G. M. Tuomson.—On the Origin of the New Zealand Flora. 491 
Stated concisely, his conclusions are that for a long period of time Aus- 
tralia was divided into two islands, a western and an eastern. In the 
former of these, the peculiarly characteristic Australian genera, both of 
plants and animals, originated. The eastern island stretched in a long 
narrow line from the tropics to the south of Tasmania, and in connection 
with its tropical portion there was probably a prolongation of New Zealand 
to the north-west. By this bridge, with its southerly and south-easterly 
tamifications, a stream of immigrants set in from the tropical regions 
further north, so that numerous genera and even species of plants, as well 
as some animals, were spread along both shores of the sea separating New 
Zealand from Australia. The subsequent depression of the northern area 
caused a separation of New Zealand from tropical Australia, while the 
elevation of the comparatively shallow sea separating the western from the 
eastern island, united these two into the great continental island of Aus- 
tralia, over the whole of which the peculiar western forms spread rapidly, 
a apparently at a much greater rate than the tropical and eastern species 
. While the presence of the Australian, Asiatic, and Polynesian elements 
in — New Zealand flora are traceable to this former land connection, the 
antarctic and South American forms are believed to be due to immigration 
from outlying islands and extensions of land to the south, and the Euro- 
Pean, or more correctly the arctic element, is explained by the extraordin- 
arily aggressive character of the so-called Scandinavian flora, which has 
enabled it to push its colonists over the three great southern areas, ViZ., 
South Africa, South America and Australasia. 
Mr. Wallace’s explanations of the origin of our flora must commend 
themselves as extremely satisfactory to every one capable of judging of the 
questions under consideration. Our subsequent knowledge may modify 
some of his conclusions to a slight extent, but it is by the publication of 
such hypotheses and theories, and the application of them for the solution 
of difficult problems, that correct ideas are most rapidly attained. Not 
ouly is our interest heightened by such speculations, but definite issues are 
‘Placed before our minds, and we are enabled to judge more and more accur- 
ately of these, and to recognize how vast the field to be traversed is. Itis 
well to bear in mind that as our stock of facts increases, so also does our 
nowledge of our ignorance, and that the latter often increases ina much — 
_ More rapid ratio than the former. We hegin by diseussing ¢ a ee 
ere perhaps that wo have —— information ac d to 
