DISEASES OF THE PLANT. 



317 



Fig. 4 



distinguishable by the different portions of the root affected, 

 and by the presence of insects accompanying the progress 

 of the disease. There is nothing in the evidence we have 

 before us to lead us to infer that the two forms of disease 

 could not exist in the 

 same root; in some 

 instances (fig. 4) such 

 may have been the 

 case, and thus have 

 led to the many con- 

 flicting opinions that 

 have been expressed 

 on the subject. From 

 the details of cultiva- 

 tion, obtained in re- 

 ply to the Highland 

 Society's circular,and 

 from Dr. Anderson's 

 valuable deductions, 

 we would suggest 

 that the amount of 

 available potash in 

 the soil may in some 



way exert an influence on one or both forms of disease. It 

 was found that it occurs far more frequently and far more 

 severely on light than on heavy soils, and that on the stiff 

 clays it is rarely observed ; and again, that it may, in most 



original state if the circumstances which induced their abnormal condition be 

 not constantly sustained. 



Turnips of ordinary size we're planted on a piece of unmanured soil three 

 years in succession, the produce being reduced each year in weight to a con- 

 siderable extent. In the fourth year the bulb had entirely disappeared, and 

 the root had resumed its original wild state. The produce each year is thus 

 given : 



Turnip affected by both forms of Disease. 



Weight per Acre. 

 Tons.cwts. qrs. Iba. 



1843 4332 



1844 2410 



1845 .. . 13 2 4 



Avernge weight of 

 built in Ibs. 



-52 



-36 



. -11 



