240 LEVINE: STUDIES ON PLANT CANCERS—IV 
cm. But when these results are contrasted with crown galls 
resulting from Emulsion ta, another culture twenty-one days 
old, the growths resulting from the younger cultures are seen 
to be slightly larger. Comparing the size of the crown galls in 
axillary buds the young cultures and the old produced results 
almost identical; (compare Emulsions I and VI). C ultures 
twenty-one and forty days old were contrasted by inoculating 
Emulsions 4 and 5 into midveins of leaves. The larger growths 
appeared on the leaves which were inoculated with the younger 
bacteria. Yet the inoculation of Emulsion V in the midvein of 
the tobacco leaf produced a larger growth than did Emulsion ITI, 
another culture twenty-one days old. It appears that so long 
as the Bacterium wmefaciens is viable the age of the culture has 
little effect on the size on the gall produced. A culture two days 
old is no more effective in producing crown galls in tobacco than 
are cultures three to five weeks old. 
THE EFFECTS OF VARIOUS GUANTITIES OF SIMILAR DILUTIONS 
The size of galls produced when different quantities of similar 
dilutions of Bacterium tumefaciens were inoculated in the to- 
bacco was compared. Comparing results with the prick and 
the trocar methods it seems that inoculation through a trocar 
wound produces a slightly larger growth than is produced by 
pricking the plant five to ten times with a needle carrying an — 
emulsion of the same dilution; (compare 2a and 2a’). The dif- 
ference may be explained, however, not on the basis of the quan- 
tities of the bacteria introduced, but on the degree of injury to 
the cells caused by the trocar method as compared with the 
pricking method. 
When two different quantities of Bacterium tumefaciens were 
inoculated by the same method the difference in results was 
negligible. One drop of emulsion Id and 0.8 cc. of the same 
emulsion called Id’ (for convenience of record) were inoculated 
into axillary buds of the tobacco. Similar results were obtained. 
The average size of the crown gall in each series of experiments 
was 1.9 cm. Sixteen plants were inoculated in the leaf axils 
with an average dosage of 0.25 cc. of emulsion 6a’ (an emulsion 
equal to 6ain strength). While these results were not compared 
with those obtained by using a drop of 6a in the leaf axil it was 
found that the average size of the growths with 0.25 cc. of 
