CHAPTER X 



DISEASES OF THE POTATO 



By M. F. Barrus 



When healthy potatoes are planted in a warm, moist soil, 

 vigorous sprouts will grow up from the tubers. These 

 develop into vines with green expanded leaves. On 

 underground stems there will be formed young tubers 

 which enlarge greatly in the latter period of the growth 

 of the plant. When the healthy tuber is planted, the 

 food stored within is used for the production of tissue 

 for roots, stems and leaves. As soon as the leaves have 

 expanded they perform the important task of making 

 food during daylight from the carbon dioxide of the air 

 and from water and soil solutions absorbed by the roots. 

 This food is used for the maintenance and further growth 

 of the plants, and whatever is made in excess of this is 

 stored in the tuber largely in the form of starch. After 

 the vines have obtained their greatest growth, the leaves 

 make a large excess of food above that needed for main- 

 tenance, and consequently the storage of food in the tuber 

 takes place rapidly. It is plainly to be seen, therefore, 

 that in order to have a large amount of food stored in 

 the tubers, that is, to have a large yield, it is necessary 

 first to have a good growth of vines and to have them 

 remain healthy until the tubers become of maximum size. 

 A destruction of the leaves by any means reduces the 

 yield of tubers. 



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