PLANT LIFE. 25 



tion of cell walls, production of various secretions, res- 

 piration, formation of new cells, etc. 



Plants Require Energy. All activities of plants re- 

 quire energy. Protoplasm obtains the energy to do 

 its work by the oxidation (i. e., combustion) of food. 

 The food is in many cases digested and carried to the 

 different cells in solution, and there is oxidized by the 

 oxygen taken in from the air. Carbon dioxide, a gas 

 which will not support life, is produced and is given 



SECTION OF LEAF. 



off. These processes are the same in the cells of ani- 

 mals and plants. The differences lie mainly in the 

 way the food and oxygen reach the cells. In animals 

 we find regular digestive and respiratory systems while 

 these are practically lacking in plants, where there is 

 no general blood system to carry food and oxygen to 

 the cells and carbon dioxide away from them. 



Plants Manufacture their Food. Common plants 

 differ further from animals in the fact that they manu- 

 facture their own food. All the common animals 

 have to take in their food from outside, but all green 

 plants manufacture their food in their green parts. 



