SUNLIGHT AND PLANT GROWTH 63 



Growth without sunlight. Some plants, like bac- 

 teria, molds, and mushrooms, do not have green matter ; 

 and these plants must live on ready-made food. Bac- 

 teria live in the bodies of plants and animals, and their 

 food lies all about them ready to be absorbed. Molds 

 live on plant and animal substances, such as bread, 

 jelly, or decaying flesh. The mushrooms can grow 

 only in soil rich in decaying plant and animal matter. 

 Only green plants, which use the sunlight, can live 

 on the mineral matter of the soil and the carbon taken 

 from the carbon dioxide of the air. 



The importance of sunlight is seen in the fact that 

 the dried tissues of plants, like corn, wheat, or trees, are 

 mostly carbon which came entirely from the air and 

 was made part of the plant by the action of sunlight 

 upon the green leaves. Only the ash of a burned 

 plant is the material which came from the mineral 

 matter of the soil. 



Thus, in addition to soil, water, and air, the crops must 

 have sunlight in order to grow and yield harvests for 

 man. 



QUESTIONS 



1. What substance is manufactured in the green parts of a 

 plant under the influence of sunlight ? 



2. What is the name of this building-up process ? How does 

 this process differ from respiration of plants ? 



3. What kinds of plants grow without sunlight ? How do 

 the food materials of such plants differ from those of green 

 plants ? 



