WHALF.Y: RUBBER 19 



South America. A correct estimate of the number of such trees and the amount 

 of rubber that could be obtained from them would be very difficult to make. 

 Published guesses have indicated as many as 300,000,000 trees, a probably 

 fantastic figure, with an attainable yield of 50,000 tons of rubber annually, 

 but there are many serious complications involved in the collection of this 

 wild rubber in large quantities. 



Cooperative arrangements have been made with 14 of the Latin American 

 countries for the development of rubber plantations. These plantations have 

 the double aim of increasing the available supply of rubber during the present 

 emergency if it is prolonged and assuring a dependable Western Hemisphere 

 supply of rubber in the future. A summary of the plan for establishing a self- 

 sustaining rubber-growing industry has been published by Brandes (1941). 



In addition all plants holding any promise of being useful in providing a 

 domestic source of rubber are being thoroughly investigated. 



Hevea brasiliensis. The most important source of rubber is Hcvca 

 brasiliensis, the Para rubber tree. This tree, apparently long known to the 

 South and Central American Indians, made its first appearance in white man's 

 records in the early 18th century. 



In 1770 Priestley discovered that rubber, in this case from India, would 

 erase pencil marks, hence the name rubber and the persistence of the term 

 India rubber even after the majority of our rubber came from a South Ameri- 

 can tree. In 1823 Charles Mcintosh found that rubber is soluble in benzene. 

 This discovery broadened the uses for waterproofing as previously only freshly 

 collected latex could be used for coating cloth. 



In 1839 Goodyear came accidentally upon the knowledge that rubber could 

 be vulcanized by mixing with sulphur and heating. This resulted in an elastic 

 material which did not become sticky in hot weather and could stand much 

 lower temperatures than crude rubber without becoming brittle. An amazing 

 number of uses were immediately found for the vulcanized product. The 

 demand rose so rapidly that whereas in 1849 rubber was collected from Hevea 

 brasiliensis only in the vicinity of the city of Para, in 1850 some 25,000 people 

 were concerned in its collection in the State of Para alone, and collectors had 

 ascended far up the tributaries of the Amazon. As the uses of rubber in- 

 creased it was collected in varying amounts from many different plants but 

 the Para rubber tree remained the most important, except perhaps for a brief 

 period just after the turn of the century when guayule became a very large 

 producer. 



In 1876 Henry Wickham, later knighted in consideration of his contribu- 

 tions to the British Colonial interests, took seeds of Hevea brasiliensis from 

 the Amazon region to Kew. He then introduced the tree, using Kew-grown 

 material, into India, Ceylon, the Straits Settlements, and the Dutch East 



