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SCIENCE PROGRESS 



removed from certain Hevea trunks. After the lapse of two 

 days, incisions were made near the wound and also on parts 

 of the trunk at the same level farthest away from, i.e. opposite, 

 the injury. Fully double the quantity of latex was obtained 

 from the cuts near the wound, as compared with that yielded 

 by those incisions made opposite. 



Attention was then directed to the time-interval necessary 

 in order to render this response recognisable. After twelve 

 hours no difference was observed between the volume of latex 

 yielded by the two classes of incisions. Sometimes after twenty- 

 four hours and generally after two days, the effect of wounding 

 on the yield, however, was marked. Apparently the drier the 

 soil the longer the time required for the response to appear. 

 The experience of planters and others since has shown that 

 two days is, as a rule, the best interval between successive 

 tappings, but some estates tap every day with good returns. 



The following table gives in concise form the results of a 

 somewhat elaborate experiment conducted at Peradeniya from 

 March to June 1899. 1 Four trees were employed, and a hori- 

 zontal row 7 of ten similar incisions made per tree per tapping. 

 Each fresh row of incisions was made near those of the pre- 

 ceding tapping, in order that the wound-response might take 

 effect. The interval between tappings was usually five days. 

 A less allowance would most likely have made the experiment 

 still more striking. 



This experiment brought out the effect of wounding on the 

 flow of latex in a still more favourable light ; and considering 

 that at the fourteenth tapping, when the experiment had to be 

 brought to a conclusion, the volume was the largest collected, 

 it would appear that the limit to the full advantage to be gained 

 from wound-response had not yet been reached. 



From a practical point of view this experiment is defective in 



1 Parkin, loc. cit. 135-40. 



