(97) 
as well as the various qualities of paper into the structure 
of which it enters. Here also are specimens of straw and 
other specimens illustrating the several stages and sub- 
stances connected with the production of straw paper. 
Rubber and Allied Products. Cases 37-39.—The first 
case in the west wing contains rubber and allied pro- 
ducts. Here are the implements and utensils used in 
collecting the rubber “milk” from the trees which grow 
in tropical forests. Rubber is derived mostly from trees 
belonging to the mulberry family, spurge family, and dog- 
bane family. Rubber, India-rubber, or elastic consists 
chiefly of the peculiar substance caoutchouc, which, in the 
form of an emulsion, constitutes the milky juices of many 
plants, existing in special milk-tubes of the bark and wood. 
The bark is cut or punctured, when the milk exudes and is 
caught in some receptacle. The milk is coagulated by 
various methods, mostly by subjecting it to the action of 
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, the Para Rubber tree, 
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. 
Varnish Resins. Cases 40-42.—The varnish resins 
roper are mostly dug from the earth, where they have 
laid imbedded for ages in a sort of fossil state. Their 
value for varnish purposes is due to the fact that they 
dissolve with great difficulty, thus possessing the quality 
