274 How THE FARM PAYS. 



Mildew consists of a white fibrous growth, the fibres separately 

 being too fine to be visible to the eye, and this growth generally 

 appears on the leaves, but sometimes on the fruit as well. It cannot 

 be doubted that this outward appearance is merely the symptom of 

 an internal disease, originating from some cause of the nature above 

 mentioned. Kust consists of small orange-yellow or reddish oval 

 bodies, so thickly interspersed among the white fibres of mildew as 

 to give the leaf the appearance of being covered with red dust. 

 Other forms of rust consist of cup shaped bodies, made up of these 

 very small reddish ovals. Smut consists of a mass of small, brownish, 

 round or variegated shaped spores, some being beautifully reticulated 

 and marked when seen under the microscope. It usually occupies 

 the place of the seed in oats and wheat, and also in corn; but in corn 

 it also appears in masses, breaking through the stems, leaves and 

 flowers or tassel, thus showing that the whole plant is impregnated 

 with the disease. No doubt in most cases rust and smut are sown 

 with the seed, either adhering to it or infecting it internally. The 

 so-called potato rot is one of these fungoid, parasitic diseases, closely 

 allied to the smut of grain. 



But a good deal has yet to be learned in regard to the nature of 

 these parasitic diseases, and until our knowledge is more complete it 

 interests us more to consider what can be done to avoid them. This 

 is generally to see that the trees and plants chiefly affected by them 

 are maintained in vigorous health by the best cultivation, and by 

 fertilizing with lime and potash, which are principal!}' needed by 

 them. And as far as the common farm crops are concerned, to avoid 

 too frequent repetition of them upon the same fields, practicing as wide 

 a rotation as may be possible, to avoid exhausting the soil of the 

 most needed elements of their growth. Also by preventing the 

 infection of healthy plants by destroying the contagion; cutting off 

 and burning blighted limbs; rooting out rusted plants and destroying 

 them in some effective manner, but by no means permitting them to 

 get into the manure; by carefully destroying all smutted fodder, all 

 diseased potato tops; and every particle of smut in the seed sown, by 

 using the pickle referred to in the chapter on the Culture of Wheat. 

 No doubt, too, the regular use of lime in the rotation of manuring 

 may have a good effect in adding to the fertility of the soil and in 

 giving greater vigor to the vegetation. Finally, knowing how 

 infinitely small and light are the spores or seeds of these mildews, 

 rusts and smuts, we should not be surprised to find them abundantly 

 distributed in the air, in water and in the soil, so that we cannot 

 wonder that any weak plant may become infected with them just at 

 the time when it offers the most favorable conditions for their growth. 



