Fungous Diseasfs or Plants, Pi A(.n \'i:llo\vs 151 



another plant pathologist of the Netherlands, M. \V. Reijerinck, 

 confirmed I\vano\vski"s filtration experiments and added knowl- 

 edge. He, Smith believed,"' "showed that the virus of tobacco 

 mosaic without developing any visible growth would pass in ten 

 days from the upper to the lower layers of an agar plate. He 

 ascribed the disease, therefore, to a ' Contagiiim v'lvum jluidinn: " 

 Beijerinck, AUard" said further. 



found that diseased sap so filtered as to be entirely free from bacteria still 

 retained its power to infect healthy plants, in this respect confirming 

 Iwanowski. He showed that a very minute quantity of this filtered juice 

 produced the disease in immature, growing tissue. He held that dried 

 mosaic material retained its infectious properties for some time, and like- 

 wise, that it was not rendered innocuous by remaining in the soil through- 

 out the winter. Like Mayer and Iwanowski, he found that heating mosaic 

 virus to the boiling point rendered it harmless. He proved that the virus 

 traveled considerable distances in plants but produced obvious symptoms 

 only in immature tissues. Beijerinck claimed that the soil around diseased 

 roots may infect healthy roots and that plants in some instances appar- 

 ently reco\cred from the disease temporarily. Previous to the work of 

 Beijerinck all investigators were strongly inclined to establish a bacterial 

 origin for it, although at that time no direct proof had been obtained. 



It must be remembered that as late as 1882 "most of the very 

 numerous papers on bacteria [had] treated the subject from a 

 purely medical point of view," and only incidentally had any 

 bearing botanically.^^ In America not until 1888 was the move- 

 ment to establish agricultural experiment stations brought to 

 full fruition. Adequate experimental laboratories and thoroughly 

 trained students for the study of bacterial diseases of plants 

 remained few until well into the 1890's, and few were the 

 specialists and number of facilities in Europe. 



During the summer of 1887 Scribner, accompanied by Professor 

 Pierre Viala of Montpellier, France, author in 1885 of a special 

 treatise on grape diseases," visited the principal vineyard regions 

 of the nation and investigated various grape-vine maladies. In 

 1887 Scribner, by a paper, " On a new fungus disease of the 

 vine,"^' announced to the Society for the Promotion of Agri- 



•* Uem, 27. 

 "^Op. at., 438 f. 



" W. G. Farlow, Accounts of the progress of botany for the years 1879-1883, 

 Smithsonian Reports, 313, 1880; 391, 1881; 551, 1882; 681, 1883. 

 *' E. F. Smith, Fifty years of pathology, op. cit., 21. 

 "Prof. Soc. Prom. Agric. Sci. 8th meet., 74-76, 1887. 



