30 Proceedings of the Royal Irish Academy. 



arises as to whether the organism causing Black Stalk-rot of the potato may 

 also produce rotting of the turnip under natural conditions in the field. A 

 complete answer to this question mirst be left for future work to provide ; but 

 fi'om a swede, which was attacked by a brown bacterial rot, we succeeded m 

 isolating an organism which would rot swedes, but which could not be induced 

 to cause a rot in potatoes. A qviite different type of bacterial rot of a white 

 kind was observed m turnips, one of the characteristics of which was that the 

 foHage of the affected plants became strongly wilted. Preliminary trials with 

 the pulp of such rotten turnips showed that it did produce a rot in potato 

 tubers. This pulp was then plated out, and ultimately an organism was isolated 

 fi'om it which caused a rapid rot in the turnip and also in potato-tubers. In 

 the latter, however, the rot was neither rapid nor profound, and it did not show 

 quite the characters of the decay produced by the Black Stalk-rot organism. 

 The organism was a peritriehously multi-flagellate rod, which ra size was 

 both distinctly broader and longer than the Black Stalk-rot organism. Hence 

 it would appear that tiu'nip-rot and Black Stalk-rot are probably not caused 

 by identical organisms, although the Black Stalk-rot organism does not seem 

 to be specifically pathogenic to the potato, as is stated by van Hall to be 

 apparently the case with his Bacillus atrosepticus. Much further work is, 

 however, required in this direction before it would be possible to decide with 

 certainty whether one and the same organism may be responsible for rotting 

 both ia potatoes and turnips. 



VII. Comparison of the Organism causing Black Stalk-rot with allied 



Organisms. 



It may be recalled that the following organisms have been described as 

 being responsible for bacterial disease in potatoes, viz., Bacillus caulivorus 

 Prill, et Del (France), Bacillus solanacearum Smith (U.S.A.), Bacillus 

 solanineola Del. (France), Bacillus atrosepticus van Hall (Holland), Baxillus 

 pliytophthorus Appel (Germany), and Bacillus solanisaprus Harrison (Canada). 

 Wlien compared with these, it is quite clear that om* organism is not identical 

 with any of the first three named, for the first of them produces a green 

 fluorescence in its culture media, and the two others are nou-liquefiers of 

 gelatine, whereas our organism produces no green colom-, and is decidedly a 

 liquefier. With regard to the three last named, a comj)arison of characters 

 shows that oiu- organism has some points in common with each of them. It 

 differs, however, from Bacillus atrosejjticus, since that organism is described as 

 occurring chiefly as isolated indi'viduals, whereas ours is more frequently 

 found in pairs. The former is also decidedly smaller in size, in spite of 

 variations in both cases, and its action on milk appears to be different frorn 



