32 Order POALES 
Perigynia about 3 mm. long; scales green with 
colored margins. 25. C. meadii. 
Perigynia less than 3 mm. long; scales dark colored 
with green margins or green midrib. 
Scales brown with lighter margins, not awn- 
tipped. 10. C. parryana. 
Seales black or brown with green midrib, awn- 
tipped. 11. C. buxbaumii. 
Pistillate spikes loosely few-flowered. 
Pistillate spikes not globose, usually over 1 cm. long. 
Tips of perigynia bent outward. 
With a bent beak. 23. C. laxiflora. 
Nearly or quite beakless. 24. C. tetanica. 
Tips of perigynia straight or nearly so. 
Perigynia 3-4 mm. long. 23. C. oligocarpa. 
Perigynia 2 mm. long. 27. C. aurea. 
Pistillate spikes globose, 4-8 mm. long. 
28. C. eburnea. 
Spikes solitary, scales with white scarious margins. 
32. C. filifolia. 
Achenes lenticular; stigmas two. 
Spikes unlike, the upper usually staminate and the lower pistillate. 
Pistillate spikes densely flowered. 
Orifice of perigynia entire or nearly so. 
Scales green. 15. C. aquatilis. 
Scales colored. 
Scales equal to the perigynia in length, obtuse to acumi- 
nate. 12. C. stricta. 
Scales longer than perigynia, very acute. 13. C. haydeni. 
Orifice of perigynia toothed. 
Teeth larger, perigynia ribbed when mature; scales acute. 
14. C. nebraskensis. 
Teeth minute; scales blunt, shorter than the perigynia. 
45. C. interior. 
Pistillate spike few-flowered. 27. C. aurea. 
Spikes alike or nearly so, all with both staminate and pistillate 
flowers. 
Staminate flowers above the pistillate, rarely mixed with them. 
Spikes forming a Bees head. 
Perigynia about 2 mm. long, beak entire, edges not serrate. 
33. C. stenophylla. 
Perigynia 3 mm. long, or more. 
Scales 2-4 times as long as perigynia. 34. C. douglasii. 
Scales little longer than perigynia. 44. C. muhlenbergii. 
Spikes not forming globose heads. 
Perigynia over 3 mm. long, or scale only half as long as 
the perigynium. 
Beak of perigynium much longer than body, usually 2-4 
times as long. 
Base of perigynium not thickened, beak about twice as 
long as body of perigynium. 35. C. stipata: 
Base of perigynium thickened, disc-like; beak 3—4 times 
as long as the body. 36. C. crus-corvi. 
