204 RUBBER AND 



leads to rapid coagulation without reagents, and to the 

 production of a rubber which is excellent in appear- 

 ance. Rubber of this kind is not, however, desired by 

 manufacturers, and the mixed character of the sample 

 is easily detected by experts. Manihot rubber requires 

 slightly different treatment in manufacture from the 

 produce of Hevea, and the mixed product is therefore 

 unsatisfactory. 



The yields from young trees appear to be similar to 

 those from Hevea ; in subsequent years, however, the 

 increase in yield is not so great. In Nyassaland in 1910 

 four hundred four-year-old trees are said to have yielded 

 an ounce of dry rubber apiece from only two tappings, 

 and the cost of collection was only ^d. per Ib. In 

 this case the tapping consisted of making vertical rows 

 of pricks. At Peradeniya, Ceylon, experiments in paring 

 were carried out on trees only three and a half years old 

 at the beginning of the experiment, planted at the rate 

 of 200 to the acre. About four ounces of rubber per 

 tree were obtained in a year by 70 tappings. A yield 

 of nearly 50 Ibs. per acre was thus obtained at an earlier 

 age than that at which a similar amount of rubber could 

 safely be extracted from Hevea trees. The cost of pro- 

 duction, however, was hign. 



Among other species of Manihot, M. dichotoma was 

 introduced into Ceylon in 1908. So far, none of the 

 new species have succeeded so well as Manihot 

 Glaziovii. The growth of the trees and the thickness 

 of bark were poorer at equal ages, and in the few 



