362 
Willis ,— The Sources and Distribution of the 
Of the remaining families of the New Zealand flora, nine at least are 
composed of so few species, and range so uniformly along the whole length 
of the islands, that age and area will not permit of any deductions as to 
their source. There thus remain twenty-six families. Of these several, e.g. 
Orchidaceae, can be easily separated into two well-marked groups, one 
commencing at the North Cape and ranging to a greater or less distance 
southwards in New Zealand, and the other commencing at the south end 
and ranging northwards, so that it seems justifiable to infer that these 
families have invaded New Zealand both from the north and from the south. 
But when these have been taken out, there still remain a few families like 
Stackhousiaceae, Epacridaceae, and Myrsinaceae (Australian families) which 
have a fairly marked maximum in the middle of New Zealand, and range 
from that to the north and to the south. There is little or no evidence to show 
by which (if either) of the two routes already discussed these plants arrived. 
From what has been said above, it will be clear that whilst the applica¬ 
tion of age and area to the problem may lead to fairly good evidence as to 
what has happened in the past in New Zealand itself, the hypothesis cannot 
be used in its present early stages to give evidence for or against the question 
of the relative age of trees, shrubs, and herbs. This question is really a very 
large one, and rendered much more complex by such questions as polyphy- 
letic origin, &c. 
Age tends to extinguish Old Species? 
Like the question of the greater age of woody vegetation, this is 
a very large problem, and I shall simply endeavour to show that it is 
a somewhat complex one, not easily to be solved off-hand. Dr. Sinnott 
proposes an hypothesis to the effect that ‘ the longer a successfully invading 
species remains in an isolated area . . . the less common it tends to become 
until it is actually “ swamped ” out of existence—quite the reverse of the “ age 
and area” idea’. He suggests that ‘ some may simply be exterminated 
outright, and some by continual crossing with new forms may ultimately 
lose their specific identity’. 
There is no doubt that the fact that genera are common in these floras 
with endemics only, and no wides, is a feature which requires explanation ; 
but as the genera with endemics only behave exactly like those which also 
contain wides, or like the endemic genera, the fact that it cannot at the 
moment be explained does not in the least militate against the hypothesis 
of age and area. Age and area may not agree with other views as to this 
or that, but it must be remembered that it is based upon very clear and 
definite figures, which must either be controverted or explained in some 
other way—they are far too striking to go without any explanation. It is 
somewhat difficult to controvert figures which simply represent bald facts, 
and if age and area be not accepted, it is consequently necessary to have 
