78 American Midland Naturalist Monograph No. 2 



2. Perigynia 2-4 mm. long. 



3. Beak of the perigynium entire or emarginate, not more than 0.5 mm. 

 long; perigynium oval, plano-convex; spikes 2 or 3, each 2-5-flowered; 



tamarack swamp, Lake Villa, Lake Co., Gleason & Shobe 



C. trisperma Dewey 



3. Beak of the perigynium bidentate, serrulate, 0.5-1 mm. long. 



4. Perigynia deltoid; spikes 4-6; anthers 1-2 mm. long; swampy mead- 

 ows C. sterilis Willd. 



4. Perigynia ellipsoid; spikes 2-3, widely spreading at maturity; anthers 



0.7-0.9 mm. long; damp soil. [C scirpotdes Schk., ex p.} 



C. interior Bailey 



1. Perigynia thin- or wing-margined. 

 5. Perigynia 1-2 mm. wide. 

 6. Leaves 4-8 mm. wide. 

 7. Perigynia 4-5 mm. long. 



8. Tips of the perigynia appressed; inflorescence compact, stiff; mead- 

 ows and ditches, comm.on. [C. tribtiloides var. sangamonensis 

 Clokey] C. trthuloides Wahl. 



8. Tips of the perigynia spreading; inflorescence fiexuous, nodding; 



moist ground. [C. tribuloides var. reducta Bailey] 



C. projecta Mack. 



7. Perigynia 3-4 mm. long. 



9. Margins of the perigynium abruptly contracted near the ba.se of 



the beak; meadows and thickets, chiefly in the n. half of the 



state. [C. cristata Schw., non Clairv.] C. cristatella Britt. 



9. Margins uniform, not at all contracted. 



10. Inflorescence moniliform; body of the perigynium suborbicular; 



woods and roadsides C. jestucacca Schk. 



10. Inflorescence an elongated (2.5-5 cm.) interrupted head; body 

 of the perigynium oval; woods, common. [C. mirabilis 



Dewey, non Host} C. normally Mack. 



6. Leaves 0.5-4 mm. wide. 

 11. Perigynia lanceolate. 



12. Perigynia 7-10 mm. long, bidentate at apex, longer than the 

 glumes, appressed, straw-colored, flattened, the translucent 



margins finely serrulate; wet ground in woods 



C. mushngumensis Schw. 



12. Perigynia 4.5-6 mm. long. 



13. Plants strongly stoloniferous, the stems arising from an 

 elongated rhizome; sandy soil, rare; Kankakee, Hill; Peoria 



Brcndel C siccata Dewey 



13. Plants not stoloniferous, the stems tufted; marshes and wet 



meadows, common C. scoparia Schk. 



1 1 . Perigynia oval or lance-ovate to obovate. 



14. Perigynia lance-ovate, widest near the middle or base. 



15. Perigynia 3-3.5 mm. long; spikes closely aggregated, not 



clavate at base; marshes and ditches, n. Ill 



C bebbii Olney 



