i88 



BACTERIA IN RELATION TO PLANT DISEASES. 



May 21. Tomato plants (6) were used for this experiment. The inoculations were made from potato-cultures Nos. 



4 and 5, May 12, descended from colony on plate poured after exposure to liquid air (from Virginia, 1903). 



They were made on shoots of plants which had been cut back and repotted. 

 Result. No wilt. Pricked area became blackened and somewhat swollen. 

 May 24. Tomato plants (6 vines about 9 to 12 inches high), were inoculated from beef-bouillon Nos. 19, 21, 22, of 



June 9 (1903?), and potato No. 26, June 9 (1903?). 



Result. No wilt (June 17). The stems became swollen and put out adventitious roots. 

 j u ly j Eleven tomato plants were inoculated with potato-cultures Nos. i to 6 of July 2, from plate colonies, from 



potato stem from Woodridge, D. C. (see pi. 30). Made 10 to 12 pricks in each stem with a No. 12 needle. 

 Result. Very successful. All but 2 showed the disease July 8, and one of these two was inoculated with a gas-forming 



organism. (Consult fig. 97 for appearance of an inoculated plant at end of third day.) 

 A ugusl 8. Potato plants (8 pots) of the Green Mountain variety, received about 36 inoculations on leaves and young 



shoots. The plants were stocky and only a few inches 



high. Needle-punctures varied in number from i to 



20. The cultures used were slant agar subcultures, 



Nos. 3 and 4, August 6, from potato stem from 



Woodridge, D. C. 



Result. Very successful ; first signs on third day. (See pi. 3 1 .) 

 August 25. Potato plants (3 pots) were inoculated with 



potato-cultures Nos. i and 2, August 19, and litmus- 



potato-agar No. 2, August 15 (from potato-stem 



from Woodridge, D. C.). Part of the plants were 



inoculated with descendants of culture after passing 



through the thermostat (37-5 C.), and part with 



descendants of culture held at room temperature. 



Made 10 to 12 needle-pricks in upper internodes. 

 Result. The plants were too old. None contracted the dis- 

 ease. All of them died down from thrips or other 



causes. 

 September 6. Fourteen tomato plants were inoculated from 



subcultures in tubes of litmus-lactose-agar, Nos. 3, 



5, 7, 15, and 17, September i (Woodridge, D. C., 



organism). Part of the plants were inoculated 



from culture grown at 37.5 C., part from descend- 

 ants from culture grown at 37.5 C. (pi. 29), part 



inoculated from descendants from culture grown in 



ice-box, and part inoculated with organism grown 



at room temperature since its isolation (pi. 28). 



The inoculations were made on young shoots coming 



up from plants cut back. 

 Result. No rapid wilt. For the most part only swollen stems 



and slow progress of the disease. 



October 6. Six tomato plants of as many varieties were inocu- 

 lated from slant agar Nos. i and 2, October 3, from 



No. 2, August 29 (Woodridge, D. C., organism from 



potato). The stems were pricked 3 to 4 inches 



from the top. 

 Result. No wilt. The stems became somewhat swollen and 



pushed out adventitious roots; they also became 



slightly black around the pricks. 

 October II. This experiment was made with 5 tomato plants, 



inoculating them near the tips in tender tissues in 



most cases, and directly from tomatoes which were 



inoculated October 6, and which had not wilted 



but showed pricked area swollen and considerably 



discolored (Woodridge, D. C., organism from potato 



through tomatoes 102 and 103). The plants inocu- 

 lated were 10 to 18 inches high. 

 Result. None of the plants ever wilted. Slight swelling and 



discoloration in the pricked area less than in the 



preceding. 

 October 24. Tomato (2 plants) of the varieties Red Pear and 



Honor Bright, were inoculated direct from tomato 



No. 109, inoculated October n, which had swollen 



and discolored at pricked part more than the others 



(Woodridge, D. C., potato through tomato twice). 

 Result. Negative. 

 October 2(5. Six tomato plants of as many varieties (1.5 to 2 feet high, not yet branched) were inoculated on stems 3 to 



6 inches from the top with potato cultures Nos. 2 to 5, October 22, from agar-stabs Nos. 7 to 1 1, August 26 



(Woodridge, D. C., potato). 

 Result. No wilt. The stems became considerably swollen and adventitious roots were formed, but lurtner tfian 



the bacteria had no effect upon the plants. 



*FlO. 06. Tomato-plant inoculated July 7, 1903, with Bacterium solanacearum (South Carolina strain). Photo- 

 graphed July 14. Plant inoculated by needle-pricks from a pure culture 5 days old. 



Fig. 96.* 



