NOTES AND QUERIES. 1 87 



fungus are at once obvious when the potatoes are examined. 

 They show the usual structure and appear as rounded brown 

 strands which, on coming into contact with the tuber, become 

 slightly flattened. They may continue for some distance tightly 

 attached to the tuber without piercing the corky skin, but 

 usually penetration soon takes place, and wherever this happens 

 a darker coloured sunken patch is seen on the skin, below which 

 the cells are killed and partially disorganised. On cutting open 

 the tubers the effects of the disease are clearly seen. In some, 

 penetration by the rhizomorphs is only slight, and here only 

 small patches of dead brown cells are produced. In other cases, 

 the rhizomorphs have grown deeply into the tuber, and large 

 cavities, resulting from the disintegration of the tissue, are formed 

 which become partially filled up with masses of white mycelium 

 and rhizomorphs : these cavities are surrounded by a dark 

 brown zone of dead tissue of the tuber and this, in turn, by a 

 region where the hyphae can be seen penetrating the still living 

 cells. As a result of the attack a cork combium is formed 

 around the diseased portions, and the infected cells are more 

 or less isolated by a layer of cork. Where the attack is severe 

 the tubers, when stored, shrivel and dry up. An examination 

 of the garden in which the potatoes were grown resulted in the 

 discovery of large numbers of rhizomorphs in the soil, but no 

 fructifications were found, and on inquiry it was ascertained 

 that none had been seen. The source from which the 

 rhizomorphs were developed was found to be an old sycamore 

 stump, situated about four yards from the edge of the potato 

 plot, which showed very clearly the results of infection by 

 Armillaria mellea. 



The garden possesses a rather heavy wet soil, and this may 

 be a factor bringing about the development of the disease. The 

 fact that it has occurred in this garden for several years shows 

 that it is not due to seasonal peculiarities. A more detailed 

 account of the disease, with figures, will be published shortly. 



Malcolm Wilson. 



An Overhead Saw^ for Estate Work. 



( With Plate ) 



I enclose a photograph (Plate V.) of an overhead saw I fitted 

 up nine years ago, over a travelling bench saw, for cutting up 



