THE GEEEN ALG.E (C'HLOEOPHYCE.E) 



209 



that are the result of the union of similar motile gametes, 

 as in such green algae as llothrix and Cladopliora. Others, 

 of which Funis is a representative, reproduce by means of 

 oospores that are formed by the union of sperms and eggs.^ 



193. Uses by man. At one time the world's supi)ly of iodine 

 A\'as derived from the broA\'n algae ; now it can usually be pre- 

 pared more economically by chemical means. Soda was for- 

 merly secured from these plants, but chemical processes have 

 driven out the laborious methods 

 of securing that substance duectly 

 from plants. Gelatinous foods and 

 a sugar known as mannite are se- 

 cured from some species of brown 

 algae. In some coastal portions of 

 this country the farmers collect 

 and carry inland great quantities of 

 brown algae and spread them over 

 the cultivated land as a fertilizer. 



194. The red algae. The red 

 algae QRhodojjhiieea'') chiefly inhabit 

 deeper ^I'ater than do the brown 

 algae. The class is almost -wdiolly 

 confined to salt water, and the few 

 that do live hi fresh water do not 

 exhibit well the color characteristics of the class. <_^ue com- 

 mon fresh-water genus is Batracliosjiermum (Fig. 172). 



The marine forms of this group present most striking shapes 

 and colors. The}' are of different shades of red, varying from 

 the most brilliant to tliose that are dark and somber, while 

 some are a deep purple. C'hloroph}dl is present, but often is 

 completely obscured by the other colors. Sometimes all the 

 colors are obsciired by deposits of calcareous material upon 

 the plants. 



1 If desired to study further the details of reproduction of the brown 

 algae, see Coulter, Barnes, and Cowles, College Botany, Vol. I ; also Bergen 

 and Davis, Principles of Botany. 



Fi I i . 1 72 . X red alga (Batracho- 

 spfytmnn), which is fairly com- 

 mon in fresh waters 



Slightly magnified 



