4 Proceedings of the Royal Irish Academy. 



organism, Iwanoff considered that the disease was of the same type as that 

 produced in America by Bacillus solanacearum. 



At the beginnmg of the present century Delacroix paid considerable 

 attention to a bacterial disease of the potato in France, which was entirely 

 different from the gangrene of the stem studied about ten years previously by 

 Prillieux and himself. In his first communication on the subject (9), he states 

 that in the early stages of the disease the foliage becomes yellow, arid then by 

 degrees dries up. The stems become thinner and die from below upwards, 

 and the tubers are also found to be diseased. Microscopic examination of the 

 tissues of the affected stems showed a development of yellowish gummy 

 matter and of thyloses in the wood vessels. The bacteria found were, he then 

 considered, not dissimilar to the Bacillus solanacearum of E. F. Smith in 

 America. This first communication is further of interest because Delacroix 

 states that, from the oral testimony of Dr. Johnson, of Dublin, and from the 

 inspection of a small specimen sent three years before, the same disease 

 appeared to be common in Ireland. It should, however, be noted that the 

 evidence of the presence of this particular disease in Ireland does not rest on 

 any experimental basis, as no cultures appear to have been made from the 

 Irish material. 



In a second paper on the same subject, Delacroix (10) enters more into 

 detail regarding the characteristics of the organism concerned in the disease. 

 Whereas, as mentioned above, he at first thought it was perhaps identical with 

 Smith's B. solanacearmn, he now concludes that this is not the case, and 

 describes his organism as a new one under the name of Bacilh(,s solanincola. 

 This organism grows well on the ordinary culture-media without colouring 

 them. Broth is rendered viscous by it ; and a pellicle is formed on the surface. 

 He states here that gelatine is liquefied by this organism, but only slowly, and 

 merely on the surface. In Delacroix and Maublanc's " Maladies parasitaires 

 des plantes cultiv^es," published in 1909, however, it is stated on p. 38 that 

 it was by error that B. solanincola was described as liquefying gelatine ; hence 

 it must now be regarded as a non-hquefier. Other details of the organism are 

 given ; and the successful results of inoculation experiments with pure cultures 

 are described ; so that B. solanincola may be looked upon as having been 

 proved with certainty to be pathogenic to the potato. 



In a further paper (11) Delacroix repeats and amplifies his earlier accounts 

 of this disease and of the organism producing it; and here again he states 

 that from the inspection of further specimens of diseased plants, and of 

 microscopical preparations supplied by Dr. Johnson, he is convinced that the 

 same disease exists in Ireland. It must, however, again be pointed out that 

 the mere inspection of diseased plants and of microscopical preparations is not 



