H. WORMALD 107 



with a single dead spur, near the upper end, bearing a number of 

 powdery pustules; all the flowering spurs, fifteen in number, on that 

 branch below the dead spur were killed, while all the barren spurs (i.e. 

 bearing leaves only), eleven in number, were unaffected. Barren spurs 

 and young vegetative shoots were not attacked directly but became 

 wilted when borne on that portion of a branch distal to a canker which 

 had encircled the branch, or when borne on a spur which also carried 

 one or more infected trusses. 



By the middle of June it was found that where diseased trusses were 

 borne singly on short, simple (unbranched) spurs, 0-5 cm. to 1-0 cm. in 

 length, growing from the younger portions (5-7 mm. in diameter) of 

 the branches the fungus had traversed the tissues of the spurs and 

 penetrated to the branch itself producing a canker completely encircling 

 it and causing the wilting and death of those parts beyond the canker. 

 On older portions (to about 1-5 cm. in diameter), bearing simple spurs 

 to 2 cm. in length, the canker at the base of each affected spur had 

 reached about half way round the branch. 



A similar condition obtained in the case of spurs killed during the 

 previous season, and it may be stated generally that when infection had 

 occurred through a spur to 3 cm. in length a well-defined canker was 

 produced extending upwards and downwards along the branch for 

 several centimetres; the lateral extension of the canker was less than 

 the longitudinal but on those portions of the branches two or three years 

 old it was sufficient to completely girdle them. When the spurs were 

 longer they were often killed to the level of their insertion on the branch, 

 but on those 5 or 6 cm. in length the fungus as a rule had failed to reach 

 the branch and the lower portions of such spurs were still alive. 



The fungus may grow downwards from the infected truss along one 

 side of the spur while the other side remains alive and unattacked. 

 One spur had pustules over an area extending two-thirds round it but 

 at the apex there were two young growing apples. On another the 

 pustules had developed over the terminal portion and along the whole 

 of one side, the other side being still alive for about half its length as 

 shown by a living shoot near the middle ; a section across this spur 

 showed the tissues on the one side to be brown as far as the pith, while 

 on the other they were still green. 



A few old cankers were found from which the layers of dead tissue 

 were in process of being removed by the formation beneath them of 

 callus which was growing over and healing the cankered surface. These 

 cankers at this sta<2;e showed no trace of the fungus but they bore such 



