THE MICROBIOLOGY OF THE ATMOSPHERE 



it may even be more plentiful in winter than in summer (Maunsell, 1958; 

 Hamilton, 1959). To the allergist the winter is a period of allergen-free 

 outdoor air. Spring brings the deciduous tree-pollens, followed by those 

 of conifers in early summer and, more important, by grass pollens char- 

 acterizing the 'hay-fever' season. Late summer brings the moulds and 

 what are known as the 'weed pollens' (including the notorious ragweeds, 

 Ambrosia spp., in North America), extending into early autumn. Late 

 autumn, like the winter, is relatively free from allergens. 



Hamilton (1959) recorded the temperatures at which various spore 

 types were in the air in maximum numbers (Table XXI). 



TABLE XXI 



TEMPERATURES AT WHICH HIGHEST CONCENTRATIONS WERE RECORDED. 



(Hamilton, 1959.) 



Spore Category 

 Leptosphaeria. 

 Ventiiria. 



Nolanea, '' Penicilliuni' . 

 Yellow basidiospores. 



Fusiform (thin) ascospores, Sporobolomyces, Tilktiopsis. 

 Coniophora, Etitomophthora, Fusiform (fat) ascospores, 



Lactarius. 

 Cladosporiiim, Dicoccum, Erysiphe, Helicomyces, Periconia, 

 Ustilago. 



']S~19 23-9-26-I Ahernaria, Chaetomium, Filiform ascospores, Ganoderma, 

 P/iytophthora, Polythrincium, Pullularia, Sordaria^ T/iele- 

 phora, Torula, uredospores. 

 80-84 267-28-9 Brown basidiospores, Yellow basidiospores, Botrytis, Epi~ 

 cocciim, Fusiform (thin) ascospores, Helmint/iosporium, 

 Macrosporiwn, Psilocybe. 

 85-89 29-4-3 1 7 Hyaline basidiospores. 



EFFECT OF LOCALITY 



The air-spora near the ground tends to be dominated by local sources, 

 and these components of local origin are seen against a background of 

 others from many distant sources. Volumetric sampling shows that some 

 species are practically ubiquitous, whereas others are more or less con- 

 fined to certain localities. Valuable surveys of airborne pollen are given 

 by Hyde (1952, 1956, 1959), and of fungus spores by Werff (1958). 



Species of Cladosporimn belong to the ubiquitous group. They dom- 

 inate the day-time spora in temperate regions and in the moist tropics 

 (Hirst, 1953; Cammack, 1955; Gregory & Hirst, 1957; Pady, 1957; 

 Hamilton, 1959; Kramer et al. 1959). This phenomenon agrees with 

 surveys by gravity sampling methods in Britain and New Zealand (Dye 

 & Vernon, 1952; Menna, 1955; Richards, 1954^). The dominance of 

 various types of basidiospores (ballistospores) at night is probably also 

 a widespread phenomenon whose magnitude is now becoming apparent. 



120 



