VI CONTENTS 



Page 



Figures 55, 56. Photomicrographs of: 



55. Lyngbya 123 



56. Oscillatoria 125 



57, 58. Drawings of: 



57. Phormidium 127 



58. Raphidiopsis 129 



TABLES 



Page 



Table 1. List of algal genera observed in the phytoplankton of the United 



States 4 



2. Commonly occurring genera of algae observed in the phytoplankton of 



the United States 6 



3. Dominant genera of algae observed in the phytoplankton of the United 



States 7 



4. Taxonomic groupings of commonly occurring and dominant genera of 



algae of the United States 8 



A Note on the Illustrations in this Book: 



The drawings of alga genera shown in figures 

 1, 2, 3, 4, 6, 7, 9, 10, 13, 16, 17, 18, 19. 

 20, 32, 43, 46, 47, 48, 53, 54, 57, 58 were 

 redrawn from originals in Smith, 1950, pub- 

 lished by the McGraw-Hill Book Company and 

 are shown here under license from McGraw-Hill. 

 The scanning electron-micrographs were made 

 by Bruce W. Lium and to*. Thomas Shoaf III, 

 U.S. Geological Survey. The photomicrographs 

 were made by the author. 



