202 A TEXTBOOK OF THEORETICAL BOTANY 



Reproduction 



The whole body of the Fungus functions as a zoosporangium and its 

 contents divide up into a large number of uniflagellate, spherical zoospores 

 which escape through an operculum formed at the top of the sporangium 



/■.•^'.-■.■. 



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Fig. 193. — Rhizophidium glohosum. A and B, Zoospore penetrating wall of host cell, 

 with development of rhizoids. C, Mature zoosporangium. Contents not shown. 

 D, Escaping zoospores. E, Small zoosporangia on host cell. (After Atkinson.) 



(Fig. 193). Whether these bodies ever fuse in pairs or not is unknown, 

 though this has been recorded in allied genera. The motile cell soon settles 

 down by its flagellated end, and the flagella are withdrawn. From the attached 

 end the rhizoidal system is developed, while the remainder of the cell 

 enlarges and grows into a sac resembling the parent, which will in time 

 become a fresh zoosporangium. 



An interesting development which is worth referring to here is seen in 

 certain allied genera. In some, after the development of the rhizoidal system, 

 a swelling appears immediately inside the host wall which is termed the 

 subsporangial swelling. In certain genera this remains small and it is the 

 cell outside which forms the zoosporangium. A series of examples (Fig. 194), 

 however, are known which lead up to a condition where the subsporangial 

 swelling becomes the zoosporangium, while the original external cell remains 

 quite small and after penetration may disappear. At the same time rhizoids 

 develop not merely from the base but all over the surface of the new spor- 



