78 RUBBER AND 



the later yields per tapping is therefore certainly not 

 exaggerated by the conditions of the experiment. 

 Under these conditions, after the tapping has been in 

 progress for three and a half years, it appears that the 

 longer the interval between successive tappings up to 

 an interval of about a week the greater is the yield per 

 tapping. 



If we consider the total yields of rubber per month, 

 this yield is greatest at first from the trees tapped at 

 more frequent intervals. The relative yield from the 

 trees tapped at longer intervals however gradually 

 increases. After three and a half years' continuous 

 tapping, the yield from trees tapped once a week may 

 become as great as or greater than that from trees 

 tapped at any shorter interval. A discussion of the 

 practical importance of these conclusions may be 

 reserved for a later page. 



Overtapping. 



The results just recorded naturally lead on to a 

 discussion of the amount of tapping which can be 

 performed without injury to the tree. Overtapping may 

 be considered either in relation to the excision of bark 

 or to the removal of latex. It is usual to discuss only 

 the former kind of loss in this connection, but there is 

 no doubt that a tree can be overtapped by pricking 

 only, without any removal of bark tissue. In many 

 systems of pricking the damage done to the bark is at 



