To T. H. Farrer [27 November 1869]1
Down, | Beckenham, Kent.
My dear Mr Farrer
I send the following extract from a letter recd yesterday from F. Müller in S. Brazil, as a caution about Passiflora in contrast with Tacsonia.2
Do not trouble yourself to acknowledge this
Yours very sincerely | Ch Darwin
“In one of your letters you called my attention on perennial Passiflora. I have in consequence planted several species into my garden; only 2 have as yet flowered, & these are self-sterile. In one species the first flowers, which appeared after transplantion, had contabescent anthers.
As to the fertilization of Passiflora, Delpino thinks in his interesting “Ulteriori osservazioni sulla Dicogamia”, which I recd a few days ago) that in the larger species this is effected by humming birds. I had come to the same conclusion by observing how frequently these flowers are visited by humming-birds, while I did not yet see neither humble-bees, nor butterflies, nor any other large insects able to fertilize them.”
Encloses extract from a letter from Fritz Müller about humming-birds visiting Passiflora, "as a caution about Passiflora in contrast with Tacsonia".
[Signed with CD’s name by Emma Darwin.]