SOME CHARACTERISTICS OF THE VIRUS 

 DISEASES OF PLANTS 



By E. J. BUTLER, CLE.. D.Sc, MB. 

 Director, Imperial Bureau of Mycology 



The occurrence in plants of diseases caused by filterable viruses 

 was first demonstrated by Iwanowski ^ in 1892 and fully 

 established by Beijerinck ^ in 1898. Their studies showed that 

 the juice of tobacco plants infected with the " mosaic " disease 

 was capable of communicating the disease to healthy plants 

 after passage through the Chamberland filter. Similar mosaic 

 diseases are now known in a number of plants. 



A little earlier than this, however, Erwin F. Smith ' had 

 investigated a very serious peach disease in the United States, 

 and conclusively established the fact that, though no parasitic 

 organism could be detected, a communicable virus was present 

 in the diseased parts, and could be artificially transmitted to 

 healthy trees provided organic union (as by budding diseased 

 buds on healthy wood) was effected. Unlike tobacco mosaic, 

 the virus of " peach yellows " has never been extracted and 

 handled, nor is any other method of transmission established 

 than that by organic union, though it is evident that other 

 methods exist in nature since the disease is highly infectious 

 and even has periods of epidemic outbreak. Whether the 

 other two allied diseases of the peach subsequently described 

 under the names " peach rosette " and " little peach " are 

 regional effects of the same common cause or are distinct 

 diseases is not certainly known.* The " peach yellows " type 

 of disease has since been found in a few other cases, chief 



1 Iwanowski, D., Bulletin de I'Academ. Imper. d. Science St. Petersbourg, 

 N.S., V, p. 67, 1892. 



2 Beijerinck, M. W., Over een Contagium vivum fluidum als oorzaak van 

 de Vlekziekte der Tabaksbladen, Verhand. Kon. Akad. van Wetensch. Amster- 

 dam, 2nd Sect., vi, 5, 1898. 



3 Smith, Erwin F., Peach Yellows: a Preliminary Report, U.S. Dept. 

 of Agric, Bot. Division, Bull., ix, 1888 ; Additional Evidence on the 

 Communicab'lity of Peach Yellows and Peach Rosette, ibid., Division of Veg. 

 Path. Bull., i, 1891. 



* Blake, M. A., Cook, M. T., and Connors, C. H., Recent Studies on Peach 

 Yellows and Little Peach, New Jersey Agric. Exper. Stat, Bull., 356, 1921, 



416 



