452 Journal of Agricultural Research voi.xii. No. 7 



colonies. It was possible, in some cases, to make transfers directly from 

 these colonies to tubes of agar and secure pure cultures. In others, 

 dilution poured plates were first made, and the organism was transferred 

 from certain of the colonies which developed to tubes of agar. Diseased 

 material was collected several times subsequently, and numerous speci- 

 mens were received by mail, so that opportunity was afforded during the 

 season to isolate the organism from several sources. 



Some preliminary inoculations were made on June 13 in which the 

 inoculum consisted of macerated, diseased leaves upon which a quantity 

 of water was poured. About 100 young tobacco plants growing in a 

 flat in the greenhouse were then sprinkled with this water. Four days 

 later infections were evident by the appearance of numerous yellow spots 

 with pin-point-like centers. 



On the evening of June 28 two potted tobacco plants, about i8 inches 

 in height, were inoculated with pure cultures of Bad. tabacum. A 

 watery suspension from agar cultures was sprinkled upon these plants, 

 after which they remained covered with a bell jar for 36 hours. On the 

 morning of July 2 numerous chlorotic areas had formed, which by July 5 

 had changed to large dry spots, typical of wildfire. No difficulty was 

 experienced in reisolating the organism from these lesions. 



On July 10, 16 plants which had been transplanted in the field on 

 June 14 were inoculated by sprinkling them with suspensions made from 

 bouillon cultures. These plants were not seen again until July 15, when 

 large brown areas had formed abundantly, whereas adjacent uninocu- 

 lated plants remained healthy. 



Another series of inoculations, involving 18 plants growing in pots 

 placed outside of the greenhouse, was made on July 25. In this case 

 the leaves were immersed in a bacterial suspension. Seventy-two hours 

 later the first evidence of infection was observ^ed. Here again the 

 organism was recovered from mature lesions. 



Another set of inoculations, involving 12 potted tobacco plants, was 

 made with what proved to be Boat, tabacum isolated from spots on 

 cowpeas (Vigna sinensis) which had been planted between the hills in 

 a badly diseased tobacco field. The spots on cowpeas, from which these 

 isolations were made, were very similar in appearance to 3- or 4-day-old 

 lesions on tobacco. Eight tobacco plants were inoculated on July 27 

 and four on August 2. Inoculation was effected by sprinkling the plants 

 with a bacterial suspension. By August i in the first case and August 9 

 in the second there was no doubt that the diseased areas, which had 

 formed upon all of the inoculated plants, were typical of wildfire. The 

 organism was reisolated from these spots and, together with transfers 

 from the original cultures from cowpeas, was used in inoculating cowpeas. 

 Here again the same method as before was used in making inoculations. 

 Only a few spots developed upon the several plants employed in two sets 

 of inoculations. These spots were similar to those on cowpeas growing 



