2. 
74. 
Inflorescence with long branches; culms terete, 3 
to 20 mm. thick at the base. (Also, style 2-cleft; 
achenes plano-convex; scales reddish to deep brown). 
5. Scales glabrous, not gummy or spotted, the green 
midrib projecting as an awn; basal sheath mem- 
branaceous, with scarious margin...........+..+. S.» validus, 
5. Scales pubescent, with many gummy dots, midrib 
mucronate; basal sheath firm, with fibrillose 
margin. Expected (S. acutus). 
1. Involucre of 2 or more flat leaves; culms leafy. 
6. 
Culms sharply 3-angled, solitary or scattered; 
spikelets 1 to 5 cm. long, 5 to 11 mm. thick. 
(Also, midribs of scales awned). 
7. Achenes equilaterally 3-angled; freshwater marsh 
habitat. Expected (S. fluviatilis). 
7. Achenes plano-convex to obtusely 3-angled; salt 
marsh habitat. (Also, spikelets reddish-brown, 
blunt or rounded at apex; ligule scarious)...... S. robustus 
Culms obtusely angled, or sometimes sharply at 
summit; spikelets 2 to 15 mm. long, 1 to 3 mm. thick. 
(Also, spikelets 35 to over 100, in decompound 
umbelliform panicles). 
8. Bristles retrorsely barbed; culms solitary or few; 
stolons thick and scaly. 
9. Bristles barbed nearly to base; lower sheaths © 
reddish. Expected (S. expansus). 
9. Bristles barbed only above the middle; all 
sheaths greenish. 
10. Bristles twice as long as achene; spikelets 
reddish-brown. Expected (S. polyphyllus). 
10. Bristles not exceeding achene; spikelets 
pale to dark brown. (Also, scales round). S. atrovirens 
8. Bristles smooth or with few hairs; culms tufted; 
stolons absent. 
11. Bristles barely exceeding the scales. 
Expected (S. lineatus), 
11. Bristles greatly exceeding scales at maturity. 
(Also, lateral spikelets in the ultimate fascicles 
pedicelled, central one sessile; spikelets reddish- 
DEOWN, OVOLd) 0. siccvcccececresetecleseseses es Oe CUbITcosUS 
