PLATE i 
Photomicrographs of cross sections of tomato-stem galls showing some responses of 
the cells which surround the bacteria. 
A. —A cross section of a two-day-old inoculation showing the puncture, which is 
lined with bacteria at a, and lateral migration of the bacteria in the subepidermal 
region at b. X56. 
B. —A cross section of pith from an eight-day-old inoculation showing an inter¬ 
cellular space at c which contains bacteria. New walls (d) have been laid down in 
the surrounding pith cells in the portion of the cell nearest to the position of the bacteria. 
X223. 
C. —An enlargement of the invaded intercellular space shown in B.' Here it may 
be noted that the nuclei e, lie in a position close to the bacteria, as if in response to 
some stimulus. This dislocation of the nuclei may assist in explaining the loss of 
polarity in gall cells. X502. 
D. —A cross section in the cortex of a tomato stem eight days after inoculation. 
Small gall cells are found to form a sheath, as at f, about the position of the bacteria, as 
at g. Here it appears that the host cells form a sheath about the position of the 
bacteria. X 56. 
E. —An enlargement of the region at X in D. The hyperplastic cells (f) appear 
to form a sheath about the invaded intercellular space (g). X169. 
The preparations photographed for this plate were all paraffin sections stained with 
carbol ruchsin diluted 1 :ioo, liquid measure, with water, and counterstained with light 
green in clove oil. 
(436) 
