304 Robinson and JValkden.—A Critical Study of Crown Gall. 
Changes in Inoculated and Control Shoots 
According to whether the cut surface of the shoot is in contact with the 
soil when the shoot is treated as a cutting, or the cut surface is left exposed 
to the air, minor differences in behaviour are observed. The differences 
Text-fig. i. Series of radial longitudinal sections through upper ends of stems at various 
intervals after inoculation, illustrating stages in gall formation : A after 6 days, B after 9 days, 
C after 15 days, D after 4 months, E after 5^ months. A, B, and C x 9 ; D and E x 3. 
The dotted areas represent the position of actively dividing tissues. The blackest lines in the 
vascular bundles and cortex in A, B, and c represent positions where bacteria were observed. 
are found in both the inoculated and uninoculated shoots and are partly 
due to differences in polarity and partly to the different conditions in the 
soil and in air. Text-figs, i and 2 illustrate various stages in the develop¬ 
ment of galls, which have arisen on the upper ends of stems in air and on 
the lower ends of cuttings in soil, respectively. The general development is 
similar in the two cases, but the tumour growth is more superficial in the 
cuttings, the severed vascular bundles being more quickly covered over by 
proliferating tissue than in the aerial shoots. It is noteworthy also that in 
