LEVINE: STUDIES ON PLANT CANCERS—IV 241 
Bacterium tumefaciens in the leaf axil was 2.7 cm. which is slightly 
larger than the average for galls produced by inoculating the 
axil of a leaf of a decapitated plant with 6a and smaller than 
the average for galls resulting from a drop of 6e (forty times 
weaker) inoculated in the leaf axil, a region which gives the 
maximum reaction to the crown gall organism. 
SUMMARY AND CONCLUSION 
1. Tobacco plants of uniform age and size and growing 
under uniform conditions of soil and light were inoculated with 
Bacterium tumefaciens to determine the effect of various dilutions 
of a given culture on the size of the crown gall produced. In 
these experiments I have not counted the organisms in the inocu- 
lating medium, but have used measured quantities of inoculum 
varying from ordinary agar culture emulsion to dilutions 1 : 100. 
2. No constant difference was noted in the size of the crown 
gall resulting from an inoculation with the undiluted bacterial 
emulsion and a suspension forty times weaker. 
3. The difference in the quantity of the suspension inoculated 
showed that the quantity of Bacterium tumefaciens was not effect- 
ive in increasing the size of the gall. The differences observed 
when trocar and needle are compared must be referred to the 
relative degree of injury and number of cells exposed. 
4. Suspension from cultures of Bacterium tumefaciens two 
days old were found to be no more effective in producing crown 
gall in tobacco than were cultures twenty-one and forty days old. 
5. It is concluded that the number of cells of Bactertum 
tumefaciens inoculated into the tobacco is not significant in 
determining the size of the crown gall. A smaller number of 
bacteria favorably lodged in tissue capable of response will 
produce a crown gall equal in size to that produced by a larger 
number 
6. The size of the crown gall is rather dependent upon the 
region of the host inoculated and the vitality of the host, than 
upon the number of bacteria starting the infection. 
LITERATURE CITED 
Tappeiner, —, 1878. Ueber eine neue Methode Tuberculose zu 
erzeugen. Virchow’s Archiv 74: 393-400. 
