8o RUBBER AND 



period for renewal has been underestimated. From the 

 point of view of bark-removal the trees have been over- 

 tapped. This is the criterion of overtapping which is 

 most often adopted in practice. It would probably be 

 better however to extend the idea of overtapping 

 somewhat further, and to recognise that it is possible 

 for a tree to be overtapped owing to the excessive 

 removal of latex, although there may be a considerable 

 area of untapped bark still available for tapping. 



In the case of young growing trees planted with 

 plenty of space, the yield of latex may be expected to 

 increase steadily from year to year, so long as the bark 

 is preserved in good condition. The ideal rate of 

 tapping may be defined as that rate which is associated 

 with the greatest increase in yield as time goes on. Any 

 quicker rate may consequently be regarded as involving 

 overtapping from the point of view of latex removal. 

 In the case of the old trees at Henaratgoda, the rate of 

 tapping associated with the greatest increase in yield 

 proved to be considerably slower than the rate required 

 for a degree of bark renewal which would generally 

 be regarded as complete. 



Yield at different levels of the trunk. 



The bark is thickest near the base of the tree, and it 

 is here that the greatest flow of latex is obtained. On 

 29 trees tapping was carried on by six V cuts placed 

 each one foot below the next, the lowest cut being one 



