I should be sorry to give up the view that an old and very large continuous territory would generally produce organisms higher in the competitive sense than a smaller territory. I may, of course, be quite wrong about the plants of Australia (and your facts are, of course, quite new to me on their highness), but when I read the accounts of the immense spreading of European plants in Australia, and think of the wool and corn brought thence to Europe, and not one plant naturalised, I can hardly avoid the suspicion that Europe beats Australia in its productions. If many (i.e. more than one or two) Australian plants are TRULY naturalised in India (N.B. Naturalisation on Indian mountains hardly quite fair, as mountains are small islands in the land) I must strike my colours. I should be glad to hear whether what I have written very obscurely on this point produces ANY effect on you; for I want to clear my mind, as perhaps I should put a sentence or two in my abstract on this subject. (70/4. Abstract was Darwin's name for the "Origin" during parts of 1858 and 1859.)
I have always been willing to strike my colours on former immense tracts of land in oceans, if any case required it in an eminent degree. Perhaps yours may be a case, but at present I greatly prefer land in the Antarctic regions, where now there is only ice and snow, but which before the Glacial period might well have been clothed by vegetation. You have thus to invent far less land, and that more central; and aid is got by floating ice for transporting seed.
I hope I shall not weary you by scribbling my notions at this length. After writing last to you I began to think that the Malay Land might have existed through part of the Glacial epoch. Why I at first doubted was from the difference of existing mammals in different islands; but many are very close, and some identical in the islands, and I am constantly deceiving myself from thinking of the little change which the shells and plants, whilst all co-existing in their own northern hemisphere, have undergone since the Glacial epoch; but I am convinced that this is most false reasoning, for the relations of organism to new organisms, when thrown together, are by far the most important.
When you speak of plants having undergone more change since old geological periods than animals, are you not rather comparing plants with higher animals? Think how little some, indeed many, mollusca have changed. Remember Silurian Nautilus, Lingula and other Brachiopods, and Nucula, and amongst Echinoderms, the Silurian Asterias, etc.
What you say about lowness of brackish-water plants interests me. I remember that they are apt to be social (i.e. many individuals in comparison to specific forms), and I should be tempted to look at this as a case of a very small area, and consequently of very few individuals in comparison with those on the land or in pure fresh-water; and hence less development (odious word!) than on land or fresh-water. But here comes in your two-edged sword! I should like much to see any paper on plants of brackish water or on the edge of the sea; but I suppose such has never been published.
Thanks about Nelumbium, for I think this was the very plant which from the size of seed astonished me, and which A. De Candolle adduced as a marvellous case of almost impossible transport. I now find to my surprise that herons do feed sometimes on [illegible] fruit; and grebes on seeds of Compositae.
Many thanks for offer of help about a grant for the Abstract; but I should hope it would sell enough to pay expenses.
I am reading your letter and scribbling as I go on.
Your oak and chestnut case seems very curious; is it not the more so as beeches have gone to, or come from the south? But I vehemently protest against you or any one making such cases especial marvels, without you are prepared to say why each species in any flora is twice or thrice, etc., rarer than each other species which grows in the same soil. The more I think, the more evident is it to me how utterly ignorant we are of the thousand contingencies on which range, frequency, and extinction of each species depend.