52 



JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



That canker is something of the nature of a parasite, we have 

 evidence in its spreading and attacking previously uninjured 

 tissue. 



CANKER IN APPLES, SHOWING THE PRESENCE OF A FUNGUS, Nectria ditissima. 



Decay itself is brought about by the action of living organisms 

 on matter that is already dead, and effects the changes that crumble 

 organic substances into dust. There is some truth in the statements 

 that cold and undrained soil, severe pruning, extreme variations 

 of temperature, late growth, and unripened wood, give rise to 

 canker, just as bad treatment will undermine the constitution of 

 a human being and prepare the way for disease. The real enemy 

 does but take advantage of the weakened state of the victim. 

 Some varieties of apples and pears are more prone to canker than 

 others, and especially in some soils that may be cold, undrained, 

 or are underlaid by a gravelly subsoil. Here, again, we may point 

 to the natural constitution of the trees in question. Great im- 

 provements have been effected by drainage, by ameliorating or 

 supplying fresh soil, all of which point to the fact that more or 

 better nourishment is needed to enable the trees to make healthy 

 growth in order to contend against an invisible but powerful 

 foe. The baneful effects of canker may to a great extent be 



