66 RUBBER AND 



a gradual increase in yield may be shown, so long as the 

 tapping is not severe enough to cause definite injury. 



Relation of yield to volume of bark. 



The evidence already given is sufficient to show that 

 the amount of latex which can be removed from a 

 Hevea tree in one year, must be very large in comparison 

 with the quantity which was present in the vessels prior 

 to the commencement of tapping. In further illustra- 

 tion of this point we may take the case of an excep- 

 tionally large and vigorous tree, the yield from which 

 was separately recorded for a considerable period. 



This particular tree is one of those originally planted 

 at Henaratgoda in 1876. Its girth at three feet from the 

 ground was 102 inches in December 1908 when the ex- 

 periment was begun; and it had increased to 115 inches 

 in December 1911, at which date the available records 

 come to an end. The tree therefore continued its 

 normal rate of growth of upwards of three inches per 

 annum throughout the whole course of the experiment. 



The tree was tapped daily on the three-V system 

 described above, and in the space of a little more than 

 two years, four similar areas of bark had been com- 

 pletely tapped. The renewed bark on the first area 

 was then retapped, and was nearly completed at the 

 end of December 1911. During this last period tapping 

 was carried out daily during alternate months, with 

 monthly intervals of rest. The yield of dry rubber was 

 as follows: 



