PLATE 74 
Plasmodiophora brassicae: 
A. —Somewhat later stages of medullary growth than those shown in Plate 73. The 
cylinder was first split into two halves. Note that the bundles of the lower half are 
being still further split up. X 35 * 5 - 
B. —Another cylinder being split into two equal halves. This figure shows how 
the medullary cells increase in size during the first two or three divisions. Two or 
three rows of cells bordering on the diseased tissue still have the characteristics of 
medullary ray cells, but the cells of the row adjoining the diseased tissue are much 
larger than ray cells. X 40. 
70394°—18 - 5 
