CYPERACEAE 43 



B. Style-branches or stigmas 3 : achene trigonous. 

 Scales falling away from the persistent rachis of the flattened spikelets. 

 Wings of the rachis, if any, permanently attached to it. 

 Scales tipped with recurved awns : low annual. 5. C. inflexus. 

 Scales obtuse, acute or acuminate, not awn-tipped. 

 Wings of the rachis none, or very narrow. 

 Scapes smooth : plants annual. 6. C. compressus. 



Scapes rough : plants perennial. 7. C. Schweinitzii. 



Wings of the rachis distinct. 

 Scales mucronate. 8. C. dentatus. 



Scales not mucronate. 

 Scales wholly or partially purple-brown : achene linear-oblong. 



9. C. rotundus. 

 Scales straw-colored : achene obovoid. 10. C. esculentus. 



Wings of the rachis separating from it as interior scales : annual. 



11. C. erythrorhizos, 

 •Scales and rachis of the spikelets deciduous. 



Achene narrowly linear-oblong, 25^-4 times as long as thick. 

 Spikelets distinctly flattened, several-many-flowered. 



12. C. strigosus. 

 Spikelets nearly terete to a little flattened, i-few-flowered. 



Spikelets loosely spicate. 13. C. refracltis. 



Spikelets capitate or capitate-spicate. 

 Spikelets all reflexed : scapes almost always rough. 



14. C. relrofractus. 

 Spikelets spreading or only the lower ones reflexed : scapes smooth. 

 Spikes globose. 15. C. ovularis. 



Spikes cylindric to oval or obovoid. 16. C. Lancastriensis. 



Achene oblong to obovoid, not more than twice as long as thick. 

 Rachis wingless or narrowly winged. 17. C.filicnhnis. 



Rachis-wings broad, membranous. 18. C. echinatus. 



1. Cyperus flavescens L. Yellow Cyperus. (Man. p. 161 ; I. V.f. 

 343.) In marshy grounds, Me. to Mich., Fla. and Mex. — Pennsylvania: 

 Northampton, Eastou ; Delaware, Wawa ; Philadelphia, on the 

 Delaware River ; Franklin ; Huntingdon ; Lancaster. 



2. Cyperus diandrus Torr. Low Cypfrus. (Man. p. i6x ; I. F. /". 

 544.) In marshy places, N. B. to Minn, S. C. and Kans. — Pennsylvattia : 

 Montgomery ; Chester ; Huntingdon ; Lancaster ; York ; Erie. 



3. Cyperus rivularls Kunth. Shining Cyperus. (Man. p. 161; I. 

 F. /. S-^S-) I1 wet soil. Me. to Mich., N. C. and Mo. — Pennsylvania: 

 Northampton, Island Park ; Delaware. 



4. Cyperus Nuttallii Eddy. Nuttall's Cyperus. (Man. p. 161 ; 

 I. F.y. 5t?<5. ) In salt or brackish marshes, Me. to Fla. and Miss. — Penn- 

 sylvania : Philadelphia, on and about ballast. 



5. Cyperus inflezus Muhl. Awned Cyperus. (Man. p. 162; I. F. 

 f. 54g.) In wet sandy soil, Vt. to N. W. Terr., Fla. and Mex. — Penn- 

 sylvania : Northampton ; Chester ; Lancaster ; Dauphin. 



6. Cyperus compressus L. Flat Cyperus. (Man. p. 162; I. F. 

 /. 550. ) In fields, Md. to Fla. Also in trop. Am. and the Old World, 



