450 LEVINE: STUDIES ON PLANT CANCERS—I 
shoot. This is shown in Fic. 6, which represents a leaf forty- 
five days after inoculation with Bacterium tumefaciens. The 
control notch developed a much larger and more vigorous leafy | 
shoot. 
FIG. 7 represents an old detached leaf, 140 days after inocula- - 
tion. Here again several of the inoculations were made near the 
bud Anlagen. To the left are seen the large plants which have 
developed from the control notches. At the right, in the fore- 
ground, are seen three galls; next to the lower ones there appear 
small dwarfed plants. It appears that the galls have interfered 
with the normal development of these leafy shoots when compared 
with the large normal plants seen to the left. 
A: STdondon in the midvein 
It may be assumed that the midvein may have totipotent 
cells which by the inoculation of Bacterium tumefaciens can be 
stimulated to develop leafy shoots. Forty leaves of B. calycinum, 
both young and old, detached from and attached to the mother 
plants, were inoculated with Bacterium tumefaciens by means of 
pricking the midvein of the leaf with a fine needle. All produced 
crown galls within a month after the inoculation. Fics. 2 and 3 
show the appearance of such galls on young leaves forty days after 
the inoculations were made. Fic. 8 represents an old leaf attached 
to the mother plant. A large gall has been formed on the midvein 
by inoculating it with the bacterium five months previously. The 
tumor is a charcteristic crown gall consisting of a great number 
of tubercles. This leaf was carefully guarded in the hopes that 
these tubercles would produce leafy shoots. Fic. 9 represents the 
gall shown in Fic. 8, nine months after inoculation. The leaf 
became detached and withered. The gall has grown considerably 
larger, taking on a cylindrical shape, and has become covered 
with numerous tuberosities. No leafy shoots were formed. 
4. Inoculation of the growing region of the stem 
A large number of B. calycinum plants were also inoculated 
with Bacterium tumefaciens in the growing region of the stem with 
the object of stimulating there the possible totipotent cells to 
leafy shoot formation. Fic. 10 (a, b,c, e, f) represents a few of the 
