So coal question settled--Q.E.D. Sneer away!
Many thanks for your welcome note from Cambridge, and I am glad you like my alma mater, which I despise heartily as a place of education, but love from many most pleasant recollections...
Thanks for your offer of the 'Phytologist;' I shall be very much obliged for it, for I do not suppose I should be able to borrow it from any other quarter. I will not be set up too much by your praise, but I do not believe I ever lost a book or forgot to return it during a long lapse of time. Your 'Webb' is well wrapped up, and with your name in large letters OUTSIDE.
My new microscope is come home (a "splendid plaything," as old R. Brown called it), and I am delighted with it; it really is a splendid plaything. I have been in London for three days, and saw many of our friends. I was extremely sorry to hear a not very good account of Sir William. Farewell, my dear Hooker, and be a good boy, and make Sigillaria a submarine sea- weed.
Ever yours, C. DARWIN.
CHARLES DARWIN TO J.D. HOOKER. Down [May 6th, 1847].
My dear Hooker,
You have made a savage onslaught, and I must try to defend myself. But, first, let me say that I never write to you except for my own good pleasure; now I fear that you answer me when busy and without inclination (and I am sure I should have none if I was as busy as you). Pray do not do so, and if I thought my writing entailed an answer from you nolens volens, it would destroy all my pleasure in writing. Firstly, I did not consider my letter as REASONING, or even as SPECULATION, but simply as mental rioting; and as I was sending Binney's paper, I poured out to you the result of reading it. Secondly, you are right, indeed, in thinking me mad, if you suppose that I would class any ferns as marine plants; but surely there is a wide distinction between the plants found upright in the coal- beds and those not upright, and which might have been drifted. Is it not possible that the same circumstances which have preserved the vegetation in situ, should have preserved drifted plants? I know Calamites is found upright; but I fancied its affinities were very obscure, like Sigillaria. As for Lepidodendron, I forgot its existence, as happens when one goes riot, and now know neither what it is, or whether upright. If these plants, i.e. Calamites and Lepidodendron, have VERY CLEAR RELATIONS to terrestrial vegetables, like the ferns have, and are found upright in situ, of course I must give up the ghost. But surely Sigillaria is the main upright plant, and on its obscure affinities I have heard you enlarge.
Thirdly, it never entered my head to undervalue botanical relatively to zoological evidence; except in so far as I thought it was admitted that the vegetative structure seldom yielded any evidence of affinity nearer than that of families, and not always so much. And is it not in plants, as certainly it is in animals, dangerous to judge of habits without very near affinity. Could a Botanist tell from structure alone that the Mangrove family, almost or quite alone in Dicotyledons, could live in the sea, and the Zostera family almost alone among the Monocotyledons? Is it a safe argument, that because algae are almost the only, or the only submerged sea-plants, that formerly other groups had not members with such habits? With animals such an argument would not be conclusive, as I could illustrate by many examples; but I am forgetting myself; I want only to some degree to defend myself, and not burn my fingers by attacking you. The foundation of my letter, and what is my deliberate opinion, though I dare say you will think it absurd, is that I would rather trust, caeteris paribus, pure geological evidence than either zoological or botanical evidence. I do not say that I would sooner trust POOR geological evidence than GOOD organic. I think the basis of pure geological reasoning is simpler (consisting chiefly of the action of water on the crust of the earth, and its up and down movements) than a basis drawn from the difficult subject of affinities and of structure in relation to habits.