232 



ESSENTIALS OF BOTANY 



298. Discussion. — Fucus is a much more 

 highly developed plant than any of the blue- 

 green or green algae studied in the previous 

 sections. It has a complete cellular 

 structure and there is considerable 

 division of labor among the differ- 

 ent parts of the plant. It has a 

 special holdfast, air-bladders to 

 serve as floats,^ a tough midrib run- 

 ning lengthwise of the branches and 

 strengthening them, and expanded 

 margins of the 

 branches, afford- 

 ing ample 



Fig 



162. Eockweed 

 (Fucus) 



A, antheridia borne on branch- 

 ing bairs ( X 160) ; B, three 

 sperms from the same 

 (X 330). 



surface for 

 photosyn- 

 thetic work. 



The outer layers of cells are espe- 

 cially devoted to photosynthesis 

 and the inner ones to storage of 

 food material. The 

 brown cell-contents 

 contained in Fucus 

 and other brown algse 

 is highly efficient in 

 photosynthesis. 



There is no asexual 

 process of reproduc- 

 tion in Fucus. Sexual 

 reproduction is ac- 

 complished by the eggs and sperms becoming forced out 



1 These are absent in some species (Fig. 161) . 



Fig. 163. Rockweed (Fucus). 



A, oogonium, its contents dividing into eight 

 oospheres ( X 160) ; B, an oosphere, escaped, 

 surrounded by many sperms (X 160) . 



