Chap. IV. OF THE FOOD OF PLANTS. 7 



To that if wheat were to be fown again, it would be on land that 

 had refted five years from that kind of grain. 



The moft ignorant in farming will allow, that only poor crops 

 will be obtained by fuch management ; becaufe all forts of plants 

 exhauft the earth : and befides, during the fallow, great pains is 

 taken in plowing, by which means the earth is broken, the fpaces 

 between its particles are multiplied, and confequently it is rendered 

 fit for producing plants v/hich require a fine tilth, fuch as wheat, 

 and is not exhaufled by other produdlions. 



In ihort, if each plant drew from the earth only the particular 

 juice proper for itfelf, poppies, thiftles, cs'c. which kill wheat, 

 would do it no hurt. Wheat might, in that cafe, grow as well 

 in a common, as in a well plowed field. Let it not be alledged, 

 that the ftalks of weeds are what hurt the wheat, and not the 

 roots by the juices they confume; for if dry branches were to be 

 fet in fuch numbers as to make a greater fliade than thofe weeds, 

 they would not equally prejudice the growth of the wheat. 



Thofe who think that every plant draws a particular juice from 

 the earth, allow that the fubftances proper for the nourhhment 

 of each plant, ought to be diflblved in a quantity of water fuflicient 

 to convey them into the plant. But if weeds abforb all that 

 water, none will remain for the nourifhment of the plant which 

 is cultivated. 



An obfervation which feems of greater force than thofe yet men- 

 tioned, is, that a poor land, when refted, produces of itfelf a num- 

 ber of plants ; and after having continued to feed thofe produdlions 

 for years together, without any culture, it is flill able to bear 

 fome good crops. The reafon of this is faid to b«, that the plants 

 which grow fpontaneoufly upon that land, have not exhaufted the 

 fubllance which is necefiary for the food of wheat. 



It is likewife obferved, that lands which have long borne fain- 

 foin or lucerne, afterwards produce very fine wheat. 



Anfiver. This obfervation feems to contradii^ the opinion of 

 plants of dififerent fpecies, being nourilhed by the lame kind of 

 juices. But it is to be obferved, i. That lands are neither fo 

 fpeedily, nor fo well improved by being refted, as by proper culture. 

 2. While land is relied, the rains, dews, and winds, lodge in it 

 many particles fit for the nourifhment of plants. The grafs or 

 weeds which grow on it afford food to cattle, which enrich the 

 land with their dung ; and the roots and leaves of the grafs or 



weeds 



