at any such connection should have existed except at a very
remote period. But if we have to go back so far for an explanation, a much
simpler one presents itself, and one more in accordance with what we have
learnt of the general permanence of deep oceans and the great changes that
have taken place {526} in the distribution of all forms of life. Just as we
explain the presence of marsupials in Australia and America and of
Centetidae in Madagascar and the Antilles, by the preservation in these
localities of remnants of once wide-spread types, so we should prefer to
consider the few genera common to Australia and South Africa as remnants of
an ancient vegetation, once spread over the northern hemisphere, driven
southward by the pressure of more specialised types, and now finding a
refuge in these two widely separated southern lands. It is suggestive of
such an explanation that these genera are either of very ancient groups--as
Conifers and Cycads--or plants of low organisation as the Restiaceae--or of
world-wide distribution, as Melanthaceae.

_The Endemic Genera of Plants in New Zealand._--Returning now to the New
Zealand flora, with which we are more especially concerned, there only
remains to be considered the peculiar or endemic genera which characterise
it. These are thirty-two in number, and are mostly very isolated. A few
have affinities with Arctic groups, others with Himalayan, or Australian
genera; several are tropical forms, but the majority appear to be
altogether peculiar types of world-wide groups--as Leguminosae,
Saxifrageae, Compositae, Orchideae, &c. We must evidently trace back these
peculiar forms to the earliest immigrants, either from the north or from
the south; and the great antiquity we are obliged to give to New
Zealand--an antiquity supported by every feature in its fauna and flora, no
less than by its geological structure, and its extinct forms of
life[143]--affords ample time for the changes in the general distribution
of plants, and for those due to isolation and modification under {527} the
influence of changed conditions, which are manifested by the extreme
peculiarity of many of these interesting endemic forms.

_The Absence of Southern Types from the Northern Hemisphere._--We have now
only to notice the singular want of reciprocity in the migrations of
northern and southern types of vegetation. In return for the vast number of
European plants which have reached Australia, not one single Au