684 RUBBER 



fungi aids greatly in the attempt to account for many of 

 the points elucidated during the investigation. 



Preventive Measures. 



The fact that spottings and discolorations can be 

 reproduced artificially by adding spores to the latex 

 indicates that inoculation naturally takes place during 

 the period elapsing between the tapping of the tree and 

 the coagulation .of the latex. Later experiments show 

 the difficulty of external inoculation after preparation. 



Thus the direct method of prevention appears to lie in 

 the sterilization of the latex. Formalin in the proportion 

 of i part in 800 parts of latex is very useful in preventing 

 the appearance of the spots. Experiments carried out 

 on estates, however, show that when formalin is used to 

 sterilize latex there is nearly always a very small pro- 

 portion of rubber which still develops spots. Probably 

 the formalin does not kill the spores, but merely inhibits 

 their development, so that the rubber is almost dry before 

 enough mycelium is produced to show visible spots. 

 With thin pale crepe rubber, in which the spottings prove 

 most troublesome, there ought to be no difficulty in 

 drying the rubber so quickly that, with the addition of 

 the small amount of formalin indicated to the latex, spots 

 are prevented from developing. 



Sodium bisulphite also is useful, when added to latex 

 in the right proportions, in preventing spottings in thin 

 pale crepe rubber. Care must be exercised, for if larger 

 quantities than necessary are added, especially when 

 acetic acid is used in coagulating the latex, the chances 

 of the fungi developing are considerably improved, owing 

 to the slower drying of the rubber. The spotting of 

 thin crepe rubber on one estate was completely eradicated 

 by adding to 50 gallons of latex 5 oz. of sodium bisulphite 

 in 5 pints of water. The rubber at the same time was 

 worked as thin as possible. 



External Inoculation in relation to Spotting. 



The question as to whether spottings can arise through 

 spores germinating on the surface of the rubber after 



