372 Chief of a Laboratory of Plant Pathology 



it is certain that no forms of bacteria demonstrable by existing methods are 

 directly concerned in the causation of cancer, and, notwithstanding the 

 stronger claims made in behalf of Blastomycetes, I am glad to learn that 

 Dr. Gaylord rejects these claims and takes a position in this regard opposed 

 to that of San Felice, Roncali, Plimmer, Leopold, and others. He interprets 

 as Protozoa the bodies which he regards as parasites. 



In 1901 Smith had not really begun to study the physiology 

 and pathology of plant tumors, the mechanisms involved in -the 

 formation of pathogenic overgrowths in plants. He furnished 

 specimens of Plasmodiophora brasskae to more than one specialist 

 in human cancer research; and, years later, in his textbook Intro- 

 duction to Bacterial Diseases of Plants ^^ referred to a period when 

 much study was "put upon the club-root of turnips and cabbages 

 (due to Plasmodiophora brassicae) by various persons who thought 

 they saw in it certain resemblances to animal cancer." Club-root 

 of cruciferous plants, he pointed out, is attributable to a myxo- 

 mycete and, while cell hypertrophy and more or less cell multi- 

 plication are characteristics, among other differences the over- 

 growth is not an active hyperplasia. 



Nothing preserved among his laboratory memoranda shows that 

 during the years 1901-1903 he was studying either this subject or 

 crown gall in plants. If he did study either, the research was 

 more incidental than primary, and what, if any, crown gall study 

 was made was doubtless confined to investigating another plant 

 disease of possible bacterial origin. This does not seem probable, 

 however, since crown gall at that time was not thought to be 

 caused by a bacterium, and Smith himself affirmed 1904 as the 

 year when first he and his laboratory assistants began the real 

 investigation which led to the discovery and isolation of Bacterium 

 tumefaciens Smith and Townsend as its cause. He said: 



60 



My first acquaintance with this disease was on peach trees from Cali- 

 fornia and the South in 1892-3, at which time an effort was made, chiefly 

 by means of the microscope, to find in the galls a fungous or plasmodial 

 parasite. As nothing constant of this nature was discovered and bacteria 

 were not then in mind the subject was dropped. It was taken up again in 

 1904 on Paris daisies received from New Jersey with bacteria definitely in 

 mind because the overgrowths superficially resembled olive tubercle '''■ in 



"6»p. cit., 551. 



*® Synopsis of researches, op. cit., 39. 



*' See Smith's and Rorer's Bull. 131, iv, "Recent Studies of the Olive-Tubercule 



