22 HOW PLANTS FEED 



Carbon from the Air. It seems strange that a part 

 of the grass could come out of the air. We can see the 

 mineral matter left in the bottom of the tea-kettle, and 

 so can easily believe that the soil water contains mineral 

 matter. But we can not see the air, and it is hard to 

 understand how matter can come out of the air to make 

 a plant that we can see, handle and weigh. But, just 

 as the soil water has solid mineral matter dissolved in it, 

 so the air has a gas called carbon dioxide mixed with it. 

 This gas is formed of two substances: carbon, which is a 

 solid that we can see and handle; and oxygen, a gas that 

 we can not see. When the oxygen is taken out of the 

 carbon dioxide, the solid carbon is left, just as when the 

 water is taken out of the sugar solution the solid sugar 

 is left. 



Chlorophyll with the Sun making Starch. The car- 

 bon dioxide enters the leaves of plants through very small 

 openings. It then enters the cells and comes in contact 

 with a substance called chlorophyll, which is the green 

 coloring matter of the leaves. Here a wonderful change 

 takes place. When the sun is shining, the carbon dioxide 

 and a part of the water that the cells contain are decom- 

 posed, that is, they are separated into the parts that form 

 them. Some of these parts, including the carbon, then 

 unite again and form a new substance that is very different 

 from either the carbon dioxide or the water. This new 

 substance is starch, or something of very similar compo- 

 sition. (Figure n.) It may be formed in any part of 

 the plant that is green, that is, in any part which has 

 cells that contain chlorophyll. But it is formed chiefly 

 in the leaves. 



