CHAPTER VIII 



AGE AND AREA {contd.). INVASIONS 



The acceptance of the hypothesis of Age and Area involves 

 various changes in our way of looking at many problems of 

 geographical distribution, and of other branches of Botany, and 

 we must go on to further illustrate its (published) implications 

 and possibilities. The facts upon which it is based, as illustrated 

 by the preceding two chapters, are so clear and so definite that 

 they cannot go without an explanation; either one must accept 

 Age and Area, or one must find some other explanation for them 

 — a thing that no one has yet attempted. 



If the distribution of plants about the world has been very 

 largely the result of their age, it is clear that it should be com- 

 paratively easy to make predictions about it, as has already 

 been shown. The very first prediction I employed (127) was the 

 following, which will serve as a text for this chapter : 



Let W be a species arriving at the centre of New Zealand from 

 abroad, and following the rule exactly in its dispersal (there is 

 reason to suppose that it would not do so unless the direction were 

 east and west, not north and south as in New Zealand; but this 

 does not affect the prediction). Such exactness probably never 



