50 
HOUSEHOLD BACTERIOLOGY 
Nitrogen 
Not Taken 
Direct 
green leaves through their chlorophyl cells are able 
to take most of their carbon from the carbon dioxide 
of the air. Some oxygen is also taken from the air, 
but most of it is absorbed by the rootlets from the 
ground air, the water in the soil, or from organic com¬ 
pounds in solution in the water. Hydrogen is ob¬ 
tained from water and other compounds containing 
hydrogen and is taken in through the rootlets. 
No plants can take their nitrogen directly from the 
air. Although this gas with oxygen comprises the 
major part of the atmosphere in which all vegetation 
is bathed, it is not taken in through the leaves as the 
carbon dioxide is. 
A government bulletin says: “Ever since anything 
has been known in regard to plant nutrition and the 
necessary part that various gases and minerals play 
in the successful growing of crops, scientific men have 
realized the great importance of conserving the world's 
store of nitrogen and have made every effort either to 
husband or to increase all available sources of supply. 
In the early days, when it was first realized that 
nitrogen was so essential to plant life—in fact, was at 
the very foundation of agriculture—no particular 
alarm was felt. Botanists had demonstrated that plants 
obtained their carbon from the carbon dioxide of the 
air, and since this gas is present in so much less quan¬ 
tity than nitrogen it was believed that by no possible 
means could the most essential of plant foods be ex¬ 
hausted. However, when it was shown that plants 
