308 Geographical Distribution of Plants 
thought singular that he should have been elected a “correspondant” 
of the Académie des Sciences in the section of Botany, but it is not 
surprising that his work in Geographical Botany made the botanists 
anxious to claim him. His heart went with them. “It has always 
pleased me,” he tells us, “to exalt plants in the scale of organised 
beings.” And he declares that he finds “any proposition more easily 
tested in botanical works? than in zoological.” 
In the Introductory Essay Hooker dwelt on the “continuous 
current of vegetation from Scandinavia to Tasmania’,” but finds 
little evidence of one in the reverse direction. “In the New World, 
Arctic, Scandinavian, and North American genera and species are 
continuously extended from the north to the south temperate and 
even Antarctic zones; but scarcely one Antarctic species, or even 
genus advances north beyond the Gulf of Mexico.” Hooker con- 
sidered that this negatived “the idea that the Southern and Northern 
Floras have had common origin within comparatively modern geo- 
logical epochs’.” This is no doubt a correct conclusion. But it is 
difficult to explain on Darwin’s view alone, of alternating cold in 
the two hemispheres, the preponderant migration from the north to 
the south. He suggests, therefore, that it “is due to the greater 
extent of land in the north and to the northern forms...having... 
been advanced through natural selection and competition to a higher 
stage of perfection or dominating power®.” The present state of the 
Flora of New Zealand affords a striking illustration of the correctness 
of this view. It is poor in species, numbering only some 1400, of 
which three-fourths are endemic. They seem however quite unable 
to resist the invasion of new comers and already 600 species of foreign 
origin have succeeded in establishing themselves. 
If we accept the general configuration of the earth’s surface as 
permanent a continuous and progressive dispersal of species from 
the centre to the circumference, ie. southwards, seems inevitable. 
If an observer were placed above a point in St George’s Channel 
from which one half of the globe was visible he would see the greatest 
possible quantity of land spread out in a sort of stellate figure. The 
maritime supremacy of the English race has perhaps flowed from the 
central position of its home. That such a disposition would facilitate” 
a centrifugal migration of land organisms is at any rate obvious, and 
fluctuating conditions of climate operating from the pole would 
supply an effective means of propulsion. As these became more 
1 Life and Letters, 1. p. 98. 2 Ibid. 1. p. 99. 
3 Introductory Essay to the Flora of Tasmania, London, 1859.. Reprinted from the 
Botany of the Antarctic Expedition, Part u1., Flora of Tasmania, Vol. 1. p. ciii. 
4 p. civ. 5 Loc. cit. 
5 Origin of Species (6th edit.), p. 340; cf. also Life and Letters, u. p. 142. 
