PLATE 20 
A. —Longitudinal section through a node of a stalk showing symptoms of rootrots. 
The darkened vascular bundles are stained by a dilute solution of methylene blue 
which was absorbed by the plant. Compare the number of bundles which are func¬ 
tioning with the number shown in Plate 21. The nonfunctioning bundles have the 
largest accumulations of iron and aluminum in the zone B region. 
B, C.—Relative numbers of functioning vascular bundles in transverse sections of 
diseased stalks. B shows the intemode section and C a section through zone A. 
