# To W. E. Darwin [2–3 August 1862]1

Down

Saturday

My dear William.—

I am very sorry to hear about your mare. I never knew what an unfortunate family we are in horse-flesh. It really is most provoking.—2 Mamma orders me to compliment you on what a capital hand you have taken to write: it is very good. Aunt Susan was much pleased with your very nice note to her, which she sent on to us.—3

Now for business: Lythrum is a really wonderful case & will be worth an enormous amount of labour; & labour, by Jove, there will be, for I find I must castrate every flower. It will be a grand ending to my work on dimorphism.— The enclosed splendid diagram shows what I have hardly a doubt is the case: you must study it; the red lines show which pollen will fertilise which stigmas;4 all the other crosses I expect to be sterile or little fertile. In the long-styled (your long pistilled)5 the longer anthers are always yellow: has not this deceived you about maturity of flowers? Please let me hear.— I had overlooked difference in colour of filaments;— thanks.—

It wd. be enormous advantage if you could have patience to gather at least 100 twigs & class them, & then I shd. give fact on your authority:6 employ the Boys;7 but caution them to gather only one twig from each plant.— I noticed slight difference in pollen of long & short stamens in the long-styled; & considerable difference between green & yellow pollen in the mid- & the short-styled plants. I wanted 3 good specimens. (not crushed with little damp, not wet, moss) to compare pollens: I suspect those that go in pairs in diagram are alike or nearly alike.—

I dare not trust specimens in my garden for some are monstrous. I also wanted specimens from same locality to get relative heights of stamens & pistils, & to put in spirits for Artist. You will not have time to do it; but if you could make me with camera in same position outlines of all six pollens, I would have them engraved from your outlines: these outlines would show whether there are three or more than three sizes & shapes. Pollen had better be dry; it sticks to glass I find; but whether when perpendicular I know not. But I do not think you will have time for the outlines.—8

If my diagram is the truth, is it not very curious & complex case? nothing like it, is known in whole organic world. See how well corresponding heights will carry pollen on proboscis from flower to flower. Do Humble or Hive-bees visit the flowers? ask George to see to this.—

Did you say that the other sp. of Lythrum grows with you?—Vaucher says it has only 2 forms;9 I am intensely curious to see them; & if you can I would get you in autumn to send me 3 or 4 plants of each kind.

GoodBye my dearest old man.— Lenny is going on very well.10 We are perplexed to death what to do. The Doctors urge in strongest terms to avoid all chance of infection; so did my Father in bad cases, & this has been very bad. All the children are now perfectly safe, if we can avoid future infection.—11

C. Darwin

I think I have plants enough of Lythrum salicaria, but could you mark two of mid-styled.

Sunday Evening

P.S. I kept back my letter, because I received this morning the specimens.12 They have been very useful: I return stamps. I am perplexed about pollen, & I believe I must measure all again distended by water: the breadth of dry grains seem to vary much from some cause.— Will you mark with string (3 strings for long-styled, 2 for mid & 1 for short-styled) 3 plants of Lythrum, as I much want a few pods, (wrapped up separately when ripe) to count seeds in each, to know natural product, & to compare shape of pods.—

George is a rare hand at watching insects13 & beg him to observe carefully what part of body of bee the knobbed stigma of long & mid-styled rubs against, when Bee sucking: no doubt the short anthers & stigma of short-styled rubs against the proboscis. After a Bee has visited several flowers of mid- & short-styled & long-styled flowers, it would be grand to catch him & kill him & see with lens whether one part of body did not abound with the green pollen & another part with yellow. Ask George to study my diagram & he will see what I mean; it is like the two pollens of Cowslip on proboscis of moth & Bees.

George ought to look out for Epipactis latifolia now in flower, & see what insects visit it.14 Good Night— Lenny sat in arm-chair for $\frac{1}{2}$ an hour.— Goodnight my three dear Boys.— | C. D.

I shall weary you about Lythrum.

[Enclosure]15

[DIAG]

## Footnotes

Dated by the relationship to the letters from W. E. Darwin, 1 August 1862, 2 August [1862], and 5 August 1862. The letter was written on Saturday and Sunday; 2 August 1862 fell on Saturday.
The reference is to CD’s sister, Susan Elizabeth Darwin. In a letter to William of [late July 1862] (DAR 219.1: 59), Emma Darwin reported that ‘Aunt Susan’ had ‘a great fancy for larking down to Southampton with the boys’, and suggested that William should write to invite her.
See enclosure.
See letters from W. E. Darwin, 1 August 1862 and 2 August [1862].
William examined and classified specimens from 102 plants of Lythrum salicaria on 6 August 1862 (see letter from W. E. Darwin, 5 August 1862); CD cited his results, along with those given in the letter from W. E. Darwin, 1 August 1862, in ‘Three forms of Lythrum salicaria’, p. 174 (Collected papers 2: 110).
Francis and George Howard Darwin arrived in Southampton on a visit to William on 2 August 1862 (see letter from G. H. Darwin, [after 5 August 1862] and n. 3).
There are camera lucida drawings of the two sets of pollen from each of the three forms of Lythrum salicaria, all with August 1862 dates, in DAR 27.2 (ser. 2): 27–32 bis. William enclosed the first of these with the letter from W. E. Darwin, 5 August 1862. Although CD referred to William’s drawings in ‘Three forms of Lythrum salicaria’, p. 172 (Collected papers 2: 108–9), he did not reproduce them as engravings.
Vaucher 1841, 2: 371. CD refers to Lythrum hyssopifolia (see letter to H. C. Watson, 8 [August 1862]). See also ‘Three forms of Lythrum salicaria’, pp. 190–1 (Collected papers 2: 124).
Leonard Darwin was recovering from scarlet fever (see Emma Darwin’s diary (DAR 242), and letter to W. E. Darwin [24 July 1862]).
During the latter part of Leonard’s illness, the other Darwin children had been sent away with their former nurse, Brodie, who was at Down at the time (Emma Darwin 2: 178; see also letter to W. E. Darwin, 4 [July 1862] and n. 8).
In June, George Darwin had made a series of observations on the insects visiting orchids (see letter to J. D. Hooker, 30 [June 1862] and n. 16, and letter to Asa Gray, 1 July [1862] and nn. 7–9).
The following year, CD made his own observation of insects visiting Epipactis latifolia on plants that grew near his home, and concluded that they were pollinated by a species of wasp (see ‘Fertilization of orchids’, p. 150 (Collected papers 2: 146–7)). He remarked in a note dated 13–14 August 1863: ‘We had all often watched and saw no insect visiting though Bees abounded!’ (DAR 70: 56).
In the original, the red lines were drawn in crayon; they are represented in the diagram by dashed lines. The diagram is reduced to 50% of its original size.

## Summary

Discusses Lythrum, "a really wonderful case"; asks WED to make observations and collect specimens; sends a diagram which shows what crosses he believes are fertile.

Would like George to watch bees visiting the flowers; wants some pods from different forms to compare shapes and count seeds.

## Letter details

Letter no.
DCP-LETT-3678
From
Charles Robert Darwin
To
William Erasmus Darwin
Sent from
Down
Source of text
DAR 185: 70, DAR 210.6: 102
Physical description
8pp

## Please cite as

Darwin Correspondence Project, “Letter no. 3678,” accessed on 22 August 2019, http://www.darwinproject.ac.uk/DCP-LETT-3678

Also published in The Correspondence of Charles Darwin, vol. 10

letter