133 



TAPPING EXPERIMENTS ON RAMBONG AND 



PARA. 



Professor Dr. A. Weberbauer records in the last December number 

 of the ** Tropcnpflanzer" some interesting experiments he made in 

 Camerun on the tapping of certain species of rubber bearing plants. 

 We abstract his remarks on Ficus elastica (Eambong) and Hevea 

 Braziliensis (Para). 



In tapping Ficus elastica he used the ordinary tapping knife 

 ( " die Kaeuflichen Kautschukmesser " ). In the outer layer of bark, 

 which contains little or no latex, a groove was cut to the depth at 

 which the first drops of latex show themselves, then with an ordinary 

 penknife a deep cut was made in the bottom of the groove. The author 

 claims that wounds in the cambium, which cannot always be avoided, 

 will heal more quickly, if caused by the sharp pocket knife than by 

 the ordinary coarser tapping knife. 



The weights given are those of well-dried rubber. 



In the first experiment two trees with stems of about equal girth 

 were taken. 



In (a) a cut of 16 centimetres (about 6i inches) was made in a 

 sloping direction. 



In (b) the cut was 22 centimetres (about 8f inches) and parallel 

 with the axis of the stem, that is vertical in the case of an upright 

 growing tree. The yield from (a) was 2*1 grams (1000 grams— 2f lbs.) 

 from (b) 1'2 grams ; so that the sloping cut, though shorter than the 

 other, yielded nearly twice as much rubber. 



In another experiment six cuts were made on the same branch 

 and on succeeding days, except that a clear day intervened between 

 the second and third. All cuts were made at right angles to the long 

 axis of the branch, which grew horizontally. The time of day, 9 to 12 

 o'clock, was much the same in each case, and so was the weather. 

 The first cut yielded 12'17 grams ; The second, close to but behind 

 No. 1 on the same side of the stem, gave 0'87 grams ; The third, on 

 the same side as No. 2. and about 4 inches distant from it, yielded 

 2'03 grams ; The fourth was on the same side as No. 3 and distant 

 about 8 inches, the yield was 2'20 grams. The fifth was on the oppo- 

 site side to the previous ones and lay under the first : it yielded 8*80 

 grams. The sixth was on the same side of the stem as the fifth but 16 

 inches distant from it : yield 2*26 grams. 



The first cut gave more than double as much rubber as the three 

 others together which were on the same side of the branch. The 

 farther the cuts are from each other the greater is the yield. On the 

 opposite side of the stem, the fifth cut gave nearly four times as much 

 latex as the sixth, though the distance between them was relatively large. 

 Therefore if Ficus elastica is tapped with sloping cuts, and if a good 

 number of these are made in a short time, they should, if they lie on 

 the same side of a stem or a branch, be made considerable distances 

 apart, otherwise there is only a useless injuring of the tree. In his 



