644 RUBBER 



Opinions are now divided between tapping on one-half, 

 one-third, or one-quarter of the circumference. As a 

 variant of the half, tapping opposite quarters at the same 

 time is practised. In some Peradeniya experiments, 

 which again are open to objection, tapping on one-third 

 gave almost the same as tapping on opposite quarters 

 for a year, though the yield in the latter case fell off more 

 rapidly towards the end of the period than in the former. 



There is, unfortunately, no straight experiment which 

 compares tapping on opposite quarters with tapping on 

 half the circumference. As a rule the difference in the 

 area has been combined with a difference in the method 

 or pattern of tapping, such as a full herring-bone on half 

 the circumference versus half herring-bone on opposite 

 quarters. 



Tapping on one-third the circumference has been 

 adopted in some cases, but it has the disadvantage that 

 it is difficult to change subsequently to quarters on the 

 same area. 



The view is now generally accepted that this question 

 must be decided from the point of view of the welfare 

 of the tree rather than that of yield. Fitting's results 

 have been fully appreciated by the planting community, 

 though it has been overlooked that tapping all round the 

 tree was condemned on physiological grounds by Parkin 

 in 1899, even for single incision tapping. 



The Direction of the Tapping Cut. 



In 1906 Mr. C. O. Macadam, of Culloden Estate, found 

 that tapping to the left yielded more rubber than tapping 

 to the right of the vertical channel. No reason was dis- 

 covered for this until 1909, when it was found that in 

 Hevea the vessels and latex tubes, in general, sloped up 

 to the right, and consequently a cut to the left severed 

 more latex tubes than an equal and equally sloped cut 

 to the right. This has been completely confirmed by 

 Dr. de Jong, who finds that the difference in yield is 

 almost exactly accounted for by the difference in the 

 number of latex tubes severed. 



On this finding, a half herring-bone to the left yields 

 more than a half herring-bone to the right, while the 



