Cyperaceae 77 
FF. Stem 3-angled. 
I. Spikelets sessile or very nearly so, in a dense head-like cluster. 
J. Involucre-leaf 1. 
K. Leaves mere sheathing bracts; involucre-leaf 1—-3 cm. long; spikelets 
obtuse; spikelet-scales not 2-cleft. E. 
S. olneyi Gray 
KK. Leaves 1—3, well developed; involucre-leaf 415 cm. long; spike 
lets blunt; spikelet-scales 2-cleft. W. E. 
S. americanus Pers. 
JJ. Involucre-leaves 2 or more. 
L. Involucre-bracts scale-like, 48 mm. long; spikelets 6—8 mm. long. U. 
S. criniger Gray 
LL. Involucre-bracts leaf-like, at least one of them 1—4 dm. long; spike- 
lets 15—-30 mm. long. 
M. Scales of the spikelet whitish to brownish. E. (S. brittonianus. ) 
S. campestris Brit. 
MM. Scales of the spikelet reddish by numerous elongated red mark- 
ings. W. S. robustus Pursh 
II. Spikelets or some of them plainly stalked, in a loose umbel-like cluster. 
N. Spikelets 10—-20 mm. long, their scales awned. W. 
S. robustus Pursh 
NN. Spikelets 3—10 mm. long, their scales awnless. 
O. Spikelet mostly solitary at the ends of the umbel-rays; perianth-bris- 
tles smooth, 6. E. S. lineatus Michx. 
OO. Spikelets in dense clusters at the ends of the umbel-rays; perianth- 
bristles barbed, 4—6. 
P. Akenes 3-angled; perianth-bristles 6; styles 3. E. 
S. atrovirens Willd. 
PP. Akenes plano-convex; perianth-bristles 4; styles 2. W. C. E. 
S. microcarpus Presl. 
ELEOCHARIS SPIKE-RUSH 
Annual or perennial, mostly with rootstocks; stem simple, 2—4-angled or terete. 
Leaves reduced to sheaths or the lowest rarely with a blade. Spikelets terminal, solitary, 
without involucre, scaly; scales convex, spirally imbricated. Perianth of O—12 bris- 
tles; bristles usually retrorse-barbed. Stamens 2—3. Style 2-cleft, the base persistent 
and becoming a tubercle on the tip of the akene; tubercle often constricted where it 
joins the akene. Fruit an akene, 3-angled or lens-shaped. (Gk. elos—=a marsh, chairo— 
to rejoice; because it grows in wet places. ) 
A. Akene 3-angled; style 3-cleft. 
B. Akene smooth, its tubercle awl-shaped.  E. 
E. rostellata Torr. 
BB. Akene ribbed, its tubercle short and wide. W.C. E. (E. acicularis bella.) 
E. acicularis R. & S. 
AA. Akene biconvex; style 2-cleft. 
C. Tubercle of the akene constricted at base. 
D. Annual, tufted, without rootstocks. 
E. Mature akene black; upper leaf-sheath oblique at tip; tubercle of akene 
wider than high. C.E, capitata R. Br. 
