THE AIR-SPORA NEAR THE EARTH'S SURFACE 



(2), (5) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 

 (3) 



Key to references 



(i) Miquel (1886), (2) Hirst (1953), (3) Hamilton (1959), (4) Gregory & Sreeramulu 

 (1958), (5) Sreeramulu (1959), (6) Cammack (1955), (7) Gregory & Stedman (1958), 

 (8) Gregory et al. (1955), (9) Waggoner & Taylor (1958), (10) Panzer et al. (1957). 



DIURNAL PERIODICITY OF THE FINE-WEATHER SPOR.'V 



Concentrations of spores of a single species or a group of related 

 species often show diurnal rhythms comparable with those observed by 

 Miquel {see above). This effect was studied in detail by Hirst (1953), whose 

 mode of presenting the results has proved a convenient model for sub- 

 sequent workers. Hourly or two-hourly concentrations are obtained on as 

 many days as possible. At regular intervals throughout the day, the mean 

 spore concentration is plotted as a percentage of the maximum. Geometric 

 means are preferred to arithmetic means, and separate curves can be 

 drawn for different weather types. Examples are shown in Fig. 20. 



The time of day when various organisms reach maximum concentration 

 in the Hirst trap and similar volumetric samplers is listed in Table XX. 

 Ill-defined peaks or multiple peaks may perhaps be due to failure to 

 discriminate in visual counts between two morphologically similar spore- 

 types belonging to different organisms. Several patterns of diurnal 

 periodicity are now obvious. 



(i) The bacterial pattern found by Miquel at Montsouris, with two 

 maxima and two minima, remains an unexplained phenomenon worthy of 

 re-examination. 



(ii) The nocturnal pattern contains a group of organisms appearing in 

 highest concentration at some hour between sunset and dawn. This 

 group comprises all of the ballistospore forms so far studied (notably 

 Sporobolomyces, Tilletiopsis, basidiospores of hymenomycetes), and also 

 certain fusiform ascospores. In cooler weather, however, coloured bas- 

 idiospores may reach a maximum in the afternoon (Gregory & Stedman, 

 1958). 



117 



