60 THE TAPPING OF RUBBER PLANTS 



elaborated in the leaves, to all parts of the plant, m- 

 eluding the roots. The sieve-tubes of the cortex which 

 serve as channels for the transmission of the food-pro- 

 ducts are quite distinct from the laticiferous vessels. 



It will be evident from the preceding account that 

 when incisions are made in the bark of a rubber tree 

 there is a possibility of causing damage to the cambium 

 if the cut penetrates too deeply, and that whatever 

 method of tapping is employed, some interference with the 

 transference of nutritive material in the plant will be 

 caused. 



The laticiferous vessels are most numerous in the inner 

 layers of the cortex, and it is therefore essential, in order 

 to obtain a good flow of latex, that the incisions should 

 be sufficiently deep. On the other hand, care must be 

 taken that the cuts do not unduly penetrate or expose 

 the wood, as this will injure the cambium and thus retard, 

 or even prevent, the formation of the new tissue required 

 to heal the wounds. 



It is, of course, impossible in practice to tap the inner 

 layers of the cortex without occasionally penetrating 

 to the wood, but with the exercise of care the damage to 

 the cambium can be reduced to a minimum and no per- 

 manent harm will result. If, however, a large area of 

 wood is exposed by tapping, as is frequently the case in 

 native methods, a portion of the cambium is destroyed 

 and the new tissue required to cover the wound can only 

 be formed by an ingrowth from the surrounding un- 

 damaged cambium. In such cases the healing of the bark 

 may not be complete, thus affording an entrance to insect 

 and fungoid pests, or the considerable growth of new 

 tissue required to repair the damage may result in the 

 formation of excrescences on the stem which interfere 

 with subsequent tappings. 



With reference to the possible effect of continued 

 tapping on the distribution of the food-supply in the plant 

 it may be recalled that if a complete ring of bark of 

 sufficient width be removed from a tree, the part below 

 the incision is cut off from the descending stream of 

 nutritive material in the cortex, and that as soon as 

 the reserve food-supply stored in the plant below the 

 incision is exhausted, the roots will be unable to obtain 

 the necessary nourishment and the tree will ultimately 



