TREE PRODUCTS 141 



VARIED PRODUCTS OF THE PLANT 

 LABORATORY 



An incidental use of the resinous exudate of 

 various trees is the production of chewing gum. 



The habit of gum chewing appears to have 

 originated or at least to have gained chief popu- 

 larity in America in comparatively recent times. 

 The resin that exudes from the spruce was the 

 substance that was chiefly used, under the name 

 of spruce gum, until somewhat recently. But of 

 late years the chewing gum industry has reached 

 proportions that make it impossible to meet the 

 demand from this source. And it has been found 

 that ordinary resin, combined with sugar and 

 linseed oil, with some flavoring added, serves the 

 purpose of the original spruce gum so the latter 

 is now seldom seen in the market. More re- 

 cently chicle, a gummy substance which exudes 

 from several tropical trees, has been imported in 

 great quantities, and is now supplanting all other 

 sources of gum. 



The supplying of turpentine and its products 

 gives the conifers high rank among trees that 

 produce commercial by-products of great im- 

 portance. But with the exception of the pines, 

 the trees that produce really important exudates 

 or oils or chemicals are indigenous to the tropics, 



