3°4 



CYPERACEAE. 



Vol. I. 



19. Cyperus rotundus L. Nut-grass. Fig. 739. 



Cyperus rotundus L. Sp. PI. 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 1V-3" wide, those of the involucre 

 3-5, the longer equalling or exceeding the inflores- 

 cence ; umbel compound or nearly simple, 3-8-rayed, 

 the longer rays 2'-$' long; spikelets linear, closely 

 clustered, few in each cluster, acute, 4"-io" long, 

 i"-\\" wide; scales dark purple-brown or with green 

 margins and center, 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, Missouri, Kansas and 

 Texas. Adventive in southern New York and in ballast 

 deposits at eastern seaports. Tropical America, and the 

 Old World. A troublesome weed in the South. Coco- 

 grass, Round-root. July-Sept. 



20. Cyperus Hallii Britton. Hall's Cyperus. Fig. 740. 



C. Hallii Britton, Bull. Torr. Club 13: 211. 1886. 



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, s"-8" long, i"-ii" wide; involucels seta- 

 ceous; 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 Oklahoma to Texas. July-Sept. 



21. Cyperus esculentus L. Yellow Nut-grass. Fig. 741. 



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

 Cyperus phymatodes Muhl. Gram. 23. 1817. 

 Cyperus esculentus angustispicatus Britton, Bull. Torr. 

 Club 13: 211. 1886. 



Perennial by scaly horizontal tuber-bearing root- 

 stocks, culms usually stout, i°-2l° tall, commonly 

 shorter than the leaves. Leaves light green, 2"-4" 

 wide, the midvein prominent; those of the involucre 

 3-6, the longer much exceeding the inflorescence; umbel 

 4-10-rayed, often compound ; spikelets numerous in 

 loose spikes, straw-c'olor or yellowish-brown, flat, spread- 

 ing, 6"-i2" long, i"-ii" 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, New Brunswick to Minnesota, Nebraska, 

 Florida and Texas. Also on the Pacific Coast from Cali- 

 fornia to Alaska, in tropical America, and widely distrib- 

 uted in the Old World. Sometimes a troublesome weed. 

 The species consists of numerous races, differing in length 

 and width of spikelets. Edible galingale. Earth-almond. 

 Rush-nut. Aug.-Oct. 



