180 REporRT OF DEPARTMENT OF BACTERIOLOGY OF THE 
varities, such as turnip, radish and carrot. These facts, with 
others to be set forth later, show its active invasion to occur 
in the intercellular spaces and along the planes of the middle 
lamellae. A fundamental condition of this invasion is an 
abundant moisture content in the host tissues, the more the 
better, apparently. The water-logged, or translucent appear- 
ance of the invaded tissues is doubtless due in part to the. 
expulsion of gas incident to the filling of the intercellulars with 
liquid resulting from the plasmolysis of the cells, and in part 
to the changes in the optical characters of the walls themselves. 
The fresh walls are uniformly refractive throughout with a 
slight difference between the middle and the inner lamellae. 
Almost immediately following their immersion in either a liv- 
ing culture or an aqueous solution of the precipitated enzym 
the inner lamellae begin to lose their refractiveness. This 
change in appearance is evident even to the unaided eye if thin 
sections are closely observed. It is more rapidly followed under 
the microscope, and is then seen to be associated with a swell- 
ing of the primary wall or inner lamellae, sometimes to twice 
their original thickness, and with the appearance within a 
short time of a delicate laminated structure in these swollen 
walls, as shown in the accompanying figures. The middle 

Fig. 5. <A sterile block cut from living carrot root was immersed for 2b 
hours in a broth culture of B. carotovorus, then fixed in hot absolute 
alcohol, imbedded in paraffin and sectioned. The above sketch (x 250) 
shows a large thin-walled parenchyma cell lying about three cells inward 
from the surface. The enzymic action was here complete, the cells isolated 
and the intercellular spaces gorged with bacteria, but the undissolved 
remnant of the wall kept them from invading the cell cavities. 
