THE SUN AND RAYS OF HEAT 



tive, depending on the kind of soil. We shall find later that 

 the soil of the garden or lawn, instead of being dead as we 

 thought, is really a battlefield in which millions of little 

 germs are engaged, some in causing decay of materials 

 there, others in making the decaying material available or 

 valuable for plants in the form of nitrogen compounds, 

 while still others 

 break down these 

 nitrogen compounds 

 and allow some of 

 the nitrogen to pass 

 off into the air. 



Light and heat. 

 What would you do 

 without light? We 

 must all realize the The effect of light upon a growing plant 



importance of light when we remember how much artificial 

 light means to us in our homes. All green plants need 

 light. Notice the geranium or oxalis growing in your win- 

 dow garden. The stems turn to the light, and expose as 

 much leaf surface as possible to the sun's rays. Without 

 light no green plant can exist, and without green plants 

 no animals can exist. Think this over and see if it is not 

 true. Your beefsteak came from a cow which lived upon 

 grass which grew as a result of having, among other things, 

 sunlight. . You know, too, there can be no life without 

 heat. 



The sun and rays of heat. Have you ever stopped to 

 think why it is warmer in summer than in winter ? A glance 

 at the diagram on page 52 will show you. The sun's 

 rays come more directly upon us in summer, and give us 

 more heat. If you do not believe the sun gives off heat, 



