From W. E. Darwin   20 June [1866]1

Southampton

June 20

My Dear Father

I enclose you some orders for dividends for your signature   please forward them to Uncle Ras,2 and ask him to sign & post them.

I cannot help thinking the Rhamnus is a case of dimorphic becoming diœcious;3 I will tell more in a day or two but I have not time today, & George & Edmund come here tomorrow.4 I thought it must be as you say at first, but I found that the pollen of long pistilled male was the largest, which seemed odd if that was less of a male flower than the short pistilled;5 so I examined the female flowers, & I think I have found two sizes among them corresponding to the two males flowers.6 Mem. I am probly. wrong; will write in a day or two

your affection— | W. E. Darwin

CD annotations

1.1 I enclose … post them 1.2] crossed blue pencil
2.3 I found … largest 2.4] underl red pencil
1
The year is established by the relationship between this letter and the letter to W. E. Darwin, 19 [June 1866].
2
The reference is to Erasmus Alvey Darwin.
3
In his letter to William of 19 [June 1866], CD stated that he thought Rhamnus cathartica had once existed in hermaphrodite and female forms, and that he saw no evidence that it had ever been dimorphic.
4
William refers to his brother George Howard Darwin and their cousin Edmund Langton.
5
In his research on Primula, CD had observed that pollen-grains from short-styled forms were consistently larger than those from long-styled forms (see ‘Dimorphic condition in Primula’, pp. 78–9; Collected papers 2: 45–7; see also ‘Three forms of Lythrum salicaria’, pp. 178, 190–1; Collected papers 2: 113, 123, 125). In Forms of flowers, p. 294, he noted William’s ‘very remarkable’ observation that larger pollen-grains were produced in male flowers with longer, rather than shorter, pistils, in Rhamnus cathartica. CD added that heterostyled plants tended to produce larger pollen-grains in flowers with shorter pistils, but that R. cathartica showed no evidence of having ever been heterostyled.
6
William’s notes on Rhamnus cathartica are in DAR 186: 43 and contain sketches of the four flower forms. In Forms of flowers, pp. 294–5, CD described Rhamnus cathartica as dioecious, with each sex having two ‘sub-forms’. See also letter from W. E. Darwin, [18 June 1866] and n. 2, and letter to W. E. Darwin, 19 [June 1866] and n. 4.

Please cite as “DCP-LETT-5128,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-5128