19 i Scientific Proceedings^ Royal Dublin Society. 



In two eases where healthy tubers were still attached to rhizomes, 

 portions of which at some distance from the tubers were diseased, it was 

 found that on burying them in the soil the disease progressed througli the 

 rhizomes, entered the tubers, and destroyed them. 



In its fundamental aspect the disease may be described as being of the 

 " wilt " type, and it is accompanied by a rotting of portions of some or all of 

 the underground parts of the plant. In this latter aspect the disease differs 

 from the Vertioillium wilt, which has been a subject of study at Clifden 

 for some years, and which will be described in detail, it is hoped, in a 

 later paper. In general outward appearance it closely resembles the 

 disease known as Black Stalk Rot,' due to Bacillus melanogenes P. & M. 

 Without a careful microscopical examination, indeed, it is in many cases 

 impossible to distinguish with certainty between these two diseases. It may, 

 however, be stated that in the case of the present disease (for which perhaps 

 the name " Pink-Rot Wilt " may be suggested) the browning of the vascular 

 bundles of affected stalks is not usually such a clearly marked character, 

 and there is, as a rule, less or none of the external blackening of the 

 epidermal and cortical tissues of the stalks which constitutes a well-marked 

 feature of Black Stalk Rot. Furthermore, the fact that Black Stalk Rot is 

 one of the earliest of the potato diseases to show itself in the season (being 

 evident often in the month of June) serves to some extent to distinguish it 

 from the Pink-Eot Wilt. 



The investigations made up to the present unmistakably point to the 

 conclusion that there exists a disease of the potato-plaut as a whole (not 

 merely a disease of the tubers, although this is perhaps the most serious 

 aspect of the disease from the economic standpoint) which is caused by 

 P. erythroseptica, and which has hitherto escaped observation. From one 

 point of view the disease may be looked upon as a new one ; but in all 

 probability it is one of old standing, only its recognition as specific disease 

 being really new. 



It will be observed that, in the foregoing account, it has been assumed 

 that the connection between the symptoms described and the presence 

 of the parasitic fungus is a causal one. As regards the attack on 

 the tubers, however, it has been proved definitely, by means of controlled 

 inoculation experiments with pure cultures, that the fungus in question is 

 undoubtedly the cause of the particular form of rot which occurs ; and it 

 must be admitted that experiments of a similar nature are necessary with the 



1 Pethybridge, G. H., and P. A. Murphy : " A Bacterial -Disease of the Potato Plant in Ireland, 

 and the Organism causing it." — Proc, Eoy. Irish Acad., vol. xsix, Sect. B, Ho. 1, 1911. 



