SPREADING OF DISEASE AND EPIDEMICS. 143 



mosquitoes in transferring the malaria parasite to 

 man and beetles, bees, flies, etc., of all sorts 

 probably play more active parts in this work than 

 has yet been proved, since they not only carry 

 spores attached like pollen to their hairy bodies, 

 but in many cases in their alimentary canal, to be 

 spread later in the dung. 



The part played by man in conveying fungi 

 from plant to plant counts for much. Not onl)' 

 do gardeners and farm labourers carry spores on 

 their boots and clothes as they pass from infected 

 to non-infected areas, but carted soil and manure 

 are frequently infested with spores of Smuts, Fus- 

 ariuin, Polyporus, and the sclerotia or rhizomorphs 

 of Sclerotinia, Agaricus nielleus^ DeviatopJiora, etc. 

 Man also sends diseases through the post, and by 

 rail and ship, by spores or mycelia attached to 

 seedlings, bulbs, fruits, flowers, etc., as shown in 

 several cases of potato, vine, hollyhock, lily, and 

 hyacinth diseases. Every time a carpenter saws a 

 piece of fresh timber with the saw which has been 

 used previously for cutting wood attacked with dry 

 rot, he risks infecting it with the fungus. Similarly 

 in pruning : every cut with a knife which the 

 gardener has used on infected branches may infect 

 the tree. 



Cuttings made with a soil-contaminated knife 

 and stuck into ordinary soil in dirty boxes covered 

 with equally dirty glass, present every chance for 

 infection by soil organisms ; bacteria and fungi 

 obtain access to the vessels, and derive plenty of 

 food from the juices, and the wonder is not that 



