FUNGI 235 



The time of year at which the inoculation was performed 

 appears to have had no influence on the results, provided, of 

 course, that sufficient time had been allowed to elapse for the 

 fungus to operate before observations were taken, Thus 



Relative 



Inoculated January 18 -79 66 



Inoculated April 8 79 58 



Whilst in another case, where trees were inoculated on July 4, 

 1906, November 15, 1906, and January 17, 1907, the results by 

 the end of 1907 were exactly the same in all three cases. 



It is generally held that when once a tree is attacked by silver- 

 leaf it never recovers. There can be no doubt, however, that this 

 opinion is erroneous. Observations made throughout three years 

 on trees which had been inoculated, showed that the number 

 of individuals manifesting the disease declined regularly, though 

 the virulence of the attack in those which remained affected, 

 increased; or in other words, where the disease had not been 

 taken badly, the tree might recover, whilst in other cases the 

 disease progressed gradually to a fatal conclusion. It was 

 noticeable, however, that recovery occurred in several instances 

 where the disease appeared to have been taken severely, and the 

 whole tree had become silvered. 



Per cent, trees Relative virulence 



affected in of attack. 



1906 1907 1908 1906 1907 1908 



48 trees . 79 52 44 68 70 80 



26 trees . 69 67 63 74 



In the case of trees other than plums, recovery has also been 

 noticed, as well as apparent recovery, followed by a relapse, in 

 subsequent seasons ; often, too, the trees which had recovered 

 from the outward signs of the disease, never recovered their vigour 

 completely, but gradually languished and died. This, however, 

 was not always the case. With Portugal laurels no cases of 

 recovery, or partial recovery, were noticed, but the progress of the 

 disease, if more certain, was slower in their case than in others : 

 ten trees inoculated in January 1907 showed no signs of the 

 disease that year, and only a 9 per cent, affection in 1908; this 

 rose to 60 and 75 per cent, in the next two years, and finally all 

 the trees died. None of these bushes developed stereum on the 

 dead wood. 



The degree of susceptibility of different kinds of trees to the 



