74 Pink Disease of Plantation Rubber 



Rant (10) states that he did not obtain either fruit form in his 

 cultures, but calls attention to the formation of " paraplectenchy- 

 matische mycelienknauel," which he obtained now and again in his 

 cultures and which had been previously observed by Koorders (7) in 

 cultures of Necator. The Necator-like masses obtained by us probably 

 correspond to these structures observed by Rant and Koorders. Rant 

 confined his attention chiefly to agar cultures, but in our cultures on 

 this medium we did not obtain anything approaching a fruiting form, 

 though our efforts in this direction were not long continued after we 

 found wood blocks so favourable for culture work. 



Some of the wood blocks on which cultures had been grown were 

 sectioned. It was seen that the fungus had spread to the centre of the 

 block and that the mycelium had penetrated the elements of the wood 

 in the same manner as in wood naturally infected. Tyloses were 

 absent. 



Inoculation experiments. 



Rant's inoculation experiments (10) experimentally demonstrated 

 the connection between Corticium salmonicolor and Necator decretus. 

 Our inoculation experiments to be now described were carried out to 

 test the conditions which favour or hinder the development of the 

 fungus on Hevea brasiliensis. Correlated experiments upon other 

 hosts were kept under observation at the same time. 



The first series of inoculation experiments was carried out on rubber 

 trees three-and-a-half years of age. The inoculations were made on 

 the 4th of February, 1914, with pieces of the pink incrustation obtained 

 from a diseased rubber tree. The inoculations were covered with 

 cotton wool pads which were moistened every morning for the first 

 three weeks as the weather was dry during this period. The pads were 

 kept in place by rubber bands. 



Little rain fell between the date of inoculation and March 10th, 

 but between March 10th and March 16th there were daily showers. 

 The fungus appeared during this wet spell, 13 out of 29 inoculations 

 being successful. Of this number 8 out of 13 (60 per cent.) were 

 obtained upon uninjured parts ; 5 out of 16 (30 per cent.) upon wounded 

 surfaces. These results provide further evidence that Corticium salmoni- 

 color acts rather as a vigorous parasite on uninjured parts than as a 

 wound parasite. 



Between March 16th and April 14th the weather was dry and no 

 rain fell for considerable periods. On the latter date only a few trees 



