16 DARWINISM 



wild in New Zealand. But Sir Joseph Hooker informs us 

 that the late Mr. Bidwell habitually scattered Australian seeds 

 during his extensive travels in New Zealand, yet only two or 

 three Australian plants appear to have established themselves 

 in that country, and these only in cultivated or newly moved 

 soil. 



These few illustrations sufficiently show that all the plants 

 of a country are, as De Candolle says, at war with each other, 

 each one struggling to occupy ground at the expense of its 

 neighbour. But, besides this direct competition, there is one 

 not less powerful arising from the exposure of almost all plants 

 to destruction by animals. The buds are destroyed by birds, 

 the leaves by caterpillars, the seeds by weevils ; some insects 

 bore into the trunk, others burrow in the twigs and leaves ; 

 slugs devour the young seedlings and the tender shoots, wire- 

 worms gnaw the roots. Herbivorous mammals devour many 

 species bodily, while some uproot and devour the buried 

 tubers. 



In animals, it is the eggs or the very young that suffer most 

 from their various enemies ; in plants, the tender seedlings 

 when they first appear above the ground. To illustrate this 

 latter point Mr. Darwin cleared and dug a piece of ground 

 three feet long and two feet wide, and then marked all the 

 seedlings of weeds and other plants which came up, noting 

 what became of them. The total number was 357, and out 

 of these no less than 295 were destroyed by slugs and insects. 

 The direct strife of plant with plant is almost equally fatal 

 when the stronger are allowed to smother the weaker. When 

 turf is mown or closely browsed by animals, a number of 

 strong and weak plants live together, because none are allowed 

 to grow much beyond the rest ; but Mr. Darwin found that 

 when the plants which compose such turf are allowed to 

 grow up freely, the stronger kill the weaker. In a plot of 

 turf three feet by four, twenty distinct species of plants were 

 found to be growing, and no less than nine of these perished 

 altogether when the other species were allowed to grow up 

 to their full size. 1 



But besides having to protect themselves against competing 

 plants and against destructive animals, there is a yet deadlier 

 1 The Origin of Species, p. 53. 



