540 
Reed,—On the Anatomy of some Tubers . 
pith is composed of large parenchymatous cells, and these also contain large 
quantities of starch grains. The outer surface of the stolon is covered by 
a single-layered epidermis, the cells of which have a thin cuticle on their 
outer surface. There is no development of cork on the stolon. 
The change from underground stolon to tuber is quite abrupt; there is 
no gradual transition from stolon to tuber such as obtains in the case of 
Diagram I. M., medulla. M.Ph , medullary phloem. P-xy., protoxylem. xy., xylem. 
Ph phloem. 
Helianthus tuberosus. This circumstance makes it difficult to trace clearly 
the course of the vascular bundles from stolon to tuber. 
Passing from the stolon to the base of the tuber it will be seen 
(Diagram I, Fig. i) that the ring of bundles begins to lose its definite 
arrangement into groups, as seen in transverse section, and to become 
‘ sprayed ’ outwards (Diagram I, Figs. 2 and 3 ). Thus it will be seen that 
a transverse section of a tuber at this level would cut the vascular elements 
in an oblique direction. Still farther in the tuber the ‘spraying’ has gone 
