PLATE 38 
Development of tlie tuber of the potato: 
A.—Section of mature stolon, showing general distribution and relative proportions 
of tissues. X 3°- . , A 
_Transverse section of part of vascular tissue of young tuber and cortex. X 03. 
C.—Transverse section of part of vascular tissue of a somewhat older tuber, showing 
the beginning of extensive cell division in perimedullary zone and parenchyma of 
outer phloem. X 63. . . . 
D—Transverse section of vascular tissue of partly grown tuber, showing the distri¬ 
bution of the phloem groups after a period of extensive growth in the perimedullary 
zone. X 63. 
