BACTERIUM CAMPESTRE IN SOUTH AFRICA. 



405 



During the summer months, especially during the rainy 

 weather, the disease spreads very rapidly, and develops rapidly 

 in plants which are attacked. In winter, however, when the 

 temperature is comparatively low, and there is no rain, the spread 

 of the disease is reduced to a minimum, and in plants which 

 become infected its progress is very slow. The central plant in 

 Plate (-), a, was photographed two months after inoculation, the 

 two months being December and January, when the weather 

 was warm and moist. In winter it takes six to eight months for 

 the disease to affect plants to the same extent. 



Fig. 1. 



The question as to how far leaf-eating insects are respon- 

 sible for communicating the disease in this country has not yet 

 been fully dealt with. It is certain that a number of infections 

 begin in close proximity to a hole made by such an insect, and 

 a number of experiments have been started to discover how 

 many of the common cabbage pests are responsible for the 

 carrying of the disease, but no definite results have yet been 

 obtained. These are being carried out with the co-operation 



