192 



CYPERACEAE (SEDGE FAMILY) 



17. S. vAlidus Vahl. (Great B.) Rootstock stout, scaly, horizontal; 

 mlm 0.5-2.5 m. high, 0.8-2.5 cm. thick at base, soft, light green; bf^^al 



sheaths soft, loith soon lacerate hyaline margin; decom- 

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

 Jlexuous; bractlets brownish, pubescent at tip, Jimbriate- 

 ciliate, tcith strongly excurrent 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 wim. broad. (S. lacus- 

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

 gins of ponds and quiet streams. July, 



290. S. validus. ^^^^ p^^^ 290. 



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

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

 ing tibrillose; 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. s. occidentalis. 

 /ong ; scales oblong-ovate, aristate, red-dotted, viscid above ; 



achene biconvex, 1.7-1.9 mm. 6road. — Lake-borders, Nfd. to B. C, s. to Mass., 

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



19. S. heterochaetus 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 S-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 

 292. S. heterochaetus. ^^^^^^ ^_-^ 5 ^^ j^j^j^ . jg^^^gg 



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 m. 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, 

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



293. S. fluviatilis. 



