Jones: Flora of Illinois, 23. Cyperaceae 69 



6. Base of the style swollen, peisistent as a tubercle on the achene. 



7. Spikelet solitary; bristles usually present; stems leafless 4. Eleocharis 



7. Spikelets several; bristles none; leaves filiform, the sheaths pubescent 



5. Bulbost\^lis 



6. Base of style deciduous, sometimes enlarged. 



8. Flowers with a perianth of 3 stalked sepals, or of 1 or 2 hyaline glumes. 

 9. Bristles 3; achene and glumes stipitate; plants perennial 6. Fuirena 



9. Bristles 0; achene and the solitary minute glume sessile; plants annual 



7. Hemicarpha 



8. Flowers without a perianth. 



10. Style conspicuously swollen at the base; bristles none 8. Fimbristvlis 



10. Style not at all or only slightly thickened at base; bristles usually present. 



II. Bristles few, short, not exceeding the glume 9. Scirpus 



II. Bristles apparently numerous, long, slender, silky 10. Eriophonim 



5. Spikelets 1-4-flowered, polygamous. 



12. Base of the style persistent as a tubercle on the achene; perianth bristles 



usually present; style 2-cleft II. Rh\)nchospora 



12. Style wholly deciduous; bristles 0; style 3-cleft 12. Cladlum 



1. Spikelets usually unisexual; plants monoecious, or rarely dioecious. 



13. Achenes v/hite, bony, globose, usually supported on a disk, not enclosed in a sac 



(perigynium) ; pistillate spikes I-flowered 13. Scleria 



I3.Achen2s not bony, enclosed in a perigynium 14. Carex 



1. Cyperus L. 



1. Glumes deciduous from the persistent rachilla of the spikelet. 

 2. Style 2-cleft; achenes lenticular. 



3. Spikelets straw-colored or yellowish; achenes black, glossy, the super- 

 ficial cells rectangular; wet ground. [C. flavescens sensu auth., non 

 L.} C. poaejormis Pursh 



3. Spikelets green or brown; achenes brown, dull, the superficial cells 

 quadrate. 

 4. Glumes glossy, subcoriaceous; style scarcely exserted; stamens 3; 

 moist ground, in t!ie n. part of the state, often abundant and 



forming dense mats C. rivularis Kunth 



4. Glumes dull, reddish tinged, membranous; style conspicuously ex- 

 serted; stamens usually 2; marshy ground, or margins of ponds 



and streams C. diandrus L. 



2. Style 3-cleft; achenes trigonal. 

 5. Rachis prominently winged. 



6. Glumes straw-colored or pale brown, ovate acute; achenes ovoid; 

 plants perennial with a scaly tuber-bearing rhizome; moist ground. 

 [C. phymatodes Muhl.] Chufa or Nut Sedge C. esculentus L. 



6. Glumes dark brown, lanceolate, mucronate; achenes obovoid; plants 



annual; along streams and ditches, and in fields 



C. erythrorhizos Muhl. 



5. Rachis wingless or only very narrowly winged. 



7. Plants perennial; spikelets 8-16 mm. long; stamens 2 or 3. 



8. Stem rough; spikelets ascending; glumes 3-4.5 mm. long; achenes 

 2.5-3 mm. long; sandy soil in the n. part of the state, extending 

 southw. to Mason Co C. schweinitzn Torr. 



8. Stem smooth; spikelets spreading; glumes 2-2.5 mm. long; achenes 



