On Evil in Small Doses 



first or saprophytic fungi to become a parasite. This 

 seems to have happened in the case of the very 

 common Cladosporium herbarium, which may become 

 parasitic on apple trees.^^ 



A very interesting experiment was also carried out 

 by Mr. Massee. He used a certain destructive pest of 

 the cucumber and trained it to live on decoctions of 

 cucumber leaves. When it had got well accustomed 

 to these conditions, he chose some begonias (the fungus 

 never attacks begonias, which belong to a different 

 group of plants). He first injected decoctions of 

 cucumber leaf under the epidermis of the begonia leaf, 

 and then placed the spores of his trained fungus upon 

 the epidermis. 



The germ-tubes of the fungus entered the begonia 

 stomata, discovered the cucumber decoction, and lived 

 on it ; but after a time they began to attack the leaf cells 

 of the begonia, and soon became begonia parasites. 

 It is a difficult moral question as to whether this was 

 justifiable, but it is a very interesting result.^^ 



All these facts as to the ways of fungi throw very 

 great light on the battle of secretions that must 

 ensue whenever a live leaf-cell is threatened by some 

 enemy. 



There is one remarkable instance in which flowering 

 plants have not only conquered their adversaries but 

 have even enslaved them or turned them into useful 

 bond-servants. 



The root-fungus, or Mycorhiza, of flowering plants 

 was surely at one time a mere parasitic foe, but it is 

 now extremely useful, even to trees, which utilise the 

 fungus's powers of absorption and rapid growth to their 

 own advantage. 



Almost all trees, numbers of shrubs and flowering 

 plants, ferns and their prothallia, possess this Mycorhiza. 



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