To T. H. Farrer   [27 November 1869]¹

My dear M^r Farrer

I send the following extract from a letter rec^d 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 rec^d 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.”