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Darwin Correspondence Project

To J. D. Hooker   18 September [1874]1


Sep 18

My dear Hooker

I have had a splendid day’s work & must tell you about it. Lady Dorothy sent me a young plant of U. montana, which I fancy is the sp. you told me of.2 The roots or rhizomas (for I know not which they are; I can see no scales or internodes, or absorbent hairs) bear scores of bladders from 120 to 1100 of an inch in diameter; & I traced these roots to the depth of 112 in in the peat & sand. The bladders are like glass & have the same essential structure as those of our species, with the exception that many exterior parts are aborted. Internally the structure is perfect, as is the minute valvular opening into the bladder, which is filled with water. I then felt sure that they captured subterranean insects, and after a time I found two with decayed remnants, with clear proof that something had been absorbed which had generated protoplasm. When you are here I shall be very curious to know whether they are roots or rhizomes3

Besides the bladders there are great tuber-like swellings on the rhizomes; one was an inch in length & half in breadth; I suppose these must have been described. I strongly suspect that they serve as reservoirs for water. But I shall experimentize on this head.4 A thin slice is a beautiful object, & looks like coarsely reticulated glass.

If you have an old plant (& can spare the time) which could be turned out of its pot, it would be a great gain to me if you would tear off a bit of the roots near the bottom, & shake them well in water & see whether they bear these minute glass-like bladders. I should also much like to know whether old plants bear the solid bladder-like bodies near the upper surface of the pot. These bodies are evidently enlargements of the roots or rhizomes. You must forgive this long letter & make allowance for my delight at finding this new sub-group of insect-catchers. Sir E. Tennant speaks of an aquatic species of Utricularia in Ceylon which has bladders on its roots & rises annually, to the surface as he says, by this means.5

We shall be delighted to see you here on the 26th, if you will let us know your train we will send to meet you— You will have to work like a slave while you are here

Yours affectionately | Ch. Darwin


The year is established by the relationship between this letter and the letter from D. F. Nevill, [11 September 1874].
See letter from D. F. Nevill, [11 September 1874]. Utricularia montana was the first epiphytic bladderwort that CD was able to observe. Utricularia montana is a synonym of U. alpina.
Hooker visited Down on 26 September 1874 (see letter from J. D. Hooker, 23 September 1874). In Insectivorous plants, pp. 431–2, CD described the structures as root-like rhizomes with minute bladders.
CD concluded that the tubers served as reservoirs for water during the dry season (Insectivorous plants, pp. 439–40.
The aquatic bladderwort Utricularia stellaris is described in James Emerson Tennent’s book Ceylon, an account of the island, physical, historical, and topographical (Tennent 1859, p. 124 n.).


Describes his observations on Utricularia montana.

Letter details

Letter no.
Charles Robert Darwin
Joseph Dalton Hooker
Sent from
Source of text
DAR 95: 336–7
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 9645,” accessed on 21 May 2019,

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