456 
ISLAND LIFE 
[part II. 
hypothesis, which seems necessary to explain the occurrence of 
so many species of these birds in a small area but of which w T e 
have no independent proof. There are, however, some other 
facts which would be explained by it, as the presence of three 
peculiar but allied genera of starlings, the three species of 
parrots of the genus Nestor, and the six distinct rails of the 
genus Ocydromus, as well as the numerous species in some cf 
the peculiar New Zealand genera of plants, which seem less 
likely to have been developed in a single area than when 
isolated, and thus preserved from the counteracting influence 
of intercrossing. 
In the present state of our knowledge these seem all the 
conclusions we can arrive at from a study of the New Zealand 
fauna; but as we fortunately possess a very full and accurate 
knowledge of the flora of New Zealand, as well as of that of 
Australia and the south temperate lands generally, it will be 
well to see how far these conclusions are supported by the facts 
of plant distribution, and what further indications they afford us 
of the early history of these most interesting countries. This 
inquiry is of sufficient importance to occupy a separate chapter. 
