236 CYPHRACEAE. 



2. Cyperus diandrus Torr. Low Cyperus. (Fig. 544.) 



Cyperus diandrus Torr. Cat. PI. N. Y. 90. 1819. 



Cyperus diandrus elongat us Britton, Bull. Torr. Club, 

 19: 226. 1892. 



Annual, culms tufted, slender, 2 / -i5 / tall. Leaves 

 about \" wide, those of the involucre usually 3, 

 the longer much exceeding the spikelets; clusters 

 sessile and terminal, or at the ends of 1-3 rays; 

 spikelets 4 // -9 // 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, subacute, gray, not shining, one-half as 

 long as the scale, its superficial cells quadrate, 

 about as long as wide. 



In marshy places New Brunswick to Minnesota, 

 south to South Carolina and Kansas. Aug.-Oct. 



The var. elongatus is only a form with longer spike- 

 lets, found in southern Xew York and New Jersey. 



3. Cyperus rivularis Kunth. Shining 

 Cyperus. (Fig. 545.) 



Cyperus rivularis Kunth, Enum. 2: 6. 1837. 



Cyperus diandrus var. (?) castaneus Torr. Ann. Lye. 

 N. Y. 3: 252. 1836. Not C. castaneus Willd. 1798. 



Similar to the preceding species, culms slender, 

 tufted, 4 / -i5 / tall. Umbel usually simple; spikelets 

 linear or linear- oblong, acutish, 4 // -io // 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, lenticular, some- 

 what pointed, dull, its superficial cells quadrate. 



In wet soil, especially along streams and ponds, 

 Maine to southern Ontario and Michigan, south to 

 Virginia and Missouri. Aug.-Oct. 



4. Cyperus Nuttallii Eddy. Nuttall's Cyperus. (Fig. 546.) 



Cyperus Xuitallii Eddy; Spreng. Neue Entd. i: 240. 

 "1820. 



Annual, culms slender, tufted, 4 / -i8 / tall, equal- 

 ling or often longer than the leaves. Leaves of the 

 involucre 3-5, spreading, the larger often 5' long; 

 umbel simple or slightly compound, 3-7-rayed; 

 spikelets rather loosely clustered, linear, very acute, 

 flat, spreading, J^'-i,^' long, i"-i#" wide; scales 

 yellowish-brown with a green keel, oblong, acute, 

 rather loosely spreading at maturity; 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, Maine to Mississippi. Aug.-Oct. 



