chap, xxiv.] SUMMARY AND CONCLUSION. 
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 
which 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 where 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 
