A. R. Sanderson and H. Sutcliffe 57 



The disease was originally confused with another well-known and 

 wide-spread disease of the tapped surface, viz. Black Thread or Black 

 Line Canker the causal fungus of which is a species of Phytophthora, 

 Mouldy Rot being considered a virulent form of this. 



Further investigation however showed that Phytophthora sp. was 

 never present in tissues affected by Mouldy Rot, species of Cepha- 

 losporium, Fusarum, Sphaeronema are constantly present and occa- 

 sionally several other saprophytic fungi and bacteria are to be found in 

 the tissues. 



The writers commenced their investigations of this disease in De- 

 cember 1918 and in March 1919 issued a preliminary note on the subject 

 (First Malayan Report, 1919, Rubber Growers' Association). 



The fact that a species of Sphaeronema had already been suggested 

 as the causal fungus, determined us in working first on this fungus, 

 especially as the other fungi present in the diseased tissue are common 

 and well known saprophytes. Attempts to isolate the Sphaeronema by 

 means of pycnidiospores in the usual ways all failed, chiefly owing to 

 the fact that they are exuded in a sticky mass, almost impossible to 

 separate into individuals, and foreign matter, spores etc. is held ten- 

 aciously. These spore masses refused to separate in liquefied nutrient 

 agar, and frequently were killed at the temperature necessary to keep 

 the agar in a liquid condition. 



We then tried to isolate the fungus by picking out resting spores 



under the microscope, but the results were not encouraging. Finally 



we decided to try the mycelium fairly deep in the tissues and this gave 



the best results in the shortest time. Experiments with inoculations of 



Cephalosporium and Fusarium on stripped surfaces gave always negative 



results. 



ISOLATION OF THE FUNGUS. 



Portions of old dry bark which had been affected with mouldy rot 

 were used as the starting point in investigating this disease. A portion 

 of bark 6 inches square was removed from a healthy tree and the under- 

 lying fresh tissue exposed. Inoculation was effected by scraping the 

 old infected bark, mixing the scrapings with distilled water and applying 

 with a soft brush. 



At the same time the inner surface of the bark removed was inocu- 

 lated similarly, cut into four portions 3 inches x 3 inches and kept 

 under observation in covered glass dishes. 



In 48 hours all the inoculated surfaces had become discoloured, 

 turning a dirty brown, and by the end of the fifth day the cells of the 



