THE 



TROPICAL AGRICULTURIST 



AND 



MAGAZINE OF THE 



CEYLON AGRICULTURAL SOCIETY. 



Vol. XXXII, COLOMBO, MAY 15th, 1909. No. 5. 



Reviews. 



RUBBER TAPPING METHODS. 



Physiologisehe Grundlagen zur Bewer- 

 tung der Zapfinethoden bei Kautschuk- 

 baumen. (Physiological principles by 

 which to reckon the relative value of 

 rubber-tapping methods) by Dr. Hans 

 Pitting. (Beihefte zum Tropenpflanzer, 

 Feb., 1909). 



Professor Pitting visited the tropical 

 gardens of Buitenzorg in 1907 under the 

 system of subsidies provided by the Ger- 

 man Government. He there devoted 

 himself to a scientific study of the physio- 

 logy of rubber bark in its relation to the 

 various methods of tapping in vogue, 

 with the result that he has arrived at 

 conclusions of so much interest to rubber 

 planters, that we do not think any 

 apology is needed for giving a brief 

 account of them. Professor Pitting's in- 

 vestigations draw attention to the fact 

 that the bark of the rubber tree, in 

 addition to being the seat of the forma, 

 tion and storage of latex, also provides 

 the channels through which food sub- 

 stances manufactured by the leaves find 

 their way to the roots and base of the 

 tree. Not only are these food supplies 

 necessary for the growth of the roots 

 and consequently for the general wel- 

 fare and health of the tree, but they also 

 provide the material from which the 

 actual rubber is formed in the latex 

 tubes. It is therefore of the highest 

 importance to preserve the integrity of 



the channels through which the down- 

 ward food current passes. Any trans- 

 verse cut tli rough the bark and penetrat- 

 ing to the cambium will stop the down- 

 ward current of food-bearing sap for as 

 much of the circumference of the tree 

 as the cut occupies, and it is well known 

 that if a tree is completely and effec- 

 tively ringed it must ultimately die, 

 because in this case the food supply of 

 the roots is cut off altogether. The slop- 

 ing cut made in all the ordinary methods 

 of tapping, although it does not leach 

 the cambium, also materially checks this 

 downward current, especially if it is 

 combined with the use of the pricker ; 

 and the wider the area of bark operated 

 upon becomes, the greater is the obstruc- 

 tion caused in the vitalizing current. 

 It is highly probable that the ill-effects 

 of over-tapping are quite as much due 

 to checking of the downward food sup- 

 ply as they are to the actual removal of 

 latex. Professor Fitting therefore joins 

 issue with Mr. Herbert Wright with 

 regard to the well-known dictum of the 

 latter— " The best method of tapping is 

 that which extracts the maximum 

 amount of latex from the tree with 

 removal of the minimum quantity of 

 cortical tissue, and without damaging 

 the thin layer of cambial cells." He 

 maintains, on the contrary, that the 

 best results will be obtained in the long 

 run by those methods which leave the 

 widest possible area of free bark un- 

 blocked in a vertical direction, and 

 therefore advocates such a system as the 



