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] 



