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 alge 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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