CYPERACEAE 169 



3-nerved : rachis winged: stigmas 3: achene 3-angled, broadly obovoid, 0.5-0.7 mm. 

 long, obtuse, nearly white, much sliorter than the scale. 



In swamps and sandy bogs, Virginia to Florida and Texas, mostly near the coast. Also in tropiical 

 America and in the warmer parts of Europe, Asia and Australia. Summer and fall. 



33. Cyperus dentatus Terr. 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-floAvered, mostly 

 blunt, 10-20 mm. long, nearly 4 mm. wide : scales light reddish brown, ovate-lanceolate, 

 thin, keeled, o-7-nerved, mucronate, separating from the rachis when raatui-e, 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 multiradiatus (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 tliem surpassing the umbel, ascending : 

 umbel of 5-10 rays, all of diflerent 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 

 ■7-nerved, pesistent : achenes 3-angled, broadly ovoid, 0.8 mm. long, lustrous, brown. 

 [C. dentatus fi f multiradiatus Torr. C. 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 involucre 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, appre.ssed, about 3-nerved on the 

 keel : stigmas 3, exserted : achene 3-angled, linear-oblong, about 1 mm. long, about ^ 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 Hallii Britton. Perennial l)y 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- 

 tingled, about i as long as the scale. 



On plains and prairies, Kansas and the Indian Territory to Texas. Summer and fall. 



37. Cyperus esculentus 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 cm. 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 trouVjlesome weed. Summer and fall. — A form with very slender spikelets about 2 mm. wide or 

 narrower, is C. escukntua angastispicdtus Britton ; it ranges from Massachusetts and Missouri to South 

 Carolina. Chufa. 



38. Cyperus articulatus 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 tropics. Spring to fall. 



39. Cyperus erythrorhizos Muhl. Annual. Leaf-blades 3-8 mm. wide, rough- 

 margined : scapes tufted, stout or slender, 7-50 cm. tall : bracts of the involucre 3-7, some 



