196 CYPERACEAE (SEDGE FAMILY) 



3-cleft. Achene acutely triangular. (Name composed of epiop, wool or cotton, 

 and (popbs^ bearing.) 



% 1. Spikelet solitary ; involucre none ; the lowest scale of the spike- 

 let enlarged and thickened ; stem-leaves reduced to mostly 

 bladeless sheaths a. 



a. Stoloniferous, culms solitary ; empty scales at base of spikelet 



few (7 or less) ; flowering spikelet cylindric, in fruit becom- 

 ing obovoid. 



Bristles reddish or cinnamon-color \. E. Chamissonis. 



Bristles white (HE". Chamissonis, v, albidum 



a. Nonstoloniferous, culms tufted; empty scales 10-15; flowering 



spikelet obovoid or globose, in fruit becoming depressed- 

 globose. 

 Densely tufted, the culms very many ; upper sheaths dis- 

 tinctly inflated ; culm trigonous and scabrous at tip . 2. U. callitrix. 

 Loosely tufted, culms very few ; upper sheath close ; culm 



terete, glabrous at tip Z. E. opacum. 



% 2. Spikelets 2-several ; involucre of 1-several leafy bracts h. 



b. Leaves very slender, 1-1.5 mm. broad, triangular-channeled 



throughout ; involucre a single erect short bract. 

 Upper cauline leaf with the sheath longer than the blade . 4. E. gracile. 

 Upper cauline leaf with the sheath shorter than the blade . 5. E. t&nellum. 



b. Leaves broader, flat at least below the middle ; involucral 



bracts 2 or more c. 

 c. Scales of spikelet with only 1 prominent rib ; stamens 3. 



Midrib of scale prominent only below the membranous tip ; 

 upper leaf-sheaths dark-girdled at summit. 



Leaves 1.5-4 mm. broad 6. E. angustifolium. 



Leaves 5-8 mm. broad (6) .^. angustifolium, v. majua. 



Midrib prominent to the tip of the scale ; leaf-sheaths not 

 dark-girdled. 



Spikelets mostly peduncled 1. E. mridi-carin^tum. 



Spikelets sessile in a glomerule . . . (T) E. viridi-carinaPum, v. Fellowsii. 

 c. Scales of the spikelet with several prominent ribs ; stamen 1. 



Bristles copper-color or brown 8. E. virginicum. 



Bristles white except at base (8) ^. mrginicuin, v. album. 



1. E. Chamiss5nis C. A. Mey. Culms soft, subterete, 1-8 dm. high ; basal 

 leaves slender, channeled, the upper scarcely inflated sheaths mostly bladeless ; 

 flowering spikelet 1.5-2 cm. long ; its scales brownish lead-color with broad 

 whitish margins, bluntish ; bristles reddish. (E. russeolum Fries.) — Locally 

 in bogs, Lab. to N. S. and N. B. ; Ont. ; Rocky Mts., etc. Fr. July, Aug. 

 (Eurasia.) Var. albidum (F. Nylander) Fernald. Bristles white. — Que. and 

 N. B. ; Alaska, etc. (Eurasia.) 



2. E. cdllitrix Cham. (Hare's Tail.) Culms stiff and wiry, densely tufted, 

 1.5-7 dm. high; basal leaves filiform-trigonous, scabrous; upper bladeless 

 sheaths inflated ; flowering spikelet obovoid or globose, 0.8-1.5 cm. long ; scales 

 lead-color with pale margins, ovate to ovate-lanceolate, long-acuminate; fruit- 

 ing spikelet 2.5-5 cm. broad ; bristles bright white. (E. vaginatum Am. 

 authors, not L.). — Bogs and mountain slopes, Lab. to Alaska, s. to Pa., 

 Mich., Wis., and Man. Fr. May-July. (Asia.) 



3. E. opacum (Bjo.nstr.) Fernald. Similar; culms terete, glabrous, fili- 

 form, forming loose small tufts ; leaves glabrous ; upper sheaths close; flowering 

 spikelet rarely 1 cm. long; scales lead-color, lance-attenuate; fruiting spikelet 

 2-3.5 cm. broad ; bristles sordid white. — Locally on bogs. South Ashburnham, 

 Mass. (Forbes)] Ont. to Sask. and the Rocky Mts. Fr. June, July. (Eurasia.) 



4. E. gracile Roth. Weak and slender, glabrous, the subterete culm 2-6 

 dm. high, with no young basal leaves developed at flowering season; upper 

 caidine leaf-blade smooth, round-tipped, 1-4 cm. long; involucre dark at base; 

 spikelets 2-5, mostly on short slender pubescent peduncles (0.5-3 cm. long), 

 in anthesis 7-10 mm. long, in fruit 1.5-2 cm. long ; scales lead-color or blackish; 

 achenes 1.5-2 mm. long ; bristles white. — Cold bogs and swamps. Gulf of St. 

 Lawrence to B.C., s. to Ct., Pa., Mich., Neb., and Cal. Fr. May-July. 

 (Eurasia.) 



6. E. tenlUum Nutt. Culms stiff, obtusely trigonous, scabrous above, 3-9 

 dm. high, with long slender green pointed basal leaves ; upper cauline leaf-blade 

 scabrous, pointed, 3-18 cm. long ; involucre brown or straw-color at base ; 

 spikelets 3-6, on scabrous peduncles, in fruit 2-2.8 cm. long ; scales greenish 



