LEVINE: STUDIES ON PLANT CANCERS—I 449 
OBSERVATIONS 
1. Inoculation of Bacterium tumefaciens into the notches of Bryo- 
bhyllum calycinum leaves 
The study of this material shows that in the great majority 
of cases, the notches infected with Bacterium tumefaciens, instead of 
causing the development of leafy shoots, formed ordinary crown 
galls. Fic. 1 represents a young detached leaf forty-five days 
after having been placed on soil and having had the basal notches 
inoculated with the bacterium. The apical notches were pricked 
with a sterile needle and served as controls. The inoculated 
notches show well-developed ordinary crown galls without leafy 
shoots, while the control notches on the ventral surface show the 
beginning of the development of leafy shoots. 
Fic. 2 represents an older leaf, in which the basal notches were 
inoculated forty-five days previously. In this case no galls or 
shoots have as yet been formed at the notches but the control 
notches are beginning to proliferate and the uppermost notch of 
the leaf has produced a shoot. Fics. 3 and 4 represent the ventral 
and dorsal surfaces of a detached leaf seventy days after inoculating 
the basal notches with the bacterium. All the basal, infected 
notches show well-developed galls without leafy shoots on the 
ventral surface (Fic. 3). The majority of the control, apical 
notches have already developed leafy shoots. Fic. 5 represents 
an old detached leaf grown on soil, 140 days after the basal notches 
were infected. The mother leaf is seen in the center of the figure 
with a number of well-developed shoots coming from the apical 
notches. The basal, inoculated notches all show well-developed 
crown galls. In one instance a poorly developed shoot, visible 
in Fic. 5 over the largest gall, made its appearance. A similar 
condition is shown in Fic. 7. These leafy shoots appeared much 
later in the development of the gall. This seems to show the 
dwarfing and inhibiting effect the crown gall organism has on 
the growth of the bud Anlage. 
2. Inoculation in the vicinity of the notch 
When the inoculation is made near the notch instead of in 
it, a crown gall is developed alongside of a poorly developed leafy 
