RESERVE FOODS 279 
Date seeds and Ivory nuts is due to the hemi-celluloses, in which 
form these seeds store their reserve food. (Fig. 250.) 
The fats are prominent storage forms of food in a number of 
plants and usually occur in the form of oils, known as fatty oils. 
They contain the same elements as the carbohydrates, but have 
much less oxygen in proportion to carbon, and the hydrogen and 
oxygen are not present in the proportion to form water. The 
vegetable fats are chiefly compounds of 
glycerine and fatty acids. Palmitic, 
oleic, and stearic acids are the fatty 
acids commonly found in fats, but there 
are many others, and the character cf the 
fat formed depends much upon the kind 
of fatty acid entering into the combina- 
tion. The fatty oils are usually stored 
in the seeds, but often in the flesh of 
fruits and other portions of the plant. 
Olive oil which is pressed out of the fruit 
of the Olive, Corn oil from the embryos 
of Corn, Cotton-seed oil from Cotton seed, 
Coconut oil from Coconuts, Linseed oil 
from Flax seed, and Castor oil from _ Fs. 250.—Cell walls of 
seeds of the Castor Bean are well known !Vory nut, showing the ex- 
: 7 treme thickening with hemi- 
plant oils and have an important place cellulose, which ix deposited 
in our industries. in layers forming striations. 
The fatty oils are usually present in The walls are perforated by 
the storage cells in the form of globules, the canals through which 
and like starch are insoluble in the cell the protoplasmic strands 
: pass. Highly magnified. 
sap. Before being consumed by the plant 
as food, they are converted by means of enzymes into simpler 
and soluble forms, such as glycerine and fatty acids. 
The vegetable fats are not only important animal foods, but 
are used in many ways by man in the industries. Rape oil and 
Corn oil are much used for lubricating machinery. Linseed oil 
is extensively used as a solvent for paint. Palm oil, Cotton-seed 
oil, and Coconut oil are made into substitutes for butter, besides 
being used in many other ways. Castor oil, besides being used 
as a medicine, lubricant, and illuminant, is used in manufacturing 
dyes. The use of Olive oil in foods is well known. Many of the 
vegetable oils are used in making the best soaps. 
