TAPPING 145 



their swollen trunks, covered with growths of burrs, and by 

 their rough, corrugated bark, how much they resented the ill- 

 usage. Many such trees are still to be found in Ceylon, Sumatra 

 and elsewhere, and serve the purpose of an object-lesson. 



There is no more fatal system of tapping than the use of 

 the pricker, still advocated by some. Undoubtedly the yields 

 of latex are, for a time, much increased by its use, but these in- 

 creased yields have to be paid for very dearly indeed later on. 

 The wounding of the cambium of the tree by the pricker is 

 always followed by such an extraordinary development of burr 

 growths and abnormal swellings that no smooth portions are 

 left on the bark of the trunks where it is possible to tap the 

 trees. 



By cutting out the growths, by manuring and resting the 

 trees, it has been possible to recover a good many of such trees, 

 both in Ceylon and Sumatra, but by far the greater number 

 have died out. 



It is said that Mr R. W. Harrison was the first to introduce 

 into Ceylon the system of paring away thin shavings of the bark 

 from the same incision, which is now generally followed, but 

 the system had been experimented with in the Federated Malay 

 States previous to that date. Those who have studied the 

 short, simple account of the physiology of the Hevea tree 

 given in earlier chapters must realize that, by cutting away 

 strips of bark, they are interfering with the course of the flow 

 of manufactured plant-food downwards through the cortex. 

 The length, the depth, and the number of the cuts determine 

 the extent of such interference. 



When, as in the case of the now abandoned full-spiral 

 system of tapping, the tree was entirely girdled with cuts, the 

 entire downward movement of food-supplies was practically 

 suspended, and but for the reserves of starch food stored by the 

 trees below the cuts they would have eventually died if the 

 system had been long continued. 



Some experiments made at Henaratgoda in September, 1907, 

 went to show that Hevea trees would for a long time survive 

 even complete girdling of the trunks of the trees. This was 

 due to the fact that the Hevea is a tree of comparatively rapid 

 growth, and in trees of rapid growth the sap-wood is thicker 

 and the tree is not so soon killed as the slow-growing trees. 



