RUBBER PLANTING 139 



circumference. A similar system, extending over half 

 the circumference of the tree, has however been widely 

 used on estates, and is known as the half spiral system 

 (Fig. 17). The full spiral system was once popular 

 but is now almost obsolete, as it proved too drastic. 

 In this system one or more similar cuts extended right 

 round the tree, or even girdled it more than once. There 

 was no vertical channel, but each spiral cut drained into 

 a separate collecting cup. In the full herring-bone 

 system (Fig. 15) there is a conducting channel with 

 slanting cuts on either side. The lateral cuts enter the 

 central channel alternately instead of meeting as in the 

 V system. The herring-bone method is generally pre- 

 ferred to the V system because in the latter the bark 

 at the tips of the V's is said to be specially liable to 

 injury. The full herring-bone system is often used on 

 large trees, on which the lateral cuts would have to be 

 of considerable length if the half-herring-bone system 

 were employed. To mention only one other system 

 on young trees in Malaya a single basal V (Fig. 19) is 

 often tapped. By this method trees can be tapped 

 close to the ground, although the bark at a higher level 

 is not yet ready for tapping. The basal system is also 

 being used on older trees on some estates, and it is said 

 that the yield is almost as good as when two or three 

 cuts are employed, whilst there is of course a great 

 saving of bark. 



