THE MICROBIOLOGY OF THE ATMOSPHERE 



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Bryophytes . 

 Pteridophytes 

 Pollination of phanerogams 

 Gymnosperms 

 Angiosperms 



V Horizontal Diffusion 



Dispersion of the spore-cloud 

 Diffusion as a result of atmospheric turbulence 

 Field experiments on diffusion of spore-clouds 

 Comparison of theories of W. Schmidt and Sutton 



VI Deposition Processes 



Mechanism of impaction ..... 



Wind-tunnel study of impaction 



Impaction on cylinders ..... 



Impaction on a rotating sticky cylinder 



Impaction on plane surfaces at various angles to wind 



Deposition on horizontal slides 



Deposition of Lycopodium spores on inclined plane surfaces 



Mean deposit on inclined slides 



Deposition of other spores on inclined plane surfaces 



Effect of thickness of slide .... 



Orientation of spores ..... 

 Deposition on 9 cm. diameter Petri dish 

 Retention and blow-off from clean surfaces . 

 Deposition and retention on potato and bean leaves 



VII Natural Deposition .... 

 Measurement of deposition 



Measurement of deposition coefficient, 'p 

 Loss by deposition from spore-cloud . 

 Deposition mechanisms outdoors 



Boundary-layer exchange 



Sedimentation 



Impaction 



Turbulent deposition 



Electrostatic deposition . 



Minor deposition mechanisms 



Rain-washing ('scrubbing', 'rain-out', 'wash-out' 

 Relative importance of deposition mechanisms 



VIII Air Sampling Technique .... 

 Gravity sedimentation methods . 

 Sedimentation from still air . 

 Sedimentation from wind 

 Sedimentation from artificially moving air 

 Inertial methods ..... 

 Impaction using wind movement 



viii 



