TREES THAT MANUFACTURE 117 



these rubber fields of Brazil and Bolivia and how 

 man in his rapacity thoroughly exploits both the de- 

 fenceless plant and his own weaker brother. The 

 rubber-producing trees used to be cut down, but 

 now considerations of economy have led to the use 

 of a series of circular incisions and a small clay 

 cup to catch the liquid which comes from each. A 

 tree yields anywhere from three to sixteen pounds 

 of caoutchouc annually. It is believed that the 

 caoutchouc mistletoe of Venezuela may furnish a 

 new source of rubber. The fruits of this plant con- 

 tain the much-sought substance in solid masses. 



The bark of all trees contains cork. It is the 

 growth of the cork which determines the pattern 

 of the corrugated exterior. In the cork tree, cork 

 cells are particularly and exclusively abundant, so 

 that great layers sometimes as thick as twenty 

 inches may be removed from time to time without 

 endangering the tree's life. 



One would hardly expect trees to engage in the 

 liquor business, yet there is ample evidence that 

 they do distil and brew on occasion. .We have al- 

 ready mentioned the Mahwa tree blossom of India 

 from which men make strong drink. There are 

 trees which make their own "moonshine." So 

 proper a tree as the common cherry has been known 

 to allow its fruit to ferment so viciously that whole 



