496 



ISLAND LIFE. 



[PAUT ]I. 



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 suflicient 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* 



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 

 so'.ving themselves and becoming- naturahsed on the Neil gherrie mountains 

 in the southern part of the Indian Peninsula, though an exception to the 

 rule of the inability of Austrah'an plants to become naturahsed in the 

 Northern Hemisphere, is yet quite in harmony with the hypothesis here 

 advocated. For not only is the cHmate 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 tlms enabled to 

 compete with those of the Indian Peninsula highlands with a fair chance 

 of success. 



