EQ UISE TA CE&. 1 2Q 



in a single series. Southern California in open canons (Mc- 

 Clatchie). 



ft Branches rare except when the main stem is broken. 

 \ Stems rough, ttiberculate. 



10. E. robustum A. Br. Stems 3 11 high, sometimes 

 nearly i' thick, 2048 furrowed; ridges roughened with a 

 single series of tubercles ; sheaths short, marked with black 

 girdles at base and at base of the caducous teeth ; ridges of 

 sheaths tricarinate. Ohio to California and northward. 



11. E. hiemale L. (ScouRlNG-RUSH.) Stems i 4 high, 

 8 34 furrowed ; ridges rough, with two indistinct lines of tu- 

 bercles ; sheaths rather long, marked with one or two black 

 girdles; ridges of the sheath obscurely quadricarinate. North 

 America generally. 



\\ Stems smoothish, scarcely tuberculate. 



12. E. laevigatum A. Br. Stems i 5 high, pale green, 

 14 30 furrowed ; ridges almost smooth ; sheaths elongate, en- 

 larged upward, marked with a black girdle at the base of the 

 mostly deciduous white-margined teeth, rarely with a second ; 

 ridges of sheath with central keel and rarely faint lateral ones. 

 North Carolina to California and Oregon. 



** Stems slender, tufted, 5 \o grooved. 



13. E. varlegatum Schleich. Stems ascending, 6' 18' 

 long, usually simple from a branched base, 510 furrowed ; 

 sheaths green, variegated with black above, the teeth 5 10, 

 tipped with a deciduous bristle ; central air-cavity small. Bel- 

 lows Falls, New Hampshire (Carey), Niagara Falls to Illinois 

 and northward to Greenland and Alaska. 



14. E. scirpoides Michx. Stems filiform, very numerous, 



3' 6' high, flexuous and curving, mostly 6-furrowed, with acute 



ridges ; sheaths 3-toothed, the bristle tips more persistent ; cen- 

 tral air-cavity wanting. New England to Pennsylvania, Illinois 

 and northward. 



