5 



17- 



19- 



Leaves 5-6 mm. wide, 

 transversely nerved 

 between the veins 14. 



Leaves 2-3 mm. wide, 

 not transversely nerved 

 between the veins 15. 



b. Rachis distinctly winged. 



Plants perennial by root- 

 stocks 



Basal leaves grass-like ; 

 weed of waste and culti- 

 vated ground 



Basal leaves reduced to 

 sheaths ; tall marsh sedges 

 with pseudo-septate culms 

 Culm terete 



Culm trigonous at the apex 18 

 Annuals, flowering the first 

 season 



Basal leaves reduced to 

 sheaths ; involucral leaves 

 very numerous, longer than 

 the umbels 



Basal leaves normal, half 

 as long as the culm or 

 longer 

 2. Rachis of the spikelet falling away 

 above the two lower empty scales 

 Achene narrowly linear-oblong, 

 2.5 to 4 times as long as thick 

 Spikelets spicate, several- 

 flowered 



Spikelets capitate or capitate- 

 spicate, only 1-4 — flowered. 

 Heads globose 

 Heads cylindric 

 Achene obovoid or oblong, not 

 more than twice as long as thick 

 Spikelets 1-5 — flowered 



Umbel simple, or culm mono- 

 cephalous 



Scales of the spikelets im- 

 bricated 



Spikelets loosely spicate, 

 tetragonous 



Spikelets densely spicate 

 or capitate 

 Spikelets 2-5 mm. long 

 Spikelets 1.5 mm. long 

 or less 



Spikes several, rarely 

 solitary ; leaves 2-3 

 mm. wide 



Spike solitary, rarely 

 2 ; culms and leaves 

 almost filiform 



C. vegetus 



C. surinamensis 



16. C.rotundus 



22. 



23- 



24. 



26. 



C. articulatus 

 C. nodosus 



C. giganteus 



20. C. radiatus 



21. C. pi at y st achy s 



C. globulosus 



C. cyperoides 



C. tetragon us 



25. C. cayennensis 



27. 



C. Swartzii 

 C . granularis 



