124 The Principles of Part III. 



vegetable juices are a flrong proof on their 

 fide. 



THOSE who affert, that all vegetables 

 feed on the fame food, fupport their opi- 

 nion by the following arguments. The 

 longer ground is kept in tillage, though it 

 bears grain of different fpecies, the worfe 

 it becomes : but this would not happen, if 

 plants took different particles from the 

 foil : That all fort of weeds ftarve corn, by 

 taking part of the fame nourishment : That 

 fallowing ground would be an ufelefs prac- 

 tice, fince there is fuch a diverfity of fpe- 

 cies: That it would be in vain for plants 

 to have a tafte, fmce they have no local 

 motion : That change of fpecies fucceeds, 

 not becaufe plants take only their own 

 food, but becaufe fome loofen, while others 

 bind the ground j fome roots go deep into 

 the ground, while others keep about the 

 furface : That it is true, wheat will not fuc- 

 ceed in the fame ground two years fuccef- 

 fively, becaufe it requires more food than 



that 



