To J. D. Hooker 13 April 
Down Farnborough Kent.
My dear Hooker
I am sorry for your sake to say I must write at considerable Length.— First would you object to send me list of the 12 superior men:1 I had made up my mind with you about the Pres. G. Soc.y 2
Secondly: here is to me a calamity, I have sent to Edinburgh for the “Lawsonian Collection &c”3 it is “quite out of print”. Now can Sir William lend me any old copy: the first Edit. would do perfectly; I say old, for I shd like, if permitted, to make slight (to be afterwards rubbed out) pencil-marks to guide my inspection at Kew?— It is a real misfortune that I cannot buy a copy.— By the way Berkerly most kindly has sent me some of the curious, self-hybridised (the ticket at Kew gave me a false impression) Peas4 & some other vars: so that I shall now have 45 vars. of Peas growing by the side of each other!
Thirdly, if Dr Alexander5 can give no more information, the case even for credulous me, is worthless; I have constantly observed eggs of some parasite adhering to the bodies of Nepa, a water-bug, if the Lady uses the terms correctly, it is perhaps these ova, & not of Fish.—
Fourthly. Thank you very much for the information about the seeds.6 I had fancied you had some definite opinion that seeds of certain groups could not possibly withstand salt-water. I am not yet prepared to try the experiment on so large a scale as you suggest: indeed I have hardly the means; but I am glad to find I have commenced very much on the principles you suggest, but on a much smaller scale. I have had one experiment some little time in progress, which will I think be interesting, namely seeds in salt water immersed in water of 32o–33o, which I have & shall long have, as I filled a great tank with Snow.—7 When I wrote last, I was going to triumph over you, for my experiment had in a slight degree succeeded, but this with infinite baseness I did not tell in hopes that you would say that you would eat all the plants, which I could raise after immersion. It is very aggravating that I cannot in the least remember what you did formerly say, that made me think you scoffed at the experiments vastly; for you now seem to view the experiment like a good Christian.8 I have in small bottles out of doors, exposed to variations of temp., but in shade, exposed to light, as yet only Cress, Radish, Cabbages, Lettuces, Carrots, Celery, & Onion seed; 4 great Families. These after immersion for exactly one week, have all germinated, which I did not in the least expect, (& thought how you wd sneer at me) for the water of nearly all & of the cress especially, smelt very badly, & the cress-seed emitted a wonderful quantity of mucus (the Vestiges would have expected them to turn into tadpoles)9 so as to cohere in a mass; but these seeds germinated & grew splendidly. The germination of all (especially Cress & Lettuces) has been accelerated, except the cabbages, which have come up very irregularly & a good many, I think, dead. One wd have thought from native habitat that cabbage wd have stood well. The Umbelliferæ & onions seem to stand the salt well. I wash the seed before planting them. I have written to Gardeners’ Chronicle;10 though I doubt whether it was worth while. If my success seems to make it worth while, I will send a seed list to get you to mark some different classes of seeds. To day I replant the same seeds as above after 14 days immersion.11 As many sea-current go a mile an hour: even in a week they might be transported 168 miles: the Gulf-stream is said to go 50 & 60 miles a day.—12 So much & too much on this head; but my geese are always swans.—
I have made, at cost of more trouble than worth, a list of all the naturalised plants from A. Gray13 to calculate proportions of the great Families, as I did from the Cybele:14 as you seemed to think this of some interest; I do not scruple to ask you to deliberately read over the enclosed papers;15 for Gray uses so many different expressions that I am puzzled what to do, & am afraid of being biassed from theory in any selection. Please read heading. The expressions are exactly copied. There is from context, no essential difference between “introduced” & “naturalised”. I have doubted whether to take whole list, as it stands or to strike out those with (?) or clear doubt expressed. Once I thought of selecting those best & most thoroughily naturalised; but this would be difficult to do & the number left would be few. If I were to make any selection, I wd pin paper over names, shuffle the papers & so not be biassed. will you deliberate & advise me: I will send you the results, if you like to have them. I have had to count all the species: ill-luck to the labour.— I am thinking of writing with many apologies to A. Gray to ask him a few questions on alpine plants &c.—16
Goodbye | My dear Hooker | Most truly yours | C. Darwin
I plant my salted seeds in glass tumblers (having first tried & recorded rate of germination of same seeds unsalted) so that I can see the seed all the time, before & after germination, on the chimney piece.—
Pea self-fertilisation: has forty-five varieties growing side by side.
Describes seed-salting experiments: e.g., immersion in tank filled with snow. Reports some successful germinations.
Made list of naturalised plants from Asa Gray’s Manual [of Botany] to calculate the proportions of the great families.
Please cite as
Darwin Correspondence Project, “Letter no. 1667,” accessed on 28 October 2016, http://www.darwinproject.ac.uk/DCP-LETT-1667