38 
HISTOLOGY OF VEGETABLES. 
the Cocoa-nut , the cells contain a concrete oil, which 
when extracted by pressure, is an article of considerable 
commercial importance, being much employed for com- 
bustion in lamps, and for the manufacture of candles. 
In the process of germination the oil is absorbed by the 
embryo, so that the albumen of the seed is gradually 
diminished and shrivels, a fact 
well exhibited by a Cocoa-nut 
after germination. It is some- 
what difficult to demonstrate 
the oils, in situ , in the cellular 
tissue, since the section almost 
necessarily allows the escape of 
the oil ; but, in some parts of 
the Cocoa-nut this is concrete, 
Portion of a Cocoa-nut with 
ceils full of globules of concrete and we have a better chance 
of displaying it in the cells. 
Some of these are represented in Fig. 26 . The oily 
matter consists of minute spherical globules, which 
are so closely packed as to render the section partially 
opaque. 
The presence of oily matters in vegetable cells was 
known, and even depicted by Leeuwenhoek, in the 
second volume of his works. 
Palm Oil resembles fat rather than oil, and is used 
by the natives of the western coast of Africa as a sub- 
stitute for butter. It is now extensively employed in 
the manufacture of candles, and likewise on the rail- 
roads, for greasing the wheels of the carriages, sulphur 
