

54 RELATION OF DISEASE TO SOILS AND MANURES. 



servers, that a heavy Wet clayey soil greatly favors the 

 mischief. 



(212.) It has been observed by many persons, that in 

 sand or peat the disease has not shown itself to its full ex- 

 tent ; but in quoting a general opinion, I have no precise 

 facts to warrant my making any assertion. Mr. Stone 

 states, that, " in his opinion, a light soil without manure is 

 less subject to disease than a better soil well cultivated." 



(213.) Some persons have imagined that our mode of 

 treatment is injurious, and that the process of ridging up is 

 deleterious. This, however, deserves no credit, for I have 

 seen the disease in hundreds of plants which have never 

 been banked up, and even in tubers half of which were 

 quite green from exposure to the light and air. 



(214.) Next to soils, manures have attracted attention, 

 and the guano from Ichaboe has been blamed. Now, the 

 redundancy of animal salts is calculated to materially in- 

 jure plants. I placed some crocuses in a solution of that 

 character, which grew and flourished, and became in- 

 tensely green. Instead of flowering, however, the roots 

 began after a time to die, and finally the entire plants were 

 destroyed. No doubt, guano in excess may act highly in- 

 juriously, but no evidence can be adduced that it ever 

 caused the potatoe disease. Mr. Stone states that he did 

 not use any manure except on one piece, where he applied 

 some pigeon's dung, and there he found most of the pota- 

 toes good for nothing. 



(215.) I am informed that London returns its manures 

 to Yorkshire, from whence the metropolis derives its sup- 

 plies of potatoes ; and in various parts of the country every 

 kind of manure is used to further the growth of the potatoe 

 plant. 



