On Evil in Small Doses 



Whether in the mosses and liverworts it is still a parasite 

 or of some use seems to be still rather uncertain. 



Indeed if we take the whole complex series of asso- 

 ciations with which we have been concerned in this 

 book, something of the same kind seems to happen 

 continually. 



The invasion of algae by bacteria or of others by 

 fungi seemed at first to be altogether distressful. But 

 it resulted in the great and most useful group of 

 lichens. 



Then, again, when the first rude mosses or ferns took 

 to living on dry land, the conditions of strong sunshine 

 and exposure must have seemed to them very hard and 

 destructive to all vigorous and healthy living. 



Yet the stimulus of these new evils led to a vigorous 

 response which has resulted in the world's colour be- 

 coming green through its nearly continuous covering 

 of vegetable life. 



The first visits of insects to cones and the pilfering of 

 spores by them could surely have been nothing at first 

 but an unmitigated nuisance, involving serious loss of 

 invaluable material. 



What has been the result ? 



The development of the world of flowers as well as 

 of those hovering crowds of dainty and complexly 

 fashioned butterflies, bees, and hoverflies who have 

 become servants and yet selectors of the best and most 

 beautiful blossoms. 



Even when woods, grass-lands, and scrubs had so 

 covered the world's surface that deer, cattle, goats, and 

 other herbivorous animals had developed into enormous 

 armies, the destruction caused by them is not always, as 

 we have seen, without redeeming features. It has not 

 only led to valuable substances, such as resins, india- 

 rubbers, drugs, and poisons being formed, but some- 



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