Cyperus 



Cyperaceae 



185 



Cyperus flavescens L. 



flowered, all of the flowers maturing achenes ; achenes about 0.8 mm 



long and 0.5 mm wide 14. C. erythrorhizos. 



Scales mostly 2-2.5 mm long; flowers not very closely imbricated, the 



scales usually overlapping less than half their length; achenes 1-1.5 



mm long. 

 Plants with numerous fibrous roots, annual; culms with 1-4 leaves; 

 longest rays of umbel generally less than 5 cm long, rarely one or 

 more of them longer; spikelets usually dense, reddish brown, at 



maturity easily broken into segments below the flowers 



15. C. ferruginescens. 



Plants with numerous, scaly stolons that at length bear a tuber; culms 

 very leafy; leaves usually more than 4; longest rays of umbels 

 usually 4-13 cm long, only rarely all the rays shorter; spikelets 

 usually stramineous, sometimes light reddish brown, at maturity 

 not separating into segments below the flowers.. .16. C. esculentus. 



1. Cyperus flavescens L.* Map 341. Rare in northern Indiana and in- 

 frequent in the southern part in wet, sandy soil on bars in streams and 

 ditches, in the outlets of springs, along ditches, and about artificial ponds. 



N. Y. to Mich., southw. to Fla. and Mex. ; also in Cent. Amer. and the 

 Old World. 



2. Cyperus diandrus Torr. Map 342. Infrequent to rare. My specimens 

 were found in wet, sandy soil on the borders of lakes and sloughs and in 

 mucky soil in dried-up sloughs and in like habitats along streams. 



N. B. to Minn., southw. to S. C. and Kans. 



3. Cyperus rivularis Kunth. Map. 343. Rather frequent throughout 

 the state in wet, sandy or gravelly soil on the borders of lakes and streams 

 and on bars in ditches and small streams. 



Maine, s. Ont. to Minn., southw. to N. C. and Ark. 



X Cyperus Nieuwlandii Geise. (Cyperus flavescens X rivularis.) This 

 hybrid was described by Geise (Amer. Midland Nat. 15: 245-246. 1934). 

 She reports three specimens collected by Nieuwland in the vicinity of 

 Chain Lakes in St. Joseph County. I have seen these specimens and their 

 determination seems to be correct. 



* Fernald (Rhodora 41: 529-530. 1939) has shown that the true species belongs to 

 Eurasia and Africa and that the plant of eastern North America should be designated 

 as Cyperus flavescens L. var. poaeformis (Pursh) Fern. 



