1868.] FERTILISATION OF FLOWERS. 453 



" In my opinion the best plan is to go on working and 

 making copious notes, without much thought of publication, 

 and then if the results turn out striking publish them. It 

 is my impression, but I do not feel sure that I am right, that 

 the best and most novel plan would be, instead of describing 

 the means of fertilisation in particular plants, to investigate 

 the part which certain structures play with all plants or 

 throughout certain orders ; for instance, the brush of hairs 

 on the style, or the diadelphous condition of the stamens, in 

 the Leguminosce, or the hairs within the corolla, &c. &c. 

 Looking to your note, I think that this is perhaps the plan 

 which, you suggest. 



"It is well to remember that Naturalists value observations 

 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-de- 

 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 fertilise it, 

 and to facilitate the access of the little proboscis of the hum- 

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

 long pendent tube and flexible valve-like corona which re- 

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

 would not, and admit the humming bird which would, fertil- 

 ise that flower. The suggestion is very possibly worthless, 

 and could only be verified or refuted by examination of flow- 

 ers 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 



