10-i CYPERACE.\E 



internode below. Flowers perfect. Perianth of 6-9 retrorsely barbed bristles. 

 Stamens 3. Style persistent as a beak on the top of the achene. Stigmas 2. 

 Achenes linear-oblong. 



1. D. arundinaceum (L.) Britton. Stem stout, 3-10 dm. high; leaves 

 numerous, flat, 2-S cm. long, 4-8 mm. wide, spreading; lower sheaths bladeless; 

 spikelets 12-25 mm. long, about 2 mm. wide, 6-12-flowered; glumes lanceolate^ 

 acuminate, strongly nerved, brownish; bristles longer than the achenes. D. 

 spathacewn Pers. Wet places: Xewf. — Fla. — Tex. — Ore. — B.C.; C. Am. Plain. 

 Jl-0. 



2. CYPERUS L. Galing.\le, Nut grass. 



Sub-scapose perennials or annuals. Leaves basal; blades narrow, grass-like. 

 Scapes in our species simple, triangular, with one or more bracts at the summit, 

 subtending a simple or compound, umbellate or capitate inflorescence; rays 

 u.sually very unequal in length. Spikelets flat to nearly terete. Glumes 2- 

 ranked, concave, conduplicate or keeled. Flowers perfect; perianth none. 

 Stamens 1-3. Styles deciduous from the summit of the achenes; stigmas 2 or 

 3. Achenes without a tubercle. 



Glumes falling away from the persistent rachis of the flat' spikelets. 



Style 2-cleft; achenes lenticiilar. 1. C. diandrus. 



Style .3-cleft; achenes 3-angled. 



"Wings of the rachis none or very narrow. 

 Annuals: stamen 1. 



Glumes awned or mucronate. 2. C. inflexus. 



Glumes acute, neither awned nor mucronate. 3. C. acuminalus. 



Perennials; stamens 2 or 3. 



Glumes tipped with a curved or bent awn; perennials with a rootstock. 



4. C. Fendlerianus, 

 Glumes blunt or mucronate; perennials with a corm-Uke base. 



Heads oblong; spikelets ascending; stem rough. 5. C. Schweinitzii. 

 Heads short; spikelets more or less spreading; stem smooth. 



Glumes broadly ovate; achenes 1 .5-2 mm. long. 6. C. Hotightoni. 

 Glumes oblong-ovate; achenes 2-2.5 mm. long. 7. C. Bushii. 

 Wings of the rachis prominent and separating from it as interior scales. 



8. C erythrorhi-os. 

 Spikelets wholly falling away, usually leaving the two lower glumes persistent. 



9. C. strigosus. 



1. C. diandrus Torr. Annual; stems tufted, 5-30 cm. high; leaves about 

 2 mm. wide; bracts usually 3, at least one much exceeding the spikelets; spikelets 

 in terminal capitate clusters, linear-oblong, 8-18 mm. long, flat, many-flowered; 

 glumes ovate, green, brown, or with brown margins, obtuse, 1-nerved; stamens 

 2 or 3; achenes oblong, gray. Marshy places: N.B. — S.C. — Colo. — S.D. Plain 

 — Sitbmont. Au-0. 



2. C. inflexus Muhl. Stems slender, tufted, 2-15 cm. high; leaves 1-2 mm. 

 wide; bracts 2 or 3, longer than the umbel; spikelets capitate or in 3-rayed, sessile 

 umbels, linear-oblong, 6-10-flowered, 4-6 mm. long; glumes light b^o^^^l, lance- 

 olate, several-nerved. C. aristatus Rottb. Wet sandy soil: N.B. — Fla. — Calif. 

 — B.C.;Mex. Plain— Suhm out. Jl-S. 



3. C. acuminatus Torr. Stems slender, tufted, 5-35 cm. high; leaves 

 usually less than 2 mm. wide, light green; bracts much elongated; spikelets capi- 

 tate, in 2 -4-1 ay ed umbels, flat, ovate-oblong, 4-8 mm. long; glumes oblong, pale 

 green, 3-nerved, with short, more or less recurved tips. Wet soil: 111. — La. — 

 Calif.— Wash. Plain. Jl-0. 



4. C. Fendlerianus Boeckel. Stem slender, 3-5 dm. high, triangular above, 

 scabrous on the angles; leaves flat, 2-6 mm. wide, scabrous on the margins; 

 bracts 3-6, the longer much exceeding the inflorescence; spikelets spicate, in 

 simple, often subcapitate, few-rayed umbels, oblong to cylindric, 5-15 mm. long, 

 2-3 mm. thick; glumes orbicular-ovate, striate, pale greenish bro^\■n with brown 

 or yellow margins. Wet places: w Tex. — Colo, — Ariz.; n Alex. Plain — Sub- 

 mont. Jl-S. 



5. C. Schweinitzii Torr. Stems tufted, rough, 3-7 dm. high; leaves 2-5 

 mm. witle, rough-margined; bracts 3-7, erect; spikelets spicate, in S-Q-raj^ed 

 umbels, flat, linear-oblong, 6-12-flowered, 8-16 mm. long; glumes convex, light ' 



