92 SOILS AND PLANT LIFE 



oils and proteins, using, when needed, those essential 

 elements which come to it in the soil water. 



It is from the various food materials, made in this way, 

 that the plant derives the energy that makes its own growth 

 possible. It is from them that all of its tissues are built, 

 whether wood, bark, fiber, blossoms, fruits or grains. 

 Moreover, animals depend upon these food materials 

 made by the plant just as does the plant itself, for it is 

 from them that animals derive all of their heat and energy 

 and tissue-building material. 



Thus we see that out of the raw materials — the ten 

 essential elements which come to them from the soil and 

 air — plants are able to make the food supply not only 

 for themselves, but for all animal life as well. That is 

 to say, while man may eat the flesh of animals, he may be 

 sure that these animals were in turn dependent upon 

 plants for their existence, or upon other animals, perhaps, 

 whose food supply was drawn from plants. 



As the Father of Waters, the great Mississippi, may be 

 traced to its source in the highlands of Minnesota, so the 

 food supply of the world can be traced back to its source 

 in the green leaves of plants where carbon dioxide and 

 water, and minerals from the earth, by the power of the 

 sun, unite to form the food substances that make it possible 

 for plants and animals, including man himseK, to hve. 



68. Amount of Water, Food Material and Ash in 

 Plants. — The weight lost by plants in drying repre- 

 sents the water held in the tissues. The weight lost in 

 burning represents the food manufactured in the leaves. 

 The ash remaining after burning contains all of the minerals 

 which come from the soil except the nitrogen, which escapes 

 into the air in the process of burning. 



