The Distbibution of Wart Disease. [Nov., 



ward.s at an alarming rate since 1916, several fresh cases 

 having been notified from Lincolnshire and the East Eiding of 

 Yorkshire. 



It had also spread in a south-easterly direction, outbreaks of 

 importance having occurred in Surrey, the Home Counties and 

 Kent. 



Any explanation of the spread of infection must account for 

 three essential facts: — 



(1) The appearance of the disease as of economic 

 importance from 1907 onwards. 



(2) The gTeater concentration of the disease in the 

 North and West, and the comparative freedom of the East 

 and South. 



(3) The relative suddenness of the spread of infection 

 on the Eastern and Southern side since 1914. 



The only possible explanation which will account for this 

 geographical distribution of Wart Disease is that the main 

 agent in the distribution of the disease is " seed " : although the 

 variety of potato commonly grown at different periods may have 

 determined the economic importance or otherwise of the disease. 



(To he continued.) 



