172 CYPERACEAE 



nerved, thin : stigmas 3, much exserted : achenes nai-rowly linear, about 3 mm. long, ob- 

 tuse, apiculate, about 5 times as long as thick, and i as long as the scale. 



In dry fields or woods, New Jersey to North Carolina and Missouri. Summer and fall. 



53. CyperuB dissitiflorus Torr. Perennial, bright green. Leaves somewhat overtop- 

 ping the scape, smooth or nearly so : scapes sometimes sparingly tufted, very slender, 

 3-angled, smooth : bracts of the involucre mostly 4-6, the longer ones surpassing the 

 unil)el : umbel ,of 3-5 slender rays and one or more spikes sessile in the involucre : 

 spikelets linear-subulate, slender, 5-8 mm. long, spreading, 5-7-flowered, chestnut-colored, 

 acute, not crowded, flattened: scales ovate to oblong, 2.5-3 mm. long, acute, closely im- 

 bricated: achenes 3-angled, oblong-jjrismatic or slightly broadened upward, 1.5 mm. long, 

 abruptly pointed. 



In sand, Florida to Texas. Spring to fall. 



54. Cyperus retrofrictus (L. ) Torr. Perennial by tuber-like corms. Leal-blades 

 3-5 ram. wide : scapes usually rough-puberulent, at least above, mostly longer than the 

 puberulent leaves : bracts of the involucre 4-7, the longer not greatly exceeding the umbel, 

 sometimes shorter : umbel simple : rays 5-15 cm. long, their siieaths 2-toothed : heads 

 oblong or obovoid : spikelets linear-subulate, 6-12 mm. long, about 1 mm. thick, 1-2- 

 flowered, all soon strongly reflexed : flowering scales lanceolate, acute, the upper one 

 subulate, all strongly several-nerved: stigmas 3 : achenes linear, 1.5-2 mm. long, 3- 

 angled, obtuse, apiculate, j as long as the scale. 



In sandy soil, southern New Jersey to Florida, Kentucky, Arkansas and Texas. Summer and fall. 



55. Cyperus ovularis (Michx. ) Torr. Perennial by hard tuber-like corms. Leaves 

 smooth ; blades 4-6 mm. wide : scape usually strict, smooth, 2-8 dm. tall, longer than the 

 leaves : longer bracts of the involucre much exceeding the umbel : umbel simple, few-rayed; 

 sheath of the rays truncate or slightly tootlied : spikes globose, 8-14 mm. in diameter, very 

 dense, the spikelets radiating in all directions : spikelets 4-7 mm. long, usually 3-flowered : 

 scales ovate or ovate-lanceolate, obtuse or subacute, green, strongly several-nerved : stigmas 

 3: achenes linear-oblong, 3-angled, about 1.5 mm. long, 1-3 times as long as thick. 



In dry fields and on hills, southern New York to Florida, Illinois, Kansas and Texas. — C. ovularis 

 ^pha&ricus Boeckl., differs in its usually smaller heads, the spikelets more subulate, reddish brown. 

 Arkansas to Texas. Summer and fall. 



56. Cyperus retrorsus Chapm. Perennial, pale green. Leaves overtopped by the 

 scape ; blades 3-5 mm. wide, sometimes with rough margins and nerves beneath : scapes 

 erect, 4-7 dm. tall, smooth : bracts of the involucre 7-10, mostly surpassing the umbel : 

 umbel simple, of usually 8 slender rays : spikes narrowly obovoid, 1-1.5 cm. long : spike- 

 lets densely crowded, subulate, 3 mm. long, the lower ones becoming reflexed : scales ob- 

 long or nearly so, 2.5-3 mm. long, ribbed, closely appressed : achenes 3-angled, oblong- 

 prismatic, nearly 2 mm. long, light brown. [C retroversus Chapm.] 



On the sandy shore of Caximbas Bay, Florida. Spring to winter. 



57. Cyperus cyllndriciis (Ell.) Britton. Perennial by hard corms. Leaf-blades 

 2-3 mm. wide : scapes smooth, usually tufted, 1-5 dm. tall, longer than the leaves : longer 

 bracts of the involucre much exceeding the umbel : umbel simple, the rays short, or the 

 longer 2-7 cm. long, the sheaths 2-toothed : spikes very dense, cylindric, 5-15 mm. long, 

 4-8 mm. in diameter, simple ; spikelets 3-4 mm. long, flattish, 1-2-flowercd, spreading or 

 the lower reflexed : scales green, oblong : rachis winged : stigmas 3 : achenes linear-oblong 

 about 1.5 mm. long, 3-angled, granular, apiculate, slightly more than i as long as the scale' 



In sandy soil and on the sea shore, southern New York to Florida and Texas. Summer and fall. 



58. Cyperus Plankii Britton. Similar to C cylindricus in habit, but stouter. Leaf- 

 blades mostly 2.5-4 mm. wide, smooth : scapes solitary or sparingly tufted, 3-10 dm. tall, 

 smootli, often surpassing the leaves : bracts of the involucre broader tlian tlie leaf-blades, 

 sometimes 6-7 mm. broad, the longer ones surpassing the umbel : umbel simple, of 4-10 

 rays, the larger 5-15 cm. long, mostly ascending: spikes very dense, cylindric, 15-20 mm. 

 long, 10-15 mm. in diameter, green : spikelets 5-7 mm. long, 3-4 flowered : scales ribbed : 

 rachis winged : stigmas 3 : achenes linear-oblong, 1.5 mm. long, 3-angled, coarsely granu- 

 lar, apiculate. 



On plains and prairies, Oklalioma, the Indian Territory and Texas. Spring to fall. 



59. Cyperus cylindrostachys Boeckl. Perennial, pale green. Leaves overtopped 

 by the scape ; blades 4-8 mm. wide, smooth : scapes often sparingly tufted, 3-15 dm. tall, 

 3-angled, smooth : bracts of the involucre 5-8, the longer ones much surpassing the umbel : 

 uml)el simple or compound, of 6-12 slender rays and one or more spikes sessile in the in- 

 volucre : spikes cylindric, 1.5-3.5 cm. long, mostly less than 1 cm. thick, usually com- 

 pound : spikelets subulate, 4-5 mm. long, grayish brown or tinged with yellow, numerous, 

 densely crowded, sjireading or recurved : scales oblong or nearly so, 2.5-3 mm. long, blunt, 



