106 CYPERACEAE 



Tubercle of the achenes short-conic to depressed, plainly distinguishable from 



the achene. 

 Achenes papillose. 



Stem filiform; glumes obtuse. 7. E. tenuis. 



Stem flat; glumes acute. 8. E. acuminata. 



Achenes finely reticulated. 9. E. arcnicola. 



Tubercle of the achenes long-conic, scarcely distinguishable from the body of the 



achene. 10. E. rostellata. 



1. E. thermalis Rydb. Perennial, with a creeping rootstock; stems tufted, 

 yellowish green, 3-10 cm. high, somewhat flattened, striate; spikelet obovate, 

 obtuse, 4 mm. long, 3 mm. thick; glumes very thin, ovate, acutish; achenes 

 lenticular, broadly obovate, dark brown, smooth and shining, 1 mm. long; 

 tubercle conic. Hot springs and thermal waters: Mont. Wyo. Mont. Jl-Au. 



2. E. atropurpurea (Retz.) Kunth. Stems tufted, slender, 3-10 cm. high; 

 spikelet ovoid, subacute, 3-4 mm. long, 2 mm. thick; glumes ovate-oblong, obtuse, 

 or the upper acute, purple-brown, with green midrib and narrow scarious margins; 

 bristles 2-4, fragile, white, about as long as the achenes; achenes 0.5 mm. long, 

 smooth, lenticular; tubercles depressed-conic, constricted at the base. Moist 

 soil: la. Fla. Tex. (? Colo.); trop. Am.; Eurasia. Austral. Jl-S. 



3. E. Engelmanni Steud. Stems 2-4.5 dm. high, tufted; spikelet obtuse, 

 5-15 mm. long, 2-3 mm. thick; glumes pale brown, with green midrib and narrow 

 scarious margin, ovate, obtuse; bristles about 6, not longer than the achenes, or 

 none; achenes broadly obovate, smooth; tubercle broad, low, covering the top 

 of the achene. Wet places: Mass. N.J. Tex. Calif. Wash. Plain Sub- 

 mont. Jl-S. 



4. E. monticola Fernald. Stems 1-2.5 dm. high, tufted; spikelets 6-9 mm. 

 long, 2-3.5 mm. thick, acutish; glumes chestnut-brown or purplish, with paler 

 midribs and margins, acutish; bristles 6, equalling or slightly exceeding the achenes, 

 or (in var. leviseta) represented only by the unbarbed basal portion; achenes as 

 in the preceding. Wet places: Calif. Wash.; the var. leviseta: Wash. Ida. 

 Man. Submont. 



6. E. palustris (L.) R. & S. Stems striate, 3-15 dm. high; spikelets oblong 

 to ovoid-cylindric, 6-25 mm. long, 3-4 mm. thick; glumes ovate-lanceolate or 

 ovate-oblong, purplish brown with scarious margins and green midrib, or wholly 

 green; bristles usually 4, longer than the achenes; achenes yellow, more than 1 

 mm. long; tubercle conic, constricted at the base. E. glaucescens Willd., a slender 

 form with narrower tubercle. In ponds and marshes: Lab. -Fla. Tex. -Calif. 

 B.C.; Eurasia. Plain Mont. Au-S. 



6. E. acicularis (L.) R. & S. Stems tufted, filiform, obscurely 4-angled, 

 grooved, 5-20 cm. high; spikelets narrowly ovate, acute, 3-10-flowered, 3-6 

 mm. long; glumes oblong, obtuse, or the upper acute, pale green, often with two 

 brown bands; bristles 3-4, fragile, fugaceous, shorter than the achenes; achenes 

 obovoid, pale, obscurely 3-angled; tubercle conic. Wet places: Newf. N.J. 

 N.M. Calif. B.C.; Mex.; Eurasia. Plain Mont. Jl-S. 



7. E. tenuis (Willd.) Schultes. Stems tufted, filiform, 4-angled, 2-4 dm. 

 high; spikelets narrowly oblong, acute, 6-10 mm. long, about 2 mm. thick; 

 glumes thin, obovate or obovate-oblong, obtuse, with greenish midvein and 

 scarious margins; bristles 2-4, shorter than the achenes, fugaceous or wanting; 

 achenes obovoid, obtusely 3-angled, yellowish brown; tubercle conic, short. 

 Wet places: N.S. Fla. Tex. Colo. Sask. Plain Submont. My-Jl. 



8. E. acuminata (Muhl.) Nees. Stems tufted, flattened, striate, 2-6 dm. 

 high; spikelets ovoid or oblong, obtuse, 6-12 mm. long; glumes oblong or ovate- 

 lanceolate, acute or obtusish, purple-brown with green midrib and hyaline mar- 

 gins; bristles 1-5, mostly shorter than the achenes; achenes obovoid, very ob- 

 tusely 3-angled, light yellowish brown; tubercle depressed-conic. Wet places: 

 Que Ga. La. Colo. B.C. Je-Au. 



9. E. arenicola Torr. Stems tufted, slender, 1.5-4.5 dm. high, grooved; 

 spikelets oblong to ovoid-oblong, 4-12 mm. long, 2.5-3.5 mm. thick; glumes 

 oblong or ovate, thin, blunt, with a brown apex and whitish margins; bristles 6, 

 persistent, the longer ones as long as the achenes; achenes 3-angled, oblong- 



