INDUSTRIAL USES OF PLANTS 385 



is native to China and has been long cultivated there and in 

 Japan. The milky juice hardens and darkens upon exposure to 

 air; when applied as a varnish it is highly resistant to heat and 

 unaffected by alcohol, acids, or alkalis. The process of lacquering 

 was originated by the Chinese almost three thousand years ago, 

 and is very complicated, sometimes using three to four hundred 

 coats, and requiring several years to finish. 



The OLEORESiNS, in addition to their resin, contain consider- 

 able amounts of essential oils, which impart a definite odor and 

 taste to them. Most important of this group are the turpentines, 

 which originate practically entirely in coniferous trees. The 

 production of turpentine and rosin constitute the naval stores 

 industry, one of the oldest forest industries, centered at the present 

 time in the United States. Naval stores are produced from the 

 resin, or sap, of longleaf and slash pines by chipping the surface 

 of the tree trunk and distilling the pitch or sap which flows from 

 the cut surfaces of the sap wood. Tar derived from the sap was 

 formerly used in the manufacture of wooden boats, and gave the 

 industry its name, but this product is now of minor importance. 

 Confined to the longleaf and slash pine belts of the southern pine 

 region this industry closely follows lumber, cotton, and other 

 agricultural products in its importance. Timbers that have been 

 chipped for gum are now used for sawlogs, posts, poles, etc., 

 instead of being left in the forest to waste as in former years. 



In gathering resin from the trees, chips or streaks are cut 

 through the bark into the sapwood (fig. 248). This stimulates 

 the production and flow of the sap, which is collected in clay or 

 metal cups attached below the chipped area. New cuts are made, 

 generally each week, from March to November. The resin is 

 collected at intervals of two to five weeks and taken to centrally 

 located distilling plants, where a large copper still is used to 

 separate the turpentine from the residue, or rosin. These products 

 are sold by the barrel, either to wholesalers, or through a financ- 

 ing company which makes loans to the operators and then sells 

 their products at a commission. Turpentine is used mainly as a 

 solvent and thinner for paints and varnishes, and in shoe polish 



