H. WORMALD "^ 171 



On the older parts of the branches (1-5 to 2 cm. in thickness) bearing 

 short infected spurs to 2-5 cm. in length, there was evidence, towards 

 the end of May, that the fungus was advancing beyond the level of 

 insertion of the spurs, by the appearance of longitudinal fissures in 

 the bark immediately above and below the nodes. By June 7 the 

 affected areas on the branches were slightly sunken below the general 

 surface and extended round the nodes as shallow elliptical depressions. 

 Further extension of the fungus appeared to be inhibited about that 

 date and although the margins of the cankers later became more defined, 

 no further increase occurred superficially in the majority of those 

 examined. The bark over the affected areas gradually became sulcate, 

 often, on the smaller branches, with distinct "oyster-shell" markings 

 of raised lines. 



Cankers which had produced the Monilia pustules during 1915 had 

 been labelled and all proved to be barren during 1916, no pustules being 

 present ; no further increase of the cankered surface had occurred and in 

 each case callus was growing over it beneath the ruptured bark. Some 

 cankers, several inches long, were almost completely healed (Fig. 7). 



Thus on trees where the disease has existed for two or more years 

 the following results are to be observed during the summer months : 



A. Result of infection during that year : 



(1) dead trusses of blossom ; 



(2) cankers on the branches round the bases of the shorter spurs 



bearing the wilted trusses. 



B. Result of infection during the previous year : 



(1) dead spurs bearing Monilia pustules; 



(2) cankers also bearing Monilia pustules. 



C. Result of infection two years previously : 



(1) dead spurs with rough cracked bark, not now bearing Monilia 



pustules ; 



(2) cankers more or less healed over by callus growing over the 



cankered surface from the margin towards the middle line. 



During winter affected trees are recognised by the dried remains of 

 the infected trusses (see Fig. 1). Flowers which fail to "set" into fruit 

 soon fall from the tree if the spur bearing them is not diseased. When 

 affected by the blossom-wilt Monilia, however, they are retained on 

 the tree through the winter. The leaves too, of these spurs, being killed 

 before the absciss-layer is formed, remain attached to the tree. 



In December 1916 the dead spurs and cankers caused by infection in 



