PLATE 21 
The picture in A shows a longitudinal section through the node of a normal stalk. 
The dark bundles were stained by a dilute solution of methylene blue which was 
absorbed by the plant. The bundles were practically all functioning, as is observed 
in the transverse sections through the stalk shown in B. The same treatment was 
given to this stalk as to those shown in Plate 20. 
