192 



CYPERACEAE (SEDGE FAMILY) 



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

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



sheaths soft, with soon lacerate hyaline margin ; decom- 

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

 flexuou* ; bractlets brownish, pubescent at ///>, funbriate- 

 ciliate, with strongly exntrrent midrib; spikelets solitary or 

 in glomerules of 2-5, rufescent, ovoid, 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, 

 290. S. validus. * ug> p ^ 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 2-7, 



rarely solitary, drab to reddish-brown, subcylindric, 1-2 cm. 291 g occidenta i is 

 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. 



10. 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 ; antics 



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



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



margins ; style 3-cleft ; bristles 



fragile, 2-4 ; achene greenish 



or yellowish, 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 

 ^ ^ m ^- . ^ 



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 I). C., w. to Minn., Kan., etc. July-Sept. 

 Fio. 29... 



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

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

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

 the longest 2.5-4 < Int. l<nj ; *)>ikc!>tx 1-15, ruf<*<-it, 

 ovoid to cylindric, 1.5-3 cm. l<uiu, (5-12 mm. thick, 

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



292. S. heterochaetus. 



298. S. fluviatilis. 



