74 RUBBER AND 



food production, and give up part of their organic 

 contents to the tree before they drop to the ground. 

 In April and May, on the other hand, the formation of 

 fresh leaves, flowers and fruits has successively drained 

 the resources of the tree, so that these must be at a 

 comparatively low ebb. We find, accordingly, that the 

 percentage of caoutchouc is highest in December and 

 January, and lowest in May and June. 



Variation in yield of individual trees. 



It is well known that rubber trees possess a marked 

 individuality as regards the amount of latex which can 

 be drawn from them. Tapping coolies, if left to them- 

 selves, soon discover these differences, and confine their 

 attention to the best-yielding trees. The differences are 

 often great, and to a large extent independent of the 

 girth of the trees. Among a group of 29 trees of 

 uniform age tapped daily, the highest and lowest 

 average yields for the first 30 tappings were respectively 

 1 66 and 8 cubic centimetres. The circumferences of 

 these two trees were 52 and 32 inches respectively, and 

 they were not the largest and smallest trees of the 

 group. The yield per inch of bark removed was in the 

 ratio of 317 to 25, or more than 12 to i. Such 

 differences afford good grounds for anticipating that 

 markedly increased yields could be got from plantations 

 derived from the seed of trees selected for their high 

 yielding capacity. As we shall point out at greater 



