559-) 



SEDGE FAMILY. 



17. Cyperus esculentus L. Yellow Nut-grass. 



Cyperus esculentus L. Sp. PI. 45. 1753. 

 Cyperus phymatodes Muhl. Gram. 23. 1817. 



Perennial by scaly horizontal tuber-bearing root- 

 stocks, culm usually stout, i-2^ tall, commonly 

 shorter than the leaves. Leaves light green, i"-^" 

 wide, the midvein prominent; those of the in- 

 volucre 3-6, the longer much exceeding the in- 

 florescence; umbel 4-iorayed, often compound; 

 spikelets numerous in loose spikes, straw-color or 

 yellowish-brown, flat, spreading, 6 // -i2 // long, 

 i '_, " wide, many-flowered; scales ovate-oblong, sub- 

 acute, 3-5- nerved; rachis narrowly winged; stamens 

 3; style 3-cleft; achene obovoid, obtuse, 3-angled. 



In moist fields, New Brunswick to Minnesota, south 

 rida and Texas. Also on the Pacific Coast from 

 California to Alaska, in tropical America, and widely 

 distributed in the Old World. Sometimes a trouble- 

 some weed. Aug. -Oct. 



Cyperus esculentus angustispicatus Britton, Bull. Torr. 



Club, 13:211. 1886. 

 Spikelets very slender, i" wide or less. Massachusetts to South Carolina and If tMoari. 



18. Cyperus erythrorhizos Muhl. Red-rooted Cyperus. (Fig. 560.) 



Cyperus erythrorhizos Muhl ('.ram. aa 1817. 



Annual, culms tufted, stout or slender, 3'-* tall. 

 Leaves i>"-4" wide, rough-margined, the lower 

 longer than or equalling the culm, those of the in- 

 volucre 3-7, some of them 3-5 times as long as the 

 inflorescence; umbel mostly compound, several - 

 rayed; spikelets linear, subacute, ;/' i<>" long, less 

 than i" wide, compressed, many-flowered, clus- 

 tered in oblong, nearly or quite sessile spike*; 

 scales bright chestnut brown, oblong-lanceolate. 

 mucronulatc, a ppressed, separating from the rachis 

 at maturity, the membranous wings of the rachis 

 separating as a pair of hyaline interior scales; sta- 

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

 long, pointed at both ends, pale, one-half as long 

 as the scale. 



In wet soil, especially along streams, southern On- 

 tario to Massachusetts and Florida, west to Missoari, 

 Kansas, Texas and California. 

 Cyperus erythrorhizos var. pumilus Engelm. is a low form, not worthy of varietal rank. 



19. Cyperus Halei Torr. Hale' s Cyperus. 



(Fig. 561.) 



Cyperus Halei Torr,; Britton, Bull. Torr. Club, 13: 

 213. 1886. 



Annual, culm stout, 2-3 tall, about equalled 

 by the leaves. Leaves 3 // ~4 // wide, very rough- 

 margined, those of the involucre 5-8, much elong- 

 ated; umbel compound, several -rayed; spikes cy- 

 lindric, sessile or very nearly so, exceedingly dense, 

 % f -\ f long; spikelets very numerous, linear, i% ff - 

 2J4" long, Yz" wide, spreading; scales brown, 

 keeled, indistinctly 5-nerved, oblong, mucronu- 

 late, separating from the rachis at maturity, the 

 wings of the rachis separating as a pair of hyaline 

 scales, as in the preceding species; stamens 3; 

 style 3-cleft; achene 3-angled, minute. 



In swamps, southern Missouri to Tennessee, Louisi- 

 ana and Florida. July-Sept. 



