ALGJE. 



371 



D. The Groups of Alga. — The algae are divided into 

 four groups. The first two are mainly fresh-water forms; 

 the others are mainly salt-water or marine forms. 



(1) Cyanophycea. 



— The word means 

 blue alga. They are 

 so called because a 

 blue pigment (color- 

 ing matter) occurs 

 along with the green 

 chlorophyll. Oscil- 

 latoria, No sloe, and 

 Rivularia belong to 

 this group. 



(2) Chlorophycece. 



— The word means 

 green alga. Most of 

 the common fresh- 

 water algae belong 

 to this group, and 

 forms like certain 

 members of this 

 group are thought 

 to be the remote 



Fig. 168.. — Spirogyra. ancestors of the Fig. 169. — Spirogyra. Por- 



Portion of a young y.:„y. pr 1 1 tions of adjacent filaments 



filament showing the ° " ' showing the sex process 



large spiral chloro- (3) PhcBOphyceOS. as described in the con- 



plast. _ The word means text. 



brown alga. Although chlorophyll is present, other pig- 

 ments which are brown and yellow obscure it and deter- 

 mine the color of the plant. These plants are abundant 

 along all seacoasts. They grow anchored by holdfasts 



