52 Gardening 
gen comes from the water which the roots absorb from 
the soil. The other seven elements are secured by the 
plant from various mineral compounds which it takes 
from the soil. 
The minerals most often lacking in the soil are those 
that furnish nitrogen, potassium, sulfur, and phosphorus. 
These are often supplied in manures or other fertilizers 
(page 66). When the gardener enriches the soil, he is 
providing raw materials needed in some of the many 
building operations going on in the plant. 
Garden plants are builders and storers of food. A 
weed, as a rule, uses its food for growth as fast as it makes 
it, and in its small seeds it leaves no considerable store of 
food that canbe used by man. Buta radish, cabbage, or 
bean plant makes food faster than it uses it and collects 
a surplus either for its own future use or for the use of 
its offspring. ‘These stores of food we take for ourselves, 
and we have selected for cultivation in our gardens the 
plants that will lay up for us food in largest amounts. 
The successful gardener gives his plants favorable con- 
ditions for food manufacture and provides them with 
abundant supplies of the raw materials that they must 
have for the work. 
Questions 
How does a green plant get its food? What classes of foods 
do plants build? What raw materials are used in making them? 
Why cannot animals live without plants ? 
What is photosynthesis? In what part of the plant does 
photosynthesis goon? When does it goon? Describe the struc- 
ture of a leaf. What is the function of the epidermis? How 
do gases enter and leave the leaf? How do water and minerals 
get into the leaf? ; 
