# From Francis Darwin   [after 7 July 1878]1

Bot Institut. | Würzburg

My dear Father,

I have been horribly idle about sleeping plants for you but I will really have a good look   it is quite easy; I have seen a Zygophyllum fabago which sleeps pretty well 2 leaflets moving vertically upwards.2 Porliera seems to be a different species; the twig you sent has very much the look of mine but has only 8 or 9 prs of leaflets & that gives it a dumpy look compared with yrs.3 I havn’t made it out properly— It certainly sleeps— twigs in water in the diffused light of this room are open all morning & shut early about 3   They were open in a dark cupboard after about 24 hrs. A twig kept quite under water in blazing sun out of doors is open when the plant in bed has shut leaves. Under a bell glass in a glass of water & standing in a plate of water it remained open in full sunlight   It seems to me it must depend on dampness but I half think it depends on being richly supplied with water, as a twig is in a a glass of water; as mine does not seem the same species I will try some more things.

The oats have only just begun to germinate I shall do some to day—4 Sachs5 made a calculation & said that at the most the little tip that appears at first could only manufacture make $\frac{6}{1000}$ of a milligramm dry weight in a day by assimilating; (a milligramm = 1/70th grain). Germinating seeds do not gain in weight he says.

PM   I have cut sections of a young oat $\frac{1}{5}$th inch above the ground—& it has chlorophyll in it, Sachs looked & said it was chlorophyll but rather yellow, & therefore not fully developed: Only 4 or 5 oats have come up as yet & this was the smallest—I can get younger ones tomorrow morning I hope—sections is much better than alcohol which I always thought bosh.

Since writing about Porliera this morning I found another Porliera same species but in a pot & not in open ground & its leaves were wide open while the one in ground were shut. Sachs on theoretical grounds says the one in the bed gets more water, but I asked the gardener privately & he on practical grounds says he waters the pot-plant every day & never the bedded out one.

Yr affec son | F Darwin

I will write to printers about 50 copies at once6

## CD annotations

1.1 I have been … glass of water 1.12] crossed blue crayon
1.2 I have seen … upwards. 1.3] double scored red crayon
1.2 Zygophyllum fabago] underl red crayon
2.1 The oats] pencil, opening square bracket red crayon
2.1 The oats … bosh. 3.5] ‘(Use of heliotropism)’ pencil, square brackets in ms
4.1 Since … found] underl blue crayon
4.1 Since … out one. 4.5] crossed blue crayon
4.1 another Porliera] opening square bracket red crayon
4.4 I asked … out one. 4.5] double scored blue crayon
Top of p. 2: ‘(I do not think I have said anything about function of circumnutation of Cotyledons & Hypocotyls’ pencil

## Footnotes

The date is established by the relationship between this letter and the letter to Francis Darwin, 7 [July 1878].
Zygophyllum fabago is the Syrian beancaper.
CD had sent Francis a twig taken from the plant he had borrowed from the Royal Botanic Gardens, Kew (letter to Francis Darwin, 6 [July 1878]); it had been referred to as Porliera hygrometrica (Outwards book, p. 463, Archives, Royal Botanic Gardens, Kew; see also letter from Francis Darwin, [22 June 1878], n. 6). Plants identified as Porliera hygrometrica growing in Würzburg seemed to behave differently from the plant CD had received from Kew (see letter from Francis Darwin, [29 June] 1878, and letter to Francis Darwin, 7 [July 1878] and n. 2). Porlieria hygrometrica is an unresolved name that has been used to refer to both P. hygrometra and P. chilensis; it is likely, based on the description of the leaflets, that CD’s specimen was the species now recognised as P. hygrometra, while the Würzburg plants were P. chilensis. Francis’s notes, dated between 12 and 26 July 1878, recording the movements of both specimens of Porlieria from the Würzburg garden, are in DAR 209.14: 110–11.
CD had asked Francis to measure the diameter of the cells of the pulvini of cotyledons of oats (Avena sativa) and to try to determine whether the cotyledons contained chlorophyll (see letters to Francis Darwin, 26 June [1878] and 2 July [1878]).
Julius Sachs.
CD had checked the proofs of Francis’s paper on the nutrition of Drosera rotundiflolia (F. Darwin 1878a), and recommended that Francis ask for more offprints (letter to Francis Darwin, 2 July [1878]).

## Summary

Sleep in Porlieria studied.

Oats begin germinating.

## Letter details

Letter no.
DCP-LETT-11596
From
Francis Darwin
To
Charles Robert Darwin
Sent from
Würzburg
Source of text
DAR 209.7: 157
Physical description
2pp †