io 



Fig. 5. Sections through Grafts of Plum. 



With this photograph showing the microscopic anatomy of the 

 tissues before us, it is harder than ever to see where a certain tree 

 ceases to be cherry and begins to be plum. The cells are so in- 

 differently mixed that one is tempted to believe that the specific 

 physiological character may be blended at the same time. It 

 has long been the dream of gardeners to produce new kinds of plants 

 by the graft union of diverse cions and stocks. Do not our present 

 observations show the reasonableness of such endeavors? 



Certainly not. No matter how closely the two kinds of cells may 

 lie against one another, their contents are never mingled in the pro- 

 duction of a new cell. Each new cell is produced by the division of 

 some older single cell, never by the fusion of two parent cells. Let 

 us suppose that in figure 7 the black cells are those of the quince 

 stock, while the white cells are those of the pear cion. As each 



