312 Robinson and Walkden.—A Critical Study of Crown Gall. 
In order to obtain as much precision as possible, the inoculations were 
made into a large number of shoots of similar size, age, and general vigour 
by means of single horizontal or vertical needle-pricks. PL V, Fig. io, shows 
the result of such a single horizontal needle-prick inoculation at the apex of 
a shoot of Chrysanthemum frutescens five weeks after the inoculation. Six 
galls of various sizes at the bases of leaves are seen in the photograph, and 
in addition the apex was so injured at one side that the terminal bud 
developed more feebly than usual, and the two nearest lateral buds pro- 
B 
A 
Text-fig. 4. a. Phyllotaxy diagram of the shoot of C. jrutescens shown in PL V, Fig. 10. 
The galls on the various leaves are indicated by the shade areas, and the arrow shows the direction 
taken by the needle in making the inoculation at the apex. 
B. Diagrammatic representation of the presumed path of the needle shown in relation to 
the longitudinal view of the apical region of the same shoot. 
duced shoots. The six galls, which are now widely separated from one 
another by one or more internodes, have arisen as a result of the inoculation 
of wounded rudimentary leaves at the apex of the shoot, and have been 
separated by the subsequent growth of the shoot. Bacterium tumefaciens 
is present in large numbers on the rough exterior of such galls, and can be 
readily isolated from them. A very slight inoculation wound is sufficient 
to lead to the production of such galls, and the degree of roughness of the 
surface visible may in such cases be very slight. Text-fig. 4, A, is a phyllo¬ 
taxy diagram of the shoot shown in PI. V, Fig. 10, and it will be seen that 
the position of the galls on the various leaves is consistent with each leaf 
bearing a gall, having been wounded and inoculated by the single horizontal 
needle-prick. The arrows in Text-fig. 4, A and B, show the presumed path 
of the needle. A very large number of such inoculations was made, and 
