230 



ESSENTIALS OF BOTANY 



Under the class green algae are grouped plants of many 

 degrees of complexity in their organization and mode 

 of reproduction. Complex cells like that of Vaucheria 

 are not uncommon, and other genera have cell 

 colonies of net-like form or take on thread-like 

 shapes, like (Edogonium, or leaf-like or disk-like 

 shapes, like the sea-lettuce or like Coleochcete 

 (Fig. 220). 



Highest in structure of all the green algse are 

 the stoneworts (Figs. 158, 159). 



In green algee the chlorophyll is not disguised 

 by the presence of other coloring material. Re- 

 production is of many kinds, — often, as in 

 Pleurococcus, wholly asexual, sometimes sexual, 

 by the fusion of like gametes, and sometimes, 

 as in (Edogonium and Vaucheria, sexual by 

 the fusion of unlike gametes. 



FUCUS, ONE OF THE BROWN ALG^ 



295. Occurrence. — Fucus vesiculosus, 

 or bladder wrack, one of the commonest 

 of the so-called rockweeds, is found grow- 

 er •' „ ■„\ t ^ ing usually on rocks between high- and 

 (Laminaria) , one a j o 



of the Brown low- water marks, along the northern coasts 



Algae. (Much pf l^oth hemispheres. It is often very 



rGducGci ^ . ■ 



luxuriant, completely covering the sur- 

 face of the rocks to which it clings ; and is extremely 

 tough, resisting the most violent beating of the waves. It 

 is easily recognized by the ribbon-like form (Fig. 161) with 

 frequent branching and the numerous air-bladders which 

 buoy it up in the water. 



