CHAPTER XVII 

 LIFE HISTORIES OF ALG& 



206. The Main Groups of Algae. The plants that rank 

 next in the scale of life below the liverworts are the Algae. 

 On the basis of color they fall naturally into four main 

 groups or phyla, as follows: 



1. Blue-green algae (Cyanophyceae) 



2. Green algae (Chlorophyceae) 



3. Brown algae (Phaeophyceae) 



4. Red algae (Rhodophyceae) 



Associated with these differences in color are certain dif- 

 ferences of structure, which also lead to a similar grouping. 

 In recent years the above four groups have been further 

 subdivided into seven phyla, on the basis of other char- 

 acters than color. A study of one of the commoner brown 

 algae ; Ascophyllum, will serve to illustrate many funda- 

 mental facts about the algae in general. 



ASCOPHYLLUM 



207. Habitat of Ascophyllum. This plant, and the 

 closely related Fucus, have become familiar in inland 

 markets, because they are commonly used as a packing in 

 the shipment of crabs and other kinds of "shell fish." 

 Ascophyllum and Fucus, and their near relatives, consti- 

 tute the family Fucacea. For the most part they are 

 inhabitants of the ocean, or of brackish water, or, in rare 

 cases, of fresh water. The two genera mentioned are 



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