368 E. C. ANDREWS. 
Let it be assumed that the latter types which have over- 
run Australia, and which also have such a venerable and 
weatherbeaten aspect, are ancient, while the luxuriant 
types mentioned are of recent development. To maintain 
this claim it would be necessary to account for the fact 
that the species of types such as Hugenia, Myrtus, Hry- 
thrina, and Sophora, in Australia are endemic, with the 
exception of afew waifs transported from other continents 
by marine currents, while these same genera but with 
other endemic species, occur throughout the tropics, some 
also, as Hugenia and Myrtus, occur in New Zealand, while 
the phyllodineous Acacias, Eucalyptus, Pultenzea, and 
other genera in Myrtacez and Leguminose, are confined 
to Australia or its vicinity. 
If then a bridge existed for the advance in recent time 
of Myrtus, Eugenia and Sophora, towards Australia, it 
should at the same time have permitted of the egress of 
the more ancient Australians within certain limits of soil 
and climate. 
Again, it would be necessary, in such an assumption, to 
explain the fact that a study of the seedlings of Hugenia, 
Myrtus, Sophora, Dalbergia, and other types, indicate 
plants which have long since attained their general char- 
acters while the seedlings of Hucalyptus, the phyllodineous 
Acacias, Bossisvea, and other endemic Australian types, 
suggest that these plants have only, in relatively recent 
geological time, assumed the general leaf forms possessed 
by them at present, and that the types from which they 
have sprung are closely related to the widely spread tropical 
forms, such as Hugenia and Myrtus in the case of the 
Hucalyptus, and to the tropical Acacias in the case of the 
phyllodineous Acacias. 
In the next place the luxuriant types have a very limited 
area within which to expand, even in the tropics of 
