Gray will stick up for your own weeds. Ask her whether they are not more honest downright good sort of weeds.")
But I did not sit down intending to scribble thus; but to beg a favour of you. I gave Hooker a list of species of Silene, on which Gartner has experimentised in crossing: now I want EXTREMELY to be permitted to say that such and such are believed by Mr. Bentham to be true species, and such and such to be only varieties. Unfortunately and stupidly, Gartner does not append author's name to the species.
Thank you heartily for what you say about my book; but you will be greatly disappointed; it will be grievously too hypothetical. It will very likely be of no other service than collocating some facts; though I myself think I see my way approximately on the origin of species. But, alas, how frequent, how almost universal it is in an author to persuade himself of the truth of his own dogmas. My only hope is that I certainly see very many difficulties of gigantic stature.
If you can remember any cases of one introduced species beating out or prevailing over another, I should be most thankful to hear it. I believe the common corn-poppy has been seen indigenous in Sicily. I should like to know whether you suppose that seedlings of this wild plant would stand a contest with our own poppy; I should almost expect that our poppies were in some degree acclimatised and accustomed to our cornfields. If this could be shown to be so in this and other cases, I think we could understand why many not-trained American plants would not succeed in our agrarian habitats.
LETTER 343. TO J.D. HOOKER.
(343/1. 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, January 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. (343/2. In the account of naturalised plants in Australia in Sir J.D. Hooker's "Introductory Essay to the Flora of Tasmania," 1859, page 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.)
I have now looked and found passage in F. Muller's (343/3. Ferdinand Muller.) 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, Potentilla anserina, Medicago sativa, Taraxacum officinale, Marrubium vulgare, Plantago lanceolata, P. major, Lolium perenne. All these are seeding freely. Now I remember, years and years ago, your discussing with me how curiously easily plants get naturalised on uninhabited islands, if ships even touch there. I remember we discussed packages being opened with old hay or straw, etc. Now think of hides and wool (and wool exported largely over Europe), and plants introduced, and samples of corn; and I must think that if Australia had been the old country, and Europe had been the Botany Bay, very few, very much fewer, Australian plants would have run wild in Europe than have now in Australia.