68O RUBBER 



The method of procedure may be summarized as 

 follows : 



(1) To determine the presence of fungi in the spotted 

 rubber by means of a microscopical examination. 



(2) To isolate the fungi from the rubber under micro- 

 scopical control and to obtain pure cultures. 



(3) To inoculate, artificially, known amounts of latex 

 with spores developed in pure culture in order to repro- 

 duce the spots artificially in the laboratory. 



(4) To isolate the fungi from the artificially produced 

 spots. 



The following investigation shows that the latex is 

 naturally inoculated in the field. Therefore, care must 

 be taken in deducing conclusions from artificial inocula- 

 tions, for it is almost impossible conveniently to prepare 

 a sterile latex. In this connection it is obvious that 

 supplementary observations will be most valuable, 

 especially those demonstrating characteristic features of 

 the fungi in situ in the rubber. Too much reliance, how- 

 ever, cannot be placed upon the characters of the fungi 

 in pure culture, for they vary to a large extent according 

 to cultural conditions. 



The defects of plantation rubber due to the action of 

 fungi may be distinguished as of two kinds : - 



(a) Spottings, where the discoloured area is usually 

 small. 



(b) Flushes, where there is a broad, diffused patch of 

 coloured rubber. 



Spottings are best observed in crepe rubber, whilst 

 flushes are more common in light-coloured sheet rubber. 



Four specimens were selected for investigation; in 

 each case the life-history of the causal fungus was 

 followed in pure culture. 



(i) Yellow Flush in Sheet Rubber. 



This flush appeared in sheet rubber which had been 

 coagulated with sodium bisulphite. A fungus, Peni- 

 cillium maculans (nov. sp.), was isolated from the 

 discoloured rubber, and inoculation experiments carried 

 out with spores obtained from pure cultures proved this 



