158 



CYPERACEAE 



Spikelet manifestly thicker than the culm. 



Style mostly 2-cleft; achene lenticular or biconvex. 



Upper sheath scarious, hyaline; plants perennial by 

 slender rootstocks. 

 Scales pale green or nearly white. 

 Scales dark reddish-brown. 

 Upper sheath truncate, oblique or toothed, not scarious. 

 Annuals with fibrous roots. 

 Spikelet ovoid or oblong. 



Tubercle narrower than the top of the 



achene. 

 Tubercle about as broad as the top of the 

 achene. 

 Spikelet oblong-cylindric; tubercle broad, low. 

 Perennial by horizontal rootstocks. 

 Style 3-cleft; achene 3-angled or turgid. 

 Achene reticulated or cancellatc. 



Spikelet compressed; culm filiform. 

 Spikelet terete; culm slender. 



Tubercle conic, smaller than the achene. 

 Tubercle cap-like, as large as or larger than the 

 achene. 

 Achene smooth or papillose. 



Achene smooth, white; culms capillary. 

 Achene papillose or smooth, brown, black or yellow. 

 Tubercle depressed short-conic. 

 Achene smooth. 

 Achene papillose. 



Achene 3-ribbcd on the angles. 

 Achene obtuse-angled, not ribbed. 

 Tubercle subulate or narrowly pyramidal. 

 Culms filiform, wiry, densely tufted. 

 Culms flattened, slender, elongated. 



flaccida. 

 olivacea. 



6. E. ovata. 



7- 



obtusa. 



Engelmanni. 



palustris. 



10. E. acicularis. 



11. E. simplex 



12. E. tuberculosa. 



13. E. Torreyana. 



14. E. ftielanocarpa. 



15- 

 16. 



E. tricostata. 

 E. tenuis. 



18 



Mass 



E. intermedia. 

 E. roslellala. 



to Wise, 



1. E. interstincta (Vahl) R. & S. In water: 



Fla., the W. Ind. and Mex. 



Known in our range only from Repaupo, Gloucester Co., N. J. 



2. E. mutata (L.) R. & S. (E. quadrangulata R. & S.). In ponds, 



streams and swamps: Mass. to N. J., Ont., Mich., Ala., Mo., 



Tex. and Guatemala. Also in the W. I. and S. Am. 



Conn. Guildford. 



N. Y. North Pond, Westchester Co. 



N. J. Rare in Sussex and Cape May counties, unknown elsewhere. 



Pa. Philadelphia Co. 



A rare and scattered species. 



3. E. Robbinsii Oakes. In shallow water: N. S. to Mich., south 



to Fla. 



