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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