94 THE ROYAL SOCIETY OF CANADA 



of the foot will cause the collapse of the tuini}), and the interior will 

 be found to be composed of a soft, pulpy dark mass. In such cases 

 the leaves evidently obtain their supplies by the bast ring, which is not 

 diseased. 



Isolation from naturally infected plants was easily carried out in 

 ordinary media. The rotted portion of infected turnip was crowded 

 with an organism practically in pure culture, and high dilutions were 

 necessary in order to obtain discrete colonies. After isolation from 

 the initial set of plates, the organism was again plated and replated. 



After working out the morphology and cultural characteristics, a 

 series of growing turnip plants was inoculated. These plants were 

 grown under glass. The soil used was from rotted turf and sand. 



Experiments with Growimj Plants. 



In the first trial, the crown of a turnip plant was punctured with 

 a sterile needle and then the inoculation was made with material 

 from a young agar culture. 



Two days later the point at which the inoculation had been made 

 showed an exudation of liquid to such an extent as to leave no doubt 

 of the disease producing power of the culture. 



One week later the plant showed signs of having the disease badly; 

 the stem supporting the leaves was almost fallen away from the root, 

 needing only the slightest pull to bring that about. The leaves had 

 withered and the plant had a dying appearance. 



On being cut up the turnip had the t pical appearance of the 

 original disease; from the crown downwards to half the depth of the 

 root was completely rotted, except that the shell of the root remained 

 sound. 



Microscopic examination of the diseased portion showed the organ- 

 ism in large numbers and evidently pure. Plate cultures were made 

 from the diseased part of the root and the organism re-isolated was 

 in all respects identical with the one originally isolated. 



In a second series of inoculations the root itself was inoculated 

 with organisms from a young agar culture by means of a needle 

 puncture. 



After the same interval had elapsed as noted above, an examination 

 was made. The appearance of the top part of the plant differed very 

 much from the appearance noted in trial I. The leaves appeared 

 quite normal and, to the eye, the root also seemed to be quite sound. 

 On the root being cut open, the whole of the centre of the turnip was 

 rotted, the disease having in every respect the typical characteristics. 



