i^HE PRINCIPAL RUBBER-YIELDING PLANTS 37 



Portuguese West Africa, where it is known by various 

 native names, such as "bitinga," "ecanda," and "mari- 

 anga." It is of considerable interest owing to the fact 

 that the latex is contained in the tuberous roots. 



Specimens of the roots and of the rubber obtained 

 from them have been examined at the Imperial Institute. 

 The average yield of rubber from the dry roots was found 

 to be 10-5 per cent., but the roots as received contained 

 a very large amount of moisture and only from 10 to 

 r5 per cent, of rubber. 



The rubber is of very fair quality, as will be seen from 

 the following analysis of a sample prepared by the natives 

 in Portuguese West Africa : 



Per cent. 



i\roisture 



Caoutchouc 



Resin 



Protein 



Insoluble matter 



Ash 



1 



76 

 9 

 



12 



711 



The chief defect of the sample is the large amount of 

 insoluble impurity present. For fiu-ther information 

 regarding this rubber see Imperial Institute Selected. Re- 

 ports on Rubber and Gutta Percha, pp. 409-11. 



Attempts have been made to cultivate this plant, but 

 the results so far obtained have not been very encouraging. 



11. Periploca nigrescens, Afzel. 



12. Dregea rubicunda, K. Schum. 



These two vines are found in the Belgian Congo. They 

 are stated to yield rubber, but they are not of much 

 importance as sources of tlie product. 



IV. APOCYNACEAE 



13. Funtumia elastica, Stapf {Kichxia elastica, Preuss), 

 the African rubber tree or Lagos silk rubber tree. 



This tree, which owes its name of " silk rubber tree " 

 to the fact that its seeds have an attachment of silky 

 hairs, is the most important rubber-yielding plant indigen- 

 ous to Africa. It is widely distributed in northern tropical 

 Africa, extending across the continent from Sierra Leone 

 to the East Africa Protectorate and southwards into 

 the Belgian Congo. 



