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 
