50 Gardening 
becomes very abundant in the cells. Some of it is stored 
as starch within the leaf. But the sugar is also con- 
ducted to other parts of the plant to be used by them 
immediately for food or for storage. The tuber of the 
potato is an enlarged part of the stem where large 
amounts of starch are stored. The starch that has been 
stored in a plant can be again changed to ‘sugar and 
transported to the parts where active growth is taking 
place or where seeds are being formed. 
But while most plants change their sugar to starch for 
storage, a few plants do not do this — at least not until 
the sugar has become very abundant in them. From 
two plants, sugar cane and the sugar beet, the world’s 
supply of sugar is obtained. Onions and sweet corn 
are rich in sugar, and wrinkled peas contain more sugar 
than smooth peas. 
The manufacture of fats and proteins. From sugar, 
plants make oils, in which form many plants store a 
part of their food. From the olive, coconut, flaxseed, 
cotton seed, peanut, corn, and castor bean, oils are ob- 
tained which are used for many purposes by man. 
The fats are present in larger or smaller amounts in 
all living plant cells. They are for the most part formed 
in the cells where they are found, and are not to any great 
extent transported from one part of the plant to another. 
They contain the same chemical elements as sugar and 
are believed to be formed from sugar. 
Proteins are made by combining chemically nitrogen, 
sulfur, and sometimes phosphorus with the elements of 
the sugar. Minerals supplying these are obtained from 
the soil. Without an abundant supply of the minerals 
