POTATO BLIGHT. 89 



and rain came on, after continued drought, in the 

 beginning of September, exactly at the period of the 

 most luxuriant growth of the potatoes. 



In most places no trace of disease was observed la m <>st 



places the 



in the early potatoes before the middle of August ; early P o- 

 and even after that period low-lying, cold and wet caped tin 



J after the 



fields, were chiefly attacked by it. In many plants, middle of 

 in the same field, in which the seed potatoes had 

 been destroyed by putrefraction and decay, the 

 tubers appeared quite healthy, while in others it was 

 easy to see that those tubers alone, which lay next 

 to the old potatoes, were infected and attacked by 

 the disease, and that on the side next to the old 

 tubers. 



In 1846 all the potato-plants in my garden died Theau- 

 completely off towards the end of August, before a Mrieaee i"n 



-I Q J /? 



single tuber had been formed ; and in 1847, in the 



same field, the tubers of all those plants which stood Effect of 



shade. 



under trees and in protected spots, were quite rot- 

 ten, while no trace of disease appeared in spots 

 which were more elevated and more fully exposed to 

 the current of air. The cause of the disease is the The cause 



, ... of potato 



same which, m spring and autumn, excites influenza; blight is the 

 that is, the disease is the effect of the temperature that of in- 

 and hygrometric state of the atmosphere, by which, 

 in consequence of the disturbance of the normal 

 transpiration, a check is suddenly, or for a consider- 

 able time, given to the motion of the fluids, which is 

 one chief condition of life, and which thus becomes 



