206 RUBBER AND 



to a distance of 1 2 by 1 2 or 15 by 1 5 feet at six or seven 

 years of age. The trees are deep rooting ; consequently 

 manuring and cultivation have less effect upon growth 

 and yields than in the case of Hevea. A fair yield is 

 obtained from the sixth year onward. The average 

 growth in plantations is said to be of the same order as 

 that of Hevea, the increase in girth being from three to 

 four inches per annum. 



As in the case of Castilloa, the trees can only be 

 tapped two or three times in a year, and great care has 

 to be exercised in order to avoid damage to the bark. 

 The method of tapping recommended by Christy is 

 by cutting shallow conducting grooves on a half-spiral 

 system. The slanting grooves are then to be pricked 

 with a thin-bladed spur pricker. Eight inches is 

 regarded as the best distance between the lateral 

 channels. 



The trees are first tapped during the sixth year. 

 They are then tapped twice a year until they are eight 

 years old, and afterwards three times a year. The later 

 cuts are made about two inches above the old, and a 

 fresh vertical channel is made at each tapping. On old 

 trees the tapping may be carried to a height of 30 feet. 



In a particular series of experiments, about five 

 ounces of dry rubber per tree was obtained by tapping 

 to a height of 30 feet on the double half-spiral system. 

 The average girth of the trees concerned was 28 inches. 

 Christy gives the following estimates of the average 

 annual yield per tree under plantation conditions. 



