240 



CYPERACEAE. 

 14. Cyperus dentatus Torr. Toothed Cyperus. (Fig. 556.) 



Cyperus dentatus Torr. Fl. U. S. i: 61. 1824. 



Perennial by scaly rootstocks which sometimes- 

 bear small tubers, culms rather stiff, S'-zo' tall, 

 longer than or equalled by the leaves. Leaves- 

 keeled, i // -2 // wide, those of the involucre 3-4, 

 one or two of them usually exceeding the inflores- 

 cence; umbel several-rayed, somewhat compound; 

 longer rays 1'-$' long; spikelets linear, very flat, 

 many-flowered, mostly blunt, 5 // -io // long, nearly 

 2" wide; scales light reddish-brown, ovate-lanceo- 

 late, thin, keeled, 5-7-nerved, mucronate, separa- 

 ting from the rachis when mature, their tips 

 spreading, causing the spikelet to appear toothed; 

 stamens 3; style 3-cleft, the branches exserted; 

 achene 3-angled, obtuse, mucronate, light brown, 

 much shorter than the scale. 



In sandy swamps and on river shores, Maine to 

 northern New York, south to West Virginia and South 

 Carolina. Scales often modified into tufts of small 

 leaves. Aug. -Oct. 



15. Cyperus rotundus L. Nut-grass. (Fig. 557-) 



Cyperus rotundus L. Sp. PI. 45. 1753. 

 Cyperus Hydra Michx. Fl. Bor. Am. i: 27. 



1803. 



Perennial by scaly tuber-bearing rootstocks, 

 culm rather stout, 6'-2o' High, usually longer than 

 the leaves. Leaves 1%'-$' wide, those of the invo- 

 lucre 3-5, the longer equalling or exceeding the in- 

 florescence; umbel compound or nearly simple, 3- 

 8-rayed, the longer rays 2 / -4^ / long; spikelets 

 linear, closely clustered, few in each cluster, acute, 

 4 // -io // long, \"-\yt ff wide; scales dark purple- 

 brown or with green margins and centre, ovate, 

 acute, closely appressed when mature, about 3- 

 nerved on the keel; stamens 3; style 3-cleft, its 

 branches exserted; achene 3-angled, about one-half 

 as long as the scale. 



In fields, Virginia to Florida, west to Kansas and 

 Texas. Adventive in or about ballast deposits at the 

 eastern seaports. Also in tropical America, and widely 

 distributed in the Old World. July-Sept. 



16. Cyperus Hallii Britton. 

 Cyperus. (Fig. 558.) 



Hall's 



Cyperus Hallii Britton, Bull. Torr. Club, 13: 211. 



1886. 



Perennial by scaly rootstocks, culm rather stout, 

 2-3 tall, about equalled by the leaves. Basal 

 leaves 2 // ~3 // wide; involucral leaves 3-6, the longer 

 very much exceeding the inflorescence; umbel 

 compound, its longer rays 3 / -4 / long, the raylets 

 sometimes i' long; spikelets numerous, loosely 

 clustered, linear, 7- 15 -flowered, 5 // -8 // long, \"- 

 ij^'wide; involucels setaceous; scales ovate, acute, 

 strongly 7-9-nerved, dark reddish-brown or with 

 lighter margins, their tips not appressed; stamens 

 3; style 3-cleft, its branches much exserted; achene 

 linear-oblong, 3-angled, about one-half as long as 

 the scale. 



Kansas and the Indian Territory to Texas. July- 

 Sept. 



