of Australia.'] INTRODUCTORY ESSAY. xxxi 
includes a large proportion of what would be considered varieties in all the Australian estimates. To 
be more precise, I may state, that the fertile portions of the colonies of New South Wales, Victoria, 
South Australia, and Western Australia, do not probably, in the aggregate, exceed in area Spain, 
Italy, Greece, and European Turkey, and contain perhaps half as many more flowering plants, or a* 
many as these European countries together with Asia Minor and the Caucasus do. There is. however, 
little or nothing to be learnt from such numerical comparisons of species, when not examined in re- 
lation to the generic and ordinal differences which characterize them, and to which 1 shall hereafter 
allude. 
The relative proportions of the two great classes of Flowering plants, Monocotyledons to Dico- 
tyledons, are as 1 : 4*6,* which is a close approximation to what is supposed to obtain in the vegetation 
of the whole globe (1 : 4'9),f a remarkable coincidence, when the fact I have already alluded to is 
borne in mind, that seven-eighths of the species, and two-fifths of the genera of Australia have not 
been found elsewhere on the globe. 
Kegarding the temperate and tropical Australian Floras separately, I find that the tropical 
contains about 2,200 species, and the temperate 5,800, and that the proportions of Monocotyledons to 
Dicotyledons in each are, — 
Tropical Flora . . . 1:3-5 Temperate Flora . . . 1:50 
Comparing these numbers with those obtained from similarly large areas, there is again a remarkable 
concordance,! exemplifying the established fact that the proportion of Dicotyledons increases with 
the increasing distance from the tropics. Thus we have, — 
Temperate Floras. Tropical Floras. 
Europe 1 Monocot. : Dicot. : : 1 : 52 AVestern Trop. Africa 5 Monocot, : Dicot. : : 1:36 
Russian Empire 2 . . „ „ 1 : 51 Ceylon 6 „ „ 1 : 31 
British North America 3 „ „ 1 : 3-8 India 7 „ „ 1:38 
South Africa 4 ... „ „ 1:4-2 Tropics 8 generally . „ „ 1:3-0 
Australia .... „ „ 1:5-0 Australia .... „ „ 1 : 35 
* Brown (General Remarks, p. 6) gives the proportion of Dicotyledons to Monocotyledons as rather more than 
3 : 1, from which it appears that the results of subsequent collections has been to increase the number of Dicotyledons 
relatively to that of Monocotyledons very largely. And this is as was to be expected, for the Monocotyledons are 
most widely diffused, and hence tend to preponderate unduly iu incomplete Floras. 
t According to Lmdley's ' Yegetahle Kingdom,' in which the numerical values of the Orders, as regards the 
genera and species they contain, were obtained with great labour, and are entitled to much confidence. 
% Brown, on the contrary (Gen. Remark ), found a considerable discordance on this very point, for his 
materials from New South Walea and from King George's Sound both gave the proportion of Monocotyledons 
to Dicotyledons as very nearly 1 : 3, and his Tropical Flora the same. He adds :— " I confess I can perceive no- 
thing, either in the nature of the soil or climate of Terra Australis, or in the circumstances under which our collec- 
tions were formed, to account for the remarkable exceptions to the general proportions of the two classes in the 
corresponding latitudes of other countries." 
I have satisfied myself, by a comparison of the relative distribution of Monocotyledons and Dicotyledons within 
Australia, that this discordance iraa Milj ap] an at, and due to the fact of his collections not being complete enough. 
I have elsewhere remarked that the same source of error has vitiated Brown's estimates of the proportions of the 
classes in Western Africa (Linn. Trans, xx. p. 240 note). 
1 \vman, Sylloge. 3 Hooker's ' Flora BoreaH- Americana.' 5 Hooker's ' Niger Flora.' 
2 Ledebour, 'Flora Rossica.' 4 Drege, Meyer, Harvey's MBS., etc. 6 Thwaites's * Summary.' 
7 Author's MSS. The Indian Flora here estimated includes a large number of temperate and alpine plants, 
and the proportion of Dicotyledons is hence high. 8 A. De Candolle, Geogr. Bot. p. 1188. 
