PLATE 44 
Secondary growth of the potato: 
A. —Transverse section through part of large stem bundle, showing type of xylem 
and medullary ray cells. X 234. 
B. —Transverse section through interfascicular region of mature stem, showing 
the types of first and later formed secondary xylem elements. X 234. 
C. —Transverse section through part of mature root, showing secondary phloem. 
X 540 . 
D. —Transverse section through part of mature petiole, showing secondary xylem. 
X 360. 
