319 



It had been found that these spots do not occur on smoked, 

 rubber ; and, since smoked sheet and crepe commanded a higher 

 market price, the spots were regarded as being of little or no 

 economic importance. Recently, however, there has been a decreas- 

 ing demand for smoked plantation rubber; and this, coupled with the 

 increase in the quantity of spotted rubber in this country, renders the 

 matter of some economic importance. 



Investigations were, therefore, commenced for the purpose of 

 of ascertaining the cause of the spots. It was inconceivable that 

 they were due to chemical changes in the substance of the rubber 

 and it appeared probable that they might be due directly or indirectly 

 to the growth of a micro-organism. The fact that a pink spot had 

 been attributed to Bacillus prodigiosus, which occurs in tap and pool 

 water in this country, rendered it likely by analogy that the blue or 

 bluish brown spot was due to another bacillus and, perhaps, Bacillus 

 violacens. 



Attempts were made to isolate chromogenic bacilli by transfer- 

 ing sections of the the spots to bouillon and by grinding the spotted 

 rubber with sand in a mortar and making " poured plates " in bouil- 

 lon-agar. All attempts to isolate chromogenic bacilli, however, failed. 



Recently a method of observing directly the organisms present in 

 the spots has become available. It consists in cutting thin sections 

 of spotted rubber and dissolving the caoutchouc by means of xylol or 

 benzene. If the section be placed on a slide the caoutchouc may be 

 thus dissolved and the organism may then be mounted in Canada 

 balsam and examined under a mucroscope. By this method the foil 

 lowing observations have been made : — 



The pink spot contains the mycelium of a fungus whose cel- 

 walls are coloured pink. Thehyphs vary in size from 3 microns to 5 

 microns and their walls possess an irregular outline. They are much 

 branched and frequently septate and at the ends of the branches are 

 borne singly what appear to be spores. These spores are unicellular 

 and contain refractive globular masses which afterwards become 

 brown. 



The pink discolourations on rubber may take the form of small 

 isolated spots or may attain a size of one inch in diameter. In some 

 •cases the discolouration is, however, more diffuse. 



The blue spots may be present on the same sheets as the 

 pink spots or they may occur on separate sheets. They contain 

 a mycelium composed of hyphs of a dark colour which give rise 

 to globose structures occurring in a single chain ; these may or may 

 not be spores. Attempts are being made to isolate this organism 

 and to identify it. 



The black spots sometimes exhibit a definite radial growth from 

 a central point. They contain a mycelium which is composed of 

 dark-brown hyphae; so far no structures have here been observed 

 which can be regarded as spores. 



