2g6 



favourable than in 1902), the variations of the yield were of such a 

 manner that we may deduce from the experiments that it is not 

 advisable to make long incisions. 



The long incisions also have the disadvantage that they require a 

 considerable time to heal. 



In 1901, the question arose whether reopening the incisions, above 

 as well as below, did not bring about an increase of the yield. 



To that effect the incisions on one side of each of four trees were 

 only reopened on the upper edge and those on the other side on 

 both upper and lower edge. The results were as follows: — 



No. of Tree. 



7- 



21. 



22. 23. 



a 



b 



a 



b 



a 



b a 



b 



Tapped surface M 2 « 

 Total yield, Grs. 

 Yield for Ma., Grs. 



2'33 

 380 

 163 



2'33 

 552 

 237 



i*39 

 181 

 130 



i"39 

 37o 

 266 



177 

 236 

 133 



177 1-645 



403 | 221 

 228 1 134 



i'645 

 300 

 182 



a. — Only tapped on lower edge. b. — Tapped on both edges. 



The figures shew that the incisions reopened on both upper and 

 lower edges and gave more rubber than those w r here only the lower 

 edge was worked. 



In the first case, the average yield was 143 grammes per M 2 of 

 surface and the other 238 grammes. 



The double working does not, however, give twice the product. 



In 1903, the above experiments were made with a larger number 

 of trees. 



The period of tapping was, however, remarkably dry. 



No. of Tree 



3 



8c 



9 



25 



26 



27 



28 



29 



30 



3i 



32 



33 



Surface tapped M 2 ... 



2'2 



* 43 



2' 



173 



1 '43 



i-55 



1 54 



i*39 



165 



i'55 



152 



175 



Total yield Grs. ... 



858 



512 



8lO 



50O 



780 



487 



500 



570 



877 



709 



610 



910 



Yield per M 3 Grs. ... 



390 



358 



405 



289 



545 



3H 



325 



410 



53^ 



457 



401 



520 



As no notes were taken of the very dry East Monsoon, unhappily 

 only one tree (No. 3) on which the incisions were reopened only 

 on the lower edge, can be compared with 1 1 others whose incisions 

 were reopened on both edges. 



The yield of tree No. 3 amounted to 390 grammes per M2 of 

 tapped surface, while as the average of the doubly tapped trees we 

 get 414 grammes. 



' Albeit a ta Pping of the upper and lower edge yields more rubber 

 than only working the lower edge, the bigger yield does not, how- 

 ever, cancel the disadvantages of the incisions becoming too broad 

 by a double tapping. They require a considerable time to heal. 



