LEVINE: STUDIES ON PLANT CANCERS—IV 235 
In the latter part of October harvesting began. The plan- 
tation had been plotted for identification of the test plants early 
in the season. Each test plant was now carefully removed from 
the soil. The diameters of the more globular crown galls were 
measured in several axes, averaged and recorded. ‘The averages 
of these measurements for a number of plants are shown in the 
TABLE below. Leafy crown galls and axillary leafy crown galls 
were also measured although obvious difficulties were met in 
doing this 
OBSERVATIONS 
While to actually count the number of Bacterium tumefaciens 
inoculated in a given case was impossible yet dilutions of 
emulsions of the organisms sufficiently different were used to 
show contrasted effects, if any be produced in this way. In 
1920, two hundred midveins of sixty well grown tobacco plants 
were inoculated with dilutions of Bacterium tumefaciens from 
culture fourteen days old. The dilutions were made in the 
following proportions: A, 1 : 100; B, 1 : 50; C, 1:25; D, 1 : 15; 
E,1:2;and F, 1:1. The crown galls which saaitees were all 
approximately the same size. Each intumescence measured 
approximately 0.2-0.3 cm. in diameter. These results were 
followed up by further studies in 1921. The TABLE shows the 
results. In general, they confirm the preliminary studies. In 
these later studies the stems were also inoculated at the node 
and internode as mentioned below. 
Emulsion Ia was made by collecting 4 cc. of scrapings from a 
flask culture of Bacterium tumefaciens and diluting as noted 
above. Dilution Ib consisted of 1 cc. of the emulsion mixed 
with an equal part of sterile water. Dilution Ic was mixed in 
proportion of 1:10 parts of water; Id, 1: 20; and Ie, I : 30. 
Forty-seven plants of uniform size and age and growing in the 
same plot were inoculated with one drop of Emulsion Ia, b, c, 
d, and e, of Bacterium tumefaciens in trocar incisions made in 
the axils of the upper leaves. The size of the crown galls was 
measured at the end of the season and found to be more or less 
uniform, varying within the range of the variation in size 
found in the individual plants. Dilution Ia inoculated into 
twenty-two plants by the trocar method gave an average size 
crown gall 1.8 cm. in diameter. While Id and Ic, dilutions ten 
to twenty times weaker, gave an average size crown gall slightly 
