1843— 1882] NATURALISED PLANTS 451 



other cases, I think we could understand why many not- Letter 342 

 trained American plants would not succeed in our agrarian 

 habitats. 



To J. D. Hooker. Letter 343 



Mr. Darwin used the knowledge of the spread of introduced plants in 

 North America and Australia to throw light on the cosmic migration of 

 plants. Sir J. D. Hooker apparently objected that it was not fair to argue 

 from agrarian to other plants ; he also took a view differing slightly from 

 that of Darwin as to climatal and other natural conditions favouring 

 introduced plants in Australia. 



Down, Jan. 28th, 1859. 



Thanks about glaciers. It is a pleasure and profit to me 

 to write to you, and as in your last you have touched on 

 naturalised plants of Australia, I suppose you would not 

 dislike to hear what I can say in answer. At least I know 

 you would not wish me to defer to your authority, as long as 

 not convinced. 



I quite agree to what you say about our agrarian plants 

 being accustomed to cultivated land, and so no fair test. 

 Buckman has, I think, published this notion with respect to 

 North America. With respect to roadside plants, I cannot 

 feel so sure that these ought to be excluded, as animals make 

 roads in many wild countries. 1 



I have now looked and found passage in F. Midler's 2 

 letter to me, in which he says : " In the wildernesses of 

 Australia some European perennials are " advancing in sure 

 progress," " not to be arrested," etc. He gives as instances (so 

 I suppose there are other cases) eleven species, viz., 3. Rumex, 

 Poterium sanguisorba, Poteutilla anserina, Medicago sativa, 

 Taraxacum officinale, Marrubium vulgare, Plantago lanceolata, 



1 In the account of naturalised plants in Australia in Sir J. D. Hooker's 

 Introductory Essay to the Flora of Tasmania, 1859, p. cvi, many of the 

 plants are marked " Britain— waste places," " Europe— cornfields," etc. 

 In the same list the species which have also invaded North America — a 

 large number— are given. On the margin of Darwin's copy is scribbled 

 in pencil : " Very good, showing how many of the same species are 

 naturalised in Australia and United States, with very different climates ; 

 opposed to your conclusion." Sir Joseph supposed that one chief cause 

 of the intrusion of English plants in Australia, and not vice versa, was the 

 great importation of European seed to Australia and the scanty return of 

 Australian seed. 



2 Ferdinand M tiller. 



