* PLATE 33 
Distribution of tissues and type of elements of the potato: 
A. —Transverse section of large stem bundle at time of secondary growth showing 
distribution and type of medullary rays. X103. 
B. —Transverse view of sieve plate of secondary sieve tube. X405. 
C. —Transverse section through a large stem bundle showing type of cells of peri- 
medullary zone and the extent of the latter. X103. 
D. —Transverse view of sieve plate greatly enlarged. X90. 
E. —Radial section through porous vessel, showing type of end wall and extent of 
pitting. X292. 
