THE L1BEEATION OF ENERGY IN PLANTS 



69 



In green plants during the night, when carbon dioxid is not 

 being used for starch manufacture, this gas is given off to the 

 surrounding air, which probably is not true to any great 

 extent during the daytime. The taking in of oxygen and the 

 giving off of carbon dioxid by plants corresponds to breath- 

 ing in animals. Breathing is carried on in plants through 

 the thin walls of roots, through the lenticels of stems, and 

 through the stomata of leaves. The principal distinction, 

 therefore, between breathing and respiration includes the tak- 

 ing in of oxygen, the use of oxygen by the cells (in oxidation), 

 and the giving out of carbon dioxid. The process of breathing 

 must not be confused with that of carbohydrate manufac- 

 ture, and the following outline will show the fundamental 

 difference between the two. 



