LEVINE: CROWN GALL ON BRYOPHYLLUM 453 
growth. The meristematic tissue which forms vessels and 
tracheids is stimulated to proliferate through the agency of 
the crown gall organism. These cells, on differentiation, form 
isolated parts of a poorly organized fibro-vascular system. In 
benign crown galls there is frequently a considerable increase 
in the thickness of the wood. This is likewise due to stimulated 
meristematic tissue with subsequent differentiation. The 
cortical cells are capable of responding to the stimulus to divide. 
They eventually become mature cortical cells. 
FREQUENCY OF LEAFY CROWN GALLS 
The following table shows the number of crown galls that 
are formed at the notches of leaves of Bryophyllum when inoc- 
ulated with Bacterium tumefaciens. The fourth column shows 
the number of leafy crown galls formed when the notches of the 
longitudinal half of the leaf are inoculated. The figures in the 
third column do not include the leafy crown galls. 
TABLE I 
RESULTS OF INOCULATIONS OF BACTERIUM TUMEFACIENS INTO THE NOTCHES 
OF LEAVES OF BRYOPHYLLUM CALYCINUM. 
No. of globular crown galls No. of leafy 
No. of leaves per long half of leaf Total crown galls 
17 4 68 13 
9 6 54 4 
9 5 45 8 
8 3 24 4 
3 2 6 °o 
2 I 2 2 
48 199 31 
An analysis of the results obtained from these inoculations 
shows that 17 leaves produced 68 globular crown galls. ven 
of these leaves produced in addition one leafy crown gall each, 
while three leaves produced two leafy crown galls each; the 
remaining seven leaves produced no leafy crown galls at all. 
Another group of leaves, nine in number, produced 54 globular 
crown galls, and only four leaves produced one leafy crown gall 
each. In another group of nine leaves 45 crown galls of the 
globular type were formed. Four of these produced one leafy 
