208 TROPICAL AGRICULTURE 



this method is often employed in the place of boiling. The 

 gum is marketed in blocks weighing 20 to 30 pounds. Chicle 

 was formerly used like gutta-percha in electric insulation. It 

 is now used, however, entirely for chewing gum and exclu- 

 sively in the United States. This country imported 5,896,000 

 pounds of chicle in 1914. The exportation of chicle from 

 Mexico ranges from 1,800 to 2,200 tons annually. 



There are many other trees which yield a product similar 

 to chicle. For example, Euphorbia lor i folia, a tree native to 

 Hawaii, yields a latex containing 42 per cent, of total solids. 

 The solid material contains 55.9 per cent, resin, 1.5 per cent. 

 gum, 15.8 per cent, caoutchouc, 12.6 per cent, protein, and 

 nearly 4 per cent, of ash. A laborer can collect 40 pounds of 

 latex per day. The latex of this tree is best coagulated by 

 heat 80 to 90 C. 



CAMPHOR 



Camphor is a product of a tree known as Cinnamomum cam- 

 phora, closely related to the cinnamon tree and a native of For- 

 mosa, Japan, and China. The tree has been introduced into 

 Ceylon, India, East Africa, Hawaii, California, Florida, and 

 quite generally throughout the Tropics and subtropics. The 

 camphor tree is quite hardy and will endure climates where 

 the winter temperatures fall as low as 15 F. Before the true 

 camphor came into prominent commercial use, closely related 

 products were obtained from other trees. Dryobalanops aro- 

 matica, a tree native of Borneo, Sumatra, and Malaya, was 

 used perhaps before the true camphor tree, and the product 

 obtained from it was known as Borneo camphor. Blumea bal- 

 samifera, a native tree of Burma, yields what has been known 

 as Ngai camphor. 



The true commercial camphor tree reaches a height of 100 

 feet, a diameter of 2 or 3 feet, and is densely branched. The 

 leaves are dark green, shiny, and of leathery texture. Since 

 1899, the Japanese Government has tried to maintain a mo- 



