78 ELEMENTS OF GENERAL SCIENCE 



85. Comparison with a factory. It may be interesting to 

 sum up the process of photosynthesis by comparing it with a 

 factory. This comparison may be made as follows : 



The factory Green part of the plant 



Machinery Chloroplasts 



Energy Light 



Raw material Water and carbon dioxide 



Finished product Carbohydrates 



Waste product Oxygen 



86. Importance of photosynthesis. The food supply of all 

 living things depends upon the work of green plants. Carbo- 

 hydrates make up a very large part of our own food and of 

 the food of many animals. Other food also is made, either 

 directly or indirectly, from carbohydrates. Even the meat 

 which composes part of our diet is derived from carbohy- 

 drates, for the animals from which it comes feed mainly on 

 plants. The green plants and the work which they do are 

 therefore of the very greatest importance. 



