582 Third European Journey 



from cultures of Bacterium tumefaciens', and in 1936, she and 

 Dr. Gardner announced " a hormone extracted " from the crown 

 gall bacterium. " In a theory of gall formation," they said, " it is 

 not the mere presence of the organism that leads to overgrowths 

 but rather the stimulus of certain products of the organism's 

 metabolism." At that time they obtained " no definite informa- 

 tion " as to " the chemical nature of the growth-promoting sub- 

 stance from Bacterium tumejaciens or to the best method of its 

 extraction." But the work was continued and new studies were 

 suggested. 



Dr. Kraus, Miss Brown, and Dr. K. C. Hamner began a new set 

 of investigations, results of which were announced in December.^"- 

 Many similarities in phenomena were found to exist between bean 

 plant tissues inoculated with Bacterium tumejaciens and those 

 tissues to which indoleacetic acid was applied. That Smith's work, 

 a decade after his death, was still having influence is indicated 

 by the following quotation from their published results: " The 

 histological responses of the cells of the bean plant to indole- 

 acetic acid," they said, " show many developmental patterns which 

 are almost exact duplicates of those Smith, Brown, and McCulloch 

 have shown for crown gall. Those which follow the application 

 of the indoleacetic acid are somewhat more pronounced." 



Not every research-phase of this vast subject can be treated 

 here. The various investigation-aspects of the many problems, as 

 in Smith's time, are very much in the current scientific literature. 

 Recently, R. S. de Ropp of the New York Botanical Garden has 

 evaluated the important work done on " Plant tumours and 

 Animal Cancer." ^- He points out that " the work on plant 

 tumours has brought to light three factors — virus, hormone and 

 genetic — which may act singly or in combination to produce 

 pathological growth. This trio of etiological agents," he adds, 

 " is already familiar to students of animal cancer." Three forms 

 of plant tumors which have " certain properties in common with 

 those neoplasms in animals which are collectively referred to as 

 cancers " are described, and he says that the " resemblance is 



" E. J. Kraus, N. A. Brown, and Hamner, Histological reactions of bean plants 

 to indoleacetic acid, Bot. Gaz. 98(2): 370-420, Dec. 1936; also, Bot. Gaz. 98(4): 

 735-807, June 1937. Quotation at 4l4. 



^"Nature 160(4075): 780-782, Dec. 6, 1947. See also by de Ropp, Some new 

 plant growth inhibitors, Science 112(2913): 500-501, Oct. 27, 1950. 



