CYPERACEAE 165 
the ends of 1-3 rays : scales ovate, green, brown, or with brown margins, obtuse, 1-nerved, 
appressed, membranous, dull: stigmas or style-branches 2, much exserted : achenes len- 
ticular, oblong, gray, not shining, } as long as the scale, its superficial cells quadrate and 
about as long as wide, as in the eleven following species. 
In marshy places, New Brunswick to Minnesota, South Carolina and Kansas. Summer and fall. 
3. Cyperus rivulàris Kunth. Similar tothe next preceding species. Scapes slender, 
tufted : umbel usually simple: spikelets linear or linear-oblong, acutish, 8-20 mm. long : 
scales dark green or brown, or with brown margins, appressed, firm, rather coriaceous, 
shining, obtuse: stigmas or style-branches 2, scarcely exserted: achenes oblong or oblong- 
obovoid, lenticular, somewhat pointed, dull. 
In wet soil, especially along streams and ponds, Maine to Ontario, Michigan, Nebraska, North 
Carolina and Missouri. Summer and fall. 
4. Cyperus hélvus Liebm. Annual. Leaves generally 2 or 4; blades 1-3 mm. 
wide, smooth : scapes tufted, 1-7 dm. tall, as long as the leaves or longer: bracts of the 
involucre narrower than the leaf-blades, surpassing the umbel, the longer ones 5-20 cm. 
long : umbel capitate, or 2-4 rays becoming 1-3 cm. long: spikelets few, linear to linear- 
lanceolate, 5-8 mm. long, acutish: scales straw-colored or yellowish green, ovate, obtuse, 2 
mm. long, deciduous at maturity, 2-keeled on the back: styles 2, well united: achenes 
lenticular, oval or oval-obovoid, 1 mm. long, brown, dull, barely 3 as long as the scale. 
In ditehes and moist grounds, Louisiana and Texas; also through the tropies to eastern South 
America and in the West Indies. Spring to fall. 
5. Cyperus bipartitus Torr. Annual. Leaves usually 2 at the base of the the scape ; 
blades setaceous or filiform : scapes 5-15 cm. tall: bracts of the involucre solitary or 2, but 
only one well developed and erect: spikelet ovate-oblong, 5-7 mm. long, rather obtuse, 
about 14-flowered : scales ovate, obtuse, somewhat coriaceous, closely imbricated : styles 2, 
nearly distinct : achenes lenticular, obovoid, fully 1 mm. long, obtuse. 
In sandy soil, near New Orleans, Louisiana. Summer. 
6. Cyperus Nuttallii Eddy. Annual. Scapes slender, tufted, equalling or longer 
than the leaves: bracts of the involucre 3-5, spreading, the larger often 12 em. long: um- 
bel 3-7-rayed: spikelets rather loosely clustered, linear, very acute, flat, spreading, 1-3 
em. long, 2-3 mm. wide: scales yellowish brown except the green keel, oblong, acute : 
stigmas 2, somewhat exserted: achenes lenticular, narrowly obovoid, obtuse or truncate, 
dull, light brown, 4 to 3 as long as the scale. 
In salt marshes, or drifting sand, coast of Maine to Florida and Mississippi. Summer and fall. 
7. Cyperus microdóntus Torr. Annual. Leaf-blades about 2 mm. wide: scapes 
very slender, tufted, sometimes 0.5-1 dm. high: bracts of the involucre much elongated : 
umbel commonly simple, sessile, subcapitate : spikelets linear, acute, 6-18 mm. long, less 
than 2 mm. wide, yellowish brown: scales ovate, barely 2 mm. long, acute, thin becoming 
rather lax: stigmas 2, much exserted: achenes lenticular, linear-oblong, short-pointed, 
light brown, 3 as long as the scale. 
In wet soil, on or near the eoast, Virginia aud North Carolina. Summer and fall. 
8. Cyperus Gatésii Torr. Annual, bright green. Leaves often 3-6; blades 1-4 mm. 
wide, or sometimes narrower or even filiform, not firm: scapes slender, tufted, 1-4 dm. 
tall, often surpassing the leaves: bracts of the involucre 3-5, surpassing the umbel, the 
longer ones usually 10-20 cm. long: umbel with 3-8 rays 1-5 em. long, or rarely nearly 
capitate: spikelets few, linear or linear-lanceolate, 6-15 mm. long, acute : scales light chest- 
nut-brown, oblong-lanceolate, 2-2.5 mm. long, shining, striate, deciduous at maturity: 
achenes oblong, fully 1 mm. long, grayish, abruptly apiculate, fully 3 as long as the scale. 
In springy places and low grounds, Virginia to Florida and Texas. Spring to fall. 
9. Cyperus polystáchyus Rottb. Annual, pale green. Leaves usually 4-8 ; blades 
narrowly linear, 2-4 mm. wide, smooth like the scape : scapes tufted, slender, 1-9 dm. 
tall, generally surpassing the leaves: bracts of the involucre 3-5, much longer than the 
umbel, nearly equal in length, or one or two sometimes 1-2 dm. long: umbel capitate or 
some of the rays becoming 1-3 cm. long: spikelets numerous, linear-lanceolate, 6-20 mm. 
long, acute, 15-25-flowered: scales 1.5 mm. long, gray-brown or straw-colored, acute, dull, 
deciduous at maturity : achenes lenticular, oblong, 1.2 mm. long, dull, about twice as long 
as thick, grayish. 
In ditches and low grounds, Florida to Louisiana, and in tropical America. Spring to fall. 
10. Cyperus pümilus L. Annual, pale green. Leaves often 3-4; blades gradually 
narrowed to the apex : scapes densely tufted, slender, 1-3 dm. tall, or sometimes shorter, 
mostly as long as the leaves or longer: bracts of the involucre usually 3 or 4, 1 or 2 of 
them much longer than the others, the longest one often 10 cm. in length : umbel much 
shorter than the involucre, with 3-9 rays, 1-6 cm. long and a sessile cluster of spikes, or 
sometimes all spikes sessile: spikelets linear, 4-8 mm. long, relatively few in a spike, 15- 
