SEDGE FAMILY 109 



Spikelets normally more than one, usually several, sometimes numerous. 

 Spikelets few, 1-12, appearing lateral, in a single capitate cluster. 



Annuals, with fibrous roots, tufted; achenes dark, transversely wrinkled. 

 Spikelets obtuse; achenes plano-convex. 6. S. Ilallii. 



Spikelets acute; achenes 3-angular. 7. S. saximon tonus. 



Perennials, with rootstocks; achenes plano-convex, obovate. 

 Stem sharply 3-angled. 



Spikelets acute: bracts long; glumes awned. 8. S. americanus. 



Spikelets obtuse; bracts short; glumes mucronate. 9. S. Olneyi. 

 Stem terete, striate. 10. S. neradensis. 



Spikelets numerous in small clusters of 1-7, arranged in compoimd umbels; per- 

 ennials with stout rootstocks. 

 Style 2-cleft; achenes obovate and plano-convex, brown. 



Achenes 2 mm. long, nearly as long as the glumes; spikelets ovoid. 



11. S. ralidus. 

 Achenes 3 mm. long, distinctly shorter than the glumes; spikelet oblong- 

 cvUndric. 12. S. orcidentalis. 



Style 3-cleft; achenes obcordate, 3-angled, yellowish. 13. S. helerochaetus. 



Involucre of two or more leaves with flat blades; perennials, with rootstocks. 



Spikelets 3-10. capitate, relatively large. 14. S. paludosus. 



Spikelets numerous, in compound umbels or in umbellate heads, relatively small. 

 Bristles downwardly barbed, not much exceeding the fruit. 

 Style-branches 2; achenes plano-convex; bristles mostly 4. 



1.5. 5. microcarpus. 

 Style-branches 3; achenes oblong, 3-angular; bristles 6. 



Plant dark green; glumes acute; achenes pale brown. IG. S. atrorirens. 

 Plant pale; glumes rough-awncd; achenes straw-colored. 



17. S. pcUidus. 

 Bristles 6, smooth, much exceeding the glumes at maturity; achenes 3-angled, 

 whitish. 

 Spikelets all sessile; glumes brown. IS. S. cypcrinus. 



Snikelets mostly pediceled; glumes mostl.v greenish black. 



19. >S. atrocinctus. 



1. S. coloradensis Britt. Annual; stems filiform, 2-5 cm. high; spikelet 

 bractless, linear-oblong, acutish, 3-5 mm. long, 2 mm. thick; glumes lanceolate, 

 acutish; keel green, bordered with two brown bands and scarious margins; 

 achenes brown, ojjovate, 1 mm. long, 3-gonous, finely papillose. Shores: Colo.; 

 Nev. Plain. 



2. S. pauciflorus Lightf. Rootstock filiform; stems 3-angled, filiform, leaf- 

 less, 7-25 cm. high; spikelet oblong, compressed, 4-10-flowered, 4-6 mm. long; 

 glumes brown with lighter margins and midrib, lanceolate, acuminate; bristles 

 2-G, usually longer than the achenes; achenes obovoid, abruptly beaked, finely 

 reticulate. Wet soil: Que.— Me.— N.Y.—N.M.— Calif.— B.C.; Eurasia. Mont. 

 —Subalp. Jl-0. 



3. S. caespitosus L. Stems light green, fihform, 1-4 dm. high; basal sheaths 

 numerous, the uj)per one bearing a short blade; spikelet ovoid-oblong, 4 mm. 

 long; glumes yellowish brown, ovate, obtuse; achenes oblong, 3-angled, brown, 

 acute. Bogs and wet places: Greenl. — 111. — Colo. — -AVash. — Alaska; Eurasia. 

 Mont.— Alp. Je-Au. 



4. S. pumilus Vahl. Stems terete, 1 dm. high or less, sheathed at the base; 

 upper sheath with a short blade; spikelet rounded-ovoid; glimies ovate, acute 

 or pointed, brown with green midrib and margins; achene 3-angular, smooth. 

 S. alpinus Schleicher. Alpine wet places: Canadian Rockies; Alps. Jl-Au. 



5. S. subterminalis Torr. Stem slender, terete, nodtilose, 3-10 dm. high; 

 leaves very slender, 1.5-G dm. long, 0.5-1.5 mm. wide; spikelet oblong-cylindric, 

 6-15 mm. long; bract subulate, erect, 1-2.5 cm. long; glumes ovate-lanceolate, 

 acute, light brown with green midrib; bristles 6, rarely equalling the achenes; 

 these obovoid, 3-angled, dark brown, smooth. Ponds and streams: Newf. — ■ 

 S.C— Mich.— Ida.— Wash.— B.C. Submont. Jl-Au. 



6. S. Hallii A. Gray. Stems slender, smooth, obtusely 3-angular, 1-3 dm. 

 high; upper sheath bearing a filiform blade 1-6 cm. long; spikelets 1-7, capitate, 

 oblong-cylindric, obtuse, 6-12 mm. long; bract 2-10 cm. long; glumes ovate- 

 lanceolate, greenish brown, acuminate; bristles none. Wet i)laces: Mass. — • 

 Fla.— Tex.— Colo.— Utah— Mex. Plain— Submont. Jl-S. 



7. S. saximontanus Femald. Stems slender, smooth, 1-3 dm. high, tufted, 

 short-leaved at the base; bract erect, one-half to one-fourth as long as the stem; 



