236 The Celery -Rot Bacillus 



may be evolved in quantity so small that they are dissolved in the 

 medium as produced. The results suggest that the organic compounds 

 of the peptone and bouillon may contribute to the production of gas 

 when sugar is present. 



Media containing Pectin. The experiments with synthetic media con- 

 taining saccharose showed that the organism is capable of maintaining 

 existence and propagating itself in media containing a sugar as the 

 only source of carbon. The plants susceptible to attack by the bacillus 

 are however not necessarily rich in sugar and the probability is that 

 in nature {i.e. when living in plant tissues) the requisite carbon is derived 

 principally from the pectic compounds of the cell- wall and particularly 

 the middle lamella; the bacillus is unable to ferment pure cellulose 

 as shown in an experiment in which it was grown in bouillon containing 

 strips of Swedish filter-paper without any change occurring in the latter, 

 and its action on starch is also practically negligible. 



Artificially prepared culture media containing pectin instead of 

 sugar have proved favourable for the growth of the organism. In the 

 earlier experiments of this series a solution of pectin was prepared from 

 ripe fruit by the method adopted by Buller(5). Later the gelatinous 

 mass obtained from fruit- juice by its precipitation with alcohol was 

 dehydrated by absolute alcohol and the latter finally driven off by 

 gentle heat in a drying oven at about 40° C. ; in this way the substance 

 was obtained in a dry state and solutions of known strength could be 

 prepared. 



When pectin was used instead of sugar in combination with peptone 

 and litmus a dense precipitate was produced on sterilizing. To obviate 

 this, solutions of peptone and pectin were sterilized separately and 

 then mixed. 



A. Peptone 2 gm. 

 Distilled Water 50 c.c. 



Steamed for half an hour to dissolve the peptone. 



B. Pectin (dry) 1 gm. 

 Distilled Water 45 c.c. 



Steamed until the pectin was dissolved then 5 c.c. litmus solution 

 added. 



The solutions A and B were sterilized separately, then mixed and 

 put into sterile fermentation tubes, this process being carried out over 

 a steaming sterilizer to avoid contamination. Of five tubes so prepared 

 and incubated four were inoculated in succession at intervals of 24 hours, 



