SCHIZOMYCETES. BACTERIA 



117 



" The results of these experiments show that the opportunity 

 presented for breeding and selecting races of plants resistant to 

 this common and destructive disease is excellent." 



Abundant, substantial proof has now been brought forward by 

 Smith and Townsend demonstrating the bacterial nature of this 

 disease. This work resulted from an examination of galls appear- 

 ing naturally upon the Paris daisy, Chrysanthemum frutescens. 

 From the last-named plant they were able to isolate a species of 

 bacteria which proved to be pathogenic. They reported in 1907 

 more than three hundred successful inoculations under different 

 conditions. In at least two series of experiments 100 per cent of 

 the inoculations were effective, control plants remaining wholly 

 free from galls under similar conditions. The organism was then 

 described as Bacterium tumefaciens. It produces hypertrophies 

 very readily in young tissues, particularly in fleshy organs, and 

 it sometimes induces abnormal growths on the wounded parts 

 of young cuttings. This organism was found to affect, with more 

 or less similar lesions, many plants, including the tomato, tobacco, 

 potato, sugar beet, grape, carnation, raspberry, peach, and apple. In 

 four or five days after inoculation, swellings were evident, the latter 

 on the daisy attaining an inch in diameter after a month or more. 



According to Townsend, " this work has led to the isolation of 

 pathogenic Schizomycetes from the galls of peach, hard galls of 

 apple, hairy root of apple, hop, rose, and chestnut. The organisms 

 obtained from the galls of these different plants are cross inocula- 

 ble and are very similar, if not identical in size, shape, structure, 

 and habits of growth on media with the organism from the daisy 

 gall." It is further ascertained that galls produced by the daisy 

 organism are very similar to those formed by the organism from 

 the woody plants. It is apparent that it is too early to expect 

 definite evidence as to the occurrence of biological forms or other 

 more accentuated differences. 



The organism. This species has already been studied with 

 respect to its reactions on various media, and it is described as 

 a short rod, motile by from one to three flagella. Cultivated 

 on agar the translucent white, round colonies appear slowly at 

 25 C. The margins are smooth and dense. It produces no gas. 

 Bouillon is not heavily clouded, and gelatin is not liquefied. The 



