ied into new species. It is thus quite
intelligible why only three species of orchids are identical in Australia
and New Zealand, although their minute and abundant seeds must be dispersed
by the wind almost as readily as the spores of ferns.

Another specialised group--the Scrophularineae--abounds in New Zealand,
where there are sixty-two species; but though almost all the genera are
Australian only three species are so. Here, too, the seeds are usually very
small, and the powers of dispersal great, as shown by several European
genera--Veronica, Euphrasia, and Limosella, being found in the southern
hemisphere.

Looking at the whole series of these Australo-New Zealand plants, we find
the most highly specialised groups--Compositae, Scrophularineae,
Orchideae--with a small proportion of identical species (one-thirteenth to
one twentieth), the less highly specialised--Ranunculaceae, Onagrariae and
Ericeae--with a higher proportion (one-ninth to one-sixth), and the least
specialised--Junceae, {506} Cyperaceae and Gramineae--with the high
proportion in each case of one-fourth. These nine are the most important
New Zealand orders which contain species common to that country and
Australia and confined to them; and the marked correspondence they show
between high specialisation and want of _specific_ identity, while the
_generic_ identity is in all cases approximately equal, points to the
conclusion that the means of diffusion are, in almost all plants ample,
when long periods of time are concerned, and that diversities in this
respect are not so important in determining the peculiar character of a
derived flora, as adaptability to varied conditions, great powers of
multiplication, and inherent vigour of constitution. This point will have
to be more fully discussed in treating of the origin of the Antarctic and
north temperate members of the New Zealand flora.

_Summary and Conclusion on the New Zealand Flora._--Confining ourselves
strictly to the direct relations between the plants of New Zealand and of
Australia, as I have done in the preceding discussion, I think I may claim
to have shown that the union between the two countries in the latter part
of the Secondary epoch at a time when Eastern Australia was widely
separated from Western Australia (as shown by its geological formation and
by the contour of the sea-bottom) does sufficiently account for all the
main features of the New Zealand flora. It shows why the basis of