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1 



MR. G. BENTHAM ON THE MIMOSE^. 357 



disconnecting more completely the northern and southern temperate regions. The 

 extension therefore of Mimoseae, as of other races of plants northward and southward, 

 has been quite independent. In the Adenantherese, for instance, the Persian and 

 priental Frosopides they have produced in the north have no connexion with the 

 extratropical Bichrostacliydes and Xerodadia developed in the south; even the few 

 Acacice ( Gummiferce) which may have passed the northern tropical line are by no means 

 representative of those of the Cape Colony, whilst the extraordinary luxuriance of the 

 Phyllodineous and other Australian races of Acacia have nothing to correspond witl 

 them in extratropical Asia. 



I cannot quit the consideration of dissevered representative races without alluding to 

 an instance which it is quite out of my power to account for. The connexion of the 

 tropical flora of North-east Australia with that of the Malayan archipelago and 

 Eastern Asia generally, is exemplified in a large number of Orders, genera, and species ; 

 but then this Indo- Australian flora is strictly limited to the north-eastern quarter of 

 Australia, or at most, in a very few cases, extends further down the east coast, and is 

 always observed to be very remote from that of the south-west ; and yet in the genus 

 Albizzia we have two species so closely alUed as to leave doubts whether they ought 

 really to be regarded as specifically distinct, and together perfectly isolated from any 

 other forms assumed by the genus; and yet the one, A. montana, inhabits the moun- 

 tains of Java, whilst the other, A. lophantha, is Hmited to extratropical South-west 

 Australia. The other spicate Albizzi<s, chiefly New Caledonian, are very different in an 

 essential character, the shape of the seed, as well as in many other respects. 



The conjectural conclusions hazarded from the above considerations may be summed 



up as follows ; , ., 1 1 j x 



That Mimoseje originated in some ancient warm country, whence they were enabled to 



spread gradually over the various tropical regions they now occupy. 



Thatrbefore the disruption or disappearance of their ongmal country, they had so far 

 become differentiated as to have established the majority but by no means aU the 



subgenera, or other larger groups we '^■^^^^^^l, , „,,t,,l,, insurmountable 

 That sinoe their orio-inal disseverance mto areas sepaiaitu 'v " 

 inat since tneir ori^ selection estabhshed new races of 



under ordinary circumstances, '^'jj^l^l^^^^^ ^^ave been crnbled to sprcaJ 



hip'bpT' or lower trades, more or less local, some ui vn i i. n • x, 



mgher or lower graaes, ^ _„^in.iy in the northern, more successfully m the 



into more temperate regions, veiy sparm^i^ xu 



southern hemisphere. ,., northern and southern temperate regions are or 



That in the New World, where the northern a ^^^^ ^^ _/,,,,,,,,,, ,,t, 



have been connected by «^^^ /^^''''*^'T. ^ ^^ve or less representative northern and 

 have been more or less '';^''''^^^^^ and southern extensions have been 



southern races, whilst in the Old World tliej^or 



quite independent, with very ^^'^^"^^^ ^^'^ J^ favourable to colonization, which bad in 



That the constitution of ^^^' /[''f, ^.'^^^^ ^^ nieans which we can only vaguely con- 



a few cases taken place in prehis on ^^^^ ^^^^ ^^^^ frequent in consequence of 



jecture, but which in more recent days as commerce, and that to these causes 



o 



(T 



the northern and southern extension 



the facilities 



lich m more r«^^"\"7"^^^^_ _^a commerce, and that to these 

 fl'orded by human intercourse and 



