STEM- AND TOP-GROWTH, ETC. 29 



knowledge relative to sap-movement. This is specially 

 true of the descending movement of assimilated food. As 

 an example, if a label wire is left on the stem of a young 



PIG. 11. Stem of young tree girdled by wire. (After Bailey.) 



tree we find that it soon is sunk into the bark and wood, 

 and the part above enlarges, while the stem below seems to 

 grow smaller, as shown in Fig. 11. 



