76 Cyperaceae 
umbels, naked or subtended by a I- to several-leaved involucre; scales spirally imbricate, 
usually all fertile. Flowers perfect. Perianth of 6 or numerous bristles; bristles filiform, 
smooth, soft, white or brown, straight or crisped, exserted much beyond the scales at 
maturity. Stamens 1—3. Style 3-cleft. Akenes 3-angled, oblong or ellipsoid or 
a.” oo 
obovoid. Ours in bogs. (Gk. erion=wool or cotton, phoros=bearing; referring to 
the cottony spikes. ) 
A.  Spikelet 1; lowest scale of spikelet enlarged and thickened but otherwise without 
involucre. 
B.  Perianth-bristles reddish-brown. W. (E. russeolum.) 
E. chamissonis Mey. (Brown Rabbit’s-tail) 
BB.  Perianth-bristles white. W. (Apparently E. scheuchzeri.) 
E. chamissonis albidum Fern. (White Rabbit’s-tail) 
AA. Spikelets 2—several; involucre of |—-several leafy bracts. 
C. Leaves 1—1.5 mm. wide, triangular-channelled thruout; involucre-bract 1, 
short, erect. W.C. E. E. gracile Roth (Slender Cotton-grass) : 
CC. Leaves wider, flat at least below the middle; involucre-bracts 2 or more. C. E. 
E. polystachion L. (Coarse Cotton-grass) 
SCIRPUS BULRUSH 
Annual or perennial, tufted; with creeping rootstocks. Spikelets | or more, ter- 
minal but often apparently lateral, in head-like or umbel-like clusters when several, sev- 
eral- to many-flowered, scaly, with or without involucre subtending the clusters; scales 
closely imbricated around the rachilla, lower 1—2 often empty. Perianth of 0O—6 
bristles. Stamens 1-3. Style 2—3-cleft, scarcely or not at all thickened at base, 
deciduous or only the base persistent. Akenes lens-shaped or 3-angled or obovoid. (The 
Latin name of the bulrush.) 
A.  Spikelet only 1, terminal. 
B. Involucre-bracts none. 
C. Akene 2—2.5 mm. long, its beak continuous with its body. C. E. 
S. pauciflorus Lft. 
CC. Akene | mm. long, constricted below the beak. W. 
S. nanus Spreng. 
BB. Involucre-bracts present. 
D.  Involucre-bracts shorter than the spikelet. 
E.  Perianth-bristles none. W. 
S. riparius Spreng. 
EE. Perianth-bristles 6, smooth. W. C. 
S. caespitosus L. 
DD. Involucre-bracts 2—-3 times as long as the spikelet. C. E. 
S. subterminalis Torr. 
AA. Spikelets more than | except sometimes in dwarfed plants. 
F. Stem terete. 
G. Spikelets sessile or nearly so, in a crowded head-like cluster. E. 
S. nevadensis Wats. 
GG. Spikelets stalked, in loose umbel-like clusters. 
H. Akene 2 mm. long; scales of the spikelets barely longer than the akenes. 
E. (S. lacustris, mostly.) 
S. validus Vahl. 
HH. Akene 2.5—3 mm. long; scales of the spikelets 14 longer than the 
akenes. W.C. E. S. occidentalis Chase (Tule) 
