PLATE 30 
Types of primary tissues of the potato: 
A. —Transverse section of part of large stem bundle showing sieve tubes and com¬ 
panion cells in outer phloem, type of cambium and medullary ray initials, metaxylem. 
Xs°°* 
B. —Transverse section through part of the same bundle showing inner phloem, 
pith, and cells of the perimedullary zone. X500. 
