FURTHl-R RllSl- ARCHES IN DlSHASI-S OF PLANTS 531 



June 6: Working at the microscope on nuclei of cfrown] .ufall] cells 

 in tobacco cortex (all the material was tixed in p. m.). I found very few 

 mitoses, but some in each tissue i.e., fine celled tumor, and two grades of 

 coarse-celled on the periphery. Notched nuclei occur also in all cell grades, 

 but they are most abundant in the transition tissue. Many tumor cells 

 contain 2 nuclei, and in one cell on the margin I .uiw four, with no trace 

 of any cross wall. 



lune 7: Read Ziet^ler's Pathology. Worked at the microscope. Saw 

 mitosis (one case) in stretched cell on border of tobacco cortex tumor. 

 Searched especially for dividing cells which show clearly their origin from 

 stretched cells and found 2 or 3 that are good enough to photograph. 



The beginnings-of his study of appositional growth in crown 

 gall tumors were traceable to the year 1907 when he had first 

 observed the phenomenon, and definitely to 1916 when he had 

 tried to reproduce experimentally what he had seen in 1907. He 

 had followed the same procedure, " using the hop-strain of the 

 crown gall organism and single needle-pricks as before, but the gall 

 was growing very slowly when collected and [he] got nothing 

 comparable to the earlier results which were produced " ^^ with the 

 Paris daisy strain of Bacterium tumefaciens. In 1920 his repeated 

 experiments were with this strain of the organism. 



In the spring of 1908, he had " made fourteen sets of inocula- 

 tion experiments on fish and frogs with pure cultures of Bact. 

 iiimejaciens derived from tumors on the hothouse daisy (Chrysan- 

 themum) to determine whether this organism would induce similar 

 abnormal growths in cold-blooded animals, experiments on warm- 

 blooded animals being considered unnecessary because of the low 

 maximum temperature of the organism (about 36.5° C.)."^' 

 These experiments were continued at intervals of various years 

 throughout the remainder of his research career, and were made 

 on gold fish, trout, and salamander. While inoculations yielded 

 some results,^^ nothing conclusive was ever established and as late 

 as the year 1926 he would say: ^^ 



I will never believe that cancers in animals can be produced by means of 

 [the crown gall organism] until it can be done so many times and in such 



** E. F. Smith, Appositional growth in crown-gall tumors and in cancers, ]our. 

 Cancer Research 7(1): 1-3, 1922. 



^'' Bacteria in relation to plant diseases, op. cit., 2: 182-184. 



'* For example, on February 19, 1916, Smith thought that perhaps some inocu- 

 lations on gold fish had resulted in tumors which he described in a note-book. 



" Letter to Dr. James Young, Edinburgh, Scotland, February 26, 1926. 



