92 RUBBER AND RUBBER PLANTING 



removed is probably secreted at no great distance from 

 the wounded area. 



Under the comparatively uniform conditions of the 

 climate of Western Ceylon, the yield of latex at certain 

 seasons may be nearly twice as great as at other 

 seasons. Seasonal differences of yield are partly deter- 

 mined by climatic conditions, but probably also in part 

 by the quantity of food materials available in the tree. 



The yield from different trees of the same age and 

 girth varies greatly. A difference of 1000 per cent, is 

 not at all uncommon. 



The yield is greatest near the foot of the tree, and 

 decreases gradually on passing upwards. In all prob- 

 ability the yield is roughly proportional to the volume 

 of the bark at any given level. 



The percentage of rubber in the latex shows 

 variations similar to those displayed by the total 

 yield. The percentage is highest during the period of 

 highest yield. Severe tapping leads to a marked falling 

 off in the percentage of rubber present. 



It may be concluded that in practice the rate of 

 tapping should be reduced either 



(1) if the bark is being used up at a greater rate 

 than one quarter of the available amount annually, or 



(2) if the concentration of rubber in the latex falls 

 much below thirty per cent, or 



(3) if the yield of latex fails to show an increase 

 over the amount obtained at the corresponding period 

 of the preceding season. 



