Further Ri:sharches in Diseases of Plants 547 



rescarcli, were bciiii; explored, but were not raised to tlie present- 

 day level of eftkiency and ciTectiveness. A new era of technical 

 research was in the makini;. But as yet little more than the ground- 

 work had been laid. In cancer research, Borrel's theory of the 

 carcinogenic virus was taking on more importance, because of the 

 discoveries and proof of parasites as causes of animal cancer. His 

 insistence was that " parasites take part in the spreading of viruses, 

 and " he, Oberling says,"^ " suspected from the first that in the 

 so-called hereditary cancer of mice something other than genetic 

 factors may be transmitted. More than once I have heard him 

 suggest the passage of some agent by way of the milk." Virus 

 study in cancer was almost completely, if not entirely, dissociated 

 from what study there was of virus diseases of plants, and rightly, 

 it would seem. Since these years, however, scientific knowledge of 

 viruses, their chemical composition and physical mechanisms, has 

 been greatly advanced, and a not inconsiderable portion of the 

 credit has been due to research in the plant sciences. " Most of 

 this work," Oberling explains,®*' " has been carried out on the plant 

 viruses because they are easily handled, but above all because they 

 are available in such large amounts; in certain plants with mosaic 

 disease 80 per cent of the protein is virus." 



Smith to the last years of his life believed that scientists were 

 " far from having sounded all the depths of parasitism." "' Extra- 

 ordinarily he wished to see research in parasitology advanced. 

 He realized that, in animal cancer research, the parasitic hypo- 

 thesis w^as gaining favor. Borrel in France had maintained the 

 virus theory at a time when the " greatest courage " '^^ was required 

 to do so. This year Smith, in his address, " Twentieth Century 

 Advances in Cancer Research," w^as to mention Borrel's work on 

 several points. In plant pathology, moreover, the study of para- 

 sites as causes of disease was being extended, especially in two 

 comparatively new research fields, virus diseases and diseases 

 believed to be caused by flagellate protozoa. 



This year, on December 28, the American Phytopathological 

 Society would join with the Physiological Section of the Botanical 



*^ Op. cit., vi. 

 ••Op. cit., 121. 



8 

 68 



''Twentieth century advances in cancer research, op. cit., 317. 

 Chas. Oberling, op. cit., vi. 



