238 Agricultural Bacteriology. 



the edges of the leaves. The spread of the disease in the 

 plant is along the veins and ribs to the main stem. On 

 cutting across the stem of an infected leaf one can see 

 the blackened ends of the fibrous strands (fibro vascular 

 bundles). The channels that carry the food and water 

 supply of the leaf are destroyed ; the leaf is thus deprived 

 of nourishment and dies. 



Efforts to combat the disease in the field by the re- 

 moval of diseased leaves have proved unsuccessful. 

 Preventive measures must be confined to a treatment of 

 the seed and to the growing of cabbage in a system of ro- 

 tation rather than on the same field continuously. 



Melon wilt. Squash, cucumber, and melon vines are 

 subject to a bacterial disease known as wilt since the af- 

 fected tissues are wilted, due to the plugging of the water 

 tubes with the bacteria. The disease is most prevalent in 

 the early summer and is easily told from all other 

 troubles of the melon family by the sudden wilting of the 

 leaves without any other visible symptoms. 



The bacteria live in the soil and gain entrance to the 

 plant through wounds. It is undoubtedly spread from 

 plant to plant by means of the various insects that feed 

 upon the vines. The only means of prevention is to grow 

 melons and squash in rotation with other crops. 



