72 Practical Farming 



for the manufacture of the elaborated sap in the leaves. 

 The plant gets from the soil nitrogen, phosphorus, potas- 

 sium, lime, magnesium, sulphur, and some other minor 

 things. The nitrogen originally comes from the air to the 

 soil, and we have means for getting it back from the air, 

 as we shall see. 



Each part of the plant, we have observed, has its par- 

 ticular function. The leaves, with their chlorophyll, take 

 in and decompose the carbon dioxide in the air, appro- 

 priate the carbon for starch-making, and return oxygen 

 to the air to purify it for animal hfe. The roots, with 

 their constantly multiplying areas of root hairs, take the 

 various ash elements and the nitrogen from the soil dis- 

 solved in the soil water, and carry the dissolved food up 

 through the conducting bundles of cells to the leaves. 

 There the material for construction and for the food of 

 the living matter is formed, and from this elaborated 

 material all the increase in the cells of the plant is made, 

 both to tops and roots. It is plain, then, that roots are 

 the product- of stems and leaves, and not stems and leaves 

 of roots. It is perfectly possible in most plants to place a 

 cutting under proper conditions, and from food stored in 

 the cells of the cutting to form roots, and in this way to 

 make a new plant that is identical with the plant from 

 which the cutting came. In some plants it is easy, indeed, 

 to make new plants also from cuttings of the roots, for on 

 many roots there occur what are known as adventitious 

 buds. But this fact does not contradict the statement 

 that roots are the product of stems, for the material from 

 which growth is made from a root cutting is the result of 

 materials stored there by the stems and leaves. 



