650 RUBBER 



Future Experiments. 



Some indications of the type of experiment still needed 

 have already been given, but one or two further remarks 

 on this head may be advisable. 



The experimenter should always adopt the most con- 

 servative system possible. Tapping experiments, to be 

 of any value, must be carried on for several years, and it 

 may happen that the system adopted will be out of date 

 before they are concluded. An experiment was begun 

 in 1908 in which the tapping system was a full herring- 

 bone with three cuts on half the circumference. That 

 was a conservative system then, when most estates were 

 employing six cuts on half the circumference; but it has 

 since been derided as exceptionally drastic. 



During the last four years progress in tapping methods 

 has been so rapid that moist of the older experiments are 

 of doubtful applicability to modern tapping. Experi- 

 menters nowadays must confine themselves to one or two 

 cuts on not more than one-quarter of the circumference. 



Perhaps the greatest scope for tapping experiments at 

 present lies in the direction of what may be termed 

 "change over" systems. It is recognized that in pro- 

 longed tapping on one area the yield gradually diminishes 

 as tapping proceeds, though in estate work the diminution 

 may be masked by the seasonal increase. It is also 

 becoming evident, from investigations now being carried 

 out by Mr. L. E. Campbell at Peradeniya, that the effect 

 of tapping for a prolonged period on one side is bad from 

 a physiological standpoint. These considerations favour 

 the adoption of systems in which one side is tapped for 

 two or three months, after which tapping is transferred 

 to the other side. The general course is as follows: 

 The first side is tapped for about two months. The 

 second side is then opened, and both sides are tapped 

 together for about a fortnight, until a full flow is estab- 

 lished on the second side. Then tapping is stopped on 

 the first side, but continued on the second for the next two 

 months, after which it is changed to the first side again. 

 Careful experiments dealing with the relative yields, per- 

 centage of rubber in the latex, and effect on the tree with 



