North American Cyperacea, 277 



HhizoTha tuberous- Culm 8 inches to 2 feet high, slender, sharply 

 triangular, the upper part rough on the angles. Leaves shorter than the 

 culm, about one line wide. Umbel erect, 4 — 6 rayed; the rays very 

 unequd; the longer ones nearly three inches in length. Ochrcce trun- 

 cate, entire. Involucre about twice the length of the leaves, scabrous on 

 margin. Spikelcts irregularly inserted on the summit of the rays in a 

 somewhat imbricate manner, forming a loose oblong head or cluster; the 

 florets distinct. Rachis laterally compressed. Scales concave, subco- 

 riaceous, somewhat membranaceous on the broad margin, nerved, yel- 

 lowish; with a short straight mucro a little below the apex. Interior 

 scales very narrow, hyaline, firmly united with the rachis. Stamens 3- 

 Style about as long as the nut; the segments slender, smooth. Nut ligh t 

 brown, slightly pointed, smooth, a little shorter than the scale. 



Hab. Dry sand on the shore of Lake Ontario, near Greece, 

 Monroe County, New York, Dr. Samuel B.Bradley ! ; on the 

 Arkansas river, Nuttall ! ; on the river St. Peter .^ Mr. Say! 

 (The locaUty not given in Mr. Schweinitz's Hst.) 



Obs. This very distinct species differs from all the other 

 North American Cyperi in the mode of aggregation of the 

 spikelets. They are inserted on all sides of the common 

 rachis, and stand nearly erect, instead of spreading horizontally, 

 or being in part reflexed, as in most other species. 



31. Cyperus Houghtonii. 



Culm somewhat obtusely triangular, smooth on the angles j 

 umbel simple ; the rays few, very short ; involucre 2 — 3-leaved ; 

 spikelets oblong-linear, few, approximated towards the summit 

 of the rays, 6 — 8-flowered; scales roundish-ovate, obtuse, 

 slightly mucronate ; rachis scarcely margined ; nut short, ovate, 

 obtuse. 



Rhizoma tuberous, short. Culm about a span high, the sides some- 

 what convex. Leaves shorter than the culm, narrow, smooth on the 

 margin. Umbel subsessile, or with rays scarcely half an inch long. 

 Ochrece truncate. Involucre about 3 times as long as the umbel. Spike- 

 lets half an inch in length, somewhat spreading, without setaceous bracts 

 at the base. Scales distinct, subcoriaceous, deeply concave, nerved, 



