238 
CYPERACEAE, 
8. Cyperus compréssus lL. Flat Cyperus. (Fig. 550.) 
Cyperus compressus I,. Sp. Pl. 46. 1753. 
Annual, tufted, culms slender, erect or reclining, 
smooth, 3/-10’ long. Leaves light green, about 1/7 
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’’-10’’ long, 
114’/-2’/ 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 Asia and Africa. Aug.—Oct. 
g. Cyperus Schweinitzii Torr. Schweinitz’s Cyperus. (Fig. 551.) 
Cyperus Schwetnitzit Torr. Ann. Lyc. N. Y. 3: 276. 
1836. 
Perennial by the thickened corm-like bases of the 
culms, tufted, culms rather slender, rough, at least 
above, 1°-2'%° tall, about equalled by the light 
green leaves. Leaves 1//-2'%4’’ 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 pseudovégetus Steud. Marsh Cyperus. (Fig. 552.) 
SX 
Cyperus pseudovegetus Steud. Syn. Pl. Cyp. 24. 1855. 
Cyperus calcaratus Nees; S, Wats. in A, Gray, Man. Ed. 
6, 570. 1890. 
Perennial by thickened tuber-like joints of the 
rootstocks, culm rather stout, 1°-4° high, often 
equalled by the leaves. Leaves 134/’-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, 1- 
nerved, curved, acute, longer than the linear 
3-angled slightly stalked achene; stamen 1; style 
3-cleft. 
In marshes, Delaware to Florida, west to Kansas and 
Texas. July-Sept. 
