312 THE TUKNIP CEOP. 



them the peculiar glaucous hue of the "mildew," so 

 perceptible even at a distance from the field. This con- 

 dition of the plant is seen generally when vegetation has 

 been arrested in consequence of continued drought, and is 

 due to the presence of a species of "Oidium" upon the 

 leaves, the growth of which is effectually checked by it, 

 and in the end, as in the former case, unless the plant is 

 speedily relieved by rain, and its powers restored, the 

 roots as well as the tops perish, or are greatly deteriorated 

 and of little value. This disease is far more commonly 

 met with in the south than in the north, and ap- 

 pears to visit the more mature plants with greater 

 severity than the younger ones. In many parts, there- 

 fore, where the soils or the climate predispose to this 

 visitation, it is the custom to delay sowing, even the 

 Swedes, until the end of June, so that the plant may not 

 be too advanced in its growth at the period when the 

 "mildew" may be expected to show itself. In all cases, 

 however, whether in the north or the south, it is always 

 desirable to keep the spaces between the rows well stirred 

 and pulverized at the surface at this particular period 

 (August and September), when the earth has acquired a 

 high temperature, and but little rain can be looked for. 

 This gives the surface a greater power of absorbing the 

 moisture of the dew, and at the same time increases the 

 capillary power of the soil to draw moisture upwards 

 from the strata below. As long as the healthy plant can 

 continue its regular functions of growth, there is no fear 

 of mildew. If these are arrested for any time by the 

 absence of sufficient moisture, disease and decomposition 

 must ensue. In the Agricultural Gazette for ]853, p. 

 276, there is an account of a disease attacking the Swedes, 

 the decay commencing apparently in the neck, imme- 

 diately below the top, penetrating gradually to the centre, 

 a nd ultimately cutting off all nutriment from the apex, 



