CHAPTER XXIII. 



ON THE ARCTIC ELEMENT IN SOUTH TEMPERATE FLORAS. 



European species and genera of plants in the southern hemisphere — 

 Aggressive power of the Scandinavian flora — Means by which plants 

 have migrated from north to south — Newly moved soil as affording 

 temporary stations to migrating plants— Elevation and depression of 

 the snow-line as aiding the migration of plants — Changes of climate 

 favourable to migration — The migration from north to south has been 

 long going on — Geological changes as aiding migration — Proofs of 

 migration by way of the Andes — Proofs of migration by way of the 

 Himalayas and Southern Asia — Proofs of migration by way of the 

 African highlands — Supposed connection of South Africa and Australia 

 ■ — The endemic genera of plants in New Zealand — The absence of 

 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. Tem- 

 perate South America has seventy-four genera in common with 

 New Zealand, and there are even eleven species identical in the 

 two countries, as well as thirty-two which are close allies or 

 representative species. A considerable number of these northern 



