CYPERACEAE 169 
3-nerved : rachis winged: stigmas 3: achene 3-angled, broadly obovoid, 0.5-0.7 mm. 
long, obtase, nearly white, much shorter than the scale. 
In swamps and sandy bogs, Virginia to Florida and Texas, mostly near the coast. Also in tropical 
America and in the warmer parts of Europe, Asia and Australia. Summer and fall. 
33. Cyperus dentatus Torr. Perennial by scaly rootstocks which sometimes bear 
small tubers. Leaves keeled; blades 2-4 mm. wide: scapes rather stiff, 2-5 dm. tall: 
bracts of the involucre 3-4, 1 or 2 usually exceeding the inflorescence: umbel somewhat 
compound ; longer rays 2.5-7.5 cm. long : spikelets linear, very flat, many-flowered, mostly 
blunt, 10-20 mm. long, nearly 4 mm. wide: scaleslight 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 : stigmas 3, exserted : achene 3-angled, ob- 
ovoid, about 0.8 mm. long, obtuse, mucronate, light brown, much shorter than the scale. 
Scales of the spikelets often modified into tufts of small leaf-like bracts. 
In sandy swamps and on river shores, Maine to northern New York, South Carolina and West Vir- 
ginia. Summer and fall. 
34. Cyperus multiradiàtus (Torr.) Mohr. Perennial, yellowish green. Leaves 
overtopped by the scape ; blades firm, 2-5 mm. broad, smooth : scapes solitary, 2-4 dm. tall, 
smooth : bracts of the involucre 3-5, one or more of them surpassing the umbel, ascending : 
umbel of 5-10 rays, all of different lengths: spikelets linear or linear-lanceolate, 1-2.5 cm. 
long, 3-4 mm. wide, yellow, 30-70-flowered, numerous: scales ovate, fully 2 mm. long, 
merely acute, scarious margined, minutely hooded at the apex, closely imbricated, faintly 
"-nerved, pesistent: achenes 3-angled, broadly ovoid, 0.8 mm. long, lustrous, brown. 
[ C. dentatus B ? multiradiatus Torr. ©. LeContei Torr. ] 
In sand, Florida to Louisiana. Spring to fall. 
35. Cyperus rotundus L. Perennial by scaly tuber-bearing rootstocks. Leaf-blades 
3-6 mm. wide: scapes rather stout, 1-5 dm. high, usually longer than the leaves: bracts 
of the involuere 3-5: umbel 3-8-rayed, the longer rays 5-11 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 center, ovate, acute, appressed, about 3-nerved on the 
keel : stigmas 3, exserted : achene 3-angled, linear-oblong, about 1 mm. long, about 3 as long 
as the scale. 
In fields, Virginia to Florida, Kansas and Texas. Also in tropical America, and widely distrib- 
uted in the Old World. Summer and fall. 
36. Cyperus Hállii Britton. Perennial by scaly rootstocks. Leaves with blades 
about 4-6 mm. wide: scapes rather stout, 6-9 dm. tall, about equalled by the leaves: in- 
volucral bracts 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: stigmas 3, much exserted: achene linear-oblong, 1.5 mm. long, 3- 
angled, about 3 as long as the scale. 
On plains and prairies, Kansas and the Indian Territory to Texas. Summer and fall. 
37. Cyperus esculéntus L. Perennial by scaly tuber-bearing rootstocks. Leaves 
light green ; blades 4-8 mm. wide, the midvein prominent : scapes usually stout, 3-8 dm. 
tall, commonly shorter than the leaves: bracts of the involucre 3-6, the longer much ex- 
ceeding the inflorecence : umbel 4-10-rayed, often compound: spikelets numerous in loose 
spikes, straw-color or yellowish brown, flat, spreading, 1-2.5 em. long, about 3 mm. wide, 
many-flowered: scales ovate-oblong, rather acute, 3-5-nerved: rachis narrowly winged : 
stigmas 3: achene obovoid, fully 1 mm. long, obtuse, 3-angled. 
In moist fields, New Brunswick to Minnesota, Nebraska, Florida and Texas. Also on the Pacific 
coast from California to Alaska, in tropical America, and widely distributed in the Old World. Some- 
times a troublesome weed. Summer and fall.—A form with very slender spikelets about 2 mm. wide or 
narrower, is C. esculentus angustispicátus Britton ; it ranges from Massachusetts and Missouri to South 
Carolina, CHUFA. 
38. Cyperus articulàtus L. Perennial, pale green. Leaves reduced to a few 
scales at the base of the scape or sometimes with a few well developed blades: scapes erect, 
8-20 dm. tall, transversely septate, terete, smooth : bracts of the involucre mostly 3, ovate 
or linear-lanceolate, much shorter than the umbel, erect or nearly so: umbel of 4-10 
slender, curved rays, compound: spikelets slender, narrowly linear, 2-5 cm. long, or 
sometimes shorter, deep straw-colored, not crowded, 30-50-flowered : scales elliptic or 
ovate, fully 3 mm. long, acutish or rather blunt, faintly ribbed, closely imbricated : achenes 
3-angled, oblong or cuneate-oblong, fully 1 mm. long, somewhat lustrous, pinched at the 
apex. 
In sandy swamps, South Carolina to Florida and Texas. Throughout the tropies. Spring to fall. 
39. Cyperus erythrorhizos Muhl. Annual. Leaf-blades 3-8 mm. wide, rough- 
margined : scapes tufted, stout or slender, 7-50 em. tall: bracts of the involucre 3-7, some 
