866 



AQUATIC PHYCOMYCETES 



Fig. 68. Cytology of sexual organs of Rhipidium interruptum Cornu 



A. Young oogonium; cytoplasm is vacuolate and nuclei have already begun 

 to move toward periphery; cross wall has not as yet cut off oogonium from 

 hypha; the two basal, lighter-stained nuclei have probably just recently entered 

 oogonium. B. Mature oogonium; nuclei have all, with one exception, assumed 

 a peripheral position; cytoplasm is alveolate and contains large vacuoles. C. 

 Oogonium shortly before nuclear division; differentiation into periplasm and 



