From Henry Jackson to Francis Darwin   18 November 1877

Croft Cottage. Barton Road.

Nov. 18. 1877.

Dear Darwin,

On second thoughts an-heliotropic will not do at all. It would mean non-heliotropic. I should have thought that the best nomenclature would be

prosheliotropic = solipetal
(to coin another word)
anheliotropic = neither solipetal
nor solifugal
aphheliotropic = solifugal

But I think that it would be quite possible to speak of heliotropic and aphheliotropic. I presume that the latter word would in general lose its second h, and be written apheliotropic.1 I do not know whether from a philological point of view these words are correctly formed.

I should have thought that negative heliotropic was an unhappy phrase.

Yours ever, | Henry Jackson.

F. Darwin Esq.

CD annotations

End of letter: ‘heliotropic Apheliotropic | geotropic apogeotropic’2 pencil
1
CD and Francis Darwin had evidently consulted Jackson, a classical scholar at Cambridge University, about terminology for plants’ bending or turning under the influence of light. For CD’s usage of various terms, see Movement in plants, p. 5. Solipetal and solifugal are coinages of Jackson’s own (sun-seeking and sun-avoiding), as are prosheliotropic and anheliotropic.
2
CD and Francis used the terms ‘geotropic’ and ‘apogeotropic’ in Movement in plants. They are terms for the directional growth of a plant in response to gravity.

Please cite as “DCP-LETT-11239,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-11239