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smoke, and the coagulated mass, after losing water by 
slow evaporation, takes on the dark color, toughness, and 
elasticity characteristic of rubber. Rubber is more valu- 
able in proportion as its percentage of caoutchouc is greater, 
and that of its resin less. The most important source of 
rubber is the tree Hevea brasiliensis, Para Rubber, native 
of Brazil, now very extensively planted in the East Indies. 
Several varieties of rubber may be seen in the different 
stages of refinement, together with some articles as manu- 
factured for the market. Here, too, are two allied products 
gutta-percha and balata, which are derived from the 
trunks and foliage of certain trees belonging to the sapo- 
dilla family. These trees grow in many portions of the 
tropics. 
Perfumery. Case 30.—This case contains a collection 
of the essential oils and other aromatic constituents of 
plants which are used in the making of perfumery, to- 
gether with the plant parts from which they are extracted. 
Two general methods are followed in the making of per- 
fumes from such products. By the first, the aromatic 
and volatile constituent is extracted by distillation, a 
definite portion of which is then used in making a given 
amount of perfume. By the other, some substance, 
usually an odorless fat, is brought into contact with the 
vegetable matter containing the odorous principle, and 
the latter is thus permitted to diffuse itself through the 
fat, which is used as a perfume. 
Spices and Flavoring Agents. Cases 31 to 35.—These 
substances form quite a large series in which is shown the 
parts of the plant that yield spices and flavoring extracts; 
for example, licorice. Licorice is the root of two species of 
shrubs which grow in the Mediterranean region of Europe 
and Asia. Spanish, French, Italian, Sicilian, or Greek 
licorice is the sweeter; Russian licorice is the lighter-colored. 
The underground runners are commonly included with 
the roots, but are inferior. ‘The root contains gum, sugar, 
and the sweet substance glycyrrhizin, which is extracted 
