Jones: Flora of Illinois, 23. Cyperaceae 71 



1 . Spikelet usually much thicker than the stem; glumes persistent. 

 3. Style 2-cleft; achenes lenticular or biconvex. 

 4. Perennials with rhizomes. 



5. Sheaths loose, hyaline and scarious at the summit; glumes hyaline- 

 margined; wet soil, rare. Wolf Lake, Chicago, Hill 



E. olivacea Torr. 



5. Sheaths close, not hyaline at the summit. 



6. Basal glumes of the spikelets usually 2 or 3 below the thinner 

 fertile glumes. 

 7. Tubercle elongate, much longer than broad; achenes narrowly 

 obovoid or pyriform; stems subterete, rather firm; ponds, 



swamps, and marshes, n. Ill E. pdustris (L.) R. & S. 



7. Tubercle depressed-deltoid, umbonate, or broadly ovate, as 

 broad as or broader than long; achenes broadly obovoid or 

 roundish. 

 8. Stems firm, nearly terete; fertile glumes ascending, oval, acu- 

 minate; marshes, ditches, shores, local throughout III 



E. smallii Britt. 



8. Stems soft, compressed; fertile glumes appressed, obtusish; 

 wet ground, not common; chiefly in the s. half of the state, 



extending northw. to Menard Co E. mamillata Lindb. 



6. Basal glume solitary, spathiform, usually encircling the base of the 



spikelet; wet ground E. calva Terr. 



4. Annuals, with fibrous roots. 



9. Tubercle flattened or saucer-shaped; mature achenes black, 1 mm. 

 long; wet ground. [E. capitata R. Br.; E. caribaea (Rottb.) Blake; 



E. dispar E. J. Hill} E. geniculata (L.) R. & S. 



9. Tubercle conical or deltoid, acute; mature achenes pale brownish. 

 10. Tubercle conical, narrower than the top of the achene; wet 



ground in the n. half of the state E. ovata (Roth) R. & S. 



10. Tubercle depressed-deltoid, as wide as the top of the achene. 

 11. Bristles about equalling the achene, or sometimes rudimen- 

 tary; muddy shores and along ditches 



E. engelmanni Steud. 



11. Bristles much exceeding the achene; wet ground throughout 



111., not uncommon E. obtusa (Willd.) Schult. 



3. Style usually 3-cleft; achenes trigonal or turgid. 



12. Tubercle plainly distinguishable from the achene; achenes less than 

 2 mm. long. 

 13. Achenes cancellate and striate. 



14. Spikelet flattened, 3-9-flowered, the glumes 2-3-ranked; bristles 

 3-4, fugacious; stems very slender, not more than 0.5 mm. 

 in diameter, 5-20 cm. long; wet ground and shallow water .... 

 E. acicularis (L.) R. &: S. 



14. Spikelet terete, the glumes many-ranked; bristles 0; stems 

 about 1 mm. in diameter; wet ground; Fulton, Peoria, Stark 



