THE CEARA RUBBER TREE 147 



with a knife or a pricker, no bark being removed. In 

 wetter districts, however, the trees can be tapped by 

 the herringbone or some similar excision system, the latex 

 being collected in bulk and subsequently coagulated. 

 Thus, for example, in German East Africa the incision 

 method can alone be used in the northern districts, wliere- 

 as herringbone tapping can be adopted in the south. In 

 some districts of Nyasaland where dry winds occm- 

 during the tappmg season, an excision system of tapping 

 has been found unsatisfactorj'^, as the bark does not heal 

 under such conditions, but dies back at the edges of the 

 cut and leaves the wood. 



Whichever of these two methods is to be employed, 

 it is customary, except in the case of very young 

 trees tapped by the incision system, to strip off the 

 outer layer of bark from the portion of the stem which 

 is to be tapped. This outer bark, although thin, is 

 exceedmgly hard and very quickly takes the edge from 

 the tappmg tool ; moreover, it becomes detached from 

 the inner bark in places, and some latex is liable to be 

 lost by running down between the two layers. The outer 

 bark can be very easily stripped from the stem after 

 makmg two vertical cuts at the sides of the portion of 

 bark to be tapped. In this connection, however, it must 

 be stated that some authorities consider the removal 

 of the outer bark to be umiecessary and lilcely to be 

 detrimental to the tree. 



The incision system of tappmg most commonly used 

 for Ceara trees is known as the " Lewa " method, from 

 the name of the estate in German East Africa where it 

 was first adopted, and is carried out as follows : 



The outer bark is removed from one-fourth or more of 

 the cu-cumference of the stem to a height of 6 ft., and 

 the stripped surface is then moistened with the acid juice 

 of a citrus fruit — limes, oranges, or lemons — in order to 

 facilitate the coagulation of the latex. Dilute acetic acid 

 (2 per cent.) or a mixtm^e of acetic and carbolic acids, or 

 a weak solution of calcium chloride, is also employed for 

 the purpose, as well as an infusion of the pulp of baobab 

 fruits and the juice of sisal leaves. A large number 

 of small horizontal incisions are then made by stabbing 

 the bark with the end of a thin-bladed knife having a 

 straight cutting edge, care bemg taken that the cuts do 



11 



