CHAP, XXIV.] SUMMARY AND COxXCLUSION. 



511 



it. From these geological and physical facts, and the known 

 powers of dispersal of plants, all the main features, and many of 

 the detailed peculiarities of the New Zealand flora are shown 

 necessarily to result. 



Our last chapter is devoted to a wider, and if possible more 

 interesting subject — the origin of the European element in the 

 floras of New Zealand and Australia, and also in those of South 

 America and South Africa. This is so especially a botanical 

 question, that it was with some diffidence I entered upon it, yet 

 it arose so naturally from the study of the New Zealand and 

 Australian floras, and seemed to have so much light thrown 

 upon it by our preliminary studies as to changes of climate and 

 the causes which have favoured the distribution of plants, that 

 I felt my work would be incomplete without a consideration 

 of it. The subject will be so fresh in the reader's mind that 

 a complete summary of it is unnecessary. I venture to think, 

 however, that I have shown, not only the several routes by 

 w^hich the northern plants have reached the various southern 

 lands, but have pointed out the special aids to their migration, 

 and the motive power which has urged them on. 



In this discussion, if no wliere else, will be found a complete 

 justification of that lengthy investigation of the exact nature of 

 past changes of climate, which to some readers may have 

 seemed unnecessary and unsuited to such a work as the present. 

 Without the clear and definite conclusions arrived at by that 

 discussion, and those equally important views as to the per- 

 manence of the great features of the earth's surface, and the 

 wonderful dispersive powers of plants which have been so 

 frequently brought before us in our studies of insular floras, 

 I should not have ventured to attack the wide and difficult 

 problem of the northern element in southern floras. 



In concluding a work dealing with subjects which have oc- 

 cupied my attention for many years, I trust that the reader who 

 has followed me throughout will be imbued with the conviction 

 that ever presses upon myself, of the complete interdependence 

 of organic and inorganic nature. Not only does the marvellous 

 structure of each organised being involve the whole past history 



