6 Proceedings of the Royal Irish Academy. 



occurs usually as single rods of variable length, rarely in pairs, and 

 occasionally in chains of fonr to ten. It is actively motile, and possesses long 

 flagella — the number of which is not stated. It liquefies gelatine media when 

 alkaline, but, on the whole, does not appear to be a stiong producer of 

 liquefaction. Inoculations of UTing potato-plants and tubere were canied out 

 with somewhat varying success; and although van Hall did not entirely 

 succeed in reproducing the exact symptoms of disease in potato-stalks as they 

 occur in the field, there is Kttle doubt but that he had before him a virulent 

 organism highly toxic to the potato-plant, which, with practical certainty, was 

 the cause of the stem-rot observed. 



During his experimental investigations as to the ways and means of how 

 best to pit potatoes for their successful preservation over the winter, Appel ; 1) 

 became convinced, contrary to the then somewhat generally accepted views of 

 Wehmer, that there undoubtedly did exist bacteria capable of attacking and 

 destroying the pei-feetly healthy tissues of sound potato-tubers. In a 

 preliminary communication (2) published in 1902, Appel gives a brief account 

 of his isolation of such an organism, and of its destractive action on the tuber. 

 He exhibited cultures of the organism, and showed the results of its 

 inoculation on living potato to the German Society of Botanists in Januaiy 

 of that year. A month later (-3) he was able to describe and show 

 prepaiutions of an organism to which he gave the name of BadUus 

 phytopAthonis, and which he had been able to prove, by means of inoculation 

 experiments, to be the cause of the well-known " Schwarzbeinigkeit " in 

 potato-plants. This oiganism he obtained by isolations, both from rotting 

 tubers as described in his previous note, and also from the stalks of potato- 

 plants sufiering from the disease in question. 



Two years later he published a very full and complete account of this 

 disease (4) as it occui-s in Germany, and of the organism which causes it. 

 With regard to the latter, although B. phiftopMhorus is the oiganism dealt 

 with in detail, Appel is of opinion that the same disease may be due, not to 

 this particulai- organism only, but also possibly to others closely allied to it. 

 It is possible, as Appel points out, that the oiganism he was dealing with was 

 identical with the one described as Mierocoeeus phi/tophthwus, previously 

 isolated by Frank and mentioned above. Frank's description of his oiganism, 

 however, was too meagre to admit of a complete proof of their identity ; but it 

 seems doubtful, at least, whether the toxic oiganism with which Frank worked 

 was really a micrococcus. The symptoms of disease are, in most respects, very 

 similar to those of the disease which we are about to describe as occiuTing in 

 Ireland, and there is therefore no necessity to enter into details concerning 

 . them at this point. With i^egaiid to the oiganism, it may be stated that it is 



