CYPERACEAE 179 



11. Scirpus Califdrnicus (C. A. Meyer) Britton. Perennial, similar to the next 



E receding species. Leaves reduced to basal sheaths : involucral bracts short, stoutly subu- 

 ite : umbel compound : spikelets 6-10 mm. long, acute, peduncled or some of them sessile : 

 scales brown, ovate, awn-pointed : perianth-bristles shorter than or equalling the achene, 

 short-plumose below : stigmas 2 : achene obovoid, 2 mm. long, plano-convex, nearly white, 

 narrowed above into a short tip, contracted at the base. 



In swamps, Florida to Louisiana, northern Mexico and California, and widely distributed in 

 tropical America. Summer. 



12. Scirpus campe'stris Britton. Perennial. Stems smooth, sharply triangular, 3-5 

 dm. tall. Leaves usually pale green ; blades smooth, 2-4 mm. wide : bracts of the involucre 

 2 or 3, the longer much exceeding the inflorescence : spikelets 3-10, in a dense terminal 

 simple head, oblong-cylindric, 1.5-2.5 cm. long, 5-8 mm. thick: scales ovate, pale brown, 2- 

 toothed at the apex, the midvein excurrent into an ascending or spreading awn : perianth- 

 bristles 1-3, much shorter than the achene, or none : stigmas 2 : achenes lenticular, obovoid 

 or oblong-ovoid, 3-3.5 mm. long, mucronulate, yellow-brown, their surface strongly cellu- 

 lar-reticulated. 



On wet prairies and plains, Manitoba and Minnesota to the Indian Territory, Nevada and Mexico. 

 Spring and summer. 



13. Scirpus robustus Pursh. Perennial by rootstocks. Stem stout, stiff, 3-angled, 

 with flat sides, smooth, 5-14 dm. tall : leaves dark green ; blades smooth, 5-10 mm. wide : 

 involucral bracts 2-4, elongated, similar to the leaf -blades : spikelets ovoid-oblong, stout, 

 1.5-2.5 cm. long, 8-10 mm. in diameter, 6-20 together in a dense terminal cluster : scales 

 ovate, brown, puberulent, thin, the midvein excurrent into an, at length, reflexed awn 3-5 

 mm. long : perianth-bristles 1-6, fragile, shorter than the achene, or none : stigmas 3 : 

 achenes 3-3.5 mm. long, compressed, flat on the face, convex or with a low ridge on the 

 back, obo void-orbicular, dark brown. 



In salt marshes, Nova Scotia to Florida and Texas. Summer^and fall. 



14. Scirpus sylvaticus L. Perennial by long rootstocks. Stems triangular, stout, 

 smooth, 1-2 m. tall, often overtopped by the upper leaves : leaf-blades 1-1.6 cm. wide, 

 rough on the margins : bracts of the involucre 5-8, the larger often 3 dm. long or more : 

 umbel terminal, very large, sometimes 2 dm. broad, about 3 times compound, the spikelets 

 ovoid or ovoid-oblong, 3-5 mm. long, in capitate clusters at the ends of the raylets : bract- 

 lets of the involucels small, linear or lanceolate : scales ovate-oblong, obtuse, brown with 

 a green center : perianth-bristles 6, downwardly barbed, slightly exceeding the achene : 

 stigmas 3 : achenes oblong, fully 1 mm. long, 3-angled, obtuse, nearly white, mucronulate. 



In swamps, New Hampshire to North Carolina and Georgia. Also in Europe. Summer and fall. 



15. Scirpus atrdvirens Muhl. Perennial by rootstocks. Stems triangular, rather 

 slender, leafy, 5-12 dm. high : leaf-blades elongated, nodulose, dark green, 6-12 mm. 

 wide, one or two of them usually exceeding the inflorescence : spikelets ovoid-oblong, acute, 

 densely capitate at the ends of the rays or raylets : involucels short : scales greenish brown, 

 oblong, acute, the midvein excurrent : perianth-bristles usually 6, downwardly barbed above, 

 naked below, about as long as the achene : stigmas 3 : achenes oblong-obovoid, 1 mm. 

 long, 3-angled, pale brown, dull. 



In swamps, Nova Scotia to Manitoba, Georgia and Louisiana. Summer. 



16. Scirpus polyphyllus Vahl. Perennial by rootstocks. Stems slender, sharply tri- 

 angular, 3-11 dm. tall, very leafy : leaves 3-ranked ; blades 4-6 mm. wide, rough-margined : 

 bracts of the involucre 3-6, the longer commonly somewhat exceeding the inflorescence : 

 spikelets ovoid, about 3 mm. long, capitate at the ends of the raylets : scales ovate, bright 

 brown, mostly obtuse, mucronulate : perianth-bristles 6, downwardly barbed above the 

 middle, twice as long as the achene : stigmas 3 : achenes obovoid, fully 1 mm. long, 3- 

 angled, with a broad face and narrower sides, short-pointed, dull. 



In swamps, wet woods and meadows, Massachusetts to Minnesota, Georgia, Alabama and Arkansas. 

 Summer and fall. . 



17. Scirpus Georgianus Harper. Perennial by rootstocks. Stems terete or nearly 

 so, 4-12 dm. tall : leaf-blades smooth, about 2 dm. long, and 1 cm. wide, or the upper ones 

 smaller : bracts of the involucre mostly 3, the largest surpassing the inflorescence : umbel 

 thrice compound : spikelets green, about 3 mm. long, 10-15-flowered, 5-10 in heads : scales 

 orbicular-ovate, about 1.5 mm. long, the toothed awns spreading at the tips, the midrib 

 green, with a whitish keel : perianth-bristles wanting : achenes broadly oblong, about 0.8 

 mm. long, short-beaked. 



In alluvial soil, middle Georgia. Spring and summer. 



18. Scirpus divaricatus Ell. Stems obtusely triangular, rather slender, 6-11 dm. 

 tall : leaf-blades 4-8 mm. wide, rough-margined : umbel decompound, the primary rays 



