120 
Journal of Agricultural Research 
Vol. XXV, No. 3 
Since further preliminary experiments confirmed these earlier observa¬ 
tions, it was decided to extend the scope of the investigation to include 
a study of some of the relations of Bacterium tumefaciens Smith and 
Town., to its host tissues before proceeding with applied aspects of the 
problem. A report on this work follows. 
The crowngall organism for these studies was secured at Madison, 
Wis., in 1920, from a gall found on a Kansas raspberry. Isolations were 
made by the poured plate method from portions of the gall which had 
been sterilized on the surface with mercuric chlorid. After the parasite 
was isolated, its pathogenicity was proved on both tomato and raspberry. 
Three successive platings and reisolations from the original culture of 
the organism made the author reasonably confident that he was working 
with a single strain. Repeated inoculation experiments have shown it 
to be actively pathogenic as evidenced by the production of character¬ 
istic galls. Cultural studies (in which the author is indebted to Dr. 
L. K. Jones for cooperation) have shown that it corresponds with Smith's 
description of the crowngall organism (12, p. 105-127), as isolated from 
the daisy, in all but a few respects. 
The size limits of the raspberry organism on agar cultures were found 
to be 1 to 1.6 X0.4 to 0.7 fi as compared with 1 to 3 X0.4 to 1.8 n for the 
daisy organism ( 12 , p. 106). The size of the majority was found to be 
1.1 X0.5/-1 compared with 1.2 to 2.5 X0.5 to o.8ju for the daisy organism. 
The raspberry organism turned litmus milk pink slowly, and remained 
viable on culture media as long as six months, while the daisy organism 
never turned the litmus milk pink and lived only four or five weeks on 
culture media. These differences are not considered to be of practical 
importance. Smith ( 12 , p. 127-132) has noted variations as great as 
these between different strains of crowngall bacteria. The writer, there¬ 
fore, considers that he is dealing with the crowngall organism, Bacterium 
tumefaciens . 
MODE OF ENTRY OF THE ORGANISM INTO THE HOST TISSUES 
Many writers on crowngall have stated that wounds are necessary 
for the initiation of infection. In order to determine whether or not 
the organism could enter without the intervention of wounds, the follow¬ 
ing experiment was performed. 
On the stem of each of 2 dozen tomato plants 10 droplike masses 
from a pure dextrose agar culture of the raspberry strain were applied 
with a camel’s-hair brush. Six more plants were treated in a similar 
manner, but in addition a puncture was made into the stem through 
the center of each mass. After four weeks not a single gall had developed 
from the 240 masses where there were no wounds, whereas 100 per cent 
infection had appeared in the case of the parallel inoculations accom¬ 
panied by junctures. 
This experiment was supplemented by one in which tomato seeds 
which had been sterilized on the surface with 1 to 1,000 mercuric chlorid 
solution were planted in three 2 by 10 inch glass tubes partly filled 
with sterilized soil and in two containing synthetic agar. When the 
plants had grown sufficiently, the crowngall organism was introduced 
to both the agar and soil in* large quantities in a way that precluded 
the possibility of wounding the experimental plants in the process. 
At the same time, two of the plants were inoculated near the apex of the 
stem to test their susceptibility. The inoculations were made on 
