B. T. P. Barker and O. Grove 95 



different flowers, leaves, and fruit spurs, and in the great majority of 

 cases the characteristic colonies of the organism have developed. It 

 was rarely that other organisms appeared on the plate cultures ; and 

 in such cases the foreign form was nearly always Monilia fructigena, 

 the " brown rot " fungus. It is not uncommon to find flowers attacked 

 at the same time both by this fungus and the bacillus. 



The isolation of the bacterium was especially easily effected from 

 flowers showing newly developed small, black spots on the receptacle. 

 By touching these spots with the point of a sterilised needle, and making 

 streaks with the latter over the surface of a sterile plate of the nutrient 

 gelatine, pure cultures were very often immediately obtained. From 

 older, dried up material, the growth is not so quickly developed. 



Pure stock cultures of the organism were kept on various nutrient 

 substrata and in liquid nutrients. In most cases the organism retained 

 its vitality for several weeks at least and did not lose its parasitic powers, 

 infections on fresh flow^ers and leaves giving positive results. In due 

 course, however, on most of the media tested it eventually died off ; 

 but cultures on potato blocks have retained their vitality and parasitic 

 abilities for over eight months. 



The bacillus is a rod 2-4y"'X ■5-"8yW' in dimension. Although 

 satisfactory stained preparations of the flagellae have only been obtained 

 in one or two instances after repeated trials, there seems no doubt that 

 the cells are lophotrichic. The flagellae, two or more in number, are at 

 least four to five times as long as the cells themselves. The organism 

 stains well with the usual stains, and especially so with gentian violet. 

 It is also stained by Gram's method. 



It grows well in malt extract solution (sp. gr. 1*040), glucose-peptone 

 water (5 % glucose, 1 % peptone), and in neutral and slightly acid 

 (+0'15 % normal) bouillon. 



The bacillus is highly motile in young cultures, showing quick pro- 

 gressive movements. The motility depends greatly upon aeration. 

 This is very well shown in ordinary coverslip preparations made from 

 colonies or young plate cultures, the bacillus coming to rest in about 

 two minutes at the centre of the slide, the movement being progressively 

 more active in the cells passing outwards towards the edges of the 

 slip. At the latter region or in the neighbourhood of air bubbles 

 movements continue for about 20 minutes. It then ceases and agglu- 

 tination takes place. After all have come to rest, if the slip is lifted for 

 a few moments and then replaced, nearly all the cells are found in 

 an active state of movement. 



