PRINCIPLES OF FERTILITY. 133 



The chemist finds that a plant is made up of thirteen elcmontary 

 substances, distinct and definite. The (hlference between the different 

 agricultural plants is this, that these substances exist in these plants 

 in different proportions. The same elementary materials are found 

 in a corn plant that are found in a stalk of wheat, but in the two 

 plants they are found in different proportions. These thirteen 

 elements are divided into two classes, one of which is called oiganic 

 or atmospheric. There are four of these atmospheric elements in a 

 plant, and three of these are obtained by the plant from the atmos- 

 phere alone. You will see at once that the farmer has nothing to 

 do with them. If the plant obtains a material from the atmosphere, 

 the farmer has not to suppl\- it, and he need not trouble himself 

 about it, onl}" that he wants to fully understand the nature and 

 composition of a plant. The fourth element of this class, nitrogen, 

 is found in the atmosphere, but is obtained chiefl}- from the soil ; 

 consequentl}', as you will see further on, the farmer has something 

 to do with nitrogen ; he has got to make himself familiar with it. 

 We will bear in mind that nitrogen is an element found in all plants. 



The other class of elementary substances composing a plant are 

 called mineral, inorganic or earth}^ elements. There are nine of 

 these mineral elements found in every plant. Some are found in 

 only extremely small quantities, and others in larger, but only an 

 extremely small percentage of mineral matter is found in any plant. 

 To determine the exact amount, all yon have to do is to take the 

 plant, dry it and burn it, and the organic or atmospheric elements 

 will ascend from the burning into the air from whence they came ; 

 the mineral portions are undestro^'cd by the fire and are left in 

 the form of ashes. You know that if you take a large plant, like 

 corn, and Inirn it, you have only a very small amount of ashes left; 

 and 3et every particle of these nine elementary mineral substances 

 existing in the corn plant is left in the ashes. 



Of all these nine mineral elements found in a plant, there are 

 seven of them which are found in sufficient supply in all of our 

 agricultural soils, so that practice has proved that the farmer never 

 need look out for them. That is, in changing an infertile soil to a 

 fertile one, practice has proved that the farmer has to look out for 

 onh' two of these mineral substances ; the others are alwa3"s found 

 in the soil in sufficient quantities for an indefinite succession of 

 crops. These two, which the farmer from time to time may be 

 'called upon to supply, from the fact that they are not found in 



