LEAVES 203 



except those of the epidermis, there are a number of 

 green colored bodies called chloroplasts. They are prin- 

 cipally composed of protoplasm by which a green sub- 

 stance, chlorophyll, is manufactured. (Chloron, green; 

 phyUon, leaf.) The chlorophyll gives the green color 

 to the chloroplast. It is upon the presence of this sub- 

 stance that the most important work of the plant 

 depends, and upon that work all life, including our own, 

 depends. Think of the significance of this fact. 



Food making. We have already stated that a plant 

 uses as a part of the raw materials, from which to make 

 its food, carbon dioxide and water. Out of these in- 

 organic materials leaves can manufacture starch; this 

 is their principal function. The water is obtained 

 from the soil and passes up through bundles of tubes 

 from the roots to the veins of the leaves. Carbon 

 dioxide from, the air enters through the stomates. The 

 carbon dioxide and water are then combined to form 

 starch or sugar. Starch and sugar belong to a group 

 of foods known as the carbohydrates, which are com- 

 posed of carbon, hydrogen, and oxygen. They always 

 contain twice as much hydrogen as oxygen. To form 

 carbohydrates from the raw materials we know that 

 chloroplasts and light are essential. By means of 

 protoplasm and chlorophyll, chloroplasts absorb energy 

 from the sun's rays. With this energy, the chloro- 

 plasts are able to break the compounds, water and 

 carbon dioxide, into carbon, hydrogen, and oxygen, the 

 elements of which they are composed. These three ele- 



