THE AIR-SPORA NEAR THE EARTHS SURFACE 



total alr-spora. Many other t^'pes are also found, but they are infrequent, 

 except in special localities or under special circumstances. 



The importance of basidiospores from mushrooms, toadstools, bracket 

 fungi, and especially mirror-yeasts, as components of the air-spora, 

 is a recent discovery (Gregory & Hirst, 1952, 1957). It is remarkable 

 that even the existence of the Sporobolomycetes was unrecognized until 

 1930. Basidiospores are not efficiently caught by surface traps, and con- 

 firmation of their numbers (which were doubted at first) has been slow 

 in forthcoming. However, Hyde & Adams (i960) report that at Cardiff, 

 over the whole year of 1958, the basidiospore types collectively amounted 

 to 1,059 ou'^ of the average fungus spore content of 2,164 P^r cubic metre 

 of air. Furthermore, estimating volume instead of number, they showed 

 that basidiospores came second only to grass pollen. Daily estimates with 

 a slit sampler for one year at Manhattan, Kansas, gave the numbers of 

 basidiospores as 24-3 per cent of all spores caught — second only to 

 Cladosporium (Kramer et al.^ ig^ga). 



THE AIR-SPORA AT OTHER HEIGHTS NEAR THE GROUNT) 



In general the spore concentration increases at positions nearer the 

 ground than the standard sampling height of 2 metres, and decreases at 

 greater heights. Using a Hirst trap at 24 metres in a lattice tower at 

 Rothamsted, the average spore concentration was 81-5 per cent of that 

 at 2 metres, though some spores characteristic of the night air-spora 

 were actually commoner at the higher level (Gregory & Hirst, 1957). 



Tests at heights below 2 metres with a portable suction trap in the 

 New Forest, England, showed a general decrease with height (Table XIX). 

 The difference was greatest at night, when the total spore concentrations 

 were lowest. By way of exception, Cladosporium numbers were reversed 

 at I3'00 hours: this is taken to mean that sources of Cladosporium were 

 not present close to the trap and that the air nearest the ground \^•as being 

 depleted of this organism in passage over the Earth's surface. 



TABLE XIX 



TOTAL NUMBER OF POLLEN GRAINS AND SPORES PER CUBIC METRE IN OAK- 

 BIRCH WOOD, NEW FOREST, ENGLAND, 23 JULY 1 953 (Gregory, 1 954). 



Height above ground-level 

 7 cm. 30 cm. 120 cm. 



05-00 hours G.M.T. 20,600 19,000 7^250 



13-00 hours G.M.T. 31,300 24,200 20,300 



In his studies of the 'phyllosphere' of cereal leaves, Last (1955) 

 sampled air among wheat plants at 11, 46, and 80 cm. above ground-level 

 and found 237,000, 170,000, and 41,000 spores of Sporobolomyces per 

 cubic metre, respectively. 



115 



