184 



DISEASES OF CULTIVATED PLANTS 



I have also seen it on the gooseberry in such quantity as to 

 kill the branches. 



The fungus is a wound-parasite, and it frequently follows 

 on the wounds caused by American blight (Schizoneura 

 lanosd), since the advent of which, canker has been much 



I 



MA 



'I 



FIG. 49. Nectria ditissima. i, a branch recently 

 attacked, showing concentric cracking of the bark ; 

 2, an old wound showing a rugged callus round 

 the wound ; 3, section through a stroma showing 

 perithecia, a, on its surface ; 4, a perithecium ; 

 5, section of same ; 6, conidia ; 7, a conidium 

 germinating ; 8, ascus containing spores, and 

 accompanied by paraphyses. Figs, i and 2 

 reduced ; remainder highly mag. 



more prevalent, and perhaps it is not going too far to state 

 that if we had no American blight or woolly aphis, we should 

 have no epidemic of canker. The bark is first attacked and 

 destroyed, often cracking in a concentric manner. After- 



