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Monilia disease of cherry trees is an exception, for the fungus can 

 affect the plant without the latter being injured. Spores of the fungus 

 are blown by the wind or brought by insects on the pestles of the flowers 

 and there germinate. From the first flower the whole branch is attacked 

 and dies. The same fungus forms a rot on peaches and a blight on the 

 branches of the peach tree. It is not necessary that the skin be injured 

 beforehand. I could mention several other instances of fungi which 

 attack especially fruit trees, but the ones mentioned are more generally 

 known. 



In nearly every case the fruit must be injured before the fungi can 

 establish themselves. 



(3) Animals — In the third place I have mentioned animals, but speak- 

 ing of animals I do not mean rabbits or dogs, but more especially 

 insects. This is, however, so far away from my own line of study that 1 

 will only mention a few names, names which I am sure are quite familiar to 

 you, such as Grapholitha woeberiania, Schiff ; Eccoptogaster Pruni, Ratz. 



(4) Other causes — Under the fourth heading we can bring all cases 

 not yet mentioned before. So gummosis is caused by the presence of too 

 much food in one spot, which causes the death of a number of cells. Many 

 other cases are on record in which gummosis produced through pressing, 

 cutting, supplanting or frost, but all can be brought back to the presence 

 of wounds, as in the case of graft, where the dying cells cause gummosis. 

 Cherry flowers strongly damaged by frost show gummosis on the ime 

 between the dead and living part of the petioles. 



At the time when I conducted these investigations I was very much 

 impressed by the fact that fruit trees were so easily killed by bacteria and 

 similar organisms. To my mind a tree had been something lasting, a 

 thing so substantial that it did not follow the rules of nature to which we 

 human beings are subject. It did not make any difference to a tree 

 whether a name was cut in it, a piece of the bark taken away or leaves 

 torn off, the tree continued to grow as if nothing had happened. How 

 different such a tree was in comparison with us, with our weak constitut- 

 tions and our continual dread of bacteria. When we cut ourselves or sustain 

 some other slight injury, blood poisoning is smiling in our faces, and we 

 have to apply numerous disinfectants to keep the crowds of bacteria out- 

 side the porch. And, now, it appeared that a tree was in the same poor 

 condition as we are, that a ti-ee is also besieged by untold bacteria which 

 just wait for an opportunity to take the very life out of it. In the cases 

 of fruit tree diseases already stated we find generally mentioned that 

 organisms got in through small wounds, established themselves on some 



