CHAPTER VI 



57. General characters. Algae are the simplest green 

 plants, and it is thought that the higher plants have been 

 derived from them. They grow in the water, and hence 

 their habits are adapted to a water environment. They are 

 often called seaweeds, but although they are very abundant 

 along seacoasts they are also abundant in fresh waters. 

 Some of them are so small that the individual bodies are 

 visible only under the microscope, and there is every grada- 

 tion in size from this to the bulky bodies of certain marine 

 forms. 



Although all Algae contain chlorophyll, and hence are 

 able to make their own food ( 14), they do not all appear 

 green; for in many of them the chlorophyll is obscured by 

 other coloring matters. The four great groups of Algae are 

 named from the general color of their bodies, although 

 it must be remembered that they all contain chlorophyll, 

 which makes them independent. Some representatives of 

 each group are selected for description, but they or others 

 like them must be examined before any real knowledge of 

 them can be obtained. 



1. BLUE-GREEN ALG^E (Cyanophycece) 



58. Gloeocapsa. These plants form blue-green or olive- 

 green patches on damp tree trunks, rocks, walls, etc. By 

 means of the microscope these patches are seen to be com- 



