216 Scientific Proceedings, Royal Dublin Society. 



found to be the case with the other inoculated plants which remained 

 healthy, and were microscopically examined three months after the inocula- 

 tions were made. The controls behaved in a similar manner. 



The second series of inoculations was a repetition of the first. Eight 

 healthy plants were inoculated as in the previous series. They remained 

 healthy, except in one case, and after a period of two months they were 

 subjected to microscopical examination. The seven plants showed no traces 

 of the fungus in them, except immediately at the inoculation wound, from 

 which it had not spread. The eighth plant died after the expiration of one 

 month. Mycelium was found in its vessels, but this, as the result of cultural 

 trial, was found to be Vcrticillium albo-atrum. Examination of the undecayed 

 parent tuber showed that this fungus was also present in it ; and there can 

 be little doubt but that this tuber was infected with Verticillium before 

 it was planted. 



In the third series the tubers selected for use were first carefully tested 

 to make sure Verticillium was not present in them. The Verticillium-free 

 tubers were then allowed to sprout, and when the sprouts were from two to 

 three centimetres long, one main sprout on each was inoculated with 

 F. cmruleum, through a wound made for the purpose. The other sprouts and 

 eyes were removed. The tubers were planted, and all six of them produced 

 perfectly healthy plants, as also did four tubers (not inoculated in the 

 sprouts) used as controls. The stalks were subjected to microscopical 

 examination, but no mycelium was found in their wood vessels. The newly- 

 produced tubers were also examined, and found not to be invaded at their 

 heel-ends by any fungus. 



As a result of these experiments we conclude that F. caruleum does not 

 cause a wilt disease of the plant, and in this respect it appears to differ from 

 F. oceysporum and F. triclwthecioides. 



Control of Dry Rot. — Our experience with this disease is that when once 

 a tuber begins to rot it is practically impossible to effect a cure. From 

 twenty naturally affected tubers the diseased portions (which were then 

 comparatively small) were very carefully cut out on December 19th, 1913. 

 Flowers of sulphur was then thoroughly rubbed into the wounds. After two 

 months, however, nineteen of these tubers had completely rotted. Either the 

 whole of the diseased tissue had not been cut out originally, in spite of the 

 care exercised, or re-infection from spores had then or subsequently occurred, 

 and this in spite of the presence of sulphur. 



Ten healthy tubers (variety Windsor Castle) were washed and dried. 

 Five were then inoculated with F. ccerulewn through wounds as previously 

 described. Just before the other five were quite dry they were rolled in 



