CHAPTEE VL 

 PHYSICS OF PLANT BREATHING AND BOOT ACTION. 



MECHANISM AND METHOD OF TRANSPIBATION IN PLANTS. 



170. Breathing of Plants and Animals The transpira- 

 tion of plants and the respiration of animals are processes 

 which have much in common. Both plants and animals 

 are provided with internal cavities into which air may en- 

 ter. They both breath air. While breathing air both give 

 off large quantities of moisture. The primary object of the 

 lungs is to supply the body of the animal with oxygen and 

 to remove carbon dioxide. The corresponding structure in 

 the leaves of plants is to supply it with carbon dioxide and 

 to throw off oxygen. In both cases the breathing surface 

 has a very delicate texture and is situated where it can al- 

 ways be kept wet ; the chief function of the water escaping 

 from the breathing surface is to keep it moist. 



If the lining of the lungs were to become dry and 

 parched the gases would not as readily pass through and 

 there would be like difficulty in the case of leaves, if their 

 breathing surfaces were not kept moist. In both plants 

 and animals the breathing surfaces are carefully guarded 

 from the intense sun and strong drying winds. 



171. Respiratory Organs in Plants. The air passages or 

 breathing chambers of plants are chiefly located in the 

 leaves, but they are also found to greater or less extent in 

 all the green parts. They are simply irregular chambers 

 left between the cellular tissue and are represented in the 



