144 



BOARD OF AGRICULTURE. 



the plants. See Johnston's Catechism of Agricultural Chemis- 

 try. The vegetable fixed to one spot has the mechanical impulse 

 to seek the supply of food requisite for its development. Unless 

 the food is found in the soil, or artificially supplied by us, the 

 crop will be a failure ; for, as plants are intended as food for 

 animals, nature has provided that they shall not obtain their 

 perfection without taking up a supply of the ingredients which 

 serve as food for man and beast. 



Composition of soils of different degrees of fertility, (Johnson' sS) 



Says Johnson : " The soil of which the composition is given 

 in the first column, has produced crops for sixty years without 

 manure, and still contained a sensible quantity of all the sub- 

 stances required by plants. That in the second column pro- 

 duced good crops when regularly manured ; it was in want of 

 three or four substances only, Avhich were given to it by the 

 manure. The third was hopelessly barren ; it was in want of 

 many substances which ordinary manuring could not supply. 



The materials which enter into the formation of roots, as 

 before stated, must be found in the soil or artificially supplied ; 

 for it is also a fixed law of nature that the leaves and the roots 

 shall perform their functions simultaneously — and it is also 

 believed (the experiments hitherto made go to prove this decla- 

 ration) that if one of the iin[)ortant ingredients of the plant 



