PLATE 73 
Plasmodiophora brassicae: 
Stages in the infection of medullary rays 
A. —A father large woody cylinder that is beginning to split apart through the 
abnormal growth of its medullary rays.. Several of the rays are being invaded by the 
parasite. X 40. 
B. —The woody cylinder of a cabbage root. It is being split into two almost equal 
parts by the growth of medullary tissue. X 40. 
