234 SCIENCE AND FRUIT GROWING 



countries the disease has shown signs of abating since the dates 

 mentioned, cannot be stated with any confidence, but it is 

 certainly still very rife in England. 



At the time the Woburn experiments on the subject were 

 started, the fungoid nature of the disease was not so freely 

 accepted as it is at present, some authorities attributing it to 

 overfeeding, 1 and others to mechanical injury of the trees. 

 Even where its fungoid nature was accepted, doubts existed as 

 to whether infection occurred through the fungus spores entering 

 by wounds in the branches, etc., or whether it occurred through 

 the spread of the mycelium in the ground a view advocated at 

 first by Professor Percival. 



To investigate the matter, a plantation of 112 two-year-old 

 bush plum trees was established in 1906, the varieties planted 

 being Monarch, Czar, Rivers' Early Prolific and Victoria. 



Forty-eight of these trees were inoculated early in the year 

 with stereum, and, of these, 39, or 81 per cent., showed silvering 

 before the end of July, four of them having been killed outright 

 by that time, and two others being half dead. This is a high 

 percentage of infection, especially when it is remembered that 

 the inoculation was not performed by a trained mycologist. 

 On the other hand, not one of the 64 uninoculated trees showed 

 any signs of silvering, nor have they, unless subsequently 

 inoculated, become infected during the succeeding years. These 

 results afforded ample proof that the disease was a consequence 

 of inoculation with stereum purpureum. But beyond this, of the 

 inoculated trees, 19 died during the first two years after planting, 

 and all of these developed stereum on the dead wood, whilst none 

 of the uninoculated trees died, or showed any signs of the fungus. 



In different cases the inoculation was effected in the roots, 

 branches or stems of the trees, and the results, measured either 

 by the percentage of individuals which took the disease, or by 

 the virulence of the attack in those trees which were affected, 

 showed that inoculation in the stem was the most fatal, but 

 that as regards inoculation in the roots or branches, there was 

 nothing to choose between the two. 



Massee, Journ. Hort. Soc., XXX, 36. 



