union
was at a very remote period when Leguminosae were either not differentiated
or comparatively rare.

[181] Sir Joseph Hooker informs me that the number of tropical Australian
plants discovered within the last twenty years is very great, and that the
statement as above made may have to be modified. Looking, however, at the
enormous disproportion of the figures given in the "Introductory Essay" in
1859 (2,200 tropical to 5,800 temperate species) it seems hardly possible
that a great difference should not still exist, at all events as regards
species. In Baron von Mueeller's latest summary of the Australian Flora
(_Second Systematic Census of Australian Plants_, 1889), he gives the total
species at 8,839, of which 3,560 occur in West Australia, and 3,251 in New
South Wales. On counting the species common to these two colonies in fifty
pages of the _Census_ taken at random, I find them to be about one-tenth of
the total species in both. This would give the number of distinct species
in these areas as about 6,130. Adding to these the species peculiar to
Victoria and South Australia, we shall have a flora of near 6,500 in the
temperate parts of Australia. It is true that West Australia extends far
into the tropics, but an overwhelming majority of the species have been
discovered in the south-western portion of the colony, while the species
that may be exclusively tropical will be more than balanced by those of
temperate Queensland, which have not been taken account of, as that colony
is half temperate and half tropical. It thus appears probable that full
three fourths of the species of Australian plants occur in the temperate
regions, and are mainly characteristic of it. Sir Joseph Hooker also doubts
the generally greater richness of tropical over temperate floras which I
have taken as almost an axiom. He says: "Taking similar areas to Australia
in the Western World, _e.g._, tropical Africa north of 20deg S. Lat. as
against temperate Africa and Europe up to 47deg--I suspect that the latter
would present more genera and species than the former." This, however,
appears to me to be hardly a case in point, because Europe is a distinct
continent from Africa and has had a very different past history, and it is
not a fair comparison to take the tropical area in one continent while the
temperate is made up of widely separated areas in two continents. A closer
parallel may perhaps be found in equal areas of Brazil and south tempera