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and liuman beings immunize most readily, while older ones frequently 

 fail almost entirely. Interestingly enough plants seem to be strangely 

 similar in this respect^ and the thing that stimulates cellular activity 

 for defensive purposes (immunity) apparently stimulates growth and 

 wound repair. The thing that stimulates most actively for a special 

 purpose is the thing itself, the best stimulant for wound repair being 

 the simple injury. To illustrate briefly: In my work last summer I 

 came in contact with two enemies, yellow jackets and copperheads. 

 The copperhead stimulated me to carry a club in defense, while for the 

 yellow jacket the club was of little value and 1 ratlier preferred carbon 

 bisulphide. Had I ignored my senses and allowed nature full sway, 

 as a tree does, the snake would have injected his venom and the yellow 

 jacket his toxin, and my cells would have accepted their only alter- 

 native and proceeded at once to build up a specific defense, after which 

 they would have been in better shape for development, providing the 

 poison would not have been so great as to prove fatal. Injury to a 

 tree certainly does stimulate wound repair, defense and growth. It is 

 well known that trees with many transplantings, root injuries, trans- 

 plant niueli more readily, and the nurserymen use this method of stim- 

 ulation as a routine procedure. I learn in Florida tliat in order to 

 trans])lant a good size palmetto, they are in the habit of digging' down 

 on one side and cutting the roots the year before removal. It will then 

 transplant more readily. Pruning has the same cell stimulating effect 

 if done at a time that will retain the stored nutrition. An attack of 

 disease just as surelv stimulates cellular activitv and "-owtli but it 

 is too frequentl}' followed by disaster. 



We have all lieard of driving rusty nails into trees (thinking the 

 iron produced the beneficial results), cutting a slit in the bark of the 

 limibs and trunk for "bark bound" so called, etc., all of which have 

 stimulating effects with more or less permanent injury to the treee. 

 ^^'ho knows but what the sap sucker, with his ability to dig into llic 

 bark and extract a piece of cauiibium. was not sent to us to aid in pre- 

 serving our trees by stimulating new growth? 



In my work last summer trees that were subjected to slight injury 

 before hand apparently acce])ted a larger proportion of grafts. I will 

 briefly cite two .specific illustrations. A little butternut tree located 

 near the house was the object of my efforts for over two years. Dur- 

 ing" my illness I frequently went out and pruned a few branches or put 

 on a few buds. Something would happen to me and possibly I would 



