1 868.] OF FLOWERS. 279 



far more than reasoning ; therefore your conclusions should 

 be as often as possible fortified by noticing how insects actu- 

 ally do the work." 



In 1869, Sir Thomas Farrer corresponded with my father 

 on the fertilisation of Passiflora and of Tacsonia. He has 

 given me his impressions of the correspondence : — ■ 



" I had suggested that the elaborate series of chevaux-dc- 

 frise, by which the nectary of the common Passiflora is 

 guarded, were specially calculated to protect the flower from 

 the stiff-beaked humming birds which would not fertilize it, 

 and to facilitate the access of the little proboscis of the 

 humble bee, which would do so ; whilst, on the other hand, the 

 long pendent tube and flexible valve-like corona which retains 

 the nectar of Tacsonia would shut out the bee, which would 

 not, and admit the humming bird which would, fertilize that 

 flower. The suggestion is very possibly worthless, and could 

 only be verified or refuted by examination of flowers in the 

 countries where they grow naturally. . . . What interested 

 me was to see that on this as on almost any other point of 

 detailed observation, Mr. Darwin could always say, 'Yes; 

 but at one time I made some observations myself on this 

 particular point ; and I think you will find, &c. &c.' That 

 he should after years of interval remember that he had 

 noticed the peculiar structure to which I was referring in the 

 Passiflora princeps struck me at the time as very remark- 

 able." 



With regard to the spread of a belief in the adaptation of 

 flowers for cross -fertilisation, my father wrote to Mr. Bentham 

 April 22, 1868 : — 



" Most of the criticisms which I sometimes meet with in 

 French works against the frequency of crossing, I am certain 

 are the 'result of mere ignorance. I have never hitherto 

 found the rule to fail that when an author describes the 

 structure of a flower as specially adapted for self-fertilisation, 

 it is really adapted for crossing. The Fumariaceae offer a 



