CYPERACEAE (SEDGE FAMILY) 



173 



wings to the hollow of the joint of the axis next below), deciduous when old. 

 Stamens 1-3. Sty le 2 -3-cleft, deciduous. Achene lenticular or triangular, naked 

 at the apex. Culms mostly triangular, simple, leafy at base, and with one or 

 more leaves at the summit, forming an involucre to the umbel or head. 

 Peduncles or rays unequal, sheathed at base. All flowering in late summer or 

 autumn. (Ktfireipos, the ancient name.) 



1. Scales deciduous, readily falling 1 away from the somewhat persistent 



rhachllla of the flattened spikelt-t" </. 

 a. Sty If '2-cleft ; achene lenticular, laterally compressed (the edge turned 



to the rhachilla) ; rhachilla narrow', not winged ; annuals b. 

 b. Achenes much shorter than the subtending scales c. 



c. Achenes orbicular, with narrowly oblong superficial cells . . 1. C. flavecen. 

 c. Achenes obovate or narrower, the superficial cells broad d. 

 d. Achenes oblong-obovate . 



e. Spikelets lance-oblong ; scales marked with dark brown or 



purple, or merely greenish. 



Stamens 2; style-branches conspicuously exserted . . 2. C. diandrus. 

 Stamens 8 ; style-branches scarcely exserted . . . 8. C. rivulari*. 

 . Spikelets lance-linear; scales oblong, yellow or yellowish- 

 brown throughout ; stamens 2 4. C. Nutlallii. 



d. Achenes linear-oblong or clavate ; scales ovate or oblong. 



Spikelets brownish, 1.5-2 mm. broad 5. C. microdontue. 



Spikelets greenish, about 1 mm. broad . . . . . 6. C. Gategii. 

 b. Achenes nearly as lonj; as the subtending scales .... 7. C.flavicomun 

 a. Style 3-cleft ; achene trigonous /. 

 /. Annuals ;/. 



g. Scales tapering to recurved slender tips . . . . 8. C. Aristatus. 



g. Scales without recurved tips h, 



h. Scales 2.5-3.5 mm. long 9. C. comprtMus. 



h. Scales 2 mm. or less long i. 



i. Spikelets in globose heads ; rhachilla wingless or only ob- 

 scurely winged. 



Spikelets green or whitish-brown, oblong; scales acute . 11. C. acuminatus. 

 Spikelets reddish-brown or purplish, linear; scales blunt 



or barely mucronate 18. C.futcus. 



i. Spikelets in cylindric or elongate heads ; rhachilla bearing 



freely deciduous scale-like wings 19. C. erythrorhieos. 



f. Perennials, the bases hardened and conn-like or stoloniferous j. 

 j. Scales strongly several-ribbed ; achenes 2-3 mm. long. 



Spikelets in oblong or narrowly obovoid heads . . .10. C. Schtceinitoii. 



Spikelets in globose or subglobose heads 84. C.flliculmit. 



j. Scales faintly few-nerved or nerveless ; achenes less than 2 mm. 



long X\ 

 k. Culms naked or nearly BO, the lower sheath nearly or quite 



bladeless 14. C. haspan. 



It. Culms leafy below /. 



1. Plant not stoloniferous; rhachilla wingless; stamen 1 . . 12. C. pseudovegetus. 

 I. Plant loosely stoloniferous ; scales (it-current on the rhachilla 



as wings ; stamens 3 -in. 

 m. Achenes short-obovoid ; scales with free or spreading 



mucronate tips 15. C. dentatus. 



m. Achenes linear- to oblong-cylindric ; scales appressed, 



blunt or barely mucronate n. 

 n. Scale? chestnut-color. 



Involucre shorter than the rays of the umbel, or 1 



bract slightly longer 16. C. rotundut. 



Involucral bracts numerous and much overtopping 

 the umbel 



. Scales straw-color or pale brown 



2. Rhachillas of the s pikelets soon breaking away from the main rhachis ; 



the scales falling only in extreme age o. 

 o. Annuals. 



Flowers remote, the successive scales not reaching the bases of 



the ones above on the same side 



Flowers approximate, the successive scales overlapping the bases 



of those above 



o. Perennials, with hard corrn-like bases p. 



p. Spikelets very strongly flattened 



p. Spikelets terete, subterete, or only slightly flattened a. 

 q. Spikelets reflexed, in thick cylindric or obovoid heads r. 

 r. Culms smooth and glabrous. 



Spikelets loosely spicate ; achenes 2.5-3 mm. long 

 Spikelets densely spicate and overlapping; achenes less 



than 2.5 mm. long. 



Spikelets iMMtowerad, linear-cyllndric, not rigid 

 Spikelets 1-2 flowered, subuLte, rigid .... 



17. C. Hallii. 



18. C. exculentus. 



21. C. Engelmanni. 

 20. C.f erase. 



22. C. etrigosus. 



23. C. rtfractiu. 



24. C. lancastrientit. 



25. C. hystricinus. 



