14 Bacterial Disease of the Mango 



three leaves of a young mango tree. Each leaf was covered for 24 hours 

 with a large glass tube plugged with cotton wool. Characteristic dark 

 angular spots appeared on the inoculated leaves at the end of four weeks. 

 There were no spots on the controls. 



3. Leaves on a third tree were infected successfully in a similar 

 way to that described in experiment No. 2, with the exception that the 

 bacteria were allowed to diffuse in sterile beef bouillon instead of in 

 distilled water. 



The controls remained clean. 



Inoculation with 'pure cultures. 



4. A young agar streak culture was suspended in sterile distilled 

 water, and the water was allowed to stream over both sides of two 

 leaves of a young mango tree which were covered over for 24 hours as 

 described in experiment 2. A period of cloudy and rainy weather suc- 

 ceeded the date of this inoculation and of those previously described. 



Infections were visible on the 21st day, in the form of small, angular, 

 water-soaked looking areas. After a few days these areas began to 

 change colour and rapidly became black. The discoloured tissues were 

 crowded with bacteria, and a pure culture of the specific organism was 

 at once obtained. 



There was no sign of infection on the controls. 



5. A second experiment was conducted similar to the above, but 

 small punctures were made in the leaf surface with a fine needle. In 

 this case a large proportion of the infections occurred in the neighbour- 

 hood of the needle pricks. 



Controls pricked with a sterile needle showed no sign of infection. 



6. A set of detached mango fruits was washed in 1 : 1000 mercuric 

 chloride, and then in distilled water. They were sprayed with a sus- 

 pension of a pure culture of the organism and then covered over with 

 a bell jar. After about three weeks there was a small discoloured area 

 round some of the stomata ; the blackened areas containing numbers 

 of bacteria. The observation could not be carried further as the fruit 

 was destroyed by Gloeosporium sp. No blackening was seen in the 

 controls. Other attempts to infect detached leaves and fruit all 

 resulted in failure, as, in spite of all precautions, they were always 

 attacked by Gloeosporium sp. before any infections could show them- 

 selves. 



7. Dining the .season 1912—13 no inoculations were attempted, 

 but the work was resumed in the spring of 1913. The weather was again 



