238 CYPERACEAE. 



8. Cyperus compressus L,. Flat Cyperus. (Fig. 550.) 



Cyperus compressus L. Sp. PI. 46. 1753. 



Annual, tufted, culms slender, erect or reclining, 

 smooth, s'-io' long. Leaves light green, about i" 

 wide, those of the involucre 2-3, the longer exceeding 

 the spikelets; umbel capitate or with 2-3 short rays; 

 spikelets narrowly lanceolate, acute, 4 // -io // long, 

 \Yz ff -2 ff wide, very flat, many-flowered ; scales 

 light green with a yellow band on each side, ovate, 

 acuminate, firm, keeled, several-nerved, falling away 

 from the narrowly-winged rachis at maturity; stamens 

 3; style 3-cleft; achene sharply 3-angled, obovoid, ob- 

 tuse, dull, brown, about one-third as long as the 

 scale. 



In fields, Maryland to Florida, west to Missouri and 

 Texas. Also in tropical America and in the warmer 

 parts of j\sia and Africa. Aug.-Oct. 



(Fig. 551.) 



9. Cyperus "Schweinitzii Torr. Schweinitz's Cj'perus. 



Cyf>erus Schweinitzii Torr. Ann. Lye. N. Y. 3: 276. 

 1836. 



Perennial by the thickened corm-like bases of the 

 culms, tufted, culms rather slender, rough, at least 

 above, i-2^ tall, about equalled by the light 

 green leaves. Leaves i"-2j" wide, rough-mar- 

 gined, those of the involucre 3-7, erect, the longer 

 exceeding the inflorescence; umbel simple, 3-9- 

 rayed, the rays erect, sometimes 4' long; spikelets 

 flat, in rather loose ovoid spikes, which are sessile 

 and at the ends of the rays, linear-oblong, 6-12- 

 flowered, 4 // -8 // long; scales convex, light green, 

 ovate, acute or acuminate, 9-13-nerved, falling 

 away from the rachis at maturity; stamens 3; style 

 3-cleft; achene sharply 3-angled, oblong, brown, 

 acute at each end, nearly as long as the scale, its 

 superficial cells quadrate. 



In sandy soil, especially along lakes and streams, 

 western New York and southern Ontario to the North- 

 west Territory, Minnesota and Kansas. Aug. -Oct. 



10. Cyperus pseudovegetus Steud. Marsh Cyperus. (Fig. 552.) 



Cyj>erus pseudovegetus Steud. Syn. PI. Cyp. 24. 1855. 

 Cyperus calcaratiis Nees; S. Wats, in A. Gray, Man. Ed. 

 6, 570. 1890. 



Perennial by thickened tuber-like joints of the 

 rootstocks, culm rather stout, i-4 high, often 

 equalled by the leaves. Leaves i% ff -2" wide, 

 smooth, nodulose, the midvein prominent; leaves of 

 the involucre 4-6, spreading, the longer much ex- 

 ceeding the inflorescence; umbel several-rayed, com- 

 pound, the primary rays often 4' long; spikelets 

 ovate, flat, many-flowered, light green, densely capi- 

 tate, 2 / '~3 // long; scales keeled, conduplicate, i- 

 nerved, curved, acute, longer than the linear 

 3-angled slightly stalked achene ; stamen i ; style 

 3-cleft. 



In marshes, Delaware to Florida, west to Kansas and 

 Texas. July-Sept. 



