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of permanence and durability; also that they are very 
hard, for which reason they take and retain a high polish. 
Many resins of recent production and of less value, are 
added to the cheaper varieties of varnish. Our collection 
contains representatives of practically all varnish resins 
that are in use. 
Miscellaneous Resins. Cases 43 and 44.—Resins are 
waste substances produced by the life processes of the 
plant. They are transported through the plant body in a 
liquid state, being dissolved, mostly in volatile oils. When 
the ducts or cavities containing them are broken or cut, 
they exude upon the surface and may then harden by the 
evaporation of the oil. They are collected for use by va- 
rious methods, some of which are illustrated by the speci- 
mens and pictures exhibited in the cases. 
Dye Stuffs. Case 45.—Many of the substances pro- 
duced by the living plant and stored in its body possess 
colors which can be imparted to fabrics or other articles 
immersed in their solutions. There are others which 
although themselves not colored originally, yield useful 
dyes when some chemical agent is added to them. All 
such plant substances, as well as the vegetable tissues 
containing them, are known as “‘dye stuffs.’ 00 
illustrations are logwood, brazil-wood, madder, alkanet, 
and indigo, besides which, many of ce importance are 
to be seen in our collection. 
Although the use of anilin or coal-tar colors has very 
largely replaced that of vegetable dyes, there is still a vast 
use of the latter. But for the introduction of the former, 
it is dificult to see how the demand for colors could have 
been supplied under modern conditions. 
Tanning Materials. Cases 46 and 47.—The tanning 
materials are also very important from an economic stand- 
point. They depend for their value chiefly upon the 
tannic acid that they contain, but that other constituents 
contribute is clear from the fact that a substance containing 
less tannin may be more valuable than one containing a 
