50 SOILS 



below. Water is, therefore, necessary, that soil-food may 

 be carried in and through the plant, and even to carry the 

 leaf-manufactured products back to the roots. 



The upward current from the roots passes through the 

 woody portion of the trunk, while the downward current 

 from the leaves passes beneath the bark. 



How the plant uses its food. A plant is a body of 

 cells millions of them, just like your body. These cells 

 increase in number as the plant enlarges, grows. Every 

 cell is an enclosed sac, holding within it the juice and 

 other substances necessary for its enlargement and 

 growth. The walls of these cells are made of cellulose a 

 carbon compound, produced from the carbon that enters 

 the leaves from the air. When the cell is first made the 

 cell wall is thin and tender, just as we find it in green 

 and young plants, but as it matures the wall becomes 

 hard and woody, and less appetizing and digestible. 



These plant cells are responsible for the use of the food 

 obtained from the air and from the soil, for the building 

 of plant tissue and for the formation of the compounds of 

 the plant or the fruit of the plant. 



Every live, active cell contains protoplasm, the real life 

 of the cell. When the soluble soil materials we call 

 these plant food have been carried up through the long 

 channels of cells and when they reach the leaves, they 

 come in contact with starch grains and carbonic acid. 

 Here these various compounds are decomposed through 

 the action of heat, and sunlight, and protoplasm, and 

 chlorophyl : starch is made or changed into sugar, or 

 maybe starch or some starch derivative is united with the 

 nitrates and sulphur in some way so that protein results, 

 or maybe oil or cellulose or crude fiber is manufactured 

 each is made just as the plant decrees. 



The meaning of plant-building. Before these elements 



