DISEASES AND INSECT INJURIES. 399 



of this practice is generally beneficial; the soil is kepi 

 open at bottom, and has the full benefit of the winter's 

 action. On lighter soils, or for winter crops, it is advisable 

 after sowing to roll the field, in order to consolidate the 

 soil, and close it from the action of the weather, which in 

 this instance would act prejudicially to the growing 

 plants. Mustard ploughed in this way has the reputation 

 of being obnoxious to the wireworm. If this be the case 

 it adds to its value when used for this purpose. 



In sowing mustard, either for feeding or manuring 

 purposes, it must always be recollected that the white 

 species should be used. The brown or black is never 

 sown, except for its seed, as it is not only less vigorous in 

 its habit of growth, but its seeds have the property of, 

 remaining in the soil for many years without injury, and 

 then germinating and growing, as from time to time in 

 ploughing they are brought into favourable conditions for 

 their growth. For grinding, however, the black mustard 

 is superior to the white, and, under ordinary circum- 

 stances, fetches a higher price in the market. 



The diseases and insect ravages that the crop is sub- 

 ject to have not been very particularly noticed ; its close 

 alliance, however, with those crops belonging to the same 

 order (Cruciferse), already described, would indicate that 

 it is more or less liable to the same injuries which are 

 inflicted upon them. The "fly/' however, is that which 

 is most commonly noticed ; and, as an indigenous congener, 

 the " charlock/' or wild mustard (S. arvensis), is generally 

 to be seen liberally distributed over our fields, we are 

 pretty certain to rear and to preserve on the land a 

 sufficient stock of these destructive insects until our valu- 

 able cultivated plants, turnips, cabbages, kohl-rabi, &c., 

 are ready for their entertainment. A disease of the 

 parasitic fungoid class, which is not uncommon with the 

 indigenous species, has been noticed occasionally attacking 



