THE ASSAM RUBBER TREE 



233 



with Ficus elastica in 1911, and the yield of rubber ob- 

 tained therefrom was 30,000 kilograms, i.e. about 25 kilo- 

 grams (5-5 lb.) per acre. The yiekl has increased during 

 the last few years, and it is estimated that in 1916 it will 

 amount to 258,000 kilograms (about 44 lb. per acre). 



Tapping experiments conducted in Java at Pamanoe- 

 kan and Tjiasem on 5,200 trees gave the following results : 



Age of trees. 



Years. 

 14 

 15 

 16 

 17 

 18 

 19 

 20 

 21 

 22 

 23 



Yield of rubber 



from 5,200 trees. 



kilograms. 



2,500 



2,247 



686 



Not tapped 



1,500 



2,772 



2,718 



Not tapped 



Not tapped 



1,450 



The diminution which takes place in the yield of rubber 

 from Ficus elastica trees on contmued tapping is shown 

 by the following results obtained in Assam : 



Twenty-one selected dominant trees at Charduar were 

 tapped tln-ee years in succession and furnished 46 lb., 

 48 lb., and 9 lb. of rubber in the first, second, and third 

 year respectively. 



Two groups of fifty- trees each were tapped tluree years 

 in succession by reopening the old incisions m one group 

 and by making fresh incisions in the other. The following 

 results were obtained : 



1st year. 



2nd year. 



3rJ year. 



50 trees, incisions reopened 

 50 trees, new incisions made 



lb. oz. 



55 7 

 43 



lb. oz. 

 42 4 

 35 13 



lb. oz. 

 14 8 

 24 1 



Experiments in other countries have given similar 

 results, and it seems probable that Ficus elastica trees 

 cannot be tapped regularly every year, but require to 

 be periodically rested. 



