DEPOSITION PROCESSES 



TABLE X 



EFFICIENCY (E %) OF DEPOSITION OF LycopodiwH SPORES ON UPPER AND 

 LOWER SURFACES OF POTATO AND BROAD-BEAN LEAFLETS IN TURBULENT 



WIND-TUNNEL (Gregory & Stedman, unpublished) 

 Wind velocity (metres/sec.) 



There is reasonable agreement between observation and the theory of 

 impaction, but other forms of deposition are impure and complex. Effi- 

 ciency of a collecting surface as an impactor spore-trap increases as the 

 wind-speed and particle size increase, and as the size of the collecting 

 surface decreases. Deposition on horizontal trap surfaces and leaves can 

 be predicted in terms of sedimentation under gravity at low wind-speeds, 

 but edge effects can easily predominate as wind-speed increases, and at 

 5 to 10 metres per sec. turbulence may result in deposition upwards 

 against gravity. 



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