The Individual Plant 



experiments to trace this process of self-surgery. Leaves 

 were cut in various ways or pieces punched out of them, 

 and sometimes they were only bruised at one point. ^ 



In many cases, everything outside the injured tissue 

 was deliberately sacrificed, the living protoplasm acting 

 like an army whose outpost Hne has been suddenly 

 surprised, and which deliberately abandons its advanced 

 posts and entrenches itself behind a new layer of im- 

 provised cork cells. Something of the same sort happens 

 regularly before the fall of the leaves in autumn. Not 

 only a cork scar is formed across the bases of the leaf 

 stalks, but a special separation layer is formed outside 

 the cork, and the dead leaf drops away from the clean, 

 corked-in scar. Many curious cases, in which injured 

 or worn out parts of the stem itself have been deliber- 

 ately cut off by cork scars and thrown away, have also 

 been described.^ There are other well-known cases in 

 which one is much impressed by the readiness for any 

 emergency of every live cell in the plant body. 



In the stem of Liquidambar (or Balsam of Tolu), for 

 instance, the younger wood cells will be peacefully per- 

 forming their usual duty of assisting to raise the sap or 

 of filling themselves with temporary stores of starch or 

 other reserve food material. A sudden emergency arises, 

 for some one has made a deep cut or slash through the 

 bark and into the young growing wood tissue. 



The cells at once begin to secrete resin, which at 

 first fills the intercellular spaces, forming small canals 

 or ducts ; then the cells begin to break down, and a net- 

 work of such resin canals is formed, which pours an 

 abundance of secretion over the wounded surface, com- 

 pletely covering it over and sealing it up. Other cells, in 

 the cortex, at once begin to make a cork cushion, which 

 gradually and slowly grows inward over the wound.^ 



The future of and the claims upon every living cell 

 between the dead outside cork and the dead heart wood 



154 



