C YPERA CEAE. 163 



13. Cyperus Haspan L. Sheathed Cyperus. (I. F. f. 555.) Perennial 

 by short rex stocks (sometimes annual?), roots fibrous; culms weak, tufted. 0.3-r 

 m. high. Lower leaves reduced to membranous acuminate sheaths; leaves of the 

 involucre about 2. usually less than 2 mm. wide; umbel simple or compound, the 

 longer rays 2-5 cm. long; spikelets few, capitate, linear, acute, many-flowered, 6- 

 12 mm. long, about I mm. wide; scales oblong or oblong-lanceolate, reddish-brown, 

 acute, mucronulate, keeled, 3-nerved; rachis winged; stamens 3; style 3-cleft; 

 achene 3-angled. broadly obovoid, obtuse, nearly white, much shorter than the 

 scale. In swamps. Va. to Fla. and Tex., mostly near the coast. Also in tropical 

 America and in the warmer parts of Europe, Asia, and Australia. July-Sept. 



14. Cyperus dentatus T<»rr. Toothed Cyperus. (I. F. 556.) Perennial 

 by scaly rootstocks which sometimes bear small tubers; culms rather stiff, 0.2-0.5 

 m. tall. Leaves keeled, 2-4 mm. wide, those of the involucre umbel, somewhat 

 compound; longer rays 2.5-7.5 cm. long; spikelets linear, very flat, many-flow- 

 ered, mostly blunt, 10-20 mm. long, nearly 4 mm. wide; scales light reddish- 

 brown, ovate-lanceolate, thin, keeled, 5-7-nerved, mucronate, separating 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, mucro- 

 nate. light brown, much shorter than the scale. In sandy swamps and on river 

 shores. Mr. to X. X. V.. south to W. Va. and S. Car. Scales often modified into 

 tufts of small leaves. Aug. -Oct. 



15. Cyperus rotundus L. Xut-grass. (I. F. f. 557.) Perennial by scaly 

 tuber-bearing rootstocks; culm rather stout, o. 1-0.5 m. high, usually longer than 

 the leaves. Leaves 3-6 mm. wide, those of the involucre 3-5 ; umbel 3-8-rayed, 

 the longer rays 5-1 1 cm. long; spikelets linear, clustered, few in each cluster, 

 acute. 8-20 mm. long, 2-3 mm. wide; scales dark purple-brown or with green 

 margins and centre, ovate, acute, appressed when mature, about 3-nerved on the 

 keel; stamens 3; style 3-cleft, its branches ex=erted; achene 3-angled, about one- 

 half as long as the scale. In fields, Va. to Fla., west to Kans. and Tex. Also in 

 tropical Am., and widely distributed in the Old World. July-Sept. 



16. Cyperus Hallii Britton. Hall's Cyperus. (I. F. f. 558.) Perennial 

 by scaly rootstocks; culm rather stout, 0.6-0.9 m. tall, about equalled by the 

 leaves. Basal leaves about 4-6 mm. wide; involucral leaves 3-6, the longer much 

 exceeding the inflorescence; umbel compound, its longer rays 7-10 cm. long, the 

 raylets sometimes 2.5 cm. long; spikelets numerous, loosely clustered, linear, 7—15- 

 flowered. 10-16 mm. long, 2-3 mm. 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. Kans. and the Ind. Terr, to 

 Tex. July -Sept. 



17. Cyperus esculentus L. Yellow Nut-grass. (I. F. f. 559.) Perennial 

 by scaly tuber-bearing rootstocks; culm usually stout, 0.3-0.8 m. tall, commonly 

 shorter than the leaves. Leaves light green, 4-8 mm. wide, the midvein promi- 

 nent; those of the involucre 3-6, the longer much exceeding the inflorescence; 

 umbel 4-10-rayed, often compound; spikelets numerous in loose spikes, straw-color 

 or yellowish-brown, flat, spreading, 1-2. 5 cm. long, about 3 mm. wide, many- 

 flowered; scales ovate-oblong, subacute, 3-5 -nerved; rachis narrowly winged; 

 stamens 3; style 3-cleft; achene obovoid, obtuse, 3-angled. In moist fields, N. B. 

 to Minn, and Neb., south to Fla. and Tex. Also on the Pacific Coast from Cal. to 

 Alaska, in tropical America, and widely distributed in the Old World. Sometimes 

 a troublesome weed. Aug. -Oct. 



Cyperus esculentus angustispicktus Britton. Spikelets very slender, 2 mm. wide or 

 less. Mass. to S. Car. and Mo. 



18. Cyperus erythrorhizos Muhl. Red-rooted Cyperus. (I. F. f. 560.) 

 Annual; culms tufted, stout or slender, 7-50 cm. tall. Leaves 3-8 mm. wide, 

 rough-margined, those of the involucre 3-7. some of them 3-5 times as long as the 

 inflorescence; umbel mostly compound; spikelets linear, subacute, 6-25 mm. long, 

 less than 2 mm. wide, compressed, many-flowered, clustered in oblong, nearly or 

 quite sessile spikes; scales bright che>tnut brown, oblong-lanceolate, mucronulate, 

 appressed, separating from the rachis at maturity, the membranous wings of the 



