464 LETTEES TO DAEWIN, 1843-1859 



tion of European forms in Australia and New Zealand with 

 the absence of the converse in England ; our spring frosts 

 account for the difference. In South Europe I believe 

 various Australian forms are rapidly becoming naturalised. 

 Consider too the current of export of European agricultural 

 notions and plants to Australia and consequent alteration 

 of conditions and that nothing of that kind comes back to 

 Europe. 



Your letter has interested me more than any you ever 

 wrote me (because we are both ripening I hope), but it staggers 

 me too. It opens a much wider question upon which I have 

 often pondered in vain and have hoped latterly to have 

 made more of : it is this are we right in assuming that 

 the development of plants has been parallel to that of 

 animals ? I sent out a feeler in the concluding notices of 

 my review of A. De Candolle where I indicate my view 

 that Geology gives no evidence of a progression in plants. 

 I do not say that this is proof of there never having been 

 progression that is quite a different matter but the 

 fact that there is less structural difference between the 

 recognisable representatives of Coniferae, Cycadeae, Lycopo- 

 diaceae, &c. and Dicots of chalk and those of present day, 

 than between the animals of those periods and their living 

 representatives, appears to me a very remarkable fact. . . . 



