Ɛpsilon

From Francis Darwin   [19 June 1881]1

Strassburg

Sunday

My dear Father

Now that I am not experimenting I never know the date so don’t swear at me for putting Sunday—

I have been rather alarmed by reading the report of Kraus’s experiments in the last Bot Zeitung, in which he shows the increase of water in the convex side together with variations in the amount of sugar and acid; it looks so horribly like variations in turgescence on the two sides.2 It makes me doubt whether I havn’t been too bold in saying what I have about Phycomyces; I mean whether I havn’t made too much of a hypothesis on the basis of these experiments. I have said nearly the same as I did in the English M.S. namely that the turgescence theory wont do for one celled organs, and that as we have no reason to assume two kinds of growth it is simpler to believe that each cell acts as a unicell organ in multicellar plants— Also that as a unicellr thing can circumnutate it is possible that a multicellr thing does so by means of its individual cells.3 Are you sure this isn’t too much to say?

It is rather amusing about Wortmann’s Mucor stolonifer, he first of all described it as circumnutn but when he heard of mine & saw the figures he was frightened & struck it out.4 I have seen the Mucor, it is the most extraordinary thing I ever saw, it moves about like a worm hunting for something, it moves so quick it is hard to believe it is a plant;5 he might easily have given a few sketches to show the kind of changes but he seemed to think it wasn’t necessary; I think it goes in irregular circles, & must be true circumnutation   I can show it you at Down as it is the little beast that bothered me so in my Phyco cultivation.

De Bary made a pretty “Spitz und Basis” Vöchting experiment unintentionally,6 he put some cress seedlings cut off above the level of the ground and having cotyledons & perhaps one pair of leaves, under a bell glass; (I think it was to supply oxygen to a mould); the hypocotyl bent up so diagram that the cut end rose apogeotropically, and in a day or two roots came out so:— diagram ; if this would always succeed it would be a delightful way of making cuttings; we have sowed a lot of cress on the klinostat so that we may try it again with certainly no Nachwirkung;7 I am trying my willow cutting experiment on the klino but I am afraid the shoots wont be grown enough. He seemed to think my bramble experiment good as opposed to Sachs’s root stuff &c which he thinks great bosh.8

Tell Ubbadub I saw too different Uhlans today one with pink cuffs & collar & the other with white, & they looked very pretty but they had their coats buttoned up so they hadn’t got pretty fronts to them like the Uhlan going to church9

Your affec | F. D.

1
The date is established by the reference to the review, published on 17 June 1881, of Gregor Kraus’s work on water in plant cells (see n. 2, below). In 1881, the Sunday following 17 June was 19 June.
2
Karl Goebel’s review of ‘Ueber der Wasservertheilung in der Pflanze. II. Der Zellsaft und seine Inhalte’ (On water distribution in plants. II. Cell sap and its contents; Kraus 1880) was published in Botanische Zeitung, 17 June 1881 (Goebel 1881).
3
In the conclusion to his paper ‘Ueber Circumnutation bei einem einzelligen Organe’ (On circumnutation in a single-cell organ; F. Darwin 1881b, p. 479), Francis argued that the usual explanation of variations in turgescence as the proximate cause of bending in multicellular plants could not apply in the case of a single-celled organism like the sporophore of the fungus Phycomyces nitens. Kraus had described changes in the concentration and composition of the cell sap in the cells of plant organs when bending (summarised in Goebel 1881, p. 392).
4
According to Francis, Julius Wortmann had observed circumnutation in the mycelium of a fungus (see letter from Francis Darwin, 14 May 1881 and n. 7). In his paper, ‘Ein Beitrag zur Biologie der Mucorineen’ (A contribution to the biology of Mucorales; Wortmann 1881, p. 386), Wortmann described nutation of the stolon of Mucor stolonifer (a synonym of Rhizopus stolonifer, black bread mould), but argued that the movement was idiosyncratic and irregular.
5
At this time, moulds and other fungi were considered to be part of the plant kingdom; they are now classified within their own kingdom, Fungi.
6
Anton de Bary. Francis alludes to Hermann Vöchting’s paper, ‘Ueber Spitze und Basis an den Pflanzenorganen’ (On the tip and base in plant organs; Vöchting 1880). Vöchting had maintained that the tendency of cut branches to develop buds at the apex and roots at the base was determined by the morphology of the cutting and independent of external forces like gravity (ibid., p. 596).
7
By planting the cress in a pot held in a klinostat, a rotating plant-holder used to test the influence of gravity, Francis would eliminate the possibility that the outcome of the previous experiment had been an after-effect or Nachwirkung (German).
8
Julius Sachs. For Francis’s bramble (Rubus fruticosus) experiment, see F. Darwin 1880b.
9
Francis’s son, Bernard Darwin, had become attached to a paper soldier of an Uhlan going to church (see letter to Francis Darwin, 30 May [1881] and n. 6). Uhlans were light cavalry soldiers (lancers) and the different regiments often had elaborate uniforms.

Please cite as “DCP-LETT-13220F,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-13220F