540 Scientific Proceedings, Royal Dublin Society. 



into the details of these expeiimeuts here : suffice it to say that convincing 

 evidence of the pathogenicity of the fungus has heen obtained by the use of 

 cultures which were proved both by microscopic and by cultural control to be 

 pure. 



Time has not yet permitted of any very extended series of observations 

 with regard to the pathogenicity of this fungus towards plants other than 

 the Potato. It was, however, inoculated (with the necessary controls) into 

 blocks of living tissue (prepared aseptically) of Carrot, Parsnip, Mangel, 

 Swede, and White Turnip. On the two first-named no infection whatever 

 occurred. In the case of the Mangel and Swede infection did occur, and 

 from the attacked tissues the fuugus was recovered, but the rot was neither a 

 very rapid nor a very pronounced one. The case of the White Turnip was 

 different. Here a decided rot occurred, accompanied by a browning of the 

 affected tissues, but no pink colour was developed, and the progress of the 

 rot was not so rapid as it is in the Potato. The fungus was obtained again 

 in pure culture from the affected tissues of the Turnip. 



When whole Swedes and White Turnips were inoculated through wounds 

 made for the purpose, the rot did not progress very far in the Swede, and 

 soon came to a standstill. In the 'Turnip, on the other hand, the rot went on 

 until the whole " root" was practically destroyed. Sections of the browned, 

 diseased tissues showed the presence of abundant non-septate characteristic 

 mycelium, which was both intra- as well as inter- cellular, while from this 

 tissue the fungus was obtained again in pure condition. It would, therefore, 

 appear that the fuugus is distinctly pathogenic to White Turnip. 



Preliminary inoculation experiments were also made with Scarlet-runner 

 beans. It was found that the fungus was incapable of causing infection 

 through the uninjured skin of the pods. When, however, it was placed on 

 portions of the pod from which tlie skin was removed, infection occurred in two 

 cases, and the fungus destroyed the pod, penetrated the seeds, and was 

 recovered pure from the affected tissues of the pod. In several other cases, 

 however, under apparently similar conditions, infection of the bean-pods 

 through wounds did not occur, but the lateness of the season and consequent 

 lack of material prevented further experiments in this direction, and the 

 pathogenicity of the fungus with regard to beans must be regarded as not yet 

 definitely proved. 



IV. Charactehs of the new Fungus. 



As has already been stated, the fungus exists in the diseased tubers 

 merely in the form of mycelium ramifying between the cells, and the 

 characters which are given in tlie following description apply to it as grown 



