362 PLANTS AND MAN 



market with its produce. In fifty years, the plantation rubber 

 industry had developed from the experimental confines of botani- 

 cal gardens to cover over six million acres of former tropical 

 jungle. Plantations are established by planting the cleared jungle 

 areas with seedling trees which have been started in nurseries. 

 Growth is rapid, and with care a plantation will be ready for its 

 first tapping five to seven years after the trees have been set out, 

 at which time the young trees measure about six inches in 

 diameter. The cost of establishing and maintaining a rubber 

 plantation, until the first returns from rubber are forthcoming, 

 varies from $200 to $400 per acre. 



Tapping is much more carefully done on plantation trees; a 

 sharp knife is used to make a narrow diagonal cut in the bark 

 about half way around the tree, care being taken not to injure 

 the underlying growing tissues. The tree is retapped, always 

 early in the morning, every other day; if properly carried out, 

 this removes only about an inch of bark per month from the 

 tree. This is sometimes continued throughout the year, at other 

 times for only two to eight weeks, depending upon the demand 

 for rubber. The length of life and amount of yield of rubber trees 

 under plantation care is definitely favored by the highly in- 

 telligent class of native labor available. The oldest plantations — 

 forty years or more old — are still in active production. These 

 plantations are usually part of a large rubber estate, each of 

 which has its own factory to which the collected latex is taken 

 for coagulation. Here the latex is sieved to remove any debris 

 and then left, with the adding of a weak acid solution, to coagu- 

 late over night. In the morning the coagulated rubber cake is 

 removed, rolled fiat, ribbed, or creped, and dried for a week or 

 more after which it is packed for shipment. For some types of 

 manufacture, it is better to have the rubber in a liquid form, 

 known as liquid latex. This is produced by adding ammonia to 

 the strained latex to keep it from coagulating, and shipping in 

 large tank containers. 



Final manufacture of rubber into the thousands of useful 

 articles of present day civilization is accomplished at factories 

 near to the consuming areas. In the United States, Akron, Ohio 

 is one of the leading rubber manufacturing centers. 



