Lyon: the pteridophytes of Minnesota. 247 



Family ISOETACEjE. 



Isoetes lacustris L. Sp. PL uoo. 1753. Lake quillwort. 



Probably occurs quite commonly in lakes of northern Minne- 

 sota. Not previously reported from the state. 



Herb. : MacMillan, Brand and Lyon, Devil's Track lake 

 and Hungry Jack lake, Cook county. 



Isoetes tuckermani A. Br. ; A. Gray, Man. Ed. 5, 676. 1867. 



Known to occur in but one lake. Not previously reported 

 from Minnesota. 



Herb. : Wheeler, Echo lake. 



Isoetes echinospora braunii (Durieu) Engelm. ; A. Gray, 

 Man. Ed. 5, 676. 1867. 



With Isoetes lacustris, but more frequent. 



Herb. : Arthur, Vermilion lake ; MacMillan, Brand and Lyon. 

 Many specimens from lakes of Cook county. 



Isoetes echinospora boottii (A. Br.) Engelm. A. Gray, Man. 

 Ed. 5, 676. 1867. With Isoetes tuckermani. 

 Not previously reported from the state. 

 Herb. : Wheeler, Echo lake. 

 The species of Isoetes were determined by A. A. Eaton. 



Order EQUISETALES. 

 Family EQUISETACE^E. 



Equisetum arvense L. Sp. PI. 1061. 1753. Field horsetail. 

 Common in sandy soil throughout the state. 

 Herb. : Well represented by specimens. 



Equisetum pratense Ehrh. Hanov. Mag. 138. 1784. Thicket 

 horsetail. 

 Rare, south. 

 Herb. : Lyon, Winnebago valley, Houston Co. 



Equisetum sylvaticum L. Sp. PI. 1061. 1753. Wood horse- 

 tail. 

 Throughout the state, preferring light soil in moist woods and 

 thickets. 



Equisetum fluviatile L. Sp. PI. 1062. 1753. Swamp horse- 

 tail. 

 In swamps and along borders of lakes and streams through- 

 out the state. 



Herb. : Many specimens. 



