Plate i. — Representative fields from Hirst-trap slides illustrating diverse air sporas. 

 (Magnification: all x looo. At this magnification i sq. cm. of field corresponds to 2-i cc. of air.) 



Frontispiece 



(a) Fine-weather air spora, Ascot, Berks., i2-oo hr., 27 June 1958. Showing grass and nettle 

 pollen, Cladosporiutn, Epicoccutn, etc. 



(h) Damp-air spora. Ascot, Berks., 02-00 hr., 17 June 1958. Showing spores ofGanodernia, 

 Sporobolomyces, Tilletiopsis, and other hyaline basidiospores. 



(c) Rain-type air-spora, Ascot, Berks., 04-30 hr., 13 June 1958. Showing various ascospore 

 types, Sporobolomyces, soot, etc. 



{d) Air-spora in a wheat crop at night during a thunder-storm, Harpenden, Herts., 21-30 

 hr., 10 August 1959. Showing Puccinia graminis uredospores, Cladosporium, and unidentified 

 ascospore. 



{e) Spores of MertiUus lacrymans from air of building with timber affected by dry-rot. 

 From camera-lucida paintings by Maureen E. Bunce. 



