrally, tawny at oriflce. 37. C. athrostaehya. 



Perigynia nerved ventrally, hyaUne at oriflce. 38. C. tenuirostris. 



Bracts not conspicuous, rarely sUghtly exceeding the head. 



Beak of the perigynia flattened and serrulate to tip, often strongly bidentate. 



Scales about the length of the perigynia and nearly of the same width above, 

 the perigynia nearly entirely concealed. 

 Head stiff, the spikes approximate. 



Perigynia less than 5.5 mm. long, at most faintly nerved on inner face, 

 loosely ascending; spikes suborbicular; lower bracts prominent, stiff. 



39. C. adusta. 

 Perigynia 5.5-7 mm. long, flnely many-nerved on irmer taxe, appressed; 

 spikes oblong-elliptic; bracts not stiff. 40. C. petasata. 



Head not stiff, flexuous or moniliform. 41. c. aenea. 



Scales shorter than perigynia and noticeably narrower above, the upper part of 

 perigynia largely exposed. 

 Perigynia subulate to lanceolate, at least 2 14 times £is long as wide 

 Perigynia subulate, the margin at the base almost obsolete. 



„ 42. C. Crawfordii. 



Perigyma lanceolate, the margm conspicuous to the base. 



43. C. scoparia. 



