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General Botany 



Macrocystis, which is best developed on the west coast of South 

 America. The former attains lengths of 10 to 30 feet, and the 



Apical cell 

 1 



Fig. 282. Thallus of Dictyota, a brown alga. At the right is a growing point sectioned 

 parallel and perpendicular to the flat surface to show the regularity of the cell division. 



latter, growing in 200 feet of water, may reach a total length of 

 500 feet. These large, leathery plants produce swimming spores 

 which germinate and produce a small filamentous, or single- 

 celled, generation. These in turn produce antheridia and 

 oogonia, and sperms and eggs. After fertilization the resulting 

 oospore develops into the large, leathery generation. 



Here, then, are two distinct generations — one a large food- 

 manufacturing plant which is called a sporophyte (spore-plant), 

 because it develops spores ; the other a small, or microscopic, 

 generation, the gametophyte (gamete-plant), which ends in the 

 production of gametes. 



Economic importance of the brown algse. In China, Japan, 

 and along the northern coasts various brown algae are cooked with 

 fish and used as food. Japan exports many tons of dried kelps 

 to China. 



The kelp beds of our own western coast have during recent 



