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Fig. 155 Vaucheria sessilis. Stages in development and fertilization 

 of oogonium. April 1-6, 1930. ( > 195). A, young antheridium and 

 'wanderplasm' in place from which oogonium will arise. B, young 

 oogonium. C, oogonial beak formed; 'wanderplasm' retreating into 

 thread j oil globules passing into oogonium; antheridial wall form- 

 ing. D, 'wanderplasm' out of oogonium. E, basal wall of oogonium 

 forming. F, antherozoids emerging. G, oogonial membrane forming 

 at tip, some antherozoids in egg. H, cytoplasm extruded and 

 rounded off; fertilization occurring. I, ripe egg. wp = wanderplasm. 



(After Couch.) 



the reproductive structures or after wounding. Vegetative repro- 

 duction is secured through fragmentation, whilst asexual reproduc- 

 tion is brought about by the well-known compound multiflagellate 

 zoospores, which are produced singly in club-shaped sporangia 

 that are cut off from the ends of the erect aerial branches. The 

 chloroplasts and nuclei congregate in the apex of a filament before 

 the septum is laid down and the nuclei then arrange themselves 

 peripherally. Finally, two equal flagella develop opposite each 

 nucleus and then the zoospore is ready for hberation, a process 

 which is achieved by gelatinization of the sporangium tip. This 

 compound structure must be regarded as representing a group of 

 biflagellate zoospores which have failed to separate. The zoospore 



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