Leaves 5-6 mm. wide, 



transversely nerved 



between the veins 14. C. vegetus 



Leaves 2-3 mm. wide, 



not transversely nerved 



17. 



19- 



between the veins 

 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 



15. C. siirinamensis 



16. C. rotundas 



C. articulatus 

 C. uodosus 



22. 

 23. 



C. giganteiis 



20. C. radiatus 



21. C. plat yst achy s 



C. globidosiis 

 C. cyperoides 



24. 



25- 



C. tetragon us 

 C. cavennensis 



26. 



27. 



C. Swartzii 

 C . granularis 



