418 MYCOLOGY IN RELATION TO PLANT PATHOLOGY 



they steal from the grain, feeding in a great number of places, 

 stopping entirely the flow of the already prepared and digested 

 juice, which is to nourish the grain and to be converted into pulp 

 and flour." 



The mystical and ethereal nature of the cause of disease in plants 

 was also refuted by Fabricius in a treatise published in 1774, in 

 which he maintained that smut is caused by "something origan- 

 ized," that is, something living, and by Prevost in a dissertation 

 published in 1807, in which he concluded that rust and smut dis- 

 eases are produced by "internal parasitic plants." These ideas did 

 not gain acceptance among scientists, however, and the real turn- 

 ing point in progress on the nature of disease in plants came with 

 the publication in 1853 of Die Brand Pilze, based on experimenta- 

 tion by de Barv. He showed that the rust and smut fungi are 

 entities that induce disease by growth within the host tissues, with 

 resultant modification of the structure and the function of the in- 

 fected plants. 



CONTRIBUTORY ADVANCES IN BACTERIOLOGY 



The impact of such conclusions from the work of de Barv upon 

 mycology and plant pathology can be appreciated only if con- 

 sidered in connection with discoveries that had already been made 

 or were made soon thereafter in other fields, especially bacteriol- 

 ogy. It should be remembered that for a long time scientific 

 thought was permeated with the concept that many kinds of liv- 

 ing things, especially those of microscopic proportions, originated 

 by spontaneous generation. Using goose-necked flasks containing 

 fermentable fluids, Pasteur demonstrated with finality that fermen- 

 tations may be induced by air-borne bacteria and that during 

 fermentation these bacteria generate other bacteria like them- 

 selves. This discovery led to his subsequent studies, which served 

 as the basis for the establishment of the germ theory of disease 

 in animals, a theory that soon came to pervade the entire field of 

 medicine. Concurrently came the development of laboratory 

 methods for the isolation and cultivation of organisms in pure cul- 

 ture, notably (1) the use of semisolid media, originating with the 

 work of Koch on the anthrax bacillus; (2) the use of cotton 

 stoppers, interposed between the medium and the open air to 

 strain out organisms floating in the air, first employed by 



