PLATE 2 
A. —Primordium of sorus on leaf stalk of raspberry, showing its position in the host 
tissues. Peridial or buffer cells, each accompanied by a disorganizing intercalary 
cell, at the center of the sorus. Cell division by which intercalary cells are formed 
has not occurred at the margins. 
B. —Primordium of sorus on petiole of raspberty. Terminal cells elongating, 
intercalary cells disorganizing. Cells at the margin just before division. 
