34 Proceerlings of the Royal Irish Academy. 



In spite of the fact that the origin of the seed was known, it must be con- 

 fessed that such a lai'ge proportion of diseased plants was quite unexpected. 

 It is abundantly evident that the disease can be spread by means of affected 

 " seed " which may appear to be sound This being the case, the advisability 

 of removing diseased plants as far as practicable from the field, in order to 

 prevent the apparently sound tubers of diseased plants from being selected 

 for "seed," is clearly indicated. It is perhajs a counsel of perfection to 

 recommend that only those tubers should te used for " seed " purposes which 

 can be guaranteed to be the produce of a crop free fi-om Black Stalk-rot ; but 

 the time is not far distant when it will be necessary to pay more attention to 

 the sources of potatoes for " seed " purp<Kes from the point of view of their 

 being carriers of disease not only in the ease of Black Stalk-rot, but also in 

 that of some others, such as Leaf-Eoll and CniL Expeiiments are now in 

 prt^r^s to ascertain whether the organism present in slightly affiected tubers 

 can be killed by heat without injury to the tubers themselves. As regards 

 immunity we have as yet little satisfactory evidence to go upon: but it will 

 be noted on reference to the table on p. 29 that we did not succeed in a single 

 instance in causing an infection in tubers of the Wild Champion variety. As 

 a cropper, and for quahty, however, this variety is not one which would 

 recommend itself for wide culture. 



IX. — SrjniABY. 



This paper deals with a bacterial disease of the potato plant (including the 

 tubers) in Ireland, of which, as is shown in the histoiical introduction, no 

 detailed study has up to the present been published. 



The characters of the disease are described in detail the main featiu-es 

 being discolouration and drying-up of the foliage, bi-owning of the principal 

 vascular bundles of the stem, decay of the underground portion of the stalk, 

 and rotting of the tubere. 



An account is given of the isolation of a pathogenic oi'ganism from the 

 diseased tissues and of inoculation and re-isolation experiments made with it 

 on healthy plants, which pi-ove conclusively that it is the cause of the 

 disease. 



The oi^anism is described in detail both as to its moi-phological and 

 physiol(^eal characteristics. It is a multiflagellate, peritriehous bacillus, 

 liquefying gelatine, practically non-ehromogenic, and evidently allied to, but 

 not identical with, certain other oi-ganisms which have been described in other 

 countries, both in the Old and Xew "World, as causing a similar disease in 

 potatoes. The name BaciUus mdanogcncs is suggested for it. 



