From W. E. Darwin   8 May [1866]1

Southampton

May 8.

My Dear Father.

I have got the broom and examined it:2 I enclose outlines of pollen grains,3 also sketches of anthers,4 though you probably know the differences in them.

As you will see there is not much difference in the two sets of pollen, which is odd as the the arrangements are so marked to separate the Stamens. The stamens are of two kinds, 5 on thin filaments with Versatile anthers, 5 on thick filaments with adnate anthers.5

4 of the stamens with thin filaments & versatile anthers tho’ shortish in the bud become the long stamens of the flower when ready for opening and have the lobe of the anther nearest the stigma larger and, I think a little turned in, so as when ready, to fit into the cup beneath the stigma.

the remaining stamen on thin filament has a more versatile filament than any of the others & instead of lengthening, bends back with the 4 stamens on thick filaments.6 The 5 stamens on thick filaments with adnate anthers always shed their pollen before the others; as the flower gets old the difference in size of filaments does not show so much.

The long stamened anthers are certainly larger & I think have more pollen than the short ones.

I have just taken up my botany as much as I have time for, and am grinding up Asa Gray’s Structural botany, & find it very nice7

I hope you are none the worse for your London Expedition.8 I return Etty’s letter.9

I have got some more of your photographs ready if you should want any.10

Your affect son | W E Darwin

[Enclosure 1]11

Broom

diagram
diagram

A’ B’ C’ A” B” C”

A’A”   back & front view of versatile irregularly lobed anther of long stamens B’B”   —Do—adnate regularly— Do —short stamens C’C”   Do of 5 th versatile anther on thin filaments—

[Enclosure 2]12

Broom

drawn with Camera

diagram

[Enclosure 3]

Bud

diagram

Wellish out flowers

diagram

from bud

diagram

CD annotations

4.1 the remaining stamen] ‘5th’ interl after ‘remaining’ pencil
4.2 bends back] ‘back’ del pencil; ‘upwards’ added above ‘back’ pencil
4.2 the 4] ‘the’ del pencil; ‘4’ double underl pencil; ‘5’ added above, pencil, del pencil
Enclosure 1
A’ … stamens] ‘& thin filaments’ added pencil
B’ … stamens] ‘with thick filaments’ added pencil
Verso: ‘Broom— Dichog— | Broom— Dichog’ blue crayon
1
The year is established by the reference to CD’s visit to London (see n. 8, below).
2
CD was interested in dichogamy in the common broom (Cytisus scoparius, then also known as Sarothamnus scoparius). In a note written on 29 May 1857 or later, he indicated that ‘a great many’ plants were ‘12 dichogamous’ (DAR 76: B53): that is, their stamens shed half their pollen before the stigma of the same flower became receptive. Cytisus scoparius appears in a list of plants ‘apparently adapted to prevent self fertilization’ in William Erasmus Darwin’s notebook (DAR 117: 71). Further notes on broom by William are in DAR 186: 43. William had given CD extensive assistance in his research on floral dimorphism, including drawings made with a camera lucida (see Correspondence vols. 10–12).
3
See enclosures 2, 3, and 4.
4
See enclosure 2.
5
CD was interested in the sizes of pollen-grains from stamens of different lengths in plants that, unlike Cytisus scoparius, were heterostyled; William had previously sketched and measured pollen-grains from several of those species (see, for example, Correspondence vol. 12, letter from W. E. Darwin, 14 April [1864], and Forms of flowers, pp. 248–52). CD did not mention the size of pollen-grains in his discussion of Sarothamnus scoparius in Cross and self fertilisation, pp. 163–4.
6
See enclosure 1. In addition to dichogamy in broom, CD was also interested in the flower’s particular mechanism for insect pollination (see memorandum to George Henslow, [before 19 April 1866]).
7
William refers to A. Gray 1858. CD had encouraged his son’s interest in botany after he had taken up a position as a banker in Southampton (see, for example, Correspondence vol. 10, letter to W. E. Darwin, 14 February [1862]).
8
According to Emma Darwin’s diary (DAR 242), CD was in London from 21 April to 1 May 1866.
9
William may refer to the letter from H. E. Darwin, [c. 10 May 1866].
10
William had taken a photograph of CD in spring 1864 (see Correspondence vol. 12, frontispiece, and letter from W. E. Darwin, [19 May 1864] and n. 8). CD had sent six copies of this photo to Ernst Haeckel and one to Robert Caspary (see letter to Ernst Haeckel, 20 January [1866], and letter to Robert Caspary, 4 March 1866).
11
The sketches are reproduced at approximately 50 per cent of their original size.
12
The remaining sketches associated with this letter are reproduced at approximately 40 per cent of their original size.

Please cite as “DCP-LETT-3144,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-3144