154 NATURAL HISTORY BULLETIN. 



Subkingdom PTERIDOPHYTA Cohn. 



Class I GONOPTERIDES Willd., Sp. 

 PL, vol. V, p. xxxxi. 



Order EQUISETACE/E DC, Fl. Fr., vol. II, p. 580, 



(1805). 



Genus EQUISETUM £., Sp. PL, vol. II, p. 1061 



(1753). 



Equisetum arvexse L. 



Very common in sandy or clayey soil. The fertile stems 

 appear late in April or early in May, and are soon followed 

 by the sterile shoots. The herbarium contains a large 

 series of specimens, — mostly sterile. The following 

 counties are represented: Lee (July, 1895 and June, 1897) ; 

 Henry {J. H. Mills, no date); Muscatine (Oct., 1900); 

 Johnson (T. H. Macbride, May, 1880, fertile; Sktmek, 

 1882, fertile; fertile in April and sterile in May, 1891); 

 Linn (June, 1894); Winneshiek (T. E. Savage, May, 

 1899) ; Cerro Gordo (July, 1896, June, 1899) ; Hancock 

 (July, 1896); Winnebago (Sep., 1895); Emmet {R. I. 

 Cratty, no date, fertile; Shimek\ Aug., 1899); Lyon 

 (Aug., 1896) ; Webster (July, 1897) ; Dallas (July, 1897) ; 

 Adair (J. E. Gow, Aug., 1900); Pottawattamie (J. E. 

 Cameron, May, 1898). 



EQUISETUM fluviatile L. 



Not common, in swamps in the north-central part of 

 the state. This is E. Itmosuml,. Four counties are repre- 



