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Darwin Correspondence Project

From J. D. Hooker   15 July 1874

Royal Gardens Kew

July 15/74.

Dear Darwin

The big Utricularia is not in a state for sending this weather. I will try to get a small plant with good jugs for you1

What can be the meaning of the appendages to the tips of the leaflets of enclosed Acacia Mimosa which bears huge spines like what Belt describes as harboring protective ants.2

Lychnis viscaria is over.

I will send Marsilea.3

I have put 4 Peas 12 Mustard & 12 Cabbage seeds into 5 pitchers. ditto into a tube of distilled water, ditto into a tube of Nepenthes water.4

I am at fibrin today.5 Michael Foster suggests that coagulation of protoplasm may be diseased not digestive symptom—& advises my trying Effect of Citric acid in pitchers.

Young Balfour6 will spend the day here.

I hope you are better & shall be anxious to hear.7

Ever yours | J D Hooker


A plant of Utricularia vulgaris (common bladderwort) was sent to CD on 19 September 1874 (Royal Botanic Gardens, Kew, Outwards book).
Hooker probably refers to the small lipid-rich food bodies at the tips of leaflets (now referred to as Beltian bodies) found on species of bull-horn acacias such as Acacia cornigera or A. collinsii. The large thorn-like stipules of these species are hollow and provide shelter for symbiotic ants, while the Beltian bodies are a source of food, along with nectar secreted from glands at the base of the leaflets. Thomas Belt had described the hollow thorns, nectar glands, and food bodies in Belt 1874, pp. 218–20. The genus Acacia was formerly in the family Mimosaceae and the common name mimosa was often applied to it. The family Mimosaceae is now subsumed within the family Fabaceae.
CD had asked for seeds of Lychnis viscosa in his letter to Hooker of 2 July 1874. (Lychnis viscaria is a synonym, but the plant is now known as Silene viscaria, sticky catchfly or clammy campion.) Marsilea is a genus of aquatic ferns; some species have hairy leaves.
CD had suggested experiments using cabbage and pea seeds kept in secretions from Nepenthes pitchers to determine whether exposure to the fluid would affect germination (see letter to J. D. Hooker, [before 15 July 1874]). Nepenthes is the genus of tropical pitcher-plants.
Francis Maitland Balfour.
According to Emma Darwin’s diary (DAR 242), CD had a bad attack of diarrhoea and sickness on 13 July 1874.


Asks what can be the meaning of appendages to tips of leaflets of enclosed Acacia or Mimosa.

Is at fibrin today.

Michael Foster suggests coagulation of protoplasm may be diseased, not digestive, symptom.

F. M. Balfour is at Kew today.

Letter details

Letter no.
Joseph Dalton Hooker
Charles Robert Darwin
Sent from
Source of text
DAR 103: 206–7
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9548,” accessed on 20 January 2022,

Also published in The Correspondence of Charles Darwin, vol. 22