302 American Midland Naturalist Monograph No. 7 



2. Spikelets 1 -flowered; inflorescence of 1-3 sessile heads; plants 

 with a strong sweet odor; moist ground, chiefly along streams 

 and ditches in Alexander, Jackson, Massac, Pope, and 



Wabash counties. Aug. -Oct. [Kyllinoa pumila Michx.] 



- ..-.C. densicaespitosus Mattf. & Kiikenth. 



2. Spikelets 5- to 35-flowered; inflorescence of 1 -several radiating 

 sessile spikelets and usually 1 -several rays; plants essentially 

 inodorous. 



3. Achenes black, nearly as broad as long, with transverse wrin- 

 kles; scales stramineous; wet ground, rare; Coles, Jackson, 

 Peoria, Pope, and Union counties. Aug.-Oct. [C. poae- 

 forniis Pursh] C. flavescens L. 



3. Achenes drab or gray, longer than broad, without transverse 

 wrinkles; scales usually suflfused with purple. 

 4. Styles cleft nearly to the base, persistent and conspicuously 

 exserted to 4 mm from the scales; marshy ground, or 

 margins of streams, local; Henry, Jackson, McHenry, 

 Mason, Peoria, St. Clair, and Winnebago counties. Aug.- 

 Oct. Low Cyperus C. diandrus Torr. 



4. Styles cleft to about the middle, early deciduous, included 

 or projecting to 2 mm from the .scales. 



5. Scales closely imbricate, strongly suflfused with purple; 

 moist ground, chiefly in the northern half of 111. Aug.- 

 Oct. Shining CVperus C. rivularis Kunth 



5. Scales with tips somewhat spreading, the spikelets ap- 

 pearing serrate, stramineous or purple only on the 

 margins; roadside ditch, De Soto, Jackson Co., /. 



W. Voigt 391 C. filicinus Vahl 



1. Achenes trigonous; stigmas 3. 



6. Scales with strongly reflexed acuminate tips; plants when dry 

 with fragrance of slippery elm; wet sandy soil along streams 

 or ditches throughout III. June-Sept. Awned Cyj^erus [C. in- 



flexus Muhl.J C. aristatus Rottb. 



6. Scales with tips either appressed or slightly spreading. 



7. Spikes s])herical or globose, with spikelets radiating in all 

 directions. 

 8. Scales appressed but with the tips shortly excurxed; spikes 

 to 8 mm across. 

 9. Perennial; achene narrowly lanceolate to linear; wet 



ground, rare; s. 111. July-Sept. Marsh Cyperus 



C. pseudovi'getus Steud. 



9. Annual; achene oblong; wet soil throughout 111. July- 



Sept C. acuminatus Torr. & Hook. 



8. Scales appressed to spreading, their tips straight; some of 

 the heads over 1 cm across. 



10. Scales appressed; spikelets 2- to 3-flowered; sandy 



borders of woods, or in old fields, chiefly in s. 111., 



