To Francis Darwin   29 [June 1878]1

29th.

I will go & get the best twisted stems which I can find & will despatch them by this post—2

Reflecting over what I wrote about movements due to a Pulvinus & to mere circumnutation, I believe that I quite missed the true point.—3 I think a pulvinus acts by secreting water from its cells into the inter-cellular spaces, so that we ought to get evidence (by comparing transverse sections) of cells on the concave side of petiole of leaf when asleep (which has no pulvinus) being reduced in size, compared with their size when awake.—

C. D.

Sent by today’s post—

The twisters are

Black Bryony (Tamus)

Azorean Honeysuckle

Common Do—

Aristolochia Cipho4

1
The month and year are established by the relationship between this letter and the letter to Francis Darwin, [c. 23 June 1878].
2
CD had offered to send Francis specimens of twisted plants in his letter of [c. 23 June 1878].
4
The text from ‘Sent by’ is on the reverse of the letter in Emma Darwin’s hand. Black bryony was Tamus communis (a synonym of Dioscorea communis); ‘Azorean honeysuckle’ was Bignonia capensis (a synonym of Tecoma capensis, Cape honeysuckle); common honeysuckle is Lonicera periclymenum; Aristolochia sipho is Dutchman’s pipe.

Manuscript Alterations and Comments

2.1 movements] after del illeg
2.3 its] interl
2.4 by] over ‘&’
2.5 leaf] after del ‘sleep’
2.5 when] interl
4.1 Sent … Cipho 5.5] in Emma Darwin’s hand ink

Please cite as “DCP-LETT-11577,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11577