SEDGE FAMILY. 235 
Style 2-cleft; achene lenticular, not 3-angled; scales falling from the rachis; spikelets flat. 
Achene one-half as long as the scale; umbel nearly or quite simple. 
Spikelets yellow; superficial cells of the achene oblong. 1. C. flavescens. 
Spikelets green or brown; superficial cells of the achene quadrate. 
Scales obtuse or obtusish, appressed. 
Seales membranous, dull; style much exserted. 
Seales subcoriaceous, shining; style scarcely exserted. 
Scales acute, somewhat spreading at maturity. 
2. C. dtandrus. 
3 
Achene narrowly obovate; spikelets 's'-114' long. 4. C. Nuttaliit. 
5 
6 
. C. rtvularis. 
Achene linear-oblong; spikelets 3''-9'’ long. . C. microdontus. 
Achene nearly as long as the scale; umbel sometimes much compound. 6. C. flavicomus. 
Style 3-cleft; achene 3-angled. 
Seales falling away from the persistent rachis of the flattened spikelets. 
Wings of the rachis, if present, permanently adnate to it. 
Scales tipped with recurved awns; low annual, 1’-6’ tall. 7. C. inflexus. 
Scales acute or obtuse, not awned. 
Wings of the rachis none or very narrow. 
Stamens 3; spikelets linear-oblong, 4'’—12'’ long; scales acute. 
Annual; culms smooth, 2’~10' long. 8. C. compressus. 
Perennial; culms rough, 1°-214° tall. 9. C. Schweitnitzii. 
Stamen 1; spikelets ovate, 2'’-4’’ long. 
‘Tall perennial; achene linear; scales acutish. 10. C. pseudovegetus. 
Low annual; achene oblong; scale-tips recurved. 11. C. acuminatus. 
Wings of the rachis distinct. 
Low annual, adventive from Europe; scales brown. 12. C. fuscus. 
Tall indigenous perennials (no. 13 sometimes annual ?), 
Lower leaves reduced to pointed sheaths. 13. C. Haspan. 
Leaves all elongated-linear. 
Scales mucronate, reddish brown or green. 14. C. dentatus. 
Scales acute or obtuse, not mucronate. 
Scales wholly or partly purple-brown; achene linear. 
Scales tightly appressed. 15. C. rotundus. 
Tips of the scales free. 16. C. Hallit. 
Scales straw-colored; achene obovoid. 17. C. esculentus. 
Wings of the rachis separating from it as interior scales; annuals. 
Spikes loose; spikelets 3/’—10'’ long. 18. C. exryvthrorhizos. 
Spikes dense, cylindric; spikelets 114'’-214'' long. 19. C. Halet. 
Spikelets falling away from the axis of the spikes, the lower pair of scales commonly persistent. 
Annuals; spikelets elongated, nearly terete. 
Scales imbricated; achene obovoid. 
Scales thin, dull brown; spikelets very slender. 20. C. spectosus. 
Seales rigid, yellow-brown; spikelets’ stout. 2i. (C: ferox. 
Scales distant; achene linear-oblong. 22. C. Engelmannt. 
Perennial by hard, tuber-like basal corms; spikelets more or less flattened. 
Achene narrowly linear-oblong, 3-4 times as long as thick. 
Spikelets flat, several-many-flowered. 23. C. strigosus. 
Spikelets subterete, few-flowered. 
Spikelets 6'’-12'’ long, loosely spicate; lower reflexed, 24. C. refractus. 
Spikelets 1'4''-6'’ long, densely capitate or spicate. 
Spikelets all reflexed; culms rough. 25. C. retrofractus. 
Spikelets spreading or only the lower reflexed; culms smooth. 
Heads oblong or cylindric. 
Spikelets 3/’-5’’ long, the lower reflexed. 26. C, Lancastriensts, 
Spikelets 1'4'’-2"’ long, the lowerspreading. 27. C. cylindricus. 
Heads globose. +28. C. ovularits. 
Achene oblong or obovoid, about twice as long as thick. 
Rachis wingless or very narrowly winged. 
» Scales pale green, membranous, dull. 29. C. filiculmts. 
Scales chestnut-brown, firm, shining. 30. C. Houghtoni. 
Rachis-wings membranous, broad. 
Scales firm, not appressed; spikelets loosely capitate. 31. C. Gray. 
Scales thin, closely appressed; spikelets densely capitate. 32. C. echinalus. 
1. Cyperus flavéscens L. Yellow 
Cyperus. (Fig. 543.) 
Cyperus flavescens I. Sp. Pl. 46. 1753. 
Annual, culms very slender, tufted, leafy below, 
3/-12/ tall, mostly longer than the leaves. Leaves 
1/’-1'4’’ wide, smooth, the longer usually exceed- 
ing the inflorescence; clusters terminal and sessile 
or on 1-4 short rays; spikelets in 3’s-6’s, linear, 
subacute, yellow, many-flowered, flat, 4’/’-9’’ long, 
144//-2”’ broad; scales ovate, obtuse, 1-nerved, ap- 
pressed, twice as long as the orbicular-obovate 
black obtuse lenticular shining achene; stamens 3; 
style deeply 2-cleft, its branches slightly exserted; 
superficial cells of the achene oblong. 
In marshy ground, Maine to Michigan, Florida and 
Mexico. Alsointhe Old World. Aug.-Oct. 
