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Darwin Correspondence Project

From T. H. Farrer   21 November 1868

3 Gloucester Terrace | Regents Park

21 Nov/68

My dear Mr Darwin.

Since I saw you I have been looking over some notes—made in September.1 And I think something might be made out of an attempt to explain many parts at any rate of the structure & variations of Papilionaceous flowers by your views concg insect agency & crossing. For instance I believe the following features may be traced to this cause.

1. The varied bendings of the peduncle before & in flowering so as to make wings & keel a lighting place.

2 The attachment of the wings to the keel; and of the sides of the keel to each other; in other words the more or less development of gamopetalism.2

3 The stiffness or otherwise of the filaments—correlated to the character, moist or dusty, of the pollen—and absence or presence of a brush on the style.

4. The character of the pollen

5. The Shape & position of style & stigma; and the presence or absence & position of hairs upon it.

Other points—such as shape & colour of vexillum:3 solitary carpel: & staminal coherences suggest themselves to the imagination— As regards this latter point & the free stamen—which you suggested there is one case of totally separate stamens (Chorozēma) which struck me as very curious & which may possibly give some hints. Of this I venture to send you a note.4

Now might I ask you quite at your leisure to tell me whether you think this subject at all worth following up. It is simply an amusement and relaxation to me— But one would rather spend leisure hours in a right than in a wrong direction.

I think the “hairs” also would be extremely interesting.

Believe me | Sincerely yours | T H Farrer

[Enclosure]

Eashing

Sep 27.

Chorozema

Upper part of Vexillum much bent back, lower part very stiff. Very short blunt keel: but wings long spreading and bright colored. An insect lighting on the keel if it could, would not open it: but in lighting on and pressing down the wings, the lower part of the wings presses on the keel, and thus as by a lever presses down and opens the keel, and leaves Stamens and Pistol exposed. The filamentsof stamens do not cohere.— but the separate Stamen stands apart from the rest in front. All with the exception of this stamen are bent over—and the pistol is bent over also. The anthers open inwards towards one another, and towards the Stigma. The opened cells of the separate stamen are below the stigma—those of the 9 others above it—all towards it. If any object is thrust down between the 9 Upper Stamens and pistal it brushes in going down on one side the back of some of the 9 upper anthers, and on the other side the Stigma, and in coming up it brushes the open side of the same anther cells, but not until it has passed the Stigma. If it passes between the Stigma and the separate Stamen it brushes the open anther cell in going down; but not until after it has passed the Stigma. And in going up it is the other side which will touch the Stigma from that which has touched the open anther cell. It will therefore carry away pollen from all the anther cells— but deposit none upon the stigma. The curious form of the Stamens as well as the action of the Wings on the keel are remarkable.

Below is very rough diagram of the position of the stamens and pistil with the 4 stamens on the nearer side removed.

Footnotes

CD and Farrer evidently met during CD’s visit to London from 7 to 16 November 1868 (see letter from T. H. Farrer, 2 November 1868; see also ‘Journal’ (Correspondence vol. 16, Appendix II)).
In papilionaceous flowers, the lateral petals are referred to as wings, while the two joined anterior petals are the keel. Flowers in which these petals are united are referred to as gamopetalous.
In papilionaceous flowers, the large petal opposite the keel is referred to as the vexillum or standard.
See enclosure. Chorozema or Chorizema is an Australian papilionaceous genus. For more on the genus Chorizema, including history, diagnosis, and synonymy, see Taylor and Crips 1992.

Bibliography

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

Summary

Thinks CD’s views of insect agency and crossing might explain structure and variations of papilionaceous flowers. Lists five points. Asks CD’s opinion.

Letter details

Letter no.
DCP-LETT-6470
From
Thomas Henry Farrer, 1st Baron Farrer
To
Charles Robert Darwin
Sent from
London, Gloucester Terrace, 3
Source of text
DAR 164: 49; Linnean Society of London, MS Case 6B, No. 299
Physical description
4pp

Please cite as

Darwin Correspondence Project, “Letter no. 6470,” accessed on 28 January 2020, https://www.darwinproject.ac.uk/letter/DCP-LETT-6470.xml

Also published in The Correspondence of Charles Darwin, vol. 16

letter