To J. D. Hooker   10 December [1856]¹

My dear Hooker

I thank you sincerely about the trees: it must have cost you much more trouble than I anticipated. Now that the result is what it is in N. Zealand (I find trees occur in 38 Families, & in exactly half of these the trees have separated sexes; so that it is not an attribute related to any particular systematic structure) & with the much feebler case of England, & with the great number of trees in Persoon’s Synopsis² in the mono- & dioicous classes (though I have here no accurate standard of comparison), I think it pretty certain there is a relation between trees & separation of sexes; whether or not my explanation is correct.—³ I have had lately some hard blows against my crossing theory, & hardly know what to think.⁴ I shall be very glad to hear about Tasmanian trees, & perhaps you will find the result worth a paragraph in your introduction.— It is a most tiresome drawback to my satisfaction in writing, that though I leave out a good deal & try to condense, every chapter runs to such an inordinate length: my present chapter on causes of fertility & sterility & on natural crossing has actually run out to 100 pages M.S., & yet I do not think I have put in anything superfluous.—⁵

My wife is going on capitally in every respect.— Give my best thanks to M^rs Hooker for her kind note.—

What a funny story about Lyell & the Review (which I have not yet seen); but really I think the most probable solution is that he forgot at moment that the Review was laudatory of yourself; you are the very last man whom he would suspect of praising yourself.—⁶

I have for last 15 months been tormented & haunted by land mollusca, which occur on every oceanic island; & I thought that the double creationists or continental extensionists had here a complete victory. The few eggs which I have tried both sink & are killed. No one doubts that salt-water w^d be eminently destructive to them; & I was really in despair, when I thought I would try them when torpid; & this day I have taken a lot out of sea-water, after exactly 7 days immersion. Some sink, & some swim; & in both cases I have had (as yet) one come to life again, which has quite astonished & delighted me. I feel as if a thousand pound weight was taken off my back.⁷

Adios my dear kind friend | C.D.

P.S. | I must tell you another of my profound experiments! Franky said to me, “why sh^d not a bird be killed (by hawk, lightning, apoplexy, hail &c) with seeds in crop, & it would swim.” No sooner said, than done: a pigeon has floated for 30 days in salt water with seeds in crop & they have grown splendidly & to my great surprise even tares (Leguminosæ, so generally killed by sea-water) which the Bird had naturally eaten have grown well.— You will say gulls & dog-fish &c w^d eat up the carcase, & so they w^d. 999 out of a thousand, but one might escape: I have seen dead land bird in sea-drift.—⁸

Keep in mind some difficulty about distribution of F. W. Plants, which you alluded to at Kew when I was there; & I had not time to ask you about.— I do not mean write it, but for when we meet.—

I wonder whether D^r. Harvey would think it a bore to illuminate me about separation of sexes, how far general, in Algæ?⁹ What do you think?