DESCRIPTION OF THE LEAF-SPOT ORGANISM. 9 



when 24 hours old (February 12, 1910) for inofulutiiig cauliflower 

 ])lants. This time infections resulted. The infections were very slight, 

 however, and the spots too few in number to cause any noticeable 

 injury to the plants, but the bacteria plated from these spots pro- 

 duced typical colonies on agar and characteristic growth in artificial 

 media. CauHflower plants inoculated with this new strain became 

 very generally infected, which fact seems to indicate that the organ- 

 ism had increased in virulence by passage through the host. 



On December 6, 1910, cabbage, cauliflower, turnip, rutabaga, rad- 

 ish, and mustard were inoculated in cages by spraying with sterile 

 water to wliich had been added agar-streak cultures 3 days old. All 

 of these plants were young. There were two to four of each sort. 

 The material for inoculation was obtained from a cauliflower inocu- 

 lated November 22, 1910. Infections were obtained on cabbage 

 and cauKflower (six days), but not on the other plants. Sections of 

 the spots made on the tenth day showed them to be full of bacteria. 



On March 4, 1911, three cauliflower plants were again inoculated 

 by spraying with sterile water to which had been added 2-day-old 

 agar-slant cultures. These plants were about 8 inches high and very 

 healthy. They were kept in an infection cage for two days. At the 

 end of 10 days there were very small dark specks on each of the plants. 

 These specks were in the center of a small semitransparent elevation. 

 A microscopic examination showed bacteria present in these spots. 

 The flower stalks of plant 104 also showed elongated water-soaked 

 spots, darker in the center. These also contained bacteria and plates 

 made from them yielded the organism in pure culture. The flower- 

 ing part of plant 104 bore no spots, although it had been drenched 

 with the spray. The check plant remained healthy. 



Several attempts to inoculate the heads of the cauliflower gave no 

 satisfactory results. Gromng heads were copiously inoculated and 

 kept under moist conditions, but no infections occurred. Infection 

 spots similar to those on leafstalks and midribs occurred on some 

 of the larger stalks of the flower head, while the flowering parts 

 remained free from infection. Mature heads from the market were 

 also inoculated, but as decay of the tender surface was general in 

 the checks as well as in the inoculated heads, the results are not 

 conclusive. 



DESCRIPTION OF THE CAULIFLOWER LEAF-SPOT ORGANISM. 



MORPHOLOGY. 



The organism is a short rod, forming long chains in some media. 

 Ends rounded. Size from leaf 1.5 to 2.4 [i by 0.8 to 0.9 //. Size in 

 24-hour beef-agar culture, temperature 20° to 25° C, 1.5 to 3 [i by 

 0.9 n. No spores are produced. The organism is actively motile by 



22S 



