CHAPTER V 



THE TAPPING OF RUBBER PLANTS 



General Principles. — The latex of rubber plants is usually 

 obtained by making incisions in the bark with a sharp 

 instrument, the method of " incision," or by removing 

 portions of the bark, the method of "excision." By 

 either of these methods a number of the laticiferous 

 vessels are opened and from these the latex exudes. Owing 

 to the continuous nature of the vessels, and to their 

 intercommunication in many cases, a single cut serves 

 to drain the latex from a considerable area of bark. If, 

 however, the latex is contained in isolated cells, it is not 

 so easily obtained by tapping, and in the case of the 

 Guayule plant, which exhibits this feature, the rubber 

 is extracted by mechanical methods or by treatment 

 with solvents. 



In order to understand the problems involved in the 

 tapping of rubber trees, it will be advantageous in the 

 first place to consider briefly the structure of the stem 

 and the functions of the different parts. 



The stem of a mature tree may be divided into the 

 following parts : (1) the bark, (2) the wood, and (3) the 

 pith, which, however, is usually obliterated in old trees. 



The bark as thus understood is the portion which can 

 be readily stripped off from the wood, and it includes 

 not only the true bark, i.e. the external corky layers, 

 but also the tissue known as the cortex, which plays a 

 very important part in the life-processes of the plant. 



Between the cortex and the wood there is a single 

 layer of actively dividing cells, known as the cambium, 

 and the cells cut off from the cambium externally form 

 additions to the cortex (the tissue thus produced being 

 known n.s bast), whilst those cut off internally give rise to 

 wood. The tissues produced in this way from the carn- 



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