NON-PROTOPLASMIC CELL CONTENTS 97 
however, soon disappears. They respond to osmic acid, alkan- 
nin, Sudan ITI, and cyanin stains similar to the fixed oils and fats. 
Volatile oils may be grouped into four classes: 
A. PrnENEs or TERPENES, containing carbon and hydrogen 
and having the formula of CjoH1s. Examples: Oil of Turpentine 
and various other volatile oils occurring in coniferous plants. 
B. OxyGENATED Orts, containing carbon, hydrogen and 
oxygen. Examples: Oil of cassia and other cinnamons. 
C. NITROGENATED OILs, containing carbon, hydrogen and 
oxygen with nitrogen (from HCN). Example: Oil of Bitter 
Almonds. 
D. SuLFURATED Ors, containing carbon, hydrogen and 
sulfur. Example: Volatile oil of mustard. 
21. Resins, OLEoREsINS, GuM Resins, AND BALsAms.—These 
substances represent products of metabolism in many plants 
which are formed either normally, as Turpentine, Asafcetida, 
Mastiche, etc., or as a result of pathological processes through 
injury to the plant tissues, as Storax, Benzoin, Balsam of Tolu 
and Peru, etc. They occur usually in special cavities such as 
secretion cells, glands, or secretion reservoirs. . 
Resins are amorphous, solid or semisolid, fusible substances 
insoluble in water but mostly soluble in alcohol and other organic 
solvents. They combine with alkalies to form soap. Many of 
them are oxidized oils of plants. Examples: Guaiac, Rosin, 
Mastic. 
OLEoRESINS are secretions composed of resins dissolved in 
volatile oil. Examples: Turpentine, Copaiba, Balsam of Fir 
and Venice Turpentine. 
Gum RESINS are natural compounds of resin, gum and oil. 
Examples: Asafetida, Myrrh, Gamboge. 
BALSAMs are mixtures of resins with cinnamic or benzoic acid or 
their esters and frequently both, the esters being generally called 
a volatile oil. Examples: Balsam of Tolu, Storax, Balsam of Peru. 
If sections of a resin-containing plant part are placed in a saturated aqueous 
solution of copper acetate for a week or two and mounted in dilute glycerin, the 
resin will be stained an emerald green. 
22. PiGMENTS.—JT hese are substances which give color to 
various plant parts in which they are found. They occur either 
