IOWA ACADEMY OF SCIENCES. 139 



Equiscfuui^ffurlxfllrL. Sp. PI. 1062. 1758. 



This was much more frequent formerly than now. It 

 occurs in the lake region which occupies the section of 

 Towa from Ames north to the Minnesota line. 



Iowa: Ames — Hitchcock, Bessci/. 



Equisetum hijcwale L. Sp. PI. 1062. 1753. 



This species fruits much later than E. arvense, and inhab- 

 its the same general places. 



Iowa: Creston — Stewart; Ames — Hitc/icock. 



Equisetum robustu)!/ A. Br. Engelmann. Amer. Journ. Sci, 

 46:88. 1844. 



This species also fruits much later than E. arvense, and' 

 is common in rich soils. 



Iow^a: Le Claire — Rolfs; Ames — Besscy ; Muscatine — 

 Reppert; Grinnell — Miss Williams. 



Equisetum laevigaium A. Br. Engelm. Amer. Journ. Sci. 64 : 

 78. 1844. 



Iowa: Ames— il//s.s Adams, Hitchcock; Emmet County — 

 Cratti/. 



ORDER FILICES. 

 Sub-order Polypodiaceae. 



TRIBE POLYPODIEAE. 



Pobf podium vuhjarc L. Sp. PI. 1085. 1753. 



So far as we are aware this fern occurs only on sand- 

 stone ledges of Carboniferous formation in central and 

 southeastern Iowa. In Wisconsin it is found on the 

 Potsdam sandstone, and is usually associated with 

 Fhegopteris Dryopteris, Vaccinium Pennsylvanicum^ Ly co- 

 podium lucidulum, Woodsia ohfusa, occasionally Woodsia 

 ilvcnsis, Pellaea (jracilis and Sullicantia Ohionis. On 

 the Iowa River near Steamboat Rock it is found with 

 Aspidum marginale, Phegopteris Dryopteris, Woodsia ohtusa, 



