G. M. Thomson. — On the Ongin of the New Zealand Flora. 501 



introduced, and it is by this spreading north from a common centre that we 

 must account for so many species which are found both here and in the 

 Tasmanian and AustraHan alps. Why some species should become modi- 

 fied and others remain persistent, I do not know. Thus our Fuchsias 

 and pepper trees are distinct from the species found in South America, 

 though certainly derived from that region, while our tutu plants [Coriaria 

 angustifolia and thymifolia) are identical with others found on the Andes. 

 "We cannot work out these problems with our present information, for the 

 necessary factors are wanting. 



The northern extension of New Zealand indicated by Mr. Wallace as 

 existing formerly, would bring it into very close proximity to North-eastern 

 Australia, which may then have been in form of a long, narrow island, run- 

 ning nearly north and south ; and also close to extensive sub-continental 

 areas, of which only the remains are now left in the Polynesian Islands. 

 And not only did those forms which are common to New Zealand and 

 Australia, and New Zealand and Polynesia, find their way thus southwards, 

 but it was probably by this chain that the plants of European and Asiatic 

 affinity now found in our islands were introduced. But it was only 

 at a much later period that an upheaval took place of the compara- 

 tively shallow seas separating the eastern and western portions of Aus- 

 tralia ; and that those forms now so characteristic of Australia, and which 

 had been long developing under the peculiar conditions of their isolation 

 in the western portion, overran the whole continent and stamped their 

 features so markedly on its flora. And it is to this explanation that we 

 must look in accounting for the presence of so many plants in New Zealand 

 and Eastern Australia which are not found at all in Western Australia. A 

 few specially Australian plants may have at later periods found their way 

 into this colony, as the prevalent winds here are from the west, and birds 

 are still found which have apparently strayed across the intervening expanse 

 of ocean, but their number must be almost inappreciable, and cannot affect 

 the general result. 



While many of the immigrants thus introduced may have transmitted 

 their characters almost unaltered through many successive generations, so 

 that we still rank their descendants as belonging to species yet to be 

 found outside New Zealand, others gave rise to variations and sports, and 

 in course of time the accumulation of these variations has amounted to 

 specific importance, and in some cases even to generic. 



I believe that some such explanation as that sought to be given here, 

 will account for the present geographical distribution of our flora, but it 

 will be long before we can trace the parent forms of many of our plants, and 

 detect the alterations and variations they have undergone. A knowledge of 



