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. ovularis. 



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

 Rachis wingless or very narrowly winged. 



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



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



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, 8-1 8 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, I -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. Out., 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, 1-3 cm. long, 2-3 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 veiy 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 

 brown, 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; 



