290 INDUSTRIAL PLANTS 
uncertain, but it is now known that the finest copal of 
the East is a product of the Zanzibar copal-tree while 
the best South American copal is from the nearly related 
courbaril-tree (Fig. 273). The difficulty of tracing the prod- 
uct to its source arose from the fact that the best copal is 
dug by the natives out of the earth often in tracts of country 
from which all plants that could have produced it have dis- 
appeared. The hard resin, sometimes covered by an ac- 
cumulation of three or four feet of soil, is all that remains to 
show the former existence of copal-trees at that place. It 
isa fossil. The happy accident of finding leaves, flower-buds, 
and flowers embedded in masses of Zanzibar copal, finally 
gave the last link in a chain of evidence connecting the resin 
with the species which produced it. The South American 
copal is found embedded in the earth at the base of courbaril- 
trees, and often contains bits of courbaril-bark. When the 
resin exudes from the tree and solidifies it is still too soft 
to be of commercial value; only the slow process of time, 
perhaps centuries, can bring it to that state of almost glassy 
hardness which renders it indispensable for making the most 
durable varnish. 
78. Coloring matters of some sort are almost universally 
present throughout the vegetable kingdom. In many cases 
they can scarcely be supposed to be of any benefit to the 
plant which produces them but must be regarded as merely 
waste products of the plant’s activity. This is very com- 
monly true of the vegetable coloring matters used in the in- 
dustrial and the fine arts as dyestuffs, pigments, inks, or the 
like. Such substances have been used from the remotest an- 
tiquity. In recent times, however, vegetable dyestuffs have 
come to be very largely replaced by various artificial com- 
pounds such as the well-known aniline dyes prepared by 
chemists from coal-tar. From among the vegetable pig- 
ments and dyestuffs that are still of importance in the arts 
gamboge, indigo, logwood, lampblack, and tan-bark may be 
selected as typical and familiar examples. 
Gambogeis a gum-resin obtained from the Siamese gamboge- 
tree (Fig. 274) and other Asiatic species of the same genus. 
The resinous material flows from the bark through cuts, 
