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Darwin Correspondence Project

To J. D. Hooker   28 March [1878]1

Down, | Beckenham, Kent. | Railway Station | Orpington. S.E.R.

March. 28th

My dear Hooker

I am extremely obliged for the plants, & I do hope not to give any more trouble to Kew for a long time.— Pray thank Dyer cordially about the geotropic plants: we have now excellent materials if we can make out anything about geotropism.2 Most, indeed nearly all, of the plants shall be returned in due time. But the geotropic ones must be kept until they make fresh growths.

It is very curious how differently plants withstand frost. Most of the Cassias are extraordinarily sensitive, whereas a seedling of C. pubescens will withstand quite a sharp frost; & so in many other cases.3 This gives us infinite trouble for we cannot judge except by graduated trials, how long to expose any plant so as to injure without killing it

Ever yours | Ch. Darwin


The year is established by the relationship between this letter and the letter to J. D. Hooker, 25 March [1878].
CD had requested plants from the Royal Botanic Gardens, Kew, to replace those that had been killed by his experiments on nyctitropism (see letter to J. D. Hooker, 25 March [1878]). William Turner Thiselton-Dyer was assistant director of Kew.
On the nyctitropic movements in Cassia that protect its leaves from frost, see Movement in plants, pp. 369–73. Cassia pubescens is a synonym of Senna hirsuta, woolly senna. CD described the species as Indian (ibid., p. 293 n.); however, Senna hirsuta is native to the Americas.


Movement in plants: The power of movement in plants. By Charles Darwin. Assisted by Francis Darwin. London: John Murray. 1880.


Studying geotropism.

Experiments using exposure to frost to study nyctitropism are difficult to perform because species vary in frost tolerance.

Letter details

Letter no.
Charles Robert Darwin
Joseph Dalton Hooker
Sent from
Source of text
DAR 95: 471–2
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 11452,” accessed on 20 September 2021,