122 LIST OF SEEDS, BULBS, TUBERS, ETC, 
seven angled, rather few in a whorl. Wet places, 
Niagara River, Wisconsin and northward. June. 
E. liinosum, L.:—Stems (2—5° high) — slightly 
many-furrowed, smooth, sometimes continuing un- 
branched, but usually producing ascending branches 
after fructification; sheaths appressed, with ten to 
twenty-two (commonly about eighteen) dark-brown 
and acute rigid short teeth. In shallow water; rather 
common. Air cavities none under the grooves, but 
small ones under the ridges. A form in which the 
branches bear numerous small spikes is variety Poly- 
stachyum, Bruckner. June, July. 
E. hyemale, L.:—Scouring Rush, Shave-Grass :— 
Stems 1$— 4° high, eight to thirty-four grooved, the 
ridges roughened by two more or less distinct lines of 
tubercles; sheaths elongated, with a black girdle above 
the base and a black limb; ridges of the sheaths cb- 
scurely four-carinate, the teeth blackish, membranace- 
ous, soon falling off. Wet banks; common northward. 
E. robustum, Braun: :—Stems tall and stout, some- 
times 8—10° high and nearly an inch thick, twenty 
to forty-eight grooved, the ridges roughened with one 
line of transversely oblong tubercles; sheaths rather 
short, with a black girdle at base and a black limb; 
ridges of the sheaths tri-carinate, the blackish teeth 
soon falling off. River banks, Ohio and westward. 
E. lavigatum, Braun.:—Stems 1—4° high, rather 
slender, pale green, fourteen to thirty grooved, the 
ridges almost smooth; sheath slightly enlarged upward, 
with a black girdle at the base of the mostly deciduous 
white-margined teeth, and rarely also at the base of 
the sheath; ridges of the sheath with one keel, or some- 
times obscurely tri-carinate. By streams and in clayey 
places, Ohio to Minnesota and westward. 
