200 



THE AFRICAN RUBBER VINES 



cipal stem measured lO'S metres in length and ranged in 

 circimiference from 25 to 18 cm. ; the branches which 

 were treated were 27*8 metres in length and the root 

 4*2 metres. The same method was adopted as in the 

 preceding experiments, and the yields of rubber obtained 

 were as follows : 



In this experiment also the yield of rubber from the 

 beaten bark was much greater than the amount obtained 

 from the latex. 



M. Seret concluded from the results of these experi- 

 ments that in the case of L.\owariensis only a smaU 

 proportion of the rubber present in the plant can be 

 obtained by cutting the stems into lengths and allowing 

 the latex to drain out, as the latex is usually thick and 

 does not flow freely. Three-fourths of the total rubber 

 usually remains behind in the bark, from which, however, 

 it can be extracted by beatmg. It may be noted that the 

 L. owariensis vines used in these experiments all put out 

 new shoots from the portion of the stem which was left 

 in the ground. 



In illustration of the yield of rubber obtainable by 

 tapping L. owariensis vmes, the results of an experiment 

 made by the author in the Bahr-el-Ghazal Province of 

 the Anglo-Egyptian Sudan may be quoted. The trial 

 was conducted diu-ing the dry season with a large vme of 

 L. owariensis, var. tomentella, Stapf, which had not been 

 tapped during the previous year. The incisions were 

 made with a V knife, 8 in. apart, and did not extend round 

 more than one-third of the circumference ; no stem less 

 than 6 in. in circumference was tapped. Ninety-six 

 incisions were made on the vine, and the yield of latex 

 was 280 CO., or just under 3 cc. per incision, the maximum 

 yield from an incision being 5 cc. The total yield of 



