THE AIR-SPORA NEAR THE EARTH S SURFACE 



At Rothamsted, Gregory & Hirst (1952) found that between early August 

 and late September the concentration of coloured basidiospores seldom 

 fell below 1,000 per cubic metre. From June to October, 1952, coloured 

 basidiospores formed 3-3 per cent and hyaline basidiospores 46-5 per cent 

 of the total air-spora in the size-range above about 4^, and their 

 abundance at Rothamsted in 1954 was confirmed by Hamilton (1959). 



It soon became clear that the hyaline basidiospores were mostly from 

 colonies of Sporobolomyces occurring on leaves, and that their abundance 

 varied greatly in different places. Last (1955), when sampling air within 

 a stand of wheat, found large differences in concentration of Sporobolo- 

 myces between manured and unmanured plots in the same field (Broad- 

 balk field, Rothamsted). The highest concentration of sporobolomycete 

 spores so far reported (up to i million per cubic metre) was found near 

 Chichester Harbour, England (Gregory & Sreeramulu, 1958). 



CLADOSPORIUM 



100 



RELATIVE 

 NOS. 



50 



ROTHAMSTED 



G-~ 



■0---0- 



LONDON 



01 



15 



2 3 HRS. 6.M.T. 



Fig. 21. — Diurnal periodicity of Cladosporium at London (South Kensington) and Harpen- 

 den (Rothamsted), based on Hirst trap catches from May to September, 1954. (Reproduced by 

 permission of Elizabeth D. Hamilton from Acta Allergologica, 1959.) 



In any one place it is difficult to disentangle the respective contributions 

 of local and distant sources. It might be expected that spore concentrations 

 would be lower in a city than in the near-by countryside. This was indeed 

 found by Hamilton (1959), who compared continuous records from two 

 Hirst traps, one at Rothamsted (2 metres above ground) and the other 

 in London (16 metres above ground on a roof in South Kensington). The 

 counts of total pollen were higher in London because of a large excess of 

 Platamis (plane) pollen, but grass pollen grains were 50 per cent more 

 numerous in the country. Fungus spores outnumbered pollen grains by 



121 



