vi FRESH-WATER ALGJE OF THE UNITED STATES. 



present volume. Many genera are still preserved which have liter- 

 ally no worth, but they serve for reference. They will be noticed 

 more fully under their various generic characters. 



We have added nine additional plates of Desmids illustrating one 

 hundred or more species and varieties mostly new to the United 

 States. 



In our ability to make this large addition we have had the kind 

 co-operation of collectors and workers in various parts of the coun- 

 try. Rev. H. D. Kitchel and his son H. S. Kitchel continued with us ; 

 Miss E. Butler, of Minneapolis, Minn., made some good finds. Geo. 

 B. Twitchel has been operating in a new field, Ohio. Professor F. 

 W. Cregin is active in Kansas ; W. N. Hastings is working up the 

 vicinity of Rochester, N. H., and G. M. Rafter, that of Rochester, 

 N. Y. ; Mrs. Hanson and Miss M. S. Haggin, of San Francisco, Cal., 

 have during the past Summer (1886) commenced opening up the Des- 

 midial resources of that State ; as pioneers they have done a good 

 work. G. v. Lagerheim, of Stockholm, Sweden, has published a list of 

 American Desmids, partly from the island of Cuba, but mainly from 

 Massachusetts. Mr. W. B. Turner, of England, also added a few 

 American forms from Nova Scotia and the United States, all duly 

 noticed under their generic heads. 



FRANCIS WOLLE. 



BETHLEHEM, PENNSYLVANIA, 

 DECEMBER, 1886. 



