76 RUBBER AND 



of bark accessible from the ground occupies not less 

 than four years. Under these circumstances it will not 

 be necessary to touch the oldest renewed bark until the 

 beginning of the fifth year. The system of tapping is 

 generally so arranged that this object is achieved by 

 tapping either daily or on alternate days. There is 

 evidence however that, in the case of old trees closely 

 planted and close planting is the rule on the older 

 plantations a better result can be obtained by in- 

 creasing the interval between successive tappings. 



In this connection reference may be made to 

 Table XII, which shows the annual yields from 70 old 

 and closely planted trees, divided into groups of 10, 

 which were tapped at different intervals. The rate of 

 tapping of the different groups was such that the 

 original bark would be exhausted at approximately 

 the following rates. 



TABLE XVII 

 Time occupied in tapping original bark. 



Row I. II. III. IV. V. VI. VII. 

 Years 24 6 789 10 



Although Group I gave the highest total yield, the 

 bark was so much injured by the rapid tapping that 

 no further extraction of latex was possible after May, 

 1911, and it is anticipated that some years must elapse 

 befone tapping can be resumed. All the other groups 

 show increased yields in 1911 and 1912, but the relative 

 increase is greater in the case of the groups tapped at 



