196 CYPERACEAE (SEDGE FAMILY) 



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

 and <pop6i, bearing.) 



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

 let enlargred and thickened ; stem-leaves reduced to mostly 

 bladeless sheaths a. 

 a. Stoloniferous. culms j-olitary : empty scales at base of spikelet 

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

 ing obovoid. 



Bristles reddish or cinnamon-color 1. E. Chamissonis. 



Bristles white {I) E. Chamissonis, v. albidtitn, 



a. Nonstoloniferons, 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. E. callitrix. 

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



terete, glabrous at tip S. E. opacum. 



§ 2. Spikelets 2-several ; involucre of 1— several leafy bracts b. 



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. tenellum, 

 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. angusUfoliimi. 



Leaves 5-S mm. broad . . . . . . (Q) E. angusiifolium,y.majtis. 



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

 dark-girdled. 



Spikelets mostly peduncled 7. E. tiridi-carinatum. 



Spikelets sessile in a glomerule ... (7) E. viridi-carinatum^v. Fellowsii. 

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



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



Bristles white except at base (8) .£". Tirginicum, v. album. 



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

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

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

 whitish margins, bluntish ; bnstles 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. callitrix Cham. (Hare's Tail.) Culms stiff and loiry, 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..S-5 cm. broad ; bristles bright xohite. (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 (Bjomstr.) Fernald. Similar; culms terete, glabrous, fili- 

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

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

 2-8.5 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 \loth. Weak and slender, glabrous, the subtprete culm 2-6 

 dm. high, u-ith no young basal leaves devploped at flowering season; upper 

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

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

 in anthesis 7-10 mm. long, in fruit 1.5-2 cm. long ; scales Icad-ddor 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.) 



5. E. tenellum Xutt. Culms stiff, obtusely trigonous, scabrous above, 3-9 

 dm. high, v)it/i long slender green pointed basal leaves ; upper cauline leaf-blade 

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

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



