i860.] AUSTRALIAN FLORA. 53 



Your contrast of the south-west and south-east corners is 

 one of the most wonderful cases I ever heard of. . . . You 

 show the case with wonderful force. Your discussion on 

 mixed invaders of the south-east corner (and of New Zealand) 

 is as curious and intricate a problem as of the races of men 

 in Britain. Your remark on mixed invading Flora keeping 

 down or destroying an original Flora, which was richer in 

 number of species, strikes me as eminently new and important. 

 I am not sure whether to me the discussion on the New Zea- 

 land Flora is not even more instructive. I cannot too much 

 admire both. But it will require a long time to suck in all 

 the facts. Your case of the largest Australian orders having 

 none, or very few, species in New Zealand, is truly marvel- 

 lous. Anyhow, you have now demonstrated (together with 

 no mammals in New Zealand) (bitter sneer No. 3), that New 

 Zealand has never been continuously, or even nearly con- 

 tinuously, united by land to Australia ! ! At p. lxxxix, is the 

 only sentence (on this subject) in the whole essay at which I 

 am much inclined to quarrel, viz. that no theory of trans- 

 oceanic migration can explain, &c. &c. Now I maintain 

 against all the world, that no man knows anything about the 

 power of trans-oceanic migration. You do not know 

 whether or not the absent orders have seeds which are 

 killed by sea- water, like almost all Leguminosse, and like 

 another order which I forget. Birds do not migrate from 

 Australia to New Zealand, and therefore floatation seems the 

 only possible means ; but yet I maintain that we do not know 

 enough to argue on the question, especially as we do not 

 know the main fact whether the seeds of Australian orders 

 are killed by sea-water. 



The discussion on European Genera is profoundly inter- 

 esting ; but here alone I earnestly beg for more information, 

 viz. to know which of these genera are absent in the Tropics 

 of the world, i.e. confined to temperate regions. I excessive- 

 ly wish to know, on the notion of Glacial Migration, how much 

 modification has taken place in Australia. I had better ex- 

 plain when we meet, and get you to go over and mark the list. 



