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Show 476 ISLAND LIFE. (PART II. and the explanation of this fact given by Mr. Darwin-that they are prevented doing so by the competition of better adapted forms-is held to be sufficient. In this particular case, however, we have some very remarkable evidence of the fact of their non-adaptation. The intercourse between New Zealand and Europe has been the means of introducing a host of common European plants,-more than 150 in number, as enumerated at the end of the second volume of the I-Iandboolc / yet, although tbe intercourse with Australia has probably been greater, only two or three Australian plants have similarly established themselves. More remarkable still, Sir Joseph Hooker states : "I am informed that the late Mr. Bidwell habitually scattered Australian seeds during his extensive travels in New Zealand." We may be pretty sure that seeds of such excessively common and characteristic groups as Acacia and Eucalyptus would be among those so scattered, yet we have no record of any plants of these or other peculiar Australian genera ever having been found wild, still less of their having spread and taken possession of the soil in the way that many European plants have done. We are, then, entitled to conclude that the plants above referred to have not established themselves in New Zealand (although their seeds may have reached it) because they could not successfully compete with the indigenous flora which was already well established and better adapted to the conditions of climate and of the organic environment. This explanation is so perfectly in accordance with a large body of well-known facts, including that which is known to every one-bow few of our oldest and hardiest garden plants ever run wild-that the objection above stated will, I feel convinced, have no real wejght with any naturaljsts who have paid attention to this class of questions. CHAPTER XXIII. ON THE ARCTIC ELEMENT IN SOUTH TEMPERATE FLORAS. European S~)ecies and genera of plants in the southern hemisphercAggress. Ive power of the Scanuinavian flora-Means by which plants have migrated from north to south-Newly moved soil as a:ffordinO' temporary stations to migrating plants-Elevation and depression of the snow-line as aiding the migration of plants-Chano-es of climate favourable to migration:-The migration from north to :outh has been long going on-Geological changes as aiding migration-Proofs of m~grntion by way of the Andes-Proofs of migration by way of the Hu~alaya~ and Southern Asia-Proofs of migration by way of the Afncan highlands-Supposed connection of South Africa and Australia -Tho endemic genera of plants in New Zealand-The absence o£ southern types from the northern hemisphere-Concluding· remarks on the New Zealand and south temperate floras. WE have now to deal with another portion of the New Zealand flora which presents perhaps equal difficulties-that which appears to have been derived from remote parts of the north and south temperate zones; and this will lead us to inquire into the origin of the northern or Arctic element in all the south temperate floras. More than one-third of the entire number of New Zealand genera (115) are found also in Europe, and even fifty-eight species are identical in these remote parts of the world. Temperate South America has seventy-four genera in common with New Zealand, and there are even eleven species identicc:~l in the two countries, as well as thirty-two which are close allies or representative species. A considerable number of these northern |