Jan. 1907. J 



5 



Saps and Exudations. 



system is that a return is obtained by tapping only intermediate trees, and can be 

 carried out with the definite idea of extracting every possible particle of rubber 

 from such trees, and finally felling them and uprooting the stumps. But. as I have 

 previously pointed out, itcan only be recommended on the understanding that the 

 estates will be thinned put after the fourth or fifth year and all root stumps 

 extracted. The practicability of extracting rubber, valued at over 5s. per lb., from 

 trees having a circumference of 18 to 20 inches— that is in their ith or 5th year— has 

 been proved long ago, and is taking place to-day on some very prominent and valu- 

 able estates ; it is difficult to understand the reason for any statement to the 

 contrary, in spite of what has and is still being done. 



An alternative method of obtaining rubber from such trees— by felling them 

 and macerating the bark— has been suggested. At the present time this cannot be 

 recommended, first because the yields thus obtained have been less than when the 

 trees have been tapped standing; and, secondly, because the rubber obtained by 

 maceration appears to suffer in quality owing to its being mixed with the sap of the 

 cortical cells ; nevertheless, we know that rubber is thus obtained from other plants, 

 and the results obtained justify further investigation. 



The objections which have been raised against thinning-out are briefly that 

 (1) planters are not keen to thin out, fell and uproot the plants, (2) it is a very difficult 

 matter to kill a Para rubber tree by tapping, (3) there may be interference in the 

 growth of the remaining plants, (1) diseases may be encouraged to flourish on the 

 weak trees which are not removed. 



It is admitted that by some systems of tapping it is very difficult to kill a 

 Para rubber tree within a couple of years, but from observations made on trees 

 which have been rapidly tapped on the paring and spiral system, very little doubt 

 exists in my mind as to the results obtainable. On such trees the spiral system can 

 be adopted, and at the end of twelve months the tree should be removed and the 

 stumps extracted. The unwillingness of the planters to actually fell the trees so 

 tapped is said to be encouraged by results obtained on some estates, where it is 

 reputed that the total yield, per acre, appears to be approximately the same, no 

 matter whether the trees are distanced ten or twenty feet apart ; I have never 

 seen any figures or authoritative reports which prove this. 



The interference in growth, in trees originally planted ten feet apart, 

 will vary with the soil, climatic, and other conditions, but in the case of 

 unpruned Para rubber trees at Peradeniya, and others in relatively poor> soils in the 

 low-country of Ceylon, I have previously explained that there is no very serious 

 interference in either root or foliar development up to the period specified. Occa- 

 sional branches and roots will overlap, but not to any great extent except under very 

 good conditions ; the exhaustion of the surface soil may be partly balanced by the 

 application of manures. If, however, the estate is not thinned out, considerable 

 interruption in the radial growth of stem and root structures will undoubtedly 

 occur, and it remains to be proved»whether the trees on such a property make up in 

 number what they lack in size. 



The liability of weak and closely-planted trees to the attacks of fungi and 

 insects has been raised as an objection against this system ; the liability of the 

 bark, exhausted of latex, to insect pests applies to that on any tapped tree, but in 

 neither case would it be possible to completely extract the latex from such tissues 

 except by killing them, a procedure not yet recommended. The liability to root rot 

 would be largely overcome by extracting the stumps, as is recommended on the 

 clearing itself ; on the Yatipawa plantation where the roots of felled rubber trees 

 were allowed to remain in the soil and decay, the remaining trees have recently 

 been described as healthy ; perhaps this apparent immunity can be associated with 



