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PACIFIC SCIENCE, Vol. IV, October, 1950 
ginning of Australia’s geographic isolation.) 
As far as the dingo is concerned, it is sup- 
posed that aboriginal Austral inhabitants en- 
tering Australia from Malaysia were the 
first to bring this animal to the southern 
continent. 
It is also pertinent to our thesis to note 
that zoologists believe that some of the opos- 
sums (Caenolestes) migrated to North Amer- 
ica from South America. Fossils of Marsu- 
pialia have been found in Europe and in 
North and South America, an indication that 
they must have been distributed over vast 
regions of the earth. The Marsupialia have 
survived chiefly in Australia, and for this 
reason Australia today has the oldest and 
most primitive mammal types in the world. 
Now because, geologically speaking, mam- 
mals and angiosperms are of about the same 
age, it is natural to ask if the oldest and most 
primitive of the flowering plants are also to 
be found in Australia today. The answer to 
this question would help us to determine the 
antiquity of the angiosperms. 
This is a question that is difficult to an- 
swer, if only because botanists are not in 
agreement on the most primitive species of 
angiosperms. This one question asks other 
questions: If the earliest species of angio- 
sperms could be defined, would it be found 
that they exist preeminently or even exclu- 
sively in Australia? Or, if the earliest species 
cannot be defined, is it possible to determine, 
from the Australian flora of today, which are 
the most primitive species of angiosperms 
that have succeeded in persisting until this 
time? These are the problems to be investi- 
gated in this paper. 
WHAT ARE THE MOST PRIMITIVE FAMILIES 
OF THE FLOWERING PLANTS? 
As every botanist knows, the question of 
primitiveness in flowering plants is a contro- 
versial one. Some think that certain species 
of the Monochlamydeae are the most primi- 
tive, while others think that the Polycarpicae 
among the Choripetales are the most ancient. 
Once, even certain of the Monocotyledones 
(the Pandanales) were considered for the 
distinction, although this claim, of course, 
could not be proved by any significant argu- 
ments. Inasmuch as this is hardly the place 
for a discussion of the phylogenetic criteria 
by which plants are judged, the more perti- 
nent portions of my book, Neue Ziele der 
Botanik (1938), are suggested for reference. 
If, in our search for the oldest angio- 
sperms, and in our analysis of the Australian 
flora, we hold the opinion that those families 
which are put at the head of the Monochla- 
mydeae in the Engler and Prantl system of 
classification are the ones which show the 
most primitive characteristics, we should be 
supported in this assumption by the Casuari- 
naceae found in Australia. In their original 
distribution they extended from Sumatra to 
the Philippines, New Caledonia, and the Fiji 
archipelago (Diels, 1926), and to Tahiti, the 
Austral Islands, and the Marquesas (Brown, 
1935). As yet, however, there is no reliable 
basis for the hypothesis that the Casuarina- 
ceae are more nearly related to the Gymno- 
spermae than is any other family of the An- 
giospermae. Neither can this supposition be 
proved for the Proteaceae and the Balanop- 
sidaceae, which are also placed at the begin- 
ning of the Monochlamydeae in the Engler 
and Prantl taxonomic system. In Australia 
more than half of all of the species of Mono- 
chlamydeae are Proteaceae (about 600 spe- 
cies), although the family has extended to 
southern Africa, southern Asia, and South 
America (Vester, 1940). The species of 
Proteaceae are almost exclusively ligneous 
plants, which would indicate that, phyloge- 
netically, they are rather an old group, but 
in the absence of paleontological evidence 
we cannot be certain that these species are 
really older than many others we might con- 
sider, so we have to be content only with 
supposing that they might be. 
