222 
THE SEED AND THE SEEDLING 
of plants, to secure food for himself and his animals. He has 
also found ways of enabling the plant under cultivation to 
store up more food than it could do in the natural state. 
199. Economic Uses of Seeds. — In thinking of the seeds 
used as food, we must limit the term to its botanical meaning. 
Many articles of food, such as the cereal grains, are commonly 
thought of as seeds. Their use as food has already been 
discussed. (See § 197.) The real seeds that are of greatest 
use to man as food are 
those of the pulse family, 
especially beans apd peas, 
which alone are the source 
of most of the protein 
that is obtained from 
plants. The meats of 
nuts are another source 
of protein food. Mature 
peas and beans contain 
more food matter than do 
“ green peas” and “string 
beans/’ the latter being 
valuable more for the 
bulk they furnish than 
for their food content. 
Besides their use as 
food, seeds can be used 
as medicine, castor oil 
and mustard being common remedies that are obtained 
from seeds. Castor oil is also used as a lubricant in air¬ 
planes on account of its not being affected by the cold 
of high altitudes. Two valuable products are obtained 
from cotton seeds: one the oil which is used in preparing 
foods in place of lard and butter, animal fats; the other, 
thread and cloth which are made from the fibers covering the 
outside of the seeds. The fibers are removed by a process 
Figure 210. — Bean Seedlings. 
All the food these plants have used came 
from the cotyledons, as the jar contained 
only sawdust. 
