FUNGI 237 



of plums, it was found that it was the less robust individuals 

 which took the disease more readily on inoculation, the per- 

 centage of trees becoming affected being 



Strong .... . 31 

 Weak 63 



but the virulence of the attack in those which had become affected 

 did not show such marked difference 



ist year. 2nd year. 



Strong . . 72 40 



Weak .... 65 51 



the values indicating that, though the stronger trees eventually 

 suffered less than the weaker ones, the spread of the disease in 

 them was more rapid at first, due no doubt to this spread being 

 facilitated by the more ready flow of sap. 



It was considered possible that a tree which had become in- 

 fected, and had subsequently recovered, might prove to be 

 immune from subsequent attack ; but experiment negatived this 

 possibility. Twenty-four trees which had recovered from an 

 attack were reinoculated, and the results compared with those 

 obtained on the inoculation of a similar number of trees which 

 had never suffered from the disease ; the difference in the 

 behaviour of the two sets was quite inappreciable, amounting to 

 only a few units per cent. 



As to remedial measures, only one form of treatment has been 

 suggested, and that consists in applying, either to the ground or 

 in holes drilled into the stem, sulphate of iron. The former 

 method of application has been adopted to a considerable extent 

 in New Zealand, where as much as 12 Ib. of the sulphate is 

 sometimes applied to the ground round one large tree. The 

 reports as to the effect of such a dressing are not always favour- 

 able, and, where good results have followed, these unfortunately 

 have to be discounted by the fact, now established, that trees 

 may often recover of their own accord, independently of any 

 dressing at all. The results at Woburn certainly do not favour 

 the view that such a dressing has any effect on the disease. 

 About 50 trees were examined in this way ; in one series they had 

 been inoculated before being planted, and the dressing applied 

 consisted either of I Ib. or J Ib. of iron sulphate to the square 

 yard. The means deduced from two years' observations showed 



