
1899] ORIGIN OF AUSTRALIAN FLORA 203 
flora necessarily have been peculiar and isolated? If there is one 
point on which students of biological geography are agreed it is this, 
that the antarctic continent must formerly have extended considerably 
farther north than it does now, an extension which permitted the 
migration of certain animal forms from South America to New 
Zealand, and must equally have allowed the southward migration of 
South American and New Zealand plants. This stocking of the 
antarctic continent may have occurred comparatively early in Tertiary 
times, and so long as glaciation did not supervene, a large and by no 
means peculiar or isolated flora may have flourished in the antarctic 
continent. But now, communication with lands lying to the north 
being cut off, if a glacial period occurred, the result in the southern 
hemisphere would be very different from one in the northern, for 
while in the latter there would be nothing to hinder the southward 
migration of plants, their escape from the antarctic continent would 
be cut off by the ocean, and since all antarctic lands must have been 
covered with an ice-cap during a glacial period, all, or almost all, but 
the lowliest organisms must necessarily have perished. Obviously the 
nature of the flora of the antarctic continent previous to the last 
glacial period must have depended upon the occurrence or no of a 
glacial period or of glacial periods intercalated between the last of 
such periods and the stocking of the continent when it was in connec- 
tion or close relation with lands to the north. If no such period 
intervened, then the flora must have consisted of a mixture of South 
American, New Zealand, and possibly to some extent of Australian 
types, or of descendants from such, together with endemic genera, of 
which many, for all that we know, may have been identical with 
genera characteristic of northern lands. But if a glacial period was 
intercalated, and that after the connecting lands to the northward had 
disappeared beneath the waves, then the flora of the antarctic con- 
tinent during the subsequent warm period must have been closely 
similar to that of other antarctic lands, since it would have been 
derived from the same source or sources; while if the connection with 
lands to the north was still open at the commencement of the interca- 
lated glacial period or periods, the antarctic flora would have migrated 
northward, and, the connection being still maintained, would have 
advanced southward on the return of warmer conditions, so that it 
would have borne approximately the same facies after as before the 
glaciation of the continent. If this reasoning be sound, therefore, in 
no event does it seem likely that the antarctic flora could have been 
in any special sense isolated and highly peculiar. 
As an instance of the way in which the brief—if the term may be 
allowed without offence—for the predominance of the northern flora has 
been handled, I shall cite the assumption that glaciation first affected the 
northern hemisphere. Let us hear Mr. Darwin. After alluding to 
the southward migration of species when glacial conditions obtained 
