88 CLASSICS OF MODERN SCIENCE 

 valuable varieties of plants which are used for culinary purposes, 

 have been produced in this manner, as the several kinds of cabbages, 

 lettuces, etc.; and I apprehend this is the reason of their not being 

 changed by a difference of soil. Hence I cannot give my assent to 

 the opinion of those who imagine all varieties to have been occasioned 

 by change of soil ; for, if this were the case, the plants would return 

 to their original form, if removed again to their original situation. 



