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accounted for, because the spores which rest on the 

 leaves are washed down the stem by rain, and vast 

 numbers of them enter the soil at the base of the plant. 

 If a potato plant is noticed it will be seen that the 

 stalks and stems are grooved in such a way that a 

 very large portion of the water which falls on them is 

 conducted to the centre of the plant. This provision 

 of Nature's to carry all the water to the roots is, of 

 course, highly beneficial in dry climates, but is preju- 

 dicial where the disease has become so general. 



Moulding-up to check Disease. 



The value of deep moulding is easily understood 

 when it is remembered that the zoospore lives but 

 a few minutes. Protective moulding was one of the 

 chief means adopted for preventing disease before 

 spraying was introduced, and it would be wrong to 

 discard it now. It is because moulding should be 

 thorough that the rows of potatoes should not be 

 placed too near to each other, as, when close, sufficient 

 loose earth cannot be obtained to make the ridges. 



The recommendation that the haulm of the potato 

 should be bent down so as to lie in the furrows 

 between the ridges has its value, as the spores are 

 largely carried down into them by rain, and are not so 

 easily blown away. The rain, instead of carrying the 

 spores down the stem, washes them directly into the fur- 

 row, where they are harmless. A disadvantage is that the 

 haulm does not dry so quickly after rain, consequently 

 the disease is more likely to continue developing. 



