XIV. 
Charles Austin Gardner. 
from the rest of the world by the wide expanses of the Pacific, Indian, and 
Southern oceans, the only geographical approach for terrestrial plants is by 
way of Malaya and New Guinea, a line of communication which is interrupted 
by the barrier of the Timor and Arafura seas, and the still more restricted 
barrier of the Torres Strait. Australia is, therefore, of all the great land 
masses of the earth, the most isolated, and it is this isolation that accounts 
for its peculiar flora and fauna. 
That this isolation did not always exist is evidenced by certain relation- 
ships with the vegetation of lands now far removed, such as South America, 
South Africa, Malaya, and Madagascar. These relationships are exhibited 
by those families and groups which are more or less common to two or more 
of these areas. There are certain large families, such as the Compositae, Grami- 
neae, and Cyperaceae, which have a more or less cosmopolitan distribution but, 
on the other hand, it is amongst the more restricted groups, most highly 
developed in Australia — but with relationships with other countries through 
conjunctive genera — that these relationships are most clearly exhibited. 
To give a general indication of these relationships we may take, by way of 
example, the ancient group Gymnospermae. Here we And Araucaria linking 
South America w'ith Australia by way of New Zealand and New Caledonia ; 
CalUtris and Actinostrohus of Australia have their counterpart in the African 
genus Widdringtonia ; while in Cycas there is a link with Asia, and a secondary 
link through Macrozarnia with the African Encephalartos. But when we 
consider such families as Proteaceae, Epacridaceae, Restionaceae, Goodenia- 
ceae, and Stylidiaceae, we find these relationships even more closely expressed, 
both through the general limits of areas of distribution, and through con- 
junctive genera, and even species. 
While today, in the present stage of our knowledge, it is almost impossible 
to attempt to explain the origin of the Australian flora, a floristic analysis of 
this flora shows us that it has much in common with the floras of the lands 
referred to, and thus we are forced to suppose that there existed some former 
land communications between Australia, South America, and South Africa. 
Whether the groups which today are predominantly Australian and have 
spread through the channels of communication suggested, or whether they 
are migrants which have become more abundant and diversified here than 
in their original home, is a question that may some day be answered by palaeo- 
botanists, but not by present day development. 
AVhatever may be said of the origin of the Australian flora, we must 
recognise the fact that certain elements have been instrumental in its evolu- 
tion. These elements appear to have been recruited from two or three princi- 
pal sources : an ancient Antarctic or Subantarctic Element, derived from 
a southern source, and exhibited by the existing relationships between the 
floras of Australia, New Zealand, Southern (principally Andean) South America, 
and South Africa ; and a more recent (?) Palaeotropic Element which has 
migrated to Australia by way of India, Malaya, and Melanesia. 
Diels ]30stulates a third element— the Australian Element, but an analysis 
of this clearly indicates that this so-called Australian Element is in reality 
a secondary element at the most, for it appears to have too much in common 
with both the Antarctic and Palaeotropic elements to be considered in itself 
a true element. In his definition of the Australian Element, Diels states : 
“ The Australian Element comprises numerically the majority of the plant 
species occurring in Australia. Its groups and genera occur either only m 
Australia, and have no near relations outside the continent, or they possess 
