Ethel M. Doidge 415 



Cross Inoculations. 



It has been mentioned that the organism belongs to what Smith 

 once termed the " yellow Pseudomonas group." Since five other organisms 

 of this group were under observation at the time, and all are very similar 

 in culture, it was thought advisable to carry out a series of cross inocula- 

 tions. All these organisms infect their hosts by way of stomata or 

 water pores; the inoculations were therefore made without wounding 

 the plants. 



A. 



24. 3. 20. Six tins (1-6), each containing four young tomato plants, were used. 

 These plants were about 1 ft. high and growing vigorously. One set of four plants 

 (1) was inoculated with a culture of Bacterium campestre, one (2) with B. citri, and 

 one each with (3) B. Juglandis, (4) B. Phaseoli, (5) B. malvacearum, and (6) the 

 tomato organism. 



31. 3. 20. Numerous minute, water-soaked spots on tomato seedlings inoculated 

 with organism (6) from tomato scab. Other plants show no infection. 



6. 4. 20. Spots on tomato seedlings in tin (6) have now assumed characteristic 

 form and colour. All plants in tins (1-5) perfectly sound and showing no signs of 

 infection. 



13. 4. 20. No further development. 



B. 



24. 3. 20. Six tins of lemon seedlings were used, each containing six plants 

 10-15 inches high. One group of six seedlings was inoculated with each of the 

 organisms mentioned in experiment A. The tins were numbered (1-6) as follows: 

 (1) inoculated with Bacterium campestre, (2) with B. citri, (3) B. Juglandis, (4) B. 

 Phaseoli, (5) B. malvacearum, (6) Bacterium causing tomato scab. 



30. 3. 20. Incipient cankers noticed on lemon seedlings (2) inoculated with B. citri. 



7. 4. 20. Cankers on seedlings (2) increasing in size and number. No sign of 

 infection on plants inoculated with other organisms. 



15. 4. 20. Numerous typical citrus canker lesions on leaves and stems in tin (2). 

 All other plants have remained sound and show no sign of infection. 



24. 3. 20. Six cotton plants 2 ft. to 2 ft. 6 in. high were employed, one plant 

 being inoculated with each of the six organisms mentioned in connection with 

 experiments A and B. 



29. 3. 20. Numerous minute, water-soaked spots on young leaves of plant (5) 

 inoculated with B. malvacearum. 



7. 4. 20. Spots have increased in size and assumed characteristic angular outline. 



15. 4. 20. Leaf spots on plant (5) have discoloured, and are now dark brown or 

 black. Cotton plants (1-4) and (6) inoculated with other organisms show no sign of 

 infection. . 



