2 



PREFACE 



granted by Professor Wille of Christiania. Mr. Karl Strom supple- 

 mented these collections with his own from other Norwegian lakes 

 and made determinations of certain puzzling forms. I am under 

 especial obligations to Dr. O. Borge of Stockholm, Sweden, and to 

 Charles Bullard of Cambridge, Massachusetts. Dr. Borge devoted 

 a large portion of his time during my stay in Stockholm to checking 

 over the determination of a majority of the Wisconsin Desmids and 

 comparing them with his extensive iconography. Besides demon- 

 strating a method of making mounts of individual Desmids, Mr. 

 Bullard has allowed me to consult his preparations and his unpub- 

 lished drawings of American Desmidiaceae and has placed at my 

 disposal his wide experience with the group. Although the investi- 

 gators named above have given assistance in determination of doubt- 

 ful species, I assume full responsibility for all errors of determination. 



The University of Wisconsin, 

 Department of Botany, 

 March, 1922. 



