ALG^E. 



are Thallophytes of a simple or complex structure, and 

 are of a green, yellow-green, blue-green, red or brown colour. 

 Most of them live entirely submerged in water and the major 

 portion of them inhabit the sea. They are found floating freely at 

 the surface, attached to stones, or as in a large number of the fresh- 

 water forms, adhering in gelatinous masses to the submerged 

 portions of more highly organised aquatic plants. A few prefer 

 damp situations in which they do not become immersed at all, or 

 only periodically become covered with water. 



They are mainly distinguished from the Fungi by the presence 

 of chlorophyll and consequently by their mode of life. Even in 

 the red, brown, and blue-green Alga3 chlorophyll is present, but 

 the green colour is masked by the presence of other colouring- 

 matters. As the colouring-matter is usually the same throughout 

 large groups of these plants which agree in other characters, 

 particularly in the method of reproduction, they are classified as 

 follows : 



Class 1. Rhodophycece (or the Red Algae), containing a 

 reddish colouring-matter known as phycoerythrin. 

 Mostly marine. 



Class 2. Phceophycece (or the Brown Algae), containing a 

 brown colouring-matter known as phycophasin. 

 Mostly marine. 



Class 3. Chlorophycece (or the Green Alga3), containing only 

 the green colouring-matter known as chloro- 

 phyll. Very largely freshwater plants. The 

 stored product of assimilation is in almost all 

 cases starch. 



