Investigations on the algal flora upon 

 which this book is based were first made 

 as part of the Wisconsin Geological and 

 Natural History Survey. Circumstances 

 necessitated the abandonment of plans 

 to publish in the Wisconsin Survey 

 Series. The Cranbrook Institute of Sci- 

 ence then cooperated in bringing out the 

 book after the material was expanded to 

 include the algae of Michigan. Grateful 

 acknowledgment is made to the Uni- 

 versity of Wisconsin and to the Trustees 

 of the Cranbrook Institute of Science 

 for the release of zinc cuts, and for the 

 riehts to revise and republish this vol- 

 ume. 



G. W. Prescott November, 1961 



Department of Botany 

 Michigan State University 



