192 Studies in Bacteriosis 



have often yielded pure cultures without difficulty. On two occasions, 

 from a fruit and a stem respectively a distinctly different organism was 

 found in great preponderance and in fact in almost pure condition. 

 This organism caused no disease when inoculated into plants; it is 

 briefly described below since it agrees in all its characters with Aplano- 

 bacter michiganense, which has been described by Smith (8) as the cause 

 of a disease in tomatoes. 



DESCRIPTION OF THE CAUSAL ORGANISM. 

 A. Morphological Characters. 



The organism is a small yellow oval rod measuring from 1-2/x to 

 2-0/x in length and 0-8^ to 1-0/x in width; pairs are not common but are 

 found up to 3-4 /x in length. These measurements were made on a pre- 

 paration from a broth culture incubated 24 hours at 22'^ C. fixed in 

 formalin and stained with aqueous methyl violet. 



It is a motile organism with peritrichous flagella usually from four 

 to six in number and from four to ten micra in length. The flagella stain 

 well by the method of van Ermengem (see Fig. 5). The organism rapidly 

 comes to rest when grown on sohd media, sometimes within 24 hours, 

 but remains motile for three or four weeks in broth cultures. Examined 

 in water suspension under a cover-glass the motion is of the "free 

 ' swimming" type with frequent spells of "tumbling" on the short axis. 

 At the centre of the cover-glass the motion slows down considerably 

 after half-an-hour, but continues for upwards of three-quarters of an 

 hour to one hour. 



Staining capacity. The bacillus stains readily with carbol fuchsin, 

 Victoria blue and methyl violet. It is gram negative. 



Capsules. The presence of a capsule has been suspected round 

 organisms forming a ring at the surface of broth cultures and in cultures 

 in Uschinsky solution. They could not be seen under dark-ground 

 illumination and it has not been possible to demonstrate them by 

 staining. Films from Uschinsky solution stained with gentian violet 

 frequently show a clear halo around each organism and the distribution 

 of the organisms in a crowded film is what one would expect for a 

 capsulated organism, i.e. the stained rods are never actually in contact 

 with one another. If a capsule is present it is not a very wide one and 

 does not stain by the usual methods employed for capsule staining. 



