49G 
ISLAND LIFE. 
[rAirr ii. 
greater hardiness of the former, from having been developed in 
a colder region, and one where alpine and arctic conditions ex- 
tensively prevail ; whereas the southern floras have been mainly 
developed in mild regions to which they have been altogether 
confined. While the northern plants have been driven north or 
south by each succeeding change of climate, the southern 
species have undergone comparatively slight changes of this 
nature, owing to the areas they occupy being unconnected with 
the. ice-bearing Antarctic continent. It follows, that whereas 
the northern plants find in all these southern lands a milder and 
more equable climate than that to which they have been accus- 
tomed, and are thus often able to grow and flourish even more 
vigorously than in their native land, the southern plants would 
find in almost every part of Europe, North America or 
Northern Asia, a more severe and less equable climate, with 
winters that usually prove fatal to them even under cultivation. 
These causes, taken separately, are very powerful, but when 
combined they must, I think, be held to be amply sufficient to 
explain why examples of the typical southern vegetation are 
almost unknown in the north temperate zone, while a very few 
of them have extended so far as the northern tropic . 1 
Concluding remarks on the last two chapters . — Our inquiry 
into the external relations and probable origin of the fauna 
and flora of New Zealand, has thus led us on to a general 
1 The fact stated in the last edition of the Origin of Species (p. 340) on 
the authority of Sir Joseph Hooker, that Australian plants are rapidly 
sowing themselves and becoming naturalised on the Neilgherrie mountains 
in the southern part of the Indian Peninsula, though an exception to the 
rule of the inability of Australian plants to become naturalised in the 
Northern Hemisphere, is yet quite in harmony with the hypothesis here 
advocated. For not only is the climate of the Neilgherries more favour- 
able to Australian plants than any part of the North Temperate zone, but 
the entire Indian Peninsula has existed for unknown ages as an island and 
thus possesses the “ insular ” characteristic of a comparatively poor and 
less developed flora and fauna as compared with the truly “continental” 
Malayan and Himalayan regions. Australian plants are thus enabled to 
compete with those of the Indian Peninsula highlands with a fair chance 
of success. 
