HOW PLANTS GROW H 



material, which can then be used for the growth of the young 

 root and leaves in the plant. The tiny roots push out into 

 the soil, root-hairs establish connections with the soil particles, 

 and the roots begin to absorb the mineral plant-foods in 

 solution. 



The shoot breaks through the surface of the soil, unrolls 

 the leaves, and the sunlight helps to change the materials 

 of the soil so that they can be assimilated into the parts of 

 the growing plant. In the presence of sunlight, and under 

 the life principle in the growing plant, the carbon dioxide 

 of the air enters the breathing pores of the leaf, and com- 

 bines with the water taken up by the roots to form the sugar 

 and starch substances in the leaves. The excess of water 

 needed to bring up the minerals is thrown off from the leaves 

 by transpiration, and the excess of oxygen taken in to supply 

 the carbon in the carbon dioxide gas is also given off through 

 the leaves as free oxygen. The starch material thus made 

 in the presence of and by the help of the green particles in 

 the leaf and the sunlight is then changed to sugar and is car- 

 ried by the cells downward and outward to the various tis- 

 sues of the growing plant to be assimilated into root, stem, 

 leaf, and later into flower and fruit. This process continues 

 until the plant has reached its full maturity. 



It will be of interest to note that considerable work is done 

 in causing a plant to grow. In the corn plant, for instance, 

 for every pound of dry matter produced, 350 pounds of water 

 must pass through the leaves and be transpired into the air. 

 It has been determined that this represents an energy in an 

 acre of corn producing fifty bushels equivalent to 375 horses 



