CYPERACEAE. 165 



Cyperus strigbsus compositus Britton. Umbel very compound; heads cylindric; 

 spikelets 6-12 mm. long, 4-6-flowered. S. N. Y. and Penn. to Ala. and Iowa. 



Cyperus strig6sus robiistior Kunth. Umbel compound; spikelets 16-25 mm. long, 

 10-25-flowered. Range of the type. 



24. Cyperus refractus Engelm. Reflexed Cyperus. (I. F. f. 566.) Peren- 

 nial by tuber-like corms; culm stout, smooth, 0.3-0.9 m. tall. Leaves 5-8 mm. 

 vide, rough -margined, elongated; umbel 6-13-rayed, usually compound, the longer 

 rays sometimes 20 cm. long, their sheaths terminating in I or 2 short teeth ; in- 

 volucels setaceous; raylets filiform; spikelets very narrowly linear, loosely spicate, 

 acute, flatfish, 1-2.5 cm. long, 1 mm. thick, 3-6-flowered, the upper spreading, 

 the lower reflexed ; scales yellowish-green, oblong-lanceolate, obtuse, closely ap- 

 pressed, 9-11-nerved, thin; stamens 3; style 3 -cleft, its branches much exserted ; 

 achene narrowly linear, obtuse, apiculate, about 5 times as long as thick, and one- 

 half as long as the scale. In dry fields, N. J. to N. Car. and Mo. July-Sept. 



25. Cyperus retrofractus (L.) Torr. Rough Cyperus. (I. F. f. 567.) Per- 

 ennial by tuber-like corms; culm rough -puberulent, at least above, mostly longer 

 than the puberulent leaves. Leaves 3-5 mm. wide, those of the involucre 4-7, the 

 longer not greatly exceeding the umbel, sometimes shorter ; umbel simple ; rays 

 5-15 cm. long, their sheaths 2-toothed; heads oblong or obovoid; spikelets linear- 

 subulate, 6-12 mm. long, about 1 mm. thick, 1-2 -flowered, all soon strongly re- 

 flexed. separating from the axis at maturity; flowering scales lanceolate, acute, the 

 upper one subulate, all strongly several-nerved ; stamens 3 ; style 3-cleft ; achene 

 linear. 3-angled, obtuse, apiculate, two-thirds as long as the scale. In dry sandy 



I soil, S. N. J. to Fla., west to Ky., Ark. and Tex. July-Sept. 



26. Cyperus Lancastriensis Porter. Lancaster Cyperus. (I. F. f. 568.) 

 I Perennial by ovoid or oblong corms; culm slender, smooth, mostly longer than the 

 j leaves, 0.3-0.8 m. tall. Leaves 4-6 mm. wide, those of the involucre 4-7, the longer 

 jmuch exceeding the inflorescence ; umbel simple, 5-9-rayed, the longer rays 5-10 



cm. long, their sheaths nearly truncate; heads oval, obtuse, 1-2.5 cm. long; spike- 

 lets densely clustered, 8-10 mm. long, linear, subterete, 2-4-flowered, the lower 

 reflexed, the middle ones spreading, all separating from the axis at maturity; scales 

 green, strongly several-nerved, the flowering ones lanceolate, subacute; stamens 3; 

 style 3-cleft; achene linear, obtuse, apiculate, 2-3 times as long as thick, two-thirds 

 lis long as the scale. In dry fields, N. J. and Penn. to Va. and Ala. July-Sept. 



27. Cyperus cylindricus (Ell.) Britton. Pine-barren Cyperus. (I. F. f. 

 '569.) Perennial by small hard corms ; culms smooth, usually tufted, 1-5 dm. 



ill. longer than the leaves. Leaves 2-3 mm. wide, the longer ones of the involucre 

 nuch exceeding the umbel ; umbel simple, the rays short, or the longer 2-7 cm. 

 oog, the sheaths 2-toothed; heads very dense, cylindric, 6-12 mm. long, 4-8 mm. 



neter; spikelets 3-4 mm. long, flattish, i-2-flowered, spreading or the lower 

 eflexed ; scales green, oblong ; rachis winged ; stamens 3 ; style 3-cleft ; achene 



■( .blong, 3-angled, apiculate, slightly more than one-half as long as the scale. 

 n sandy pine barrens and on the sea shore, S. N. Y. to Fla., west to Tex., mostly 

 -tear the coast. July -Sept. 



28. Cyperus oviilaris (Michx.) Torr. Globose Cyperus. (I. F. f. 570.) 

 perennial by hard tuber-like corms ; culm usually strict, smooth, 0.2-0.8 m. tall, 



mger than the leaves. Leaves smooth, 4-6 mm. wide, the longer ones of the in- 

 lolucre much exceeding the umbel ; umbel simple, few-rayed ; sheath of the rays 

 te or slightly toothed; heads globose or sometimes a little longer than thick, 

 -14 mm. in diameter, very dense, the spikelets radiating in all directions ; spike- 

 .ts 4-7 mm. long, usually 3 -flowered, separating from the axis at maturity; rachis 

 inged; scales ovate or ovate-lanceolate, obtuse or subacute, green, strongly several- 

 erved; stamens 3; style 3-cleft; achene linear-oblong, 3-angled, 2-3 times as long 

 thick. In dry fields and on hills, S. N. Y. to Fla., west to 111., Kans. and Tex. 

 lly-Sept. 



29. Cyperus filiculmis Vahl. Slender Cyperus. (I. F. f. 571.) Perennial 

 Y hard oblong corms; culm smooth, slender or almost filiform, ascending or re- 

 ined, 1.5-4.5 dm. long, usually longer than the rough-margined leaves. Leaves 

 -4 mm. wide, keeled ; spikelets densely clustered in 1-7 globose heads, linear, 

 :ute, 5-1 1 -flowered, subterete or compressed, 5-12 mm. long, 



