110 POTATOE GANGRENE AND OTHER DISEASES. 



believe that our present gangrene is only an exaggerated 

 form of the old curl. It is a common characteristic of the 

 numerous family of Aphides to render the leaf of all plants 

 which they attack curled ; I have frequently noticed in 

 my own sitting-room that the vastator curls the leaf of 

 the turnip ; and it must have been observed by very 

 many how excessively distorted the leaves of the rose-tree 

 become when suffering severely from the ravages of the 

 Aphis rosa. 



(437.) I have found, on one or two occasions, a potatoe 

 plant to be covered with the vastator, and that, instead of 

 its being destroyed by the insect in the usual manner, the 

 leaves exhibited the most exaggerated form of curl which 

 could be conceived, for they were curled more than those 

 of the most highly-curled parsley. However, I feel un- 

 willing to pass an opinion upon a disease which I have 

 not seen in its former prevalence. 



(438.) The rust is another disease. It consists of a 

 colored spot upon the leaves, which is at first small, but 

 gradually increases, and at length overruns the whole 

 leaf. Of this disease, however, I am practically ignorant. 



