DEFINITIONS AND CLASSIFICATIONS 3 



III. Chrysophyta: yellow green to golden brown (xanthophylls 



and carotenes may mask chlorophylls) ; microscopic, mostly 

 unicellular; cell wall containing silica (e.g. diatoms) ; 

 largely freshwater, but many marine forms. 



IV. Pyrrophyta: yellow green to dark brown, xanthophylls pre- 



dominant; unicellular, motile; cellulose cell wall; many 

 marine forms. 

 V. Phaeophyta: olive green to dark brown; mostly macroscopic; 



cellulose and pectin cell wall; chiefly marine. 

 VI. Cyanophyta: blue green, phycocyanin; multicellular, but 

 usually microscopic; usually with gelatinous sheath; fresh 

 water, marine, some terrestrial. 

 VII. Rhodophyta: red, phycoerythrin; usually macroscopic; pectin 

 and cellulose cell wall; mostly marine. 



These seven Divisions include over a dozen Classes, about sixty 

 Orders, hundreds of Families, and thousands of Genera. However, only 

 a few score Genera are of sufficient historical or current medical impor- 

 tance to merit individual attention. Among these are the following: 



Chlorophyta: Chlorella, Scenedesmus, Viva, Nitella, Chlamy- 

 domonas, Polytomella, Prototheca, Stichococcus, Cladophora, 

 Oedogonium 



Euglenophyta: Euglena 



Chrysophyta: Nitzschia (diatoms) 



Pyrrophyta: Gymnodinium, Prorocentrum, Gonyaulax 



Phaeophyta: Macrocystis, Nereocystis, Laminaria, Fucus 



Cyanophyta: Chroococcus, Microcystis 



Rhodophyta: Porpbyra, Gelidium, Corralina, Chondrus, Rhody- 

 menia, Gigartina 



B. PLANKTON 



The interrelationships of plankton and algae can be simply illustrated 

 by the following schematic diagram: 



PLANKTON ALGAE 



Zooplankton Phytoplankton = Microscopic Algae Macroscopic Algae 



(Seaweed) 



