Antiquity of the Angiosperms — SlJESSENGUTH 
of the larger systematic groups which are of 
very ancient age? The criteria for the recog- 
nition of phylogenetically old and new char- 
acteristics have been treated at length in my 
book ( Suessenguth, 1938: 19 et seq .) . 
Let us consider the Leguminosae first. 
Among the members of the subfamily Mimo- 
soideae the most important genus in Aus- 
tralia is Acacia , which has more than 300 
Australian species. The rest of the genera of 
the Mimosoideae in Australia number only 
about 23 species. 
Is the genus Acacia, then, an old or a new 
genus among the Mimosoideae? If we accept 
the general phylogenetic principle that free 
stamens are more primitive than fused sta- 
mens, and if we agree that the group of spe- 
cies with numerous stamens (now classified 
in the tribes Ingeae and Acacieae) is older 
than the group of species which have 10 or 
fewer than 10 stamens (now classified in the 
tribes Eumimoseae, Adenanthereae, Piptade- 
nieae, and Parkieae ) , then we must conclude 
that the species of the tribe Acacieae, with 
their free stamens, are more primitive than 
are the more or less synantherous species of 
the tribes Ingeae and Parkieae. The Acacieae, 
with the genus Acacia — in which the fila- 
ments are free or only grown together to 
form a short ring — are undoubtedly the most 
primitive of the Mimosoideae, and apparently 
the plants of the genus Acacia are the most 
primitive of all of the Acacieae. Therefore, 
Australia shows the greatest number of oldest 
types among the Mimosoideae. 
The subfamily Papilionatae presents much 
the same evidence. The most primitive tribes 
of the Papilionatae are those which have free 
stamens— the Sophoreae and the Podalyrieae. 
The Sophoreae generally have pinnate leaves, 
while the Podalyrieae have simple or digi- 
tate, rarely pinnate, leaves. Because of their 
simple leaves, the Podalyrieae may be con- 
sidered the more primitive tribe. The Podaly- 
rieae number 350 species in Australia, while 
295 
all of the other tribes of Papilionatae are far 
less numerous. 
In summary, as far as the Leguminosae 
are concerned, it can be said that the Mimo- 
soideae and the Papilionatae show the most 
pronounced development of primitive species 
in Australia. 
Among the tribes of the Labiatae, the Pro- 
stanthereae are by far the most numerous in 
Australia, having 89 species compared with 
3 1 for all of the other tribes. If we study the 
subfamilies of the Labiatae, as they are con- 
sidered by Briquet (in Engler and Pranti, 
1897), we come to the conclusion that the 
most primitive species must be those having 
no gynobasic pistil — the members of the tribes 
Ajugoideae and Prostantheroideae. When we 
investigate these two groups we learn that 
the Prostantheroideae have ovules with endo- 
sperm, while the Ajugoideae do not show 
any endosperm in their seeds — -evidence that 
the Prostantheroideae are the most primitive 
of the Labiatae. These primitive Prostanthe- 
roideae are confined exclusively to Australia. 
Among the Myrtaceae we think that the 
subfamily having dry fruits — the Leptosper- 
moideae — is the most primitive. In Australia 
there are about 596 of these species with dry 
fruits, compared with only 41 species of 
Myrtoideae which bear berries. In Australia, 
then, the older subfamily has about 14.5 
times as many species as does the younger 
one. The proportion of Leptospermoideae to 
Myrtoideae in the rest of the world is quite 
different: there are 678 species of Leptosper- 
moideae and 1,932 species of Myrtoideae, a 
ratio of 1:2.85. 
Among the Rutaceae the most primitive 
species are placed in the subfamilies which 
are inclined to apocarpy rather than in the 
subfamilies with united carpels (eg., the 
Flindersioideae, Spathelioideae, Toddalioi- 
deae) or in those with bacciform fruits (e.g., 
the Aurantioideae). The Rutoideae show a 
tendency to apocarpy, and among their sub- 
families several groups have developed: (a) 
