CYPERACEAE. l6l 



Spikelets 3-12 mm. long, densely capitate or spicate. 



Spikelets all reflexed ; culms rough. 25. C. retrofractus. 



Spikelets spreading or only the lower reflexed ; culms smooth. 

 Heads oblong or cylindric. 



Spikelets 6-10 mm. long, the lower reflexed. 



26. C. Lancastriensis^ 

 Spikelets 3-4 mm. long, the lower spreading. 



27. C. cylindricus. 

 Heads globose. 28. C. o->>ularis. 



Achene oblong or obovoid, about twice as long as thick. 

 Rachis wingless or very narrowly winged. 



Scales pale green, membranous, dull. 29. C. filiculmis. 



Scales chestnut-brown, shining. 30. C. Houghtont. 



Rachis-wings membranous, broad. 



Scales firm, not appressed ; spikelets loosely capitate. 



31. C. Grayi. 

 Scales thin, closely appressed ; spikelets densely capitate. 



32. C. echinatus. 



1. Cyperus flavescens L. YELLOW CYPERUS. (I. F. f. 543.) Annual; culms 

 very slender, tufted, leafy below, 7-30 cm. tall, mostly longer than the leaves. 

 Leaves 2-3 mm. wide, smooth, the longer usually exceeding the inflorescence ; 

 clusters terminal and sessile, or on 1-4 short rays ; spikelets in 3's-6's, linear, 

 subacute, yellow, many-flowered, flat, 8-18 mm. long, 3-4 mm. broad; scales 

 ovate, obtuse, I -nerved, appressed. twice as long as the orbicular-obovate black 

 obtuse lenticular shining achene ; stamens 3 ; style deeply 2-cleft ; superficial cells 

 of the achene oblong. In marshy ground, Me. to Mich., Fla. and Mex. Also in 

 the Old World. Aug. -Oct. 



2. Cyperus diandrus Torr. Low CYPERUS. (I. F. f. 544.) Annual; culms 

 tufted, slender, 5-40 cm. tall. Leaves about 2 mm. wide, those of the involucre 

 usually 3; clusters sessile and terminal, or at the ends of 1-3 rays; spikelets 8-18 

 mm. long, linear-oblong, acute, flat, many-flowered ; scales ovate, green, brown, 

 or with brown margins, obtuse, l-nerved, appressed, membranous, dull; stamens 

 2 or 3; style 2-cleft, its branches much exserted; achene lenticular, oblong, gray, 

 not shining, one-half as long as the scale, its superficial cells quadrate, about as 

 long as wide. In marshy places. N. B. to Minn., S. Car. and Kans. Aug.-Oct. 



3. Cyperus rivularis Kunth. SHINING CYPERUS. (I. F. f. 545.) Similar to 

 the preceding species, culms slender, tufted. Umbel usually simple; spikelets 

 linear or linear-oblong, acutish, 8-20 mm. long; scales green or dark brown, or 

 with brown margins, appressed, firm, subcoriaceous, shining, obtuse; stamens 

 mostly 3; style 2-cleft, scarcely exserted; achene oblong or oblong-obovate, len- 

 ticular, somewhat pointed, dull, its superficial cells quadrate. In wet soil, espe- 

 cially along streams and ponds, Me. to S. Ont., Mich, and Neb., Va., N. C. and 

 Mo. Aug.-Oct 



4. Cyperus Nuttallii Eddy. NUTTALL'S CYPERUS. (I. F. f. 546.) Annual; 

 culms slender, tufted, equalling or longer than the leaves. Leaves of the involucre 

 3-5, spreading, the larger often 12 cm. long; umbel 3 7-rayed; spikelets rather 

 loosely clustered, linear, very acute, flat, spreading, 13 cm. long, 23 mm. wide; 

 scales yellowish-brown with a green keel, oblong, acute; stamens 2; style 2-cleft, 

 its branches somewhat exserted; achene lenticular, narrowly obovate, obtuse or 

 truncate, dull, light brown, one-third to one-half as long as the scale, its superficial 

 cells quadrate. Salt marshes, Me. to Miss. Aug.-Oct. 



5- Cyperus microdontus Torr. COAST CYPERUS. (I. F. f. 547.) Annual; 

 similar to the preceding species; culms very slender, tufted, sometimes 0.5 m. high. 

 Leaves about 2 mm. wide, those of the involucre much elongated; umbel commonly 

 simple, sessile, capitate, or I 6-rayed; spikelets linear, acute, 6-18 mm. long, less 

 than 2 mm. wide, yellowish-brown; scales ovate, acute, thin; style 2-cleft, its 

 branches much exserted; achene lenticular, linear-oblong, short-pointed, light 

 blown, one-half as long as the scale, its superficial cells quadrate. In wet soil, on 

 or near the coast, Va. to Fla. and Tex. Aug.-Oct. 



6. Cyperus flavicomus Michx. ELEGANT CYPERUS. (I. F. f. 548.) Annual; 

 culms 0.3-1 m. tall, leafy below. Leaves 4-6 mm. wide, those of the involucre 

 3-8, the longer ones- much exceeding the inflorescence; umbels few-several-rayed; 



