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Tomato and Potato Bacteriosis. 



[JULY, 



various kinds of fungi and bacteria gain an entrance through 

 the broken fruit, which is speedily reduced to pulp. Dis- 

 eased plants gradually droop and die from the top down- 

 wards. 



In potatoes the symptoms are somewhat similar to those 

 described above. The uppermost leaves droop first, and the 

 stem becomes very conspicuously marked with blackish 

 longitudinal streaks. The vascular bundles are also browned, 

 owing to the presence of the bacterium, which travels along 

 the vessels of the underground branches and passes into the 

 tubers, where its presence is indicated by a more or less 

 decided brown ring situated a small distance from the out- 

 side of the tuber, and corresponding to the position of the 

 vascular-bundle ring of the tuber. As an infected tuber in- 

 creases in size the bacteria encroach on the central mass 

 enclosed by the vascular ring, which gradually assumes a 

 brown colour, and finally becomes soft and rotten, leaving 

 a thin outside crust intact. This shell is usually broken when 

 the potatoes are lifted, and its contents, swarming with bac- 

 teria, remain in the land. 



In the case of potatoes, Dr. Smith has shown that the 

 rapid spread of the disease is caused by insects of various 

 kinds, feeding alternately on diseased and healthy plants. 

 The numerous isolated patches of disease on the fruit and 

 leaves of the tomatoes examined at Kew support this view. 

 To prevent this the plants should be sprayed with Bordeaux 

 mixture containing an insecticide, which would answer the 

 double purpose of warding off insects and preventing 

 the appearance of Phytophthora infestans, Cladosporium 

 fulvum, &c. 



Bacteria have occurred abundantly in the substance of 

 partly ripe tomatoes; hence, owing to the difficulty experi- 

 enced in thoroughly removing the glairy coating from the 

 seed, it is highly probable that bacteria would become locked 

 up in this substance as it dried round the seed, and on being 

 released during germination would endanger the crop. Seed 

 obtained from fruit grown in an infected area should not be 

 used. 



Potato tubers showing the slightest trace of an internal 

 brown ring should not be used for "sets"; in fact, potatoes 

 from an infected district should be avoided. 



