240 CYPERACEAE. 
14. Cyperus dentatus Torr. Toothed Cyperus. (Fig. 556.) 
Cyperus dentalus Torr. Fl. U. S. 1: 61. 1824. 
Perennial by scaly rootstocks which sometimes 
bear small tubers, culms rather stiff, 8/-20/ tall, 
longer than or equalled by the leaves. Leaves 
keeled, 1/’-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/-3/ long; spikelets linear, very flat, 
many-flowered, mostly blunt, 5’’-10’’ 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 rotindus L. Nut-grass. (Fig. 557.) 
Cyperus rotundus Y,. Sp. Pl. 45. 1753. : 
Cyperus Hydra Michx. Fl. Bor. Am. 1:27. 1803. 
Perennial by scaly tuber-bearing rootstocks, 
culm rather stout, 6/—-20’ high, usually longer than 
the leaves. Leaves 1 14/3’ wide, those of the invo- 
lucre 3-5, the longer equalling or excecding the in- 
florescence; umbel compound or nearly simple, 3- 
8-rayed, the longer rays 2’-4%4’ long; spikelets 
linear, closely clustered, few in each cluster, acute, 
4’’-10’ long, 1/’-114’’ 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. Hall's 
Cyperus. (Fig. 558.) 
aa Hallit Britton, Bull. Torr. Club, 13: 211. 
I ‘e 
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 1’ long; spikelets numerous, loosely 
clustered, linear, 7—-15-flowered, 5’’-8’’ long, 1//- 
14’ 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. 
