To Fritz Müller 1 December 1
Down Beckenham | Kent
My dear Sir
I am much obliged for your letter of oct 18th, with the curious account of Abutilon & for the seeds.2 A friend of mine, Mr Farrer has lately been studying the fertilisation of Passiflora, & concluded from the curiously crooked passage into the nectary that it could not be fertilised by humming-birds; but that Tacsonia was thus fertilised.3 Therefore I sent him the passage from your letter, & I enclose a copy of his answer.4 If you are inclined to gratify him by making a few observations on this subject, I shall be much obliged & will send them on to him.
I enclose a copy of my rough notes, on your Escholtzias, as you might like to see them.
Somebody has sent me from Germany two papers by you, one with a most curious account of Alisma,5 & the other on Crustaceans. Your observations on the Bronchiæ & heart have interested me extremely.6
Alex. Agassiz has just paid me a visit with his wife. He has been in England two or three months, & is now going to tour over the continent to see all the zoologists.7 We liked him very much. He is a great admirer of yours, & he tells me that your correspondence & book first made him believe in Evolution.8 This must have been a great blow to his father, who, as he tells me, is very well & so vigorous that he can work twice as long as he, the son, can.9 I have been very sorry to hear from him that Dana is quite broken down in health.10 As I was sure that you would wish it, I gave him a copy of the English translation of your book.11 By the way Mr Murray takes stock of his books in November, & informs me that of the thousand published of your book, 537 are unsold; & this I think is a very fair sale for a purely scientific work.12
Dr Meyer has sent me his translation of Wallace’s Malay Archipelago, which is a valuable work;13 & as I have no use for the translation, I will this day forward it to you by post, but to save postage viâ England. With every good wish believe me, my dear Sir, | Yours very sincerely | Ch. Darwin
Escholtzia Californica 1869.14
Many plants were raised from crossed seed from self-sterile plants, from S. Brazil, sent by F. Müller.15 Two plants were covered with nets; & 8 flowers on the two were crossed with pollen from distinct plants, & all produced very fine pods; a medium one contained 80 seed & none contained much fewer seed.
8 flowers on the 2 plants were fertilized with pollen from same flower & produced 7 pods; the finest of these contained 25 seed, the next finest 16 seed, & several others from 4 to 7 or 8 seed; average about 12 seed.
Later in the season, though the uncovered plants still produced pods, 12 flowers were self-fertilized, & they produced only 2 pods, containing 3 & 6 seed; so the colder temperature checked self-fertilization.
There was this difference between the 2 covered plants, that one spontaneously produced only 1 pod with no seed, yet it produced some when artificially self-fertilized; whilst the other plant spontaneously produced 8 pods, the finest of which contained 30 seed, the next finest 12, & several others from 3 to 6 seed.— Hence these 2 plants differed a little in their self-sterility. It was most curious to observe the more sterile plant of the two after it had been uncovered for about a week & insects had access, how it became completely covered with young pods;—wonderfully good evidence of benefit of a cross. These Brazilian plants appear under our climate much more self-fertile than their parents in Brazil, & very much less self-fertile than our English plants— Effect partly inherited, partly the result of external conditions.16
Role of humming-birds in plant fertilisation.
Alexander Agassiz has visited Down.
Sales of Facts and arguments for Darwin.
Encloses copy of T. H. Farrer letter  and observations on the self-sterility of Eschscholzia.
- Letter no.
- Darwin, C. R.
- Müller, J. F. T.
- Sent from
- Source of text
- British Library (Loan 10: 31) (by kind permission of English Heritage)
- Physical description
- 4pp, encl 4pp
- experiment, scientific observation
- fertilisation and generation
- fertility and/or sterility
- relation of organism to organism
Please cite as
Darwin Correspondence Project, “Letter no. 7018,” accessed on 29 August 2016, http://www.darwinproject.ac.uk/DCP-LETT-7018