12. Cyperus diflFormis L. Fig. 222. 



Annual sedge with fibrous roots and cespitose culms; culms smooth, 15-50 cm. 

 tall; leaves 2 to 4 on a culm, about as long as the culm, 1-4 mm. wide, scaberulous 

 on margins near apex; involucral leaves 2 or 3, unequal in length; inflorescence 

 umbellate, the globose heads of spikelets sessile or on rays to 7 cm. long; spikelets 

 linear, obtuse, subcompressed, 4-8 mm. long; rachis straight, unwinged; scales 

 roundish, obtuse, 0.6-0.8 mm. long, membranous, green with brown sides, 

 readily deciduous; stamens 1 or 2; achene trigonous, obovate, minutely mucronu- 

 late, 0.5 mm. long, pale-greenish-brown, the surface minutely cellular. 



Common weed in rice fields, Okla. (LeFlore Co.) and Ariz. (Mohave Co.); 

 Okla., N.M., Ariz., Calif, and Mex., nat. of Asia. 



13. Cyperus aristatus Rottb. Fig. 223. 



Tufted annual with persistent coffee-and-chicory or curry powder odor (like 

 Ulmus rubra, Phyllanthus ericoides, Gnaphalium obtusifolium, flowers of Bomba- 

 caceae, etc.); culms 1-20 cm. long, the longer leaves often equaling or surpassing 

 them; inflorescence of 1 to 3 heads, essentially sessile at the summit, often with 

 1 to 6 additional shortly peduncled ones; bracts 2 to 4, the longer ones far- 

 surpassing the inflorescence, often ascending; heads 5-20 mm. thick, often slightly 

 prolate, with 2 to 50 spikelets; spikelets 4-14 mm. long, 2-3 mm. broad, about 

 0.5 mm. thick, laterally compressed, straight, with 5 to 30 scales, brown to yellow- 

 brown to tawny-brown, the axis essentially wingless, at maturity eventually decidu- 

 ous as a unit from the head axis; scales deciduous either before or after fall of 

 the spikelet axis, 2-2.5 mm. long, about in the distal third the length being a 

 very slender sharp acuminate-subulate prominently recurved tip, with 7 or 9 

 evenly distributed nerves; stamen 1; achene 0.7-1 mm. long, 0.2-0.5 mm. broad, 

 from nearly linear-oblong to obovoid, dark-brown. C. inflexus Muhl. 



In wet soils, on edge of lakes and ponds and marshes, in Okla. (Stephens, 

 Mcintosh, Alfalfa, LeFlore and Johnston cos.) to Ariz. (Navajo and Coconino, s. 

 to Cochise, Santa Cruz and Pima cos.) throughout Tex. (except Plains Country), 

 scattered, spring-early winter; nearly cosmopolitan in temp, and trop. areas. 



In extreme south coastal Texas occurs the var. Runyonii O'NeiU with the 

 achenes at the extremes of greatest length and narrowness allowed here. 



14. Cyperus amabilis Vahl var. macrostachyus (Boeck.) Kiikenth. 



Rachilla articulated with the rachis at the base, wingless; bracts 3 to 6, scarcely 

 if at all exceeding the inflorescence; rays to 10; spikelets 10-18 mm. long, 

 1.5-2.5 mm. wide, lustrous, reddish-brown, digitate-radiate in heads; scales 3- 

 nerved, aristate, 1.5-2.7 mm. long; achene trigonous; style branches 3; stamen 

 1 (rarely 2). 



Ariz. (Santa Cruz Co.) ; to S.A. 



15. Cyperus seslerioides H.B.K. 



Tufted perennial forming tough fibrous black mats (bulblike bases connected 

 by extremely short branching rhizomes); culms 10-25 cm. long, erect, basally 

 about 1 mm. thick, apically about 0.5 mm. thick; leaves 2 or 3 per culm, basal, 

 1-2 mm. broad; inflorescence (excluding bracts) 6-12 mm. long, contracted into 

 a single densely flowered several-lobed subhemispheric whitish or pallid-brownish 

 ( Dichromena-Uke) head; bracts 3 or 4, linear, 2 to 10 times as long as the head, 

 spreading or reflexed; spikelets 3-7 mm. long, 2-2.5 mm. broad, compressed, 

 with 10 to 20 flowers, the axis wingless and persistent as a unit after the scales 

 have fallen; scales 1.5-2.7 mm. long, 1.1-1.6 mm. broad, membranous, 3-nerved, 

 acuminate, sharp; stamen 1; achene 0.7-1 mm. long and nearly as thick, sub- 

 orbicular, strongly 3-angled with concave sides, maturing to a very dark-brown. 



435 



