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.
Down Beckenham | Kent
My dear Sir
I am much obliged for your letter of oct 18
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, & the other on Crustaceans. Your observations on the Bronchiæ & heart have interested me extremely.
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. 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. 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. I have been very
sorry to hear from him that Dana is quite broken down in
health. As I was sure that you would wish it, I gave him a
copy of the English translation of your book. By the way
Escholtzia Californica 1869.
Many plants were raised from crossed seed from self-sterile plants, from S. Brazil, sent by F. Müller. 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.
- f1 7018.f1The year is established by the relationship between this letter and the letter from Fritz Müller, 18 October 1869.
- f2 7018.f2Müller evidently enclosed seeds with his letter of 18 October 1869 to replace those that had been damaged earlier (see letter to Fritz Müller, 18 July  and n. 5).
- f3 7018.f3For Thomas Henry Farrer's observations, see Correspondence vol. 17, Appendix IV.
- f4 7018.f4CD sent a copy of the extract from Müller's letter of 18 October 1869 with his letter to T. H. Farrer, [27 November 1869]. For Farrer's original reply, see the letter from T. H. Farrer, 28 November 1869. Both the enclosures to the letter to Müller are copies made by Emma Darwin.
- f5 7018.f5The reference is evidently to a pre-publication copy of `Die Bewegung des Blüthenstieles von Alisma' (The movement of the pedicle in Alisma; F. Müller 1870a); CD's heavily annotated copy is in the Darwin Pamphlet Collection--CUL. See also Correspondence vol. 16, letter to Fritz Müller, 3 April  and n. 3. The person in Germany who sent the papers has not been identified.
- f6 7018.f6The second article sent was `Bemerkungen über Cypridina' (F. Müller 1870c); an annotated copy is in the Darwin Pamphlet Collection--CUL. Müller observed that two species of Cypridina with branchiae had hearts, while a third species lacked both (F. Müller 1870d, p. 269).
- f7 7018.f7The reference is to Alexander and Anna Russell Agassiz; for more on their European tour, see G. R. Agassiz ed. 1913, pp. 97--114.
- f8 7018.f8CD refers to Für Darwin (F. Müller 1864a). For more on Agassiz's correspondence with Fritz Müller, see Dobbs 2005, pp. 100--1; some of Agassiz's letters to Müller are in G. R. Agassiz ed. 1913, pp. 48--52, 91--4.
- f9 7018.f9Louis Agassiz had been an outspoken critic of CD's theories; for his views on evolution in the late 1860s and early 1870s, see Lurie 1988, pp. 372--7, and Winsor 1991, pp. 150--1. See also letter from Louis Agassiz, 6 July 1869.
- f10 7018.f10On the health problems of James Dwight Dana, see ANB.
- f11 7018.f11The reference is to the translation of F. Müller 1864a (Dallas trans. 1869).
- f12 7018.f12See letter from John Murray, 17 November 1869. Murray was the publisher of Dallas trans. 1869.
- f13 7018.f13Adolf Bernhard Meyer had sent CD his German translation (Wallace 1869c) of Alfred Russel Wallace's The Malay Archipelago: the land of the orang-utan, and the bird of paradise (Wallace 1869a). See letter from A. B. Meyer, 16 November 1869.
- f14 7018.f14The enclosure, written in Emma Darwin's hand, is a copy of notes written by CD that are now in DAR 76: B31--2.
- f15 7018.f15Müller had sent CD seeds of Eschscholzia californica (the California poppy) earlier in the year, and CD had reported on their growth; see letter from Fritz Müller, 12 January 1869, and letter to Fritz Müller, 18 July  and n. 6. CD included the information in Cross and self fertilisation, pp. 111--12.
- f16 7018.f16For CD's published discussion on the self-sterility of Eschscholzia californica in Brazil, and the effect of changed conditions on the plant's reproductive system, see Cross and self fertilisation, pp. 343, 358, 444, and 449.