CYPERACEAE | 177 
Scapes triangular: upper sheath with a linear blade: perianth-bristles 
upwardly barbed. 
Perianth-bristles wanting: scales keeled. 
ERURG EM nores more than 1, usually several or numerous, often apparently 
ateral. 
Spikelets few, 1-12, appearing lateral. 
Scapes not sharply 3-angled : plants annual. 
. Clintonti. 
S. carinatus. 
co 
tn 
Achene strongly transverse-rugose : ls aac aa wanting. 5. S. Hallit. 
Achene smooth or very slightly roughened : perianth-bristles 4-6. 6. S. debilis. 
Seapes sharply 3-angled: plants perennial by rootstocks. 
Spikelets acute: scales awned: involucral bract much surpassing the 
inflorescence. 7. S. Americanus. 
Spikelets obtuse: scales mucronate: involucral bract only slightly sur- 
3 passing the inflorescence. 8. S. Olneyi. 
Spikelets several or numerous, in umbels or umbel-like clusters. 
Scapes sharply 3-angled : leaves with blades about as long as the scape. 9. S. cylindricus. 
Scapes terete: leaves reduced to mere sheaths. 
Perianth-bristles downwardly barbed : achene.gray, abruptly mucronate. 10. S. lacustris. 
Perianth-bristles short-plumose below: achene nearly white, nar- 
rowed above. 11. S. Californicus. 
Involucre of 20r more bracts with flat blades. 
Spikelets not in dense globular heads. 
Spikelets few to several, capitate to umbellate, relatively large. i 
Spikelets in simple clusters: achenes obovoid-oblong, pale brown. 12. S. campestris. 
Spikelets in often compound clusters: achenes orbicular-obovoid, dark 
brown. 18. S. robustus. 
Spikelets very numerous, in compound umbels or umbelled heads, relatively 
small. 
i we aa downwardly barbed, or wanting: spikelets in umbelled 
eads. 
Perianth-bristles present. 
Perianth-bristles equalling or slightly exceeding the achene: leaf- 
blades 6-16 mm. wide. 
Spikelets 3-8 in each head : scales obtuse : perianth-bristles barbed : 
throughout. 14. S. sylvaticus. 
Spikelets 8-20 in each head: scales acute: perianth-bristles not 
barbed below. 15. S. atrovirens. 
Perianth-bristles twice as long as the achene: leaf-blades 4-6 mm. 
wide. 16. S. polyphyllus. 
Perianth-bristles wanting. 17. S. Georgianus. 
Perianth-bristles smooth or slightly pubescent : umbel mostly decompound. 
Perianth-bristles shorter than the scales or scarcely exceeding them. 
Perianth-bristles about as long as the achene: scales rather acute. 
Inflorescence merely terminal: spikelets 1 mm. thick: achenes ae 
not papillose. 18. S. divaricatus. 
Inflorescence terminal and lateral: spikelets 2-3 mm. thick ee 
achenes papillose. 19. S. fontinalis. 
Perianth-bristles much longer than the achene: scales mucronate. 20. S. lineatus. 
Períanth-bristles much exserted|beyond the scales at maturity 
Spikelets sessile, in small heads. 21. S. cyperinus. 
4 Spikelets, at least some of them, distinctly uncled. 22. S. Ertophorum. 
Spikelets very numerous in one or several dense globular heads. 23. S. Cubensis. 
1. Scirpus nànus Spreng. Annual. Roots fibrous: scapes filiform, flattened, 
grooved, tufted, erect or ascending, 2-5 cm. high, each bearing a scarious bladeless sheath 
near the base: spikelets solitary, terminal, ovoid-oblong, rather acute, 3-8-flowered, 2-3 
mm. long, not subtended by a bract : scales ovate or lanceolate, pale green, the lower ob- 
tuse, the upper subacute: perianth-bristles about 6, downwardly barbed, longer than the 
achene : stigmas 3: achenes oblong, 1 mm. long, 3-angled, pale, pointed at each end. 
: In muddy places in salt marshes, Cape Breton Island to Florida and Texas and about salt springs 
in New York and Michigan. Also on the Pacific coast of North America and on the coasts of Europe. 
Summer and fall. 
2. Scirpus caespitdsus L. Perennial. Scapes smooth, terete, densely tufted, light 
green, erect or ascending, almost filiform, wiry, 10-40 em. long : basal sheaths numerous, 
membranous, imbricated, acuminate, the upper one bearing a short very narrow blade : 
spikelet solitary, terminal, few-flowered, ovoid-oblong, about 4 mm. long, subtended by a 
subulate involucral bract of about its own length : scales yellowish brown, ovate, obtuse or 
subacute, deciduous: perianth-bristles 6, smooth, longer than the achene: stigmas 3: 
achenes oblong, 1.5 mm. long, 3-angled, smooth, brown, acute. 
cun pop and on moist rocks, Greenland to Alaska, south to the mountains of New England, the 
Adirondacks, western New York, Illinois, Minnesota and British Columbia, in the Rocky Mountains to 
Colorado, and on the higher summits of the southern Alleghenies. Also in Europe and Asia. Summer. 
3. Scirpus Clintonii A. Gray. Perennial. Scapes tufted, triangular, very slender, 
erect, 10-40 cm. tall, roughish on the angles: lower sheaths imbricated, one or more of 
-them bearing short subulate blades, the upper one bearing a flat, narrowly linear blade 
shorter than the stem : spikelet solitary, terminal, ovoid, few-flowered, 3-4 mm. long, sub- 
tended by a subulate involucral bract: scales ovate, pale brown, acute : perianth-bristles 
3-6, filiform, upwardly barbed, as long as the achene or longer : stigmas 3: achenes oblong, 
1.5 to nearly 2 mm. long, sharply 3-angled, brown, smooth, obtuse. 
In dry fields and thickets, New Brunswick to Michigan and North Carolina. Local. Summer. 
12 
