E.: Experiments on splash dispersal of fungus spores

istic of many bacterial plant pathogens and slime-spored fungi. The mechanism of splash has been studied in the laboratory under simplified conditions with water drops falling from known heights on to thin films of a suspension of conidia of Fusarium solani spread on horizontal glass surfaces. The resulting splash droplets were caught, counted and measured by the naphthol green B slide method (Liddell & Wootten, 1957). Both the total number of droplets produced and of those carrying spores increased as the film thickness decreased, and as the size and velocity of the incident drop increased. One incident drop 5 mm. in diameter falling on a horizontal film of spore suspen-sion 0.1 mm. thick on a glass surface produced over 5200 splash droplets of which over 2000 carried one or more spores. The sizes of splash droplets ranged from 5 p to about 2400p, and their size distribution was of the log probability type. The median diameter was 70p for all droplets, and 140p for droplets carrying spores. The medium horizontal distances travelled by these droplets in still air was 10 and 20 cm. re-spectively. Increasing the film thickness to 0.5 and 1.0 mm. reduced the total re