THE AFRICAN RUBBER VINES 205 



Baudon records that in the French Congo 20 kilograms 

 of the rhizomes of L. ThoUonii furnished 1120 kilogram 

 of marketable rubber, a yield of 5- (5 per cent., and 

 Guynet states that in the Belgian Congo the average 

 yield of rubber from the rhizomes is 5 per cent. 



Landolphia chylorrhiza. — Geraldes records the following 

 results of experiments conducted in Angola to determine 

 the yield of rubber obtainable from the rhizomes of this 

 plant by beating the separated bark : 



Diameter of the rhizomes . . . 5 to 9 mm. 



Ratio of weight of cUy bark to weight of 



dry rhizomes .... 64-77 per cent. 



Percentage of clean rubber obtained from 



dry rhizomes .... 75 ,, ,, 



Percentage of clean rubber obtained from 



dry bark ..... 116 ,, ,, 



The composition of the clean dry rubber, excluding the 

 moist lu-e and vegetable matter present, was as follows : 



Per cent. 

 Caoutchouc . . . . 94- 31 to 95- 86 



Resin and colouring matter . 350,, 4*14 



In Angola the yield of rubber generally obtained by 

 the natives from L. chylorrhiza is from 10 to 12 per cent, 

 of the weight of the rhizomes. 



Cost of Collection. — There are little data available re- 

 garding the cost of collecting rubber from Landolphia 

 vines by the native process, but M. Seret has given the 

 following particulars on this point in the case of two of 

 his experiments at Eala, which have already been re- 

 ferred to. 



One hundred and fifty grams of rubber were obtained 

 from a Landolphia owariensis vine by coagulating the latex 

 obtamed by cutting the stem into pieces, and 720 grams 

 by beating the bark. All the operations involved in the 

 preparation of the 150 grams of rubber, including the 

 time spent in going to the place of collection, were per- 

 formed by tpsvo men in 4| hom-s, or 9 hoiu-s' labour. The 



