145. Cyperacrae 313 



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



25. Perigynium 2-2.5 mm long, glossy, not concealed 

 by the glume; wet meadows; Fulton, Peoria, and 



Stark counties (',. diandra Schrank 



25. Perigynium 2.5-3.5 mm long, dull, nearly con- 

 cealed by the glume; wet meadows, n. Ill 



C. prairea Dewey 



GROUP II 



Spikes of one kind, gynecandrous (or variable in C. sterilis and C. 

 interior), 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 without winged margins. 



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

 long; wet ground in Boone, Cook, De Kalb, and La Salle 



counties C. bromoides Schk. 



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- to 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 ovate-deltoid; glumes acute; spikes 4-6; anthers 



1-2 mm long; swampy meadows C. sterilis Willd. 



4. Perigynia flattened, ellipsoid; glumes obtuse; spikes 2-3; 

 anthers 0.7-0.9 mm long; damp soil. [C. scirpoides 



Schk., ex p.] C. interior Bailey 



1. Perigynia thin- or wing-margined. 



5. Plants strongly stoloniferous, the stems arising from an elon- 

 gated rhizome; spikes 6-12, the lowest pistillate, the middle 

 staminate, the terminal gynecandrous; sandy soil, rare; Kan- 

 kakee Co., Hill; Peoria Co., Brendel C. siccata Dewey 



5. Plants not stoloniferous, the stems tufted; spikes usually all 

 gynecandrous. 

 6. Perigynia 1-2 mm wide. 



7. Perigynia elongate-lanceolate, 2/2-6 times longer than 

 wide. 

 8. Spikes 15-25 mm long, tapering at each end; perigynia 



7-10 mm long; wet ground in woods, local 



C. muskingumensis Schw. 



8. Spikes 4-15 mm long; perigynia 3-6 mm long. 



9. Leaves 1-3 mm wide; s])ikes glossy, acute; leaf-sheaths 

 white-hyaline ventrally; marshes and wet meadows, 



common C. scoparia Schk. 



9. Leaves 3-7 mm wide; spikes obtuse; leaf-sheaths 

 green-striate nearly to auricle. 



