THE AFRICAN RUBBER VINES 195 



rubber vines consist of acid juices of plants, or acid 

 decoctions made by boiling certain leaves or fruits with 

 water. In the Belgian Congo the juice of two species 

 of Costus, G. afer and G. lucanusianus, is employed to 

 coagulate Landolphia latex ; whilst in West Africa de- 

 coctions of the fruits of the native sorrel {Hibiscus Sah- 

 dariffa), of the pulp of tamarind fruits {Tamarindus 

 indica) or of the leaves of Bauhinia reticulata are used 

 for the same purpose. The active coagulant in all these 

 cases appears to be the vegetable acid present in the 

 juice or decoction. Lemon juice or a solution of citric, 

 tartaric, or acetic acid may also be employed for effecting 

 the coagulation. In some cases a solution of salt is used 

 by the natives for the purpose. 



This method of adding a coagulant to the latex is 

 adopted for the preparation of the rubber of L. Dawei and 

 L. Klainei, and also of L. oivariensis and L. Heudelotii 

 when the latex is collected in bulk. 



The rubber obtained by these processes of coagulation 

 is treated in different ways in different parts of Africa. 

 In Uganda the freshly coagulated rubber is roUed out 

 into a biscuit or sheet, which is then allowed to dry entire. 

 In the Belgian Congo the rubber is obtamed in thin sheets 

 by placing a portion of the freshly coagulated product 

 between leaves and stampmg it with the feet. These 

 sheets are afterwards cut up into small cubes or into 

 very thin strips, which are wound into balls of varying 

 sizes and resemble those obtained by collecting the strips 

 of rubber from the incisions. In West Africa the sheets 

 of rubber are cut into thicker strips, which are afterwards 

 rolled up and form what are known as " twists " m the 

 market. 



(3) By the mechanical process of beating the bark. — This 

 method is exclusively used in the case of the small, bushy 

 forms of Landolphia, Clitandi'a, and Carpodinus, which 

 only furnish rubber from their underground stems 

 (rhizomes), the product being usually knoAvn as " root 

 rubber." It is also employed in some districts of Africa 

 for obtaining rubber from the bark of the stems and 

 roots of the vines. 



The process used in the case of the rhizomes is generally 

 as follows : 



The rhizomes are dug up and exposed to the sun for 



14 



