686 RUBBER 



Final Considerations. 



Thus there is no room for doubt as to the causes 

 of spottings and discolorations in plantation rubber. 

 Common saprophytic fungi are the -chief causes; how- 

 ever, the number of these fungi causing spots is com- 

 paratively small. The factor limiting the number of such 

 fungi capable of growing in rubber is probably the 

 absence of a specific enzyme which is capable of rendering 

 the food materials in latex more readily available. The 

 proteins in rubber probably form the food material upon 

 which the fungi live; therefore, in view of the fact that 

 rubber appears to be an unfavourable medium for the 

 development of these organisms, the possession of proteo- 

 clastic enzymes would be of the greatest service in 

 enabling them to open up food reserves not otherwise 

 available. The fact that most of the species of fungi 

 causing spots belong to the genera Pemcillium or Asper- 

 gillus is strong evidence for this view. The action of 

 sodium bisulphite as a preventive is probably due to its 

 powers of inhibiting enzyme action. Thus there is much 

 support for the view that the production of enzymes of 

 a specific character by the spot-causing fungi play an 

 important role in this problem. 



The latest work of Fol and Sohngen is interesting in 

 this respect. These investigators, working in Europe, 

 cultivated two species of Actinomyces capable of growing 

 in rubber and investigated their action on the caoutchouc. 

 Viscosity tests with infected rubber showed a decrease 

 when compared with clean, but not sufficient to make 

 any statement as to the inferiority of infected rubber. 

 Attempts to isolate an enzyme failed, though it was 

 noticed in one case that one of the organisms was capable 

 of causing a solution of the caoutchouc. 



This work, however, has little bearing upon the problem 

 as it appears in the tropics. The species of bacteria 

 with which Fol and Sohngen conducted their experiments 

 were cultivated from ditch and canal water, and only after 

 several days' incubation did they appear on the caout- 

 chouc. To cause spottings under normal conditions in 

 the rubber factories in the tropics the organisms must 



