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Darwin Correspondence Project

From H. G. Cavendish Browne   26 July 1871

Vicarage | Dungarvan | Co Waterford

July/26.71.

Sir

I hardly know whether an observed instance of consummated fertilisation in a tropical orchid by a British insect can now give you any interest, since the publication of your work in 1862 may have brought sufficient records of the same kind to hand.1 But I write on the chance that a matter in which you enabled me to find much pleasure may convey even the slightest degree of it to you.

Cutting flowers last week in a garden outside my study window a Humble-Bee followed me into the room and through it into the parlour next door, where he settled on the window. An orchid-house is entered from this window. Wishing to let the bee out of the room I opened the window and moved him gently over the cross-bar with the 〈flowe〉r-scissors. He flew at a flower of 〈Sobr〉alia macrantha alighting on the top 〈of〉 the labellum, and began at once 〈a〉 search for the nectary between the root of the labellum & the petals. Thinking his purpose was to bore down & through for the nectar I guided him over the ware of the labellum on to its surface. In a moment he was proceeding up the tube and soon found its store. He remained there plunged nearly out of sight for some seconds. He had not disturbed the rostellum on his inward progress and appeared to be entirely inside it. On backing out he tipped forward the spring of the column and emerged on the expanse of the labellum with the two large pollen masses firmly adhering to the ‘small’ of his back, in a position nearer to his tail than to his head. He now looked about, and, in my opinion, had come to the point when if the plant had been a gladiolus or fox glove he would have sought another bloom, but none other being on the Sobralia, he reentered this flower and went in as far as before, now bearing the pollen masses on his back. He returned in about four seconds, (not a quarter of the time he had expended there previously,) leaving both pollen-masses on the stigma; the discs alone remaining on his back. The operation was complete. Presently he stretched out his legs and lay on the labellum as if dead, where I left him, but on my return an hour afterwards perceived him beating about on the glass. The nectar of Guatemala had proved too potent.2

I may mention that for years I have observed these Bees in the Orchid-houses among large & suitable blooms of Cattleya, Cœlogyne, Dendrobium etc and never saw one entered or noticed by them. The Bees seemed always wild & irritated, and oppressed with the presentiment of the death that usually overtook them through not getting out again. This one came into my room hungry and following a bunch of gladioli and mignonette; and when gently extruded from the parlour he pitched on the Sobralia before he knew that he was prisoned by the glass of the hot-house; and besides all this he was in his own disposition more docile than any bee of his kind I have ever met with. He was one of the larger dusky yellowish sort. I believe from observing his action in the flower with respect to the working of the anther-spring, that if he might have tried an〈ot〉her bloom with the charge from this one on his back, he would have left it on the stigma of the second, removing its own pollinium for the use of a third, & so on; for I think that the shortness of his stay on the second occasion proves that a greater experience would have held the first visit to have been sufficient.

I think from observing him, that his forward motion did not disturb the spring of the anther, and that the presence of pollen masses on his back would not have disturbed it either; and I imagine he would have stuck these to the stigma in his forward motion; disturbance of the spring and withdrawal of the bloom’s own pollen-masses being reserved for his backward motion. Of course my observation deals only with Sobralia, and with this one bee, but so far as it goes illustrates the design that one flower shall be fertilised by the pollen of another.

I remain, Sir, | very faithfully yours | H. G. Cavendish Browne

Charles Darwin Esq:

CD annotations

Top of letter: ‘Fertilisation of an Orchid in Hot House (Sobralia)’ pencil

Footnotes

Cavendish Browne refers to Orchids.
CD recounted Cavendish Browne’s story in Orchids 2d ed, pp. 91–2.

Bibliography

Orchids: On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing. By Charles Darwin. London: John Murray. 1862.

Summary

Reports that a humble-bee fertilised a tropical orchid in his hothouse.

Letter details

Letter no.
DCP-LETT-7882
From
H. G. Cavendish Browne
To
Charles Robert Darwin
Sent from
Dungarvan
Source of text
DAR 160: 328
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 7882,” accessed on 18 September 2021, https://www.darwinproject.ac.uk/letter/DCP-LETT-7882.xml

Also published in The Correspondence of Charles Darwin, vol. 19

letter