ALG^ 



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, 

 (i) CyanophycecE. 



— The word means 

 blvs algcB. They are 

 so called because a 

 blue pigment (color- 

 ing matter) occurs 

 along with the green 

 chlorophyll. Oscil- 

 latoria, Nostoc, and 

 Rivulana belong to 

 this group. 



(2) ChlorophycecB. 



— 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 



of the Fig. 169. — Spirogyra. Por- 



higher plants. 1°"'.°^ ^f^'^'"' ^'^""^'^ 



° -t^ showing the sex process 



(3) PhceOphyceCB. as described in the con- 



— The word means '^'''• 



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 



P-«5a 



¥vi.i(>&.— Spirogyra. anCCStorS 

 Portion of a young 

 filament showing the 

 large spiral chloro- 

 plast. 



