# To Francis Darwin   15 August [1873]1

Down, | Beckenham, Kent. [Bassett, Southampton.]

Aug. 15th

My dear Frank

I am very glad to hear, & to see, the nectar-holes in the Lathyrus.2 Now I know that they occur in 4 British species, which no doubt are crossed occasionally, & they do not occur in 2 foreign species which I believe are never crossed; & this really looks as if the Bees were bothered by there being no nectar holes.3 But I saw at Abinger a Bombus lapidarius going to the base of the standard of the sweet Pea (L. odoratus) on one side & sucking nectar, so that he knew how to get to the nectar, but he did not stand on the keel & could have done nothing for fertilisation.4 It is curious about the bees biting holes (I could not find them in the $\frac{2}{3}$ withered flowers which you sent) on the right side of the keel, for from the position of the stigma bees ought to suck on the left side (standard being in front of the beholder); & if they had bitten holes on the left side I shd. have inferred that there was more honey on left side.— Perhaps the keel is more exposed on the right side. From what William has said I now remember that I observed L. maritimus at Shanklin & I have somewhere got notes on the bees sucking (not biting holes) on one side of flower;5 but W. is almost sure that the pistil in some flowers was bent to one side & in others to the opposite. It was bent so that stigma faced to the left in all the flowers which were sent by you.6

With respect to bees biting holes the sole rule which I could ever made out, has been that when many plants of the same species with a somewhat closed or irregular flowers grow close together & are visited by many bees, they then bite holes: I imagine that the honey is exhausted in many flowers, & the bees then bite holes so as to visit them more quickly.

T. H. Farrer has made out a curious case with another Legum. plant, Coronella, about which I will hereafter tell you.—7

I am very glad that the worms are flourishing: Amy seems to have the soul of a true naturalist.8

Many thanks about Drosera: the bread ought to be left embraced until the tentacles just begin to reexpand.— Do put a little bit of raw meat on a leaf, & as you are a great histologist, compare after several days its state with a bit on moss.9

It would now I think be too late in the season, but it wd. be a fine experiment to cover up under net about 4 young plants of about same size of Drosera; & leave 2 without any insects & give every leaf of the other 2 plants, (as often they expand & reexpand) insects, & then compare size of plants at end of autumn. They could then be weighed. But I fancy it would not be possible now to find young plants which had not already caught many insects.

I have been working at Mimosa here, and everything has turned out as [perversely] as possible10

Yours affecte Father | C. Darwin

When soil is loose as round banked up Celery plant, I find that the worms always make their castings within their burrows.11

## Footnotes

The year is established by CD’s reference to his visit to Abinger; this visit took place between 5 and 9 August 1873 (‘Journal’ (Appendix II)).
See letter from Francis Darwin, 14 August [1873] and n. 2. CD refers to Lathyrus maritimus.
In a note dated 17 August 1873 (DAR 77: 33), CD listed Lathyrus praetensis, L. sylvestris, L. maritimus, and L. macrorrhizus (now L. linifolius) as species in which he had found nectar holes. He found no holes in L. odoratus (sweet pea) and L. grandiflorus (two-flowered everlasting pea). In the note ‘maritimus’ has been crossed out. In Cross and self fertilisation, p. 155, CD wrote that in three native species of Lathyrus, the staminal tube was perforated by nectar passages but that the passages were covered in L. odoratus and missing in L. grandiflorus. See also letter from Francis Darwin, 14 August [1873] and n. 3
Bombus lapidarius is the red-tailed bumble-bee. Lathyrus odoratus is pollinated in its native habitat by leafcutter bees (Megachile spp.). In Cross and self fertilisation, pp. 155–6, CD described the activity of B. lapidarius in sucking nectar without depressing the keel.
CD stayed at Freshwater on the Isle of Wight in July and August 1868; William Erasmus Darwin visited twice during CD’s stay (Emma Darwin’s diary (DAR 242)). A planned two-day visit to Shanklin on the Isle of Wight is mentioned in a letter from H. E. Darwin to G. H. Darwin, [18 July 1868] (DAR 245: 296). CD’s notes on bees and Lathyrus maritimus observed at Shanklin have not been found.
The specimens that Francis sent were later identified by him as Lathyrus sylvestris, not L. maritimus (see letter from Francis Darwin, [16 or 17 August 1873]). In L. sylvestris, one side has a more easily accessible nectar passage owing to the bending of the keel.
Thomas Henry Farrer published his observations on Coronilla in 1874. See letter to T. H. Farrer, 14 August 1873 and n. 3.
In his letter of 14 August [1873], Francis mentioned the worm garden he and Amy Ruck had set up. Amy had made observations on worm-castings for CD in 1872 and helped with an experiment investigating the effect of formic acid on the development of spawn (see Correspondence vol. 20, letter to Amy Ruck, 24 February [1872], and this volume, letter to Francis Darwin, [before 15 April 1873]).
See letter from Francis Darwin, 14 August [1873] and n. 4. Francis’s training in the natural sciences at Cambridge and in medicine at St George’s Hospital, London, would have familiarised him with histological techniques. In Insectivorous plants, p. 15, CD described differences after forty-eight hours in the state of raw meat left on a leaf of Drosera (sundew) compared with meat surrounded by wet moss.
In a note dated 15 August 1873, CD described the closing up of leaves of Mimosa when they were moved from shade to bright sunshine, comparing the action to that of Drosera leaves in hot water. He also described a further experiment to test the effect of a few drops of water on a leaf. Although CD reported that the leaf moved in this case, he was doubtful of the cause, suspecting that the wind might have played a part (DAR 209.2: 43). Notes on further experiments carried out in August 1873 are in DAR 209.2: 44–7.
In his letter of 14 August [1873], Francis had noted that the worms in his worm garden made castings in the burrow itself but not on the surface.

## Summary

Observations on bees’ biting holes in Lathyrus.

Suggests an experiment FD could carry out with Drosera.

CD is working on Mimosa, and "everything has turned out as perversely as possible".

## Letter details

Letter no.
DCP-LETT-9014
From
Charles Robert Darwin
To
Francis Darwin
Sent from
Southampton
Source of text
DAR 271.3: 8
Physical description
8pp