124 FUNDAMENTALS OF SUBM I C R O S C O P I C MORPHOLOGY 



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c) 



.a) Pleurosigma angtdalum^' . Sm. contour (from Husted, 1930);/?) light microscopic 

 image scale 1500:1 (from Michel, 1940); c) light microscopic image with 

 numerical aperture 1.4, image scale 10,000:1 (from Ardenne, 1940b). 



Fig. 83. a) Electron microscopic 

 image of Pleurosigma, image scale 

 100,000:1; l)) sketch of the spatial 

 organisation of the silica wall; 

 image scale ca. 60,000:1 (from 

 MtJLLER and Pasew.\ldt, 1942). 



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f 



b) 



