312 THE FOODS WE EAT 



This experiment shows that the part of the leaf which 

 was in the sunlight made starch. Experiments show 

 that starch is always found in leaves that are exposed to 

 sunlight. We can also show that it is not found in 

 leaves that have been left in the dark for some time or 

 in such parts of leaves as have been covered. 



Other food materials are also made in the leaf, but the 

 processes are very complicated. After foods are formed 

 in the leaf, they have to be circulated through the body 

 of the plant in order to be used by or stored in the fruit, 

 the seed, the stem, or the root. 



What Kinds of Foods Are There ? If you were to ask 

 a chemist about foods, he would tell you that they were 

 composed of chemical elements put together in different 

 proportions. Such a classification would give us foods 

 like starches and sugars, which are called carbohydrates 

 because they contain carbon, hydrogen, and oxygen ; fats 

 and oils, which are composed of the same elements as the 

 carbohydrates, but in different proportions ; proteins, 

 which contain nitrogen in addition to the other three 

 elements ; water, minerals, and certain regulative sub- 

 stances of a complicated chemical nature called vitamins, 

 of which we shall learn more later. If you were to ask the 

 school nurse or a nutritional expert to classify foods, she 

 would tell you that foods may be classified as fuel foods, 

 body-building foods, and regulative or protective foods. 



SELF-TESTING EXERCISE 



Select from the following list those words that best fill the blank spaces 

 in the sentences below and arrange the words in proper numerical order. 

 A word may be used more than once. 



protective green body starches 



sun's liquids yellow fuel 



living vitamins inorganic building 



carbohydrates dead water air 



