66 



Pink Disease of Plantation Rubber 



however, they hasten the death of the branch by preventing the ascent 

 of water. 



This investigation of diseased branches explains the symptoms often 

 observed when branches of Hevea brasiliensis are affected by Pink 

 Disease. The fungus attacks the wood, vigorously pursuing its course 

 up and down the stem through the vessels. Other vessels are blocked 

 with tyloses for considerable distances while others again are filled with 

 a brown gummy substance. Thus a large proportion of the functional 





°0% 



Fig. 4. Transverse section of vessel with thin-walled tyloses, showing hyphae passing 

 through tylose cells. x 1G0. 



vessels are rendered useless. This results in a serious diminution in 

 the amount of water ascending to the leaves which droop and ulti- 

 mately die. 



Description of the Fructifications of the Fungus. 



(a) Basidial stage. Zimmermann is responsible for placing the 

 fungus in the genus Corticium and one gathers from his description and 

 the accounts of subsequent writers that the pink incrustation is the 

 basidial fructification. We found, however, that this stage was sterile 

 in more than 80 per cent, of the large number of cases examined at 



