# From George Henslow   20 October 1876

〈    〉 〈    〉 | N.W.

Oct 20/76.

Dear Sir,

I see advertised in “Nature” a new work by yourself on “The effects of Cross and Self-fertilisation of Plants: and you will see a notice of mine on the latter subject.1 I should esteem it a great kindness if you would tell me if the “conclusions” there given coincide with your own: and, if not, I should be glad to hear where you think I may be wrong in any way.

There are some points I 〈    〉 〈    〉 present, of sufficient observation  For example: the cause of protogyny. I find that Statice and Plantago2 both develop their whorls in the same, but not the usual order, as follows:—Calyx, Corolla, stamens, pistil   The pistil, however, rapidly outgrows the stamens and the styles elongating protrude beyond the corolla & mature first.

This seems to indicate the fact that the early development of the corolla tends to arrest that of the stamens (which in most flowers precede it) and so enables(?) the pistil to mature first.3 But why this is so I cannot yet see. If you can throw any light on this, I should be much obliged for your help.

Luzula campestris is another good example of protogyny.4

I have just noted some more instances corroborative of my statement that self-fertilisation is a relative condition. Thus some flowers of Œnothera biennis with petals $\frac{1}{2}$ inch long were self-fertg. and in that stage—exactly resembled the normal flowers of Œ. parviflora! Which is also self-fertilising.5

Does not this fact throw out a hint as to the origin of some “species”?

Similarly Epilobium hirsutum may be compared with the smaller—E. parviflorum.6

I find also that small flowers (dwarfed by lateness of blossoming?) of Eschscholzia californica, expanding in water, developed a profusion of pollen-tubes.7 Whether this is normally self-fertilising or not I do not know.

I hope next year to try a number of experiments protecting suspected self-fertilisers:—

Trusting you are enjoying better health than formerly | believe me to be | yrs very truly | Geo Henslow

## Footnotes

Cross and self fertilisation was advertised in Nature, 19 October 1876, p. ccxxii; Henslow’s notice, ‘Self-fertilisation of plants’, appeared in letters to the editor in the same issue (Henslow 1876b).
The Linnaean genus name Statice is now rejected and most of the species formerly described within it are now within the genus Limonium, also known as sea-lavender or marsh rosemary. Plantago is the genus of plantains or fleaworts. Both genera are in the family Plumbaginaceae.
Henslow had discussed his hypothesis concerning the order of emergence of different parts (whorls) of the flower in a letter in Nature, 19 October 1876 (Henslow 1876b, p. 544).
Luzula campestris is the field woodrush.
Oenothera biennis is the common evening primrose; O. parviflora is the small-flowered or northern evening primrose.
Epilobium hirsutum is the great willowherb; E. parviflorum is the small-flowered willowherb.
Eschscholzia californica is the California poppy. CD had learned from Fritz Müller that the species was self-sterile in Brazil, although it became partially self-fertile in England and Germany (see Correspondence vol. 14 and Cross and self fertilisation, pp. 109–17.

## Bibliography

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Cross and self fertilisation: The effects of cross and self fertilisation in the vegetable kingdom. By Charles Darwin. London: John Murray. 1876.

## Summary

Asks whether CD’s conclusions on cross- and self-fertilising plants agree with his own as set out in a notice in Nature [14 (1876): 543–4].

## Letter details

Letter no.
DCP-LETT-10646
From
George Henslow
To
Charles Robert Darwin
Sent from
London, Bentinck Terrace, 7
Source of text
DAR 166: 173
Physical description
4pp inc