THE FORMATION OF CARBOHYDRATES 115 



A Change of Gases. The giving off of water through the 

 stomata is associated with a change of gas by transfusion be- 

 tween the air within the intercellular spaces of the leaf and the 

 air on the outside. Therefore, as the water passes outward 

 through the stomata$ the carbon dioxide (CO 2 ) of the air passes 

 into the intercellular spaces, is absorbed by the protoplasm of 

 the mesophyll cells and immediately dissolved in the cell sap, 

 thus forming carbonic acid (CO 2 -f-H 2 O=CH 2 O3). The action 

 of the sunlight on the chlorophyll results in the breaking up of 

 this carbonic acid and the recombination of the elements with 

 the elements of water into other compounds. This delicate and 

 complicated process is very imperfectly understood, and the 

 first result that we can recognize with any degree of certainty 

 is glucose or grape sugar (C 6 H 12 O 6 ). 



Plants and Animals Help Each Other. We know that the 

 process results in the liberation of free oxygen (6CO 2 + 6H 2 O 

 C 6 H 12 O 6 -|-12O) which is given out through the stomata and 

 is essential for the life of animals. Therefore, we see that ani- 

 mal and plant life are more or less inter-dependent, but it is 

 very evident that animals are more dependent upon plants than 

 plants are upon animals. Plants utilize the carbon dioxide 

 which is exhaled by the animals, but they could readily obtain 

 this supply from other sources. Animals utilize the oxygen 

 given off by plants, and are absolutely dependent upon plants 

 for their food supply. 



The formation of carbohydrates, that is, starches and 

 sugars, from these crude materials (water and carbon dioxide) 

 by the action of sunlight on the chlorophyll is known as photo- 

 synthesis and is the most wonderful and most mysterious process 

 in all nature. With this as a beginning, we have the basis for 

 the formation of innumerable other plant and animal products. 

 A small part of this organized food is used immediately for cell 

 formation and growth, but the greater part is stored for fu- 

 ture use. 



