ON GUM AND SUGAR TREES 
to a wounded man. In each case coagulation 
prevents excessive hemorrhage. 
Possibly this may explain the quality of the 
latex, its capacity to coagulate having been devel- 
oped through natural selection. But under nor- 
mal conditions, at least, the latex is always fluid, 
and its properties are little more like those of 
rubber than are the properties of the maple tree 
like those of sugar. 
Of course the same thing is true of the plant 
juices that when dried or partially evaporated 
constitute the various gums and resins. As manu- 
factured in the tree they are transformed sugar 
products, and they are always in solution. Only 
when the juices are exposed to the air, as when 
they exude from an injured surface, do they coagu- 
late to form the gummy or resinous substances 
that become articles of commerce. 
In some cases the exudate may be separated 
into two or more commercial constituents. Such 
is the case with the juice of those trees that pro- 
duce turpentine. The liquid that flows from the 
tree, corresponding to the sap of the maple and 
the latex of the rubber tree, may be evaporated 
or distilled in such a way.as to be changed in part 
to a solid gummy or even vitreous substance, and 
in part to the somewhat volatile fluid familiar as 
turpentine. 
[255] 
