354 CYPERACEAE. VOL I. 



1. NARDINAE. Represented by i species. i. C.nardina. 



2. CAPITATAE. Represented by i species. 2. C. capitata. 



3. INCURVAE. Represented by i species. 3. C. incurva. 



4. DIOICAE. Represented by i species. 4. C. gynocrates. 



5. CHOKDORKHIZEAE. Represented by i species. 5. C. chordorrhiza. 



6. DIVISAE. 

 Heads not dioecious ; styles short ; perigynia short-beaked. 



Leaves narrowly involute. 6. C. stenophylla. 



Leaves i"2" wide, flat above. 7. C. camporum. 



Heads normally dioecious ; styles long ; perigynia long-beaked. 8. C. Douglasii. 



7. ARENARIAE. 



Perigynia thin-margined. 9. C. Sartu'ellii. 



Perigynia wing-margined 



Spikes numerous; head heavy. 10. C.arenaria. 



Spikes few (3-8); head slender. n. C.siccata. 



8. MUHLENBERGIANAE. 



1. Sheaths tight, often thickened at mouth ; inconspicuously if at all septate-nodulose. 



Perigynia corky-thickened at base, usually widely radiating or reflexed at maturity. 

 Perigynia beak smooth ; scales acuminate, deciduous ; spikes mostly approximate. 



Perigynia body broadly ovate, bi-convex. 12. C. retro fiexa. 



Perigynia body lanceolate or ovate-lanceolate, plano-convex. 13. C. texensis. 



Perigynia beak minutely roughened; scales obtuse or acutish, persistent. 14. C.rosea. 

 Perigynia not corky-thickened at base, spreading or ascending. 



Scales tinged with reddish-purple; perigynia more than 2" long. 15. C. muricata. 



Scales not tinged with reddish-purple ; perigynia 2" or less long. 

 Head 7}4"-i8" long, the lower spikes distinct. 



Perigynia spreading, i^" long; bracts not broadly dilated at base; scales about length 



of and narrower than perigynia, short-awned. 16. C. Muhlenbergii. 



Perigynia ascending, 2" long ; bracts broadly dilated at base ; scales (especially lower) 



exceeding and as wide as perigynia, strongly awned. 17. C.austrina. 



Head 4"-io" long, the spikes densely capitate. 



Scale body about length of broadly ovate perigynia. 18. C. mesochorea. 



Scale body much exceeded by perigynia. 



Perigynia elliptic-ovate or narrower; leaves 1^4 "-2" wide. 19. C. cephalophora. 

 Perigynia orbicular-ovate; leaves J^"-i" wide. 20. C. Leavenworthii. 



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



Culms sharply triangular, not flattened or winged. 



Perigynia dull, its beak %'-J3 length of orbicular body. ' 21. C.gravida. 



Perigynia deep green, its beak y* length of ovate body or more. 



Bracts not developed; scales one half length of body of perigynia. 22. C, cephaloldea. 

 Some bracts developed ; scales equalling body of perigynia or longer. 



Leaves i l /2 "2" wide; spikes aggregated or approximate. 23. C. aggregata. 



Leaves 2j4"-5" wide; lower spikes strongly separate. 24. C. sparganioides. 



Culms narrowly winged, more or less flattened. 



Perigynia faintly nerved on outer face. 25. C. alopecoidea. 



Perigynia strongly nerved on outer face. 26. C. conjuncta. 



9. MULTIFLORAE. 



Leaves exceeding culms ; perigynia beak equalling body. 27. C. vulpinoidea. 

 Culms exceeding leaves ; perigynia beak shorter than body. 



Perigynia ovate to suborbicular. 28. C. annectens. 



Perigynia lanceolate to ovate-lanceolate. 29. C. setacea. 



10. PANICULATAE. 



Leaves }^"-iJ^" wide; perigynia tapering into beak, rounded or truncate at base. 



Spikes approximate or little separate, the lower simple or nearly so ; perigynia dark-brown, 



rounded on inner face, i"-i 1 /^" long. 30. C. diandra. 



Spikes strongly separate, the lower compound ; perigynia light-brown, nearly flat on inner face, 



i y^'-f-Vi." long. 31. C.prairea. 



Leaves 2"- 4" wide ; perigynia very abruptly short-beaked, tapering at base. 32. C. decotnposita. 



n. STENORHYNCHAE. 



Perigynia 2"-2}^" long; beak 1-2 times length of body. 33. C. stipata. 



Perigynia 3"-3^2" long; beak 3-4 times length of body. 34. C. crus-corvi. 



12. TENELLAE. Represented by i species. 35. C. disperma. 



13. CANESCENTES. 

 Lowest bract bristle-form, much prolonged, many times exceeding its i-s-flowered spike ; spikes 



widely separate. 36. C. trisperma. 



Lowest bract much shorter or none ; spikes several-many-flowered, the upper approximate. 



Spikes 2-4, subglobose, closely approximate, forming an ovate or suborbicular head; perigynia 



scarcely beaked ; scales white-hyaline. 37. C. tenuiflora. 



Spikes i-many, the lower more or less strongly separate, the head elongate ; perigynia short to 



strongly beaked ; scales darker. 

 Perigynia broadest near middle ; beak short, smooth or moderately serrulate. 



Perigynia beak smooth or very nearly so ; scales very obtuse to acutish, strongly reddish- 

 brown tinged ; spikes closely approximate or in C. norvegica the lower remote. 

 Spikes i or more, approximate, the lower less than 2" wide. 



Spike i, rarely with a smaller one at base. 38. C. ursina. 



Spikes 2-4. 



Terminal spike strongly clavate at base ; culms rough at apex only. 



