Jones: Flora of Illinois, 23. Cyperaceae 79 



15. Perigynia 3.5-4.5 mm. long; spikes clavate at base, not aggre- 

 gated, usually in a flexuous, moniliform inflorescence; 



open woods [C. straminea of auth., not Willd.} 



C. teuera Dewey 



14. Perigynia rhombic-ovate to suborbicular, widest above the 

 middle; open woods, rare [C. straminea sensu Mack., non 

 Willd.] C. absolutescens Schw. 



5. Perigynia 2.3-4 mm. wide. 



16. Glumes aristate; perigynia obovate, 4-5 mm. long; swamps, rare, n.e. 

 Ill C. alata T. & G. 



16. Glumes acute to obtusish; perigynia oval or ovate. 

 17. Perigynia flat, thin, translucent. 



18. Perigynia 5.5-6.5 mm. long, 3-4 mm. wide; leaf-sheaths hya- 

 line; dry soil in the n. half of the state C. bicknellii Britt. 



18. Perigynia 4-5 mm. long, 2.5-7 mm. wide; leaf-sheaths green; 



wet ground in the n. part of III., rare 



C. suberecta (Olney) Britt. 



17. Perigynia thick, coriaceous or subcoriaceous, plano-convex. 



19. Body of the perigynium ovate, broadest near the base, tapering 



into the beak; in woods and along ditches, not common 



C. molesta Mack. 



19. Body of the perigynium broadly ovate to suborbicular, abruptly 



contracted into the beak; open woods and roadsides 



C. brevior (Dewey) Mack. 



Group III 



Stigmas 2; achenes lenticular; perigynia beakless or short-beaked; spikes 

 normally unisexual, i.e., the terminal spike commonly staminate, the lower 

 spikes entirely or mostly pistillate. 



1. Perigynia obovoid or subglobose, beakless, yellowish or brownish, plump, 

 nerved, about 2 mm. in length, longer than the obtuse, pale brown 



glumes; wet ground, n. Ill C. atirea Nutt. 



1. Perigynia compressed, short-beaked, the beak less than 0.5 mm. long. 

 2. Glumes obtuse, approximately equalling the perigynia. 



3. Perigynium 2.7-3.2 mm. long, strongly flattened; stems strongly phyl- 

 lopodic, the dried-up leaves of the previous year persistent; wet 

 ground, n. Ill C. substricta (Kijkenth.) Mack. 



3. Perigynium 2.2-2.7 mm. long; stems aphyllopodic; leaves of the pre- 



vious year not persistent; swamps C. stricta Lam. 



2. Glumes acuminate or acute, longer than the perigynia; stems aphyl- 

 lopodic. 



4. Perigynia 2-2.5 mm. long, turgid; moist ground in woods 



C. haydenii Dewey 



4. Perigynia 1.5-1.7 mm. long, flattened; moist ground in woods 



C. emoryi Dewey 



