256 
THE ROOT 
and mandrake, while the ground root of ginger is used in 
medicine and in cooking. The vegetable oyster is often 
found growing by roadsides where its seed has been blown 
from gardens. 
In the case of these roots, a few must always be saved to 
produce seeds for another crop, inasmuch as turnips, beets, 
carrots, parsnips, ^nd vegetable oysters are biennials, 
requiring to be planted the second season, when they use 
food stored during the first year to produce fruit and seeds. 
PRACTICAL APPLICATIONS 
Anything which concerns the condition of the soil in which 
plants are to grow and the amount of raw material available 
for food-making is important because of the relation of the 
roots to the soil and of their function to the plant. For this 
reason every one who raises plants should know the habits of 
each kind of plant he raises and try to make the conditions 
such as will best suit each kind of plant or crop. 
Soil that is well filled with roots is not subject to erosion 
as is barren soil. Use is made of this fact in planting certain 
grasses for their binding effect, especially on the coast where 
the constant washing of the waves has a tendency to change 
the coast line. 
The roots of leguminous plants become infested with 
certain bacteria found in the soil. These bacteria form 
bunches or nodules on the roots in which they live. Thus 
protected, they gather nitrogen from the air, use what they 
need, and store up the rest. This surplus is used by legumi¬ 
nous plants in making protein, part of which is found in the 
body of the plant, and part in the seeds. When the seeds 
are used as food, man and the animals secure the protein 
which they need. When the plants die, they leave the soil 
richer in nitrogen in a form that can be used by plants 
which do not have the help of the bacteria to gather it. 
So valuable is this form of fertilizer, that in some cases, 
