178 



THE AFRICAN RUBBER TREE 



The trees of Group A were used for check experiments, 

 and the trees of the other groups were subdivided into 

 tlii'ee lots, which were tapped at intervals of two, four, 

 and six months respectively. The vertical system of 

 tapping was adopted as most suitable for the experiments, 

 the Christy knife and pricker being employed. At each 

 tappmg three vertical cuts were made at equal distances 

 apart to a height of 100 inches from the base of the tree, 

 and the subsequent incisions were placed 1| to 2 in. 

 at the side of the previous cuts. 



The following table shows the results obtained : 



Average Yield (in Grams) of Dry Rubber per Tree 

 /. Two-month intervals 



//. Four-month Intervals 



///. Six-month Intervals 



It wiU be seen from these results that the largest trees 

 gave the most rubber and that the yield was diminished 

 very considerably by repeated tappings. It is interesting, 

 however, that the yield after a two months' interval was 

 practically as good as that after four or six months. With 

 reference to the best time for tai:)ping, it was found that 



