DEPOSITION PROCESSES 



The values used for Fig. 14 were obtained with highly turbulent 

 wind. Partially streamlining the flow, by removing the turbulence-generat- 

 ing obstruction from the tunnel, had little effect on the deposit — except 

 with presentation angles between 0° and 10°, and with wind-speeds below 

 5 metres per sec, when efficiency of deposition was reduced, being least 

 with the horizontal slide (0°). 



Efficiency of deposition on the back of the microscope slide was usually 

 less than i per cent. 



Decreasing the width of the slide from the customary 2-5 to a mere 

 0-5 cm., increased efficiency most at the lowest wind-speeds. This narrow 

 trap was most efficient at 5-5 metres per sec. and 90° presentation angle 

 (vertical), and a fall in efficiency at 9-5 metres per sec. and 90° was com- 

 parable with the anomalous reduction in efficiency with very narrow 

 cylinders at higher wind-speeds (Gregory, 1951). 



TABLE IX 



EFFICIENCY (E %) OF DEPOSITION ON INCLINED SLIDES IN TURBULENT 



wiNTD-TUNNEL (Gregory & Stedman, unpublished) 



DEPOSITION OF OTHER SPORES ON INCLINED PLANE SURFACES 



Lycopodium was studied in greatest detail because it is easily handled 

 and has relatively large spores. Less detailed tests were also made with the 

 smaller spores oi Lycoperdon {Calvatid) giganteum^ with Erysiphe graminis 

 conidia, and with spores of Ustilago perefinans (Table IX). In general it 



71 



