XXU FLORA OF TASMANIA. [Orders, etc., of Australia. 



The Gymnospermous Dicotyledons being regarded by many botanists as a class equivalent in 

 rank with all Angiospermous Phrenogams, and all the Australian species being endemic, I have thought 

 it might be interesting approximately to compare their proportions to other Phsenogams. They are, — 



In Australia 1 : 184 



In Europe 1 : 194 



In the Bussian Empire 1 : 160 



In India . 1 : 292 



In the whole world 1 : 315 



I may remark, that in selecting Floras for comparing the proportions of Orders, it is necessary to take 

 such as embrace a very large area, and are moreover tolerably well defined as botanical provinces. 

 Of those I have compared, India is inapphcable, being a heterogeneous assemblage of tempe- 

 rate, tropical, and alpine plants, the tropical being however so far dominant as to determine the 

 main results. Ceylon, again, is both far too small as an area, and is not a botanical province ; the 

 proportions of the Indian Orders in it are, however, on the whole, so well balanced, that it gives 

 normal results. 



The number of Natural Orders of Phaenogamic plants in Australia is about 152.* Of these none 

 are absolutely peculiar except BrunoniacecB and Tremandrece, which may without violence be re- 

 spectively appended to Goodeniacem and Buettneriacece. Of about fifty absent Orders, the following 

 are universally recognized as large and tropical Indian, and their total absence in Australia is 

 certainly anomalous; Ternstrcemiacece (if Cochlospermum be excluded), Dipterocarpea, Guttiferce 

 (exclusive of Calophyllum), Ochnacece, Connaracea, Balsaminea, Begoniacece, Vacciniece. 



The following are also tropical Indian, but are small ; some of them are not universally recognized, 

 but are appended by various authors to other Orders which do exist in Australia : — 



Samydea; : a family of Bixacece. 



Tamariscineas. * 



Myricese : of which Casuarinece are possibly a family. " 



Pyrenacantheae : referred to Antidesmew or EupliorUece. 



The following are temperate Orders, found elsewhere in the southern hemisphere, but not in 

 Australia : — 



Fumariaceas : a Suborder of Papaveracece. 

 Salicineas : almost entirely a northern Order. 

 Berberideas : ditto, except in the South American Ande^. 

 Valerianeas : ditto, except in the South American Andes. 



The Orders which, without being absolutely confined to Australia, are either peculiarly charac- 

 teristic of that country, or are almost entirely confined to it, are either very small indeed, or are 

 sections of larger Orders, as, — 



* The following estimates are founded on the assumption that there are about 200 Natural Orders in all the 

 Vegetable Kingdom, that is to say, so many Natural groups which are — 1. Types of structure common in most 

 cases to a large number of species, and containing several or many Genera; 2. Groups absolutely definable by 

 natural characters, or betraying a transition to other groups by only a small proportion of their species. My views 

 on these points accord with those of Bentham (Linn. Soc. Joum. Bot. vii. p. 31) and Asa Gray, who also consider 

 200 as a fair approximate estimate of the known Natural Orders. 



