145. ('VPERACEAE 303 



but extending northward to Peoria C^o. June-Sept. 



Round-headed Sedge [C. wolfii WoodJ 



- C. oi'iilaris (Michx.) Torr. 



10. Seales spreading; spikelets 5- to several-flowered; sand 

 prairies, rare; Mason and Whiteside counties. Aug.- 



Oct C. grayioides Mohlenbrock 



7. Spikes hemispherical, cylindrical, ellipsoidal, or lanceolate, 

 but not globose or spherical. 

 11. Spikelets arising from a central axis. 



12. Scales with a mucro 0.5-1.5 mm long; achenes 2.2-3.3 

 mm long; sandy soil chiefly in the northern part of 

 the state. Aug.-Oct. [C. houglitonii of auth., not 

 Torr.] C. schwcinitzii Torr. 



12. Scales acute or with a mucro to 0.5 mm long; achenes 



usually 1.2-2.1 mm long; some spikelets spreading 

 or slightly reflcxed : dry sandy soil ....C filiculmis Vahl 

 11. Spikelets produced pinnately along the axis. 



13. Scales 1.0-1.5 mm long; achene 0.8-1.0 mm long; 



along streams and ditches, and in fields. July-Sept. 



- - C. erythrorhizos Muhl. 



13. Scales 1.5-4.5 mm long; achene 1.0-2.8 mm long. 



14. Scales very remote, the tip of one just reaching 

 the base of the one above it, giving the spikelet 

 a zig-zag appearance; wet ground, local; Alex- 

 ander, Lake, McHenry, St. Clair, and Union 



counties. Aug.-Oct C. cngclmannn Steud. 



14. Scales approximate and overlapping. 



15. Some or all the mature spikelets reflexed; 

 spikelets subterete; moist ground, rare; Mas- 

 sac and Pulaski counties 



- C. lancastriensis Porter 



15. None of the spikelets (except sometimes the 

 lowest pair) reflexed; spikelets flattened. 

 16. Rhizomes scaly and usually ending in a 

 tuber; scales at the tips of the spikelets 

 rather blunt, giving the spikelets an ob- 

 tuse appearance; moist ground, common. 

 Aug.-Oct. Chufa or Nut Sedge 



-C. esculentus L. 



16. Rhizomes absent or merely becoming hard 



and corm-like. 



17. Plants annual; scales ferruginous or 



golden-brown ; achenes obovoid-ob- 



long, 1.0-1.7 mm long; wet ground, 



not uncommon. July-Oct. \C. spcci- 



osus sensu auth., non Vahl; C. ferax 



sensu Britt., non Rich.] 



C. jerrnginescens Boeck. 



