Jones: Flora of Illinois, 23. Cyperaceae 77 



15. Stem about 2 mm. in diameter below the head, soft and wing- 

 angled, flattened when pressed and dry. 

 16. Beak of the perigynium about half the length of tha body, 

 which is strongly nerved dorsally; sheaths rugose ventrally; 

 woods and thickets, local C. conjuncta Boott 



16. Beak about as long as the body of the faintly nerved perigyn- 



ium; sheaths not rugose; meadows, not common 



C. alopecoidea Tuckerm. 



15. Stem 1 mm. in diameter below the head, not winged. 



17. Inflorescence elongate, interrupted, 3-9 cm. long; beak of the 



perigynium shorter than the body; glumes acute; woods and 



thickets, chiefly in the n. half of the state, common 



C. sparganioides Muhl. 



17. Inflorescence short, compact, 1-3 cm. long. 



18. Beak of the perigynium equalling the body; glumes acute; 



woods and thickets C. cephaloidea Dewey 



18. Beak of the perigynium shorter than the body; glumes 

 cuspidate. 

 19. Perigynium ovoid; sandy or gravelly ridges and banks 



C. gravida Bailey 



19. Perigynium ellipsoid. 



20. Perigynium not deep green at maturity; sandy soil 



C. lunelliana Mack. 



20. Perigynium deep green at maturity; dry woods, not 



common C. aggregata Mack. 



6. Spikes numerous (10 or more). 



21. Beak of the perigynium much shorter than the body; fields and 



pastures in the n. half of the state C. brachyglossa Mack. 



21. Beak equalling the body. 



22. Glumes awned; leaves 2-5 mm., wide; swampy ground, often 



along ditches, common throughout 111 



C. vulpinoidea Michx. 



22. Glumes acute; leaves 1-3 mm. wide. 



23. Perigynium 2-2.5 mm. long, glossy, not concealed by the 

 glume; wet meadows; Stark, Peoria, and Fulton counties 



C. diandra Schrank 



23. Perigynium 2.5-3.5 mm. long, dull, nearly concealed by the 

 glume; wet meadows, n. Ill C. prairea Dewey 



Group II 



Spikes of one kind, gynecandrous, bearing both pistillate and staminate 

 flowers, the staminate occurring at the base or the middle of the spike; lateral 

 spikes sessile; stigmas two; achenes lenticular or plano-convex; perigynia 

 glabrous. 

 1. Perigynia not thin- or wing-margined. 



2. Perigynia 4-5 mm. long; beak serrulate, bidentate, 1.5-2 mm. long; wet 

 ground C. bromoides Schk. 



