get much light on this question through fossils. If you can help me, I should be very much obliged: indeed, all your letters are most useful to me. MONDAY:--Now for your first long letter, and to me quite as interesting as long. Several things are quite new to me in it--viz., for one, your belief that there are more extra-tropical than intra-tropical species. I see that my argument from the Arctic regions is false, and I should not have tried to argue against you, had I not fancied that you thought that equability of climate was the direct cause of the creation of a greater or lesser number of species. I see you call our climate equable; I should have thought it was the contrary. Anyhow, the term is vague, and in England will depend upon whether a person compares it with the United States or Tierra del Fuego. In my Journal (page 342) I see I state that in South Chiloe, at a height of about 1,000 feet, the forests had a Fuegian aspect: I distinctly recollect that at the sea-level in the middle of Chiloe the forest had almost a tropical aspect. I should like much to hear, if you make out, whether the N. or S. boundaries of a plant are the most restricted; I should have expected that the S. would be, in the temperate regions, from the number of antagonist species being greater. N.B. Humboldt, when in London, told me of some river (14/3. The Obi (see "Flora Antarctica," page 211, note). Hooker writes: "Some of the most conspicuous trees attain either of its banks, but do not cross them.") in N.E. Europe, on the opposite banks of which the flora was, on the same soil and under same climate, widely different! I forget (14/4. The last paragraph is published in "Life and Letters," II., page 29.) my last letter, but it must have been a very silly one, as it seems I gave my notion of the number of species being in great degree governed by the degree to which the area had been often isolated and divided. I must have been cracked to have written it, for I have no evidence, without a person be willing to admit all my views, and then it does follow.