248 THE ACTION OF THE LIVING CELL 



Wallace has recently made a careful histological ex- 

 amination of such outgrowths, following the action of 

 ethylene on the buds and stems of the apple, Pyrus 

 Malus, Var. Transparent. Under the action of 1% 

 ethylene in air, it was observed that the walls of the 

 cells were corroded away by a sort of solution process 

 (autolysis) induced by the ethylene. Individual cells 

 and groups of cells then separated from the tissues. 

 This process involves all the living elements between 

 the cambium and phellogen, and the cells may be 

 stimulated to division or become hypertrophied. In 

 some instances cell counts in the intumescences pro- 

 duced at the ends of cutting showed a thirty-three 

 per cent increment in numbers. 



It is interesting to compare these findings of Wal- 

 lace with the writer's observations on the prolonged 

 irritation of the gastric mucosa by mustard. In the 

 latter case, it may be remembered that a somewhat 

 analogous situation was found, the mustard oils first 

 causing a degeneration and loosening of the mucosal 

 cells, whereas later even though the mustard was re- 

 moved, the underlying tissues were found to show 

 evidences of active proliferation. It was deduced 

 (page 33) from the experimental findings that the 

 proliferation and other changes were secondary 

 changes which arose not from the direct action of the 

 mustard but because of the presence of cytost lib- 

 erated from the mucosal cells injured by the mus- 

 tard. 



If we transfer this concept to the problem of plant 

 intumescences, we may imagine the phenomena ob- 

 served by Wallace to take place as follows : The plant 

 cells in contact with the ethylene suffer injury in much 



