Studii-s on Crown Gall of Plants 435 



tubercle, but arc not readily fouiul in case of these crown galls. The same 

 remark is true respecting the bacteria in the primary tumors. They are very 

 abundant and easily discovered in the olive-tubercle, but not readily 

 detected in the crown gall, although obtainable therefrom in Petri dish 

 cultures on agar. 



The abstract, probably prepared by Smith, suggested a possible, 

 but unestablished, theory: 



It is still too early in the course of our studies to make positive statements 

 respecting the likeness or unlikeness of these growths to malignant animal 

 tumors, but it is proposed to continue this phase of the inc]uiry. There is 

 in these grov.-ths a very rapid multiplication of parcnchymatic tissues with 

 reduction and distortion of the firm conductive tissues of the plant and the 

 final decay and sloughing otT of the spongy tissues, leaving open wounds, 

 on the ma'rgins of which fresh developments of the tumor may appear. 



Smith's and- Townsend's article, "A plant-tumor of bacterial 

 origin," described the schizomycete Bacterium tumefaciens and its 

 pathogenic properties; and was published in Science, and in the 

 Centralhlatt fiir Bakteriologie II ^'^ with some additional data. The 

 organism's description followed the provisions of the chart of the 

 Society of American Bacteriologists, and its group number became 

 212.2322023.^' These were the first of many important statements 

 on this subject addressed primarily to plant pathologists. In 1922 ''^ 

 Dr. Smith presented a general summary, or outline, of the work. 

 This read as follows: 



The general outcome of these researches, continued for many years and 

 still going on, has been an entire revision of views as to the nature of the 

 disease and as to sanitary measures necessary for its restriction. We now 

 know not only the morphology and biology of the organism causing the 

 tumors but also that the type of the tumor varies with the part infected, 

 that there are several strains of the organism and probably many, that 

 isolations differ in virulence, that some colonies which look all right have 

 no virulence whatever, that on culture media and probably in the plant 

 some strains lose virulence much sooner than others, that isolations are 

 cross-inoculable to a very surprising degree, i. e., to plants of many families, 

 that some plants, immune or nearly immune to certain strains, respond 

 vigorously to other strains, and that some species are resistant to all strains 

 so far tested, e. g., olive, onion and garlic. 



*" 20(1/3): 89-91, 1907. 



" Erwin F. Smith, Nellie A. Brown, and Lucia McCulIoch, The structure and 

 development of crown gall: a plant cancer, U. S. Dep't of Agric, Bur. of Plant 

 Industry Bulletin No. 255: 16, issued June 29, 1912. 



^* Synopsis of researches, op. cit., 39-40. 



