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. (KuTrei/aos, the ancient name.) 



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



rhachilla of the flattened spikelet a. 

 a. Style 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 . 

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

 d. Achenes oblong-obovate e. 



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



purple, or merely greenish. 



Stamens 2; style-branches conspicuously exserted . 

 Stamens 3 ; style-branches scarcely exserted 

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

 brown throughout; stamens 2 



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



Spikelets brownish, 1.5-2 mm. broad 



[Spikelets greenish, about 1 mm. broad 

 b. Achenes nearly as long as the subtending scales .... 

 Style 3-cleft ; achene trigonous /. 

 /. Annuals g. 

 g. Scales tapering to recurved slender tips 

 g. Scales without recurved tips h. 

 h. Scales 2.5-3.5 mm. long 

 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 . 

 Spikelets reddish-brown or purplish, linear ; scales blunt 

 or barely mucronate 

 *'. Spikelets in cylindric or elongate heads ; rhachilla bearing 

 freely deciduous scale-like wings 

 /. 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 

 Spikelets in globose or subglobose heads 



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



long k. 

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



bladeless 



k. Culms leafy below I. 



1. Plant not stoloniferous ; rhachilla wingless; stamen 1 . 



I. Plant loosely stoloniferous ; scales decurrent on the rhachilla 



as wings ; stamens 3 rn. 

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



mucronate tips 



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



blunt or barely mucronate n. 

 n. Scales chestnut-color. 



Involucre shorter than the rays of the umbel, or 1 



bract slightly longer 



Involucral bracts numerous and much overtopping 



the umbel 



7?. Scales straw-color or pale brown 



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



the scales falling only in extreme age o. 

 0. 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 conn-like bases p. 



p. Spikelets very strongly flattened 



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

 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 3-0-flowercd. linear-cylindric, not rigid 

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



1. C.flavescens. 



2. C. diandrus. 

 8. C. rivularis. 



4. C. Nutlallii. 



5. C. microdontus. 



6. C. Gatesii. 



7. C. flavicomus 



8. O. Aristatus. 



9. C. comprtfssus. 



11. C. acuminatus. 



13. C.fusous. 



19. C. erythrorhizos. 



10. C. Schweinitzii. 

 34. C.filieulmis. 



14. C. haspan. 



12. C. pseudovegetus. 



15. C. dentatus. 



16. C. rotundus. 



17. C. Hallii. 



18. C. esculentus. 



21. C. Engelmanni. 

 20. C.ferax. 



22. C. strigosus. 



23. C. refractus. 



24. C. lancastriensis. 



25. C. hi/stricinus. 



