200 
GUMS, GUTTA-PERCHA 
tumia). Other genera yielding rubbers are Ficus, Hancornia, 
Mascarenhasia, Urceola, Willughbeia, &c. On account of 
its waterproof and extensible qualities, rubber is largely used 
for tires, balls, shoes, and numerous other purposes ; it is 
usually vulcanised by treatment with sulphur, making it 
more durable. 
Gutta=percha, a somewhat similar substance, but 
harder when cool, not extensible, and softening with heat, 
also occurs in latex, chiefly in the Sapotaceae. Species of 
Palaquium and Payena are the chief sources. It is used 
in large quantities as an insulator, in the manufacture of 
golf-balls, and for many other purposes. 
Balata, a substance intermediate in properties between 
gutta-percha and rubber, is obtained from the latex of species 
of Mimusops. 
Camphor, an aromatic crystalline body, is obtained by 
distillation from the wood or leaves of species of Cinna- 
momum, Dryobalanops, and Blumea. It is used in the 
manufacture of celluloid, smokeless powders, &c., and in 
medicine. 
II. Oils. In a vast number of seeds the non- 
nitrogenous reserves occur as oils (p. 34) ; these are termed 
fixed oils , and are obtained by pressure, or sometimes by 
pounding and boiling. Oils also occur in a few fruits or 
other parts of plants. Ethereal or volatile oils are found 
in many flowers and leaves, &c., often imparting characteristic 
perfumes to the plants containing them ; they are usually 
obtained by direct steam distillation, or by natural evapora- 
tion into a layer of fine fat, which is afterwards treated with 
alcohol or otherwise to extract the perfume. 
Fixed oils are obtained from the following among other 
genera : Aleurites, Arachis, Argania, Barringtonia, Brassica 
(rape, colza), Calophyllum, Carya, Cocus (coconut), Corylus, 
Croton, Elaeis (palm-oil), Guizotia, Gossypium (cotton-seed), 
Helianthus, Juglans, Linum (linseed), Melia, Moringa, Olea 
(olive), Papaver, Polygala, Ricinus (castor-oil), Schleichera, 
Sesamum (gingelly),Theobroma (cacao-butter), Tilia, Vateria, 
&c. Some of these are drying oils, e.g. linseed, used in 
painting ; others remain fluid, while others again are solid 
at moderately high temperatures, e.g. coconut oil in Europe. 
