H. WORMALD 239 



grown in Uschinsky's solution. Four tubes of the solution were 

 inoculated from celery agar cultures, 48 hours old, with each of the 

 two strains with the following result: — 



48 hours 7 days 



B. apiovorus Turbid, numerous Liquid almost clear, 



(4 tubes) flocculi, distinct sediment bulky, 



sediment. 



B. carotovorus Growth feebler than Turbid, 



(4 tubes) in above, less turbid, sediment thin, 



flocculi less numerous, 

 trace ol sediment. 



The general appearance of the tubes was maintained for five days 

 longer (when they were tested for acidity), those of B. apiovorus remaining 

 almost clear but with a dense bulky sediment, while those of B. caro- 

 tovorus were still turbid, the sediment forming a comparatively thin 

 layer; all gave a rather feeble acid reaction which however was un- 

 mistakable when the tubes were examined as described above. 



V. Chromogenesis. 



In my previous papers the celery bacillus was described as a yellow 

 organism as indicated by its colour when growing on sterilized potato 

 in Roux's tubes, while Bacillus carotovorus is included by Harding and 

 Morse (11) among the non-chromogenic bacteria, and in their resume of 

 its cultural features they write "Chromogenesis, ^vhite on all medial 



It was found that when the two were grown on the same medium 

 no difference in colour could be detected. Streak cultures of each 

 have usually a yellowish tinge and this is also often seen in the sedi- 

 ments of cultures in liquid media. The colour is however more pro- 

 nounced when they are grown on solid media such as sterilized potato 

 or the Soyka Milk-Rice medium^, the latter being particularly favourable 

 for investigation on chromogenesis. Cultures of each were started at 

 the same time on sterilized potato in Roux's tubes and on milk-rice 

 and kept at the room temperature (18° C). 



On potato at the end of 24 hours the colour of the growth in both 

 strains was practically that of the potato itself, the only difference 

 being that the surface of the potato was more or less glistening with 

 moisture while the bacterial mass had a matt surface. On the follow- 

 ing day yellowing was noticeable and on the fourth day the colour 

 of the culture was approximately " Cream Buff " of Ridgway's 



1 See Eyre's Bacteriological Technique, p. 189, where the method of preparing this 

 medium is given. 



