Se6t II. Agriculture and Vegetation. 125 



that ground can afford, although there is 

 fufficient nourishment left for other grains ; 

 and there would be no time left to plough 

 the ground, as wheat is fown in the har- 

 veft: and, That the difference of vege- 

 table juices depends not on the difference 

 of food, but on the particular ftruclure 

 of the veffels of plants. 



THE latter opinion muft appear to every 

 one to be nearer the truth than the former : 

 nearer the truth, I fay, becaufe the advo- 

 cates for it feem to think, that one fort of 

 food ferves all vegetables. There I differ 

 from them. We faw, by the experiments 

 in the lail fection, that the fait of hard 

 water, Epfom fait, and the vitriolated tar- 

 tar, falts very different from one another, 

 nourifhed vegetables of the fame fpecies; 

 and therefore the food is not of one kind. 

 We know that fome trees contain the acid 

 of vitriol, becaufe with their charcoal we 

 can make a fulphur. We know, likewife, 

 that fome plants contain a nitrous fait, 



while 



