222 The Celery-Rot Bacillns 



enzyme which dissolves the middle lamella of the parenchymatous cells 

 of fleshy tissues. Each of the investigators mentioned has prepared 

 the enzyme free from the living organism and finds that its action on 

 the middle lamella is similar to that of the organism itself. Potter 

 also found that the organism {Pseudomonas destructans) with which he 

 worked was able to penetrate the cell- wall and so enter the cell-cavity ; 

 though Jones considers that "this probably is to be regarded as due to 

 physical pressure rather than to solution of membrane," Potter main- 

 tains (31) that his own interpretation is the correct one and that "there 

 is certainly invasion of the cell-cavities by the bacilli." Again Erwin 

 Smith states (39) that ^'Pseudomonas campestris is capable not only of 

 destroying the middle lamella, but also of dissolving the cell-wall 

 proper." 



It is well recognised that there are bacteria which do possess the 

 power to ferment pure cellulose, as shown by Omelianski (26), while 

 Kellerman and his co-workers (19) give a list of twenty-one species of 

 bacteria which cause fermentation of cellulose. It would appear how- 

 ever that a typical soft- rot organism^ as exemplified by Jones's Bacillus 

 carotovorus is unable to penetrate the unruptured cell- wall. Van Hall 

 writes "Der Bacillus omnivorus^ ist nicht im stande, die Zellwand zu 

 durchbohren, und ein Eindringen in die Zellen findet also auch niemals 

 statt," and the observations of Jones are confirmatory of this state- 

 ment. 



When a particle of the pulp of a celery petiole inoculated from a pure 

 culture is taken a short distance behind the line where the bacteria 

 are encroaching on the living tissue and subjected to microscopic 

 examination the parenchyma is found in process of disintegration. 

 Some of the cells are seen to be free but others may still cohere in longi- 

 tudinal series while numerous bacilli are to be observed in active motion. 

 On focussing downwards and confining one's attention to a single cell 

 a layer of bacteria will come into view apparently extending across 

 the whole width of the cell. As the observer continues to apply the 

 focussing screw in the same direction the bacterial layer disappears 

 from view but presently another layer of bacteria comes into focus. 

 The bacteria are applied to the walls of the cell and the tw^o bacterial 

 layers correspond to the upper and lower walls of the cell. That the 

 bacteria are on the outer side of the wall is shown by the fact that when 

 one of the layers is sharply in focus, motile rods, also in focus, swim into 

 the field of view and out again beyond the limits of the cell. When 

 ' Harding and Mprae consider B. omnivorus to be identical with B. carotovorus Jones. 



