THE ALG.E 



177 



Sometimes the front part, which tries to rotate as it 

 becomes free, gets twisted off from the rest of the cell, 

 and then two zoospores are formed instead of one. 



The zoospore contains a great number of chloroplasts 

 and of nuclei. In this case the nuclei lie near the 

 outside, in a clear zone of protoplasm. The numerous 

 cilia are in pairs, each pair corresponding to a nucleus. 

 Evidently the whole of this great zoospore corresponds 

 to a multitude of small zoospores, not separated from 



FIG. 75. Zoospore and its germination in Vauclieriascssilis. A, 

 zoospore (sp) in the act of escaping from the sporangium. 

 Magnified about 30. B, germinating zoospore (sp), which 

 has formed two green filaments and a rhizoid (r}. Magnified 

 about 20. (After Sachs. ) 



each other. In most allied Algas we find that numerous 

 zoospores, usually with two cilia each, are formed in the 

 sporangium. 



The escape of the zoospores of Vauclieria generally 

 takes place in the morning. They swim about 

 rather lazily for a quarter of an hour or so, and 

 are so big that their movements can be followed with 

 the naked eye. Then they come to rest, and immedi- 

 ately withdraw their cilia. The zoospore germinates at 

 once, sending out a filament which attaches itself to 



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