CYPEEACEAE. 73 



10. EIGIDAE. 



Lower sheaths becoming very fibrillose; tufted bog species. 



28. C. stricta. ■ ^^• 



Lower sheaths not at all fibrillose, or slightly so. ^'■ 



Culms 0.3-0.6 m. tall; scales acute or acuminate. 29. C. Eaydeni. 

 Culms 0.2-1.1 m. tall; scales obtus"fe or the lower acute. 



Scales green. 30. C. aquatilis. 



Scales purple or brown. 31. C. Goodenovit. 



11. PRASINAE, 



Perigynia twisted toward the top; scales purple-brown. 



32. C. torta. 

 Perigynia straight; scales green, 33. C. prasina. 



12. PENDULINAE. % 



Pistillate spikes narrowly cylindric. 34. C. littoralis. 



Pistillate spikes oblong or globose. 35. C. limosa. 



13. CRYPTOCARPAE. 



Perigynia obovoid, obtuse. 36. C. crinita. 



Perigynia oblong or elliptic, acute. 37. C. gynandra. 



14. VIRESCENTES. ! 



Perigynium densely pubescent. 



Pistillate spikes obloug-cylindric, 8-20 mm. long; perigynia oval or 



ovoid, few-nerved. 38. C. virescens. 



Pistillate spikes narrowly cylindric, 12-36 mm, long; perigynia oblong, 



strongly several-nerved, 39. C. costellata. 



Perigynium nearly glabrous, at least when mature. 



Spikes 5-7 mm. thick; perigynia imbricated, flattened; top of achene 



not bent. 40. C. triceps. 



Spikes 4 mm. thick; perigynia not imbricated, swollen; top of achene 



bent, or tipped with a bent style. 41. C. Caroliniana. 



15. GRAGILLIMAE. 



Perigynia 2-4 mm. long, slightly swollen; spikes linear or linear-eylindric. 

 Plants glabrous; perigynia obtuse. 42. C. gracillima. 



Sheaths pubescent; perigynia pointed at both ends. 



43. C. aestivalis. 

 Perigynia 4-5 mm. long, manifestly swollen; spikes oblong or oblong- 

 cylindric. 44. C. Davissi. 



16. SYLVATICAE, 



45. C. longirostris. 



17. DEBILES. 



Perigynia membranous, few-ner\'ed; pistillate spikes slender. 



Leaves 5-10 mm. wide; scales two-thirds as long as the perigynia. 



46. C, arctata. 

 Leaves 2-5 mm. wide; scales one-half as long as the perigynia. 



47. C. tenuis. 

 Perigynia coriaceous, strongly many-nerved; pistillate spikes thicker. 



48. C. oblita. 



