839 



CHAPTER XXI. 



ON THE DISEASES OF PLANTS, PARTICU- 

 LARLY AS ILLUSTRATIVE OF THEIR 

 VITAL PRINCIPLE, 



Ihe diseases of Vegetables serve in many 

 instances to prove their vitality, and to illus- 

 trate the nature of their constitution. 



Plants are subject to Gangrene or Sphace- 

 las, especially the more succulent kinds, of 

 which a very curious account, concerning the 

 Cactus coccinellifer, Indian Fig, or Nopal, 

 extremely to our present purpose, is given by 

 M. Thiery de Menonville, in his work on the 

 culture of the Nopal as the food of the Cochi- 

 neal insect. This writer travelled, about 20 

 years since, through the Spanish settlements 

 in South America, chiefly noted for the culti- 

 vation of this precious insect, on purpose to 

 transport it clandestinely to some of the 



z 2 



