550 Crown Gall-Animal Cancer Analogy 



tion was first called to these parasites by Lafont in Mauritius in 1909. He 

 discovered them in Euphorbiaceae and pointed out that they were trans- 

 mitted by insects, but most of the work has been done in the last six years 

 in Portugal, Italy, Russia, Dahomey, and the United States. 



Smith said more but, it must be remembered, this was a period 

 of scientific knowledge in the making on these subjects. Modern 

 knowledge has greatly refined and extended our learning of both 

 virus and protozoan diseases of plants. 



He had been consulted by many of the early students of plant 

 virus diseases. Since 1892 Iwanowski's demonstration of the filter- 

 ability of the tobacco mosaic virus had overshadowed in importance 

 his description of cell inclusion corpuscles found associated with 

 the disease. While his filtration experiments had been confirmed, 

 his work on the cell inclusion bodies was not corroborated really 

 until the early 1920's. In 1910 Dr. Lyon in Hawaii described 

 inclusion corpuscles in Fiji disease of sugar cane.^' Kunkel's work 

 and the symposium of American plant pathologists brought the 

 discovery and its significance into real notice, and new data 

 followed. On July 19, 1920, F. S. Earle, then located in Puerto 

 Rico and studying sugar cane varieties, had called on Smith at 

 his laboratory and, during their visit, he told Smith ^^ that the 

 " pathologist of the station [there had] found a slime mould 

 constantly present in the cells " of stripe disease of cane. In 

 January Smith mentioned in his diary a " new Dutch paper from 

 Quanjer on mosaic disease of potato. He thinks," he wrote, " it is 

 in many respects like peach yellows and peach rosette to which 

 he refers. I gave him alcoholic material of both diseases last 

 year when he was in this country." May 24 appeared this entry 

 in his diary: " Dr. lodidi explained to me results of his analysis 

 of spinach mosaic. He finds decrease of total nitrogen and in- 

 crease of proteid nitrogen and also presence of nitrous nitrogen. 

 All indicating that a denitrlfication occurs in plants attacked by 

 this disease," and on July 1 Smith read the "manuscript of Dr. 

 lodidi's paper on cabbage mosaic to be published in September " 

 in the journal of the American Chemical Society. Work at Dr. 

 Harper's department of botany, Columbia University, for some 



''■' See, Gustav Seiffert, Virus diseases in man, animal and plant, op. cit., 265. 

 Also, L. O. Kunkel, Virus diseases of plants: twenty-five years of progress, 1910- 

 1935, op. cit., 53. 



'* Quotation Smith's, written into his diary. 



