276 TYPICAL FLOWERING PLANTS 



is forced through limewater, the clear limewater turns 

 cloudy. Thus it is shown that the bean leaves have given 

 off carbon dioxide. The only life process which is known 

 to produce carbon dioxide is respiration. Therefore we 

 can say that the plant respires and that this life process 

 in the plant is similar to the same life process in animals. 

 See pages 3 and 15. 



The Manufacture of Food. — The words "manufacture of 

 food' are often used in connection with plants. This 

 process may be better understood by comparing it with 

 the manufacture of some article in a factory. To manu- 

 facture an article, there must be a building with rooms; 

 machines, and power to run them ; and various substances, 

 called raw materials, which are to enter into the finished 

 product. In addition there must be a supply of water, 

 pipes in which to carry it, and forces to move it. Be- 

 sides the finished product, a factory always yields some 

 waste material. When the product has been finished, it 

 is usually packed for distribution and stored in a room to 

 which it is carried on tracks. 



In the leaf factory, the cells of the palisade and spongy 

 layer are the rooms. The machines are chlorophyll bodies, 

 and the power is furnished by the sun. The raw materials 

 are water, containing a small amount of mineral matter 

 obtained from the soil, and carbon dioxide obtained from 

 the air. The pipes in which the water comes are the 

 fibrovascular bundles, and the stomata are the places 

 where the air enters. 



The forces which move the raw material are largely 

 osmosis, capillarity, and the suction caused by transpira- 

 tion. The materials made are carbohydrates, in the form 

 of starch and sugar, and protein. Waste material is 

 oxygen. The material ready for carrying is usually in 

 the form of sugar. The storehouse may be the stem, the 



