floras, and in some monographic works. I have chosen to use famihar 

 names of long standing unless changes in such names have been 

 adopted in generally used monographic studies which are easily 

 obtainable for reference. For the most part I have followed the taxo- 

 nomy and nomenclature suggested by Pascher (1931) and employed 

 by Gilbert M. Smith (1938). The structure of the cell wall, the pig- 

 mentation, and the nature of food reserves have been used to unite 

 the Heterokontae, the Chrysophyceae, and the Bacillariophyceae to 

 form what seems to be a very natural division, the Chrysophyta. 

 This rearrangement reduces the number of groups previously recog- 

 nized among the algae. The colorless relatives of the motile algae 

 are not included here. The taxonomic arrangement employed, then, 

 takes the following plan: 



Division I. 



Division II. 



Division III. 

 Division IV. 

 Division V. 



Division VI. 

 Division VII. 



Chlorophyta (Green Algae) 



A. Chlorophyceae 



B. Charophyceae 



Ghrysophyta ( Yellow-green Algae ) 



A. Xanthophyceae (Heterokontae) 



B. Chrysophyceae 



C. Bacillariophyceae (Diatoms) 



Euglenophyta ( Euglenoids ) 

 Chloromonadophyta ( Chloromonads ) 



Pyrrhophyta ( Yellow-brown Algae ) 



A. Cryptophyceae 



B. Desmokontae 



C. Dinophyceae 



Phaeophyta (Brown Algae, marine) 



Cyanophyta ( Blue-green Algae ) 



A. Myxophyceae 



B. Chlorobacteriaceae 



Division VIII. Rhodophyta ( Red Algae, mostly marine ) 



In the following pages certain terms will be used frequently when 

 reference is made to the type of existence most characteristic of 

 a species. The name plankton, of course, refers to organisms which 



[2] 



