68 Practical Farming 



laced, never forget that they are oaks and pines, and that 

 each takes food from the soil in a different way and makes 

 a different article in the final result of its work. The soil 

 water, brought up by the roots and distributed to the leaves 

 through the elongated vessels which branch into the leaf 

 and form what we call the veins of the leaf, has food for the 

 plants in a very dilute state. The stomata of the leaves 

 then take on another office, and to some slight extent the 

 whole leaf aids in this. This is the evaporation or trans- 

 piration of moisture, in the form of invisible vapor, into 

 the air. Thus the plant condenses the watery food, re- 

 taining the food and parting with the surplus moisture. 

 Sometimes this evaporation becomes too rapid, and the 

 moisture passes off more rapidly than the roots can supply 

 it from a comparatively dry soil. The result is that the 

 leaves wilt and the stomata in the leaves close, so that 

 the evaporation is checked. The wilting of the leaf is 

 Nature's method of checking evaporation. If too long 

 continued of course the plant dies, but under ordinary 

 conditions the plant during a night will have taken up 

 more moisture from the soil and the morning finds it 

 freshened again and ready to resume work. 



If you will examine the arrangement of the leaves on a 

 branch of any plant or tree you will find that they are 

 arranged so that each leaf has its own share of exposure 

 to light and air, so that each leaf has its own opportunity 

 to do its work. 



When the leaves take in the carbon dioxide and in this 

 way get carbon by breaking up the combination with the 

 oxygen, the plant goes to work, as we have said, to manu- 

 facture the materials needed for growth, and for the sup- 



