CONTENTS. 



PAGE. 



Explanation of Plate, 7 



Value of of Mikrons in parts of an inch, 9 



Introduction, 11 



Key to the Classes of the Fresh-water AlgK, 25 



Key to the Genera of the Fresh-water Algae, 25 



Key to the Species of the Fresh-water Algae, 37 



Key to the Genera of the Desmidiese, 78 



Key to the Species of the Desmidiese, 80 



Glossary, in 



Index, 115 



