POTATO ROT. 643 



etables. Fungus growth is slow in its developments. The 

 small vessels of the tuber which lead from centre to surface be- 

 come obstructed, or partly paralyzed, and its power of throwing 

 off excrementitious matter impaired. Fungi are only symptoms 

 of a loss of vitality, mere effects. Preceding these were other 

 manifestations of disorder ; such as soapy taste, &c. " I con- 

 sider fungi to be of hereditary origin, although at first acquired." 

 The changes have been so gradual as not to be suspected. 

 Many of the external morbid growths on vegetables originate 

 within, while they are supposed to be external causes. 



The insect theory could have but a secondary effect in pro- 

 ducing or extending the rot, for many of the insects found 

 about the plant result from the decomposition of the tuber. 

 Although these cannot produce the rot, they act in conjunction 

 with other causes in producing disease. The vitality of the 

 potato may have been compromised by transplanting. It is 

 supposed to be indigenous to South America. How far it may 

 have suffered by transplantation is difficult to decide. The 

 Almighty made the races of animals and vegetables to be 

 healthy, but if his laws respecting them are violated by an in- 

 ferior cross fecundation, or want of due care in the selection or 

 preservation of seedlings, or any other extraneous circumstances 

 or agents, we may expect to find them involved in general 

 ruin. 



To preserve the identity and life of the potato — 



First. Plant a perfect germ — largest potatoes are best. 



Secondly. Plant ripe seed. 



Thirdly. The soil and climate must be congenial. 



Lastly. The different varieties must be either planted sep- 

 arately ; or, if improvement be designed, it must be accom- 

 plished through the congress of superior plants. With the 

 first requisite there is no compliance. With the second, the 

 practical farmer will not contend. The third requires a knowl- 

 edge of agricultural chemistry. The fourth is too often violated. 

 The varieties, like the different breeds of animals, are so amal- 

 gamated as to render it difficult to find pure stock. 



From these remarks it is evident that the causes, hereditary 

 or acquired, are various, operating directly or indirectly in de- 



