6o 
PHARMACEUTICAL BOTANY 
with osmic acid, a red color with alkannin or Sudan III and a blue 
color with cyanin. In Vaucheria, the Diatoms and a few of the 
other Thallophytes, fixed oil is formed in the chromatophores in- 
stead of starch as the first visible product of photosynthesis. In 
higher plants it is generally found in storage regions such as the 
parenchyma seeds, fruits and the medullary ray cells and paren- 
chyma of barks, roots and rhizomes. 
19. Volatile Oils. — These are volatile odoriferous principles found in 
various parts of numerous plants which arise either as a direct prod- 
uct of the protoplasm or through a decomposition of a layer of the 
cell wall which Tschirch designates a “ resinogenous layer.” They 
are readily distilled from plants together with watery vapor, are 
slightly soluble in water but very soluble in fixed oils, ether, chloro- 
form, glacial acetic acid, naphtha, alcohol, benzin and benzol. They 
leave a spot on paper which, however, soon disappears. They 
respond to osmic acid, alkannin, Sudan III, and cyanin stains 
similar to the fixed oils and fats. 
Volatile oils may be grouped into four classes: 
A. Pinenes or Terpenes, containing carbon and hydrogen and 
having the formula of Ci 0 H 16 . Examples: Oil of Turpentine and 
various other volatile oils occurring in coniferous plants. 
B. Oxygenated oils, 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. Sulphurated oils, containing carbon, hydrogen and sulphur. 
Example: Volatile oil of mustard. 
20. Resins, Oleoresins, Gum Resins, and Balsams. — These sub- 
stances 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 Styrax, Benzoin, Balsam of Tolu and Peru, etc. They 
occur usually in special cavities such as secretion cells, glands, or 
secretion reservoirs. 
Resins are insoluble in water but mostly soluble in alcohol. They 
combine with alkalies to form soap. Many of them are oxidized 
oils of plants. Examples: Guaiacum, Resina. 
