i868 i88i] PASSION-FLOWER 383 



fully observed the structure of insects in relation to flowers, 1 Letter 703 

 although so many have now attended to the converse relation. 

 As I imagine few or no insects are adapted to suck the nectar 

 or gather the pollen of any single family of plants, such 

 striking adaptations can hardly, I presume, be expected in 

 insects as in flowers. 



To T. H. Farrer (Lord Farrer). Letter 



Down, May 28th, 1870 



I suppose I must have known that the stamens recovered 

 their former position in Berberis? for I formerly tried experi- 

 ments with anaesthetics, but I had forgotten the facts, and I 

 quite agree with you that it is a sound argument that the 

 movement is not for self-fertilisation. The N. American 

 barberries (Mahonia) offer a good proof to what an extent 

 natural crossing goes on in this genus ; for it is now almost 

 impossible in this country to procure a true specimen of the 

 two or three forms originally introduced. 



I hope the seeds of Passiflora will germinate, for the 

 turning up of the pendent flower must be full of meaning. 3 

 I am so glad that you are able to occupy yourself a little 

 with flowers : I am sure it is most wise in you, for your own 

 sake and children's sakes. 



Some little time ago Delpino wrote to me praising the 



1 See Letter 462, also H. Miiller, Fertilisation of Flowers, Eng. 

 Trans., p. 30, on "The insects which visit flowers." In Miiller's book 

 references are given to several of his papers on this subject. 



2 See Farrer, Nature, II., 1870, p. 164. Lord Farrer was before H. 

 Miiller in making out the mechanism of the barberry. 



3 Darwin had (May I2th, 1870) sent to Farrer an extract from a letter 

 from F. Miiller, containing a description of a Passiflora visited by 

 humming-birds, in which the long flower-stalk curls up so that " the 

 flower itself is upright." Another species visited by bees is described 

 as having "dependent flowers." In a letter, June 29th, 1870, Mr. Farrer 

 had suggested that P. princeps, which he described as having sub-erect 

 flowers, is fitted for humming-birds' visits. In another letter, Oct. I3th, 

 1869, he says that Tacsonia, which has pendent flowers and no corona, 

 is not fertilised by insects in English glass-houses, and may be adapted 

 for humming-birds. See Life and Letters, III., p. 279, for Farrer's remarks 

 on Tacsonia and Passiflora; also H. Miiller's Fertilisation of Flowers, 

 p. 268, for what little is known on the subject ; also Letter 701 in the 

 present volume. 



