282 LEAVES 
The volatile oils differ not only chemically from fatty oils, but 
also in being volatile. They cause most of the odors of plants. 
Oil of Peppermint, Sassafras, Cinnamon, Cloves, Cedar, and the 
oil of the Orange rind are familiar volatile oils. A number of 
uses to the plant have been assigned to the various volatile oils, 
such as protection against destructive organisms, attraction of 
insects in the pollination of flowers, and serving as a storage form 
of food. Their pleasant odors and tastes add charm to the 
flowers of many garden plants, and before the chemists learned 
to make many of them, plants were our chief source of the per- 
fumes and essences of commerce. Their composition suggests 
their origin from the photosynthetic sugar, since nearly all of 
them contain only carbon and hydrogen, or only carbon, hydrogen, 
and oxygen. 
Closely related to the volatile oils are a number of substances, 
such as the Pine resins, india rubber, gutta percha, camphor, and 
asafetida, which are important commercially, although their use 
to the plant is not definitely known. From the Pine resins, which 
are found in the resin ducts of Pines, turpentine, pine tar, rosin, 
and pitch are obtained. India rubber is the prepared milk-juice 
obtained from a number of trees of tropical countries. Gutta 
percha, used in making surgical instruments, in filling teeth, and 
in a number of other ways, is obtained also from the milk-juice 
or latex of a number of plants. Camphor is obtained from a 
number of tropical trees and asafetida from a group of herba- 
ceous plants. 
Glucosides are complex substances and are so named because 
many of them contain glucose as one of their constituents. They 
may be considered storage forms of food since they yield a sugar 
when broken down. Amygdalin, the bitter substance in the 
seeds of the Bitter Almond, is one of the best known glucosides. 
Its formula is CyH27NOy, and when decomposed it yields glu- 
cose (CeHiO¢), hydrocyanic acid (HCN), and benzaldehyde 
(CsHsCHO). Glucosides vary much in composition and con- 
sequently in the products which they yield when decomposed. 
Thus the glucoside coniferin (CisH2Og), found in coniferous trees 
and Asparagus, yields glucose and coniferyl alcohol (CyH.203) 
when decomposed. 
Glucosides occur in all parts of the plant and are especially 
abundant in the parenchyma cells of roots, stems, and leaves. 
