PLATE XI 
PART OF A BRANCH FROM A CRAB-TREK ( PyruS Malus) BEARING NUMEROUS TUMOURS. AN APHIS ( MyZOXylltS Intliger) AND A FUNGUS 
(Nectrza ditissima) occur in connection with these cankers, and it was thought that the latter caused them, it has 
BEEN ASSERTED RECENTLY, HOWEVER, THAT A BACTERIUM (Bacterium V/ali) INITIATES THESE OVERGROWTHS 
