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 as 

 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 I 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), t 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. 



Regarding 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 . . . 1:5-0 



Comparing these numbers with those obtained from similarly large areas, there is again a remarkable 

 concordance,:]; exempbfying 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 : 5-2 Western Trop. Africa 5 Monocot. : Dicot. : : 1 : 36 



Eussian Empire 3 . . „ „ 1 : 5'1 Ceylon 6 „ „ 1:3-1 



British North America 3 „ „ 1 : 3-8 India 7 „ „ 1 : 3S 



South Africa 4 . . . „ „ 1:4-2 Tropics 8 generally . „ „ 1:3-0 



Australia .... „ „ 1:5-0 Australia .... „ „ 1:3-5 



* 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 in incomplete Floras. 



t According to Lindley's ' Vegetable 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.- 



X Brown, on the contrary (Gen. Remark ), found a considerable discordance on this very point, for his 

 materials from New South Wales and from King George's Sound both gave the proportion of Monocotyledons 

 to Dicotyledons as veiy 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 chcumstances 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 was only apparent, 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. 340 note). 



1 Nyman, Sylloge. 3 Hooker's 'Flora Bore ali- Americana.' 5 Hooker's ' Niger Flora.' 



2 Ledebour, 'Flora Rossica.' 4 Drege, Meyer, Harvey's MSS., etc. 6 Thwaites's ' Siumnaiy.' 



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. 11SS. 



