Apple "Scab" or "Black Spot." [June, 



occurs. In consequence of the increasing extent to which orchards 

 and plantations in Kent were suffering, app]e " scab " was one 

 of the first diseases which I investigated on being appointed 

 mycologist to Wye College. A number of cases were brought 

 to my notice where young trees in quite isolated positions 

 suffered regularly from the disease year after year, suggesting 

 that a continual source of infection was present on the trees. 

 An examination of the trees resulted in the finding of the 

 disease on the young wood. This was the first time the 

 occurrence of " scab "-infested wood had been noted in this 



fig. 5. — Part of a section through one of the "sooty" patches on the 

 " Bismarck " leaf shown in Fig. 2 ; {a), epidermal cells of the leaf ; (£), portion of the 

 spawn {mycelium) of the fungus feeding on the sap of the leaf ; (c), ripe spores {conidia) 

 of the fungus. — Highly magnified. 



country, although this stage had been reported from the 

 Continent and the United States. 



The general appearance of young wood attacked by the 

 " scab " is shown in the photograph in Fig. 6. According to 

 the variety of apple attacked, its appearance varies con- 

 siderably; in some cases, e.g., on " Cox's Orange Pippin," 

 the diseased wood becomes somewhat swollen and prominently 

 blistered, as is shown in Fig. 6A ; in other cases, e.g., on 

 " Wellington," the blistered appearance is less prominent, 

 and the shoot is not swollen (Fig. 6B). In other cases the 



