chap, xxiii.] ARCTIC PLANTS IN NEW ZEALAND. 
479 
Chinese, American, Malayan, and finally Australian and Ant- 
arctic types ; but whereas these are all, more or less, local 
assemblages, the Scandinavian asserts his prerogative of 
ubiquity from Britain to beyond its antipodes.” 1 
It is impossible to place the main facts more forcibly before 
the reader than in the above striking passage. It shows clearly 
that this portion of the New Zealand flora is due to wide-spread 
causes which have acted with even greater effect in other south 
temperate lands, and that in order to explain its origin we must 
grapple with the entire problem of the transfer of the north 
temperate flora to the southern hemisphere. Taking, therefore, 
the facts as given by Sir Joseph Hooker in the works already 
referred to, I shall discuss the whole question broadly, and shall 
endeavour to point out the general laws and subordinate causes 
that, in my opinion, have been at work in bringing about the 
anomalous phenomena of distribution he has done so much 
to make known and to elucidate. 
Aggressive Power of the Scandinavian Flora . — The first impor- 
tant fact bearing upon this question is the wonderful aggressive 
and colonising power of the Scandinavian flora, as shown by the 
way in which it establishes itself in any temperate country to 
which it may gain access. About 150 species have thus estab- 
lished themselves in New Zealand, often taking possession of large 
tracts of country ; about the same number are found in Australia, 
and nearly as many in the Atlantic states of America, where 
they form the commonest weeds. Whether or not we accept 
Mr. Darwin’s explanation of this power as due to development 
in the most extensive land area of the globe where competition 
has been most severe and long-continued, the fact of the exist- 
ence of this power remains, and we can see how important an 
agent it must be in the formation of the floras of any lands to 
which these aggressive plants have been able to gain access. 
But not only are these plants pre-eminently capable of holding 
their own in any temperate country in the world, but they also 
have exceptional powers of migration and dispersal over seas and 
oceans. This is especially well shown by the case of the Azores, 
where no less than 400 out of a total of 478 flowering plants are 
1 Introductory Essay On the Flora of Australia , p. 103. 
