192 



CYPERACEAE (SEDGE FAMILY) 



290. S. validus. 



17. S. vilidus Vahl. (GREAT B.) Rootstock stout, scaly, horizontal ; 

 culm 0.5-2.5 m. high, 0.8-2.5 cm. thick at base, soft, light green; basal 



sheaths soft, with soon lacerate hyaline margin; decom- 

 pound panicle lax, the rays 1-6 cm. long, slender and 

 flexuous ; bractlets brownish, pubescent at tip, fimbriate- 

 ciliate, with strongly excurrent midrib ; spikelets solitary or 

 in glomerules of 2-5, rufescent, otoid, acutish, 5-10 mm. 

 long ; scales suborbicular, a little pubes- 

 cent on the back, ciliate, mucronate ; style 

 2-cleft ; achene fuscous or dull black 

 when ripe, broad-obovoid, plano-convex, 

 mucronate, 1.3-1 . 5 mm. broad. (S. lacus- 

 tris, mostly of Am. auth., not L.) Mar- 

 gins of ponds and quiet streams. July, 

 Aug. FIG. 290. 



18. S. occidentalis (Wats.) Chase. Similar; the culms 

 harder, olive-green; basal sheaths firmer, the margins becom- 

 ing fibrillose ; panicle compound, the rays 0.5-5 cm. long, 

 stiff; bractlets red-spotted, viscid at tip, lacerate-fimbriate, 

 abruptly mucronate ; spikelets mostly in glomerules of 27, 

 rarely solitary, drab to reddish-brown, subcylindric, 1-2 cm. 

 long ; scales oblong-ovate, aristate, red-dotted, viscid above ; 



achene biconvex, 1.7-1.9 mm. broad. Lake-borders, Nfd. to B. C., s. to Mass., 

 N. Y., Great Lakes, Mo., etc. Aug., Sept. FIG. 291. 



19. S. heterochafctus Chase. Similar ; the culms slender, rarely 1 cm. thick 

 at base, pale green ; panicle compound, the suberect very slender rays 1-9 cm. 



long ; bractlets pale, aristate-acuminate, glabrous; spike- 

 lets solitary, ellipsoid, 8-14 mm. long, pale brown ; scales 

 ovate-oblong, exceeding the achenes, emarginate, short- 

 aristate, slightly red-dotted, glabrous, with erose-fimbriate 

 margins; style 3-cleft; bristles 

 fragile, 24 ; achene greenish 

 or yelloioish, 2.5-3 mm. long, 

 1.7-2 mm. broad. Marshes 

 and sheltered shores, e. Mass, 

 and Vt. to 111., Neb., and Ore. 

 July, Aug. FIG. 292. 



20. S. fluviatilis (Torr.) 

 Gray. (RIVER B.) Culm very 

 stout, 1-1.5 m. high ; leaves 



flat, broadly linear (0.7-2 cm. wide), tapering gradu- 

 ally to a point, the upper and those of the very long 

 involucre very much exceeding the compound umbel ; 

 rays 5-12, elongated, recurved-spreading, each bearing 

 1-5 ovoid to cylindrical acute pale-brown spikelets 

 (1.5-4 cm. long) ; scales slightly lacerate, the awns 

 much exceeding the cleft tip ; 

 achene obovoid, sharply and 

 exactly triangular, conspicu- 

 ously pointed, opaque, about 

 equaling the 6 rigid bristles. 



Borders of lakes and large streams, e. Mass, and 

 Vt. to D. C., w. to Minn., Kan., etc. July-Sept. 

 FIG. 293. 



21. S. robustus Pursh. Leaves flat, green, 4-10 mm. 

 broad, as long as or longer than the stout culm (0.7- 

 1.2 ra. high), those of the involucre 3 or 4. very unequal, 

 the longest 2.5-4 dm. long; spikelets 1-15, rufescent, 

 ovoid to cylindric, 1.5-3 cm. long, 6-12 mm. thick, 

 2W. s. robustns. some sessile, the others borne on short (2-6 cm. long) 



292. S. heterochaetus. 



298. S. fluvUtilis. 



