CONTENTS 



Page 



Abstract 1 



Introduction 1 



Acknowledgment 3 



Taxonomic key to the identification of commonly occurring and dominant genera 



of algae observed in the phytoplankton of the United States 9 



Descriptions of the genera 14 



Chlorophyta 14 



Actinastrum 14 



Ankistrodesmus 16 



Chlamydomonas 18 



Chodatella 20 



Coelastrum 22 



Cosmarium 24 



Crucigenia 26 



Dictyosphaerium 28 



Golenkinia 30 



Kirchneriella 32 



Micractinium 34 



Oocystis 36 



Pandorina 38 



Pediastrum 40 



Scenedesmus 42 



Schroederia 44 



Selenastrum 46 



Sphaerocystis 48 



Tetraedron 50 



Tetrastrum 52 



Euglenophyta 54 



Euglena 54 



Trachelomonas 56 



Chrysophyta 58 



Achnanthes 58 



Amphora 60 



Asterionella 62 



Cocconeis 64 



Cyclotella 66 



Cymbella 68 



Diatoma 70 



Dinobryon 72 



Epithemia 74 



Eunotia 76 



Fragilaria 78 



Gomphonema 80 



Gyrosigma 82 



in 



