ch. xvi.] FERTILISATION OF FLOWERS. 319 



though. " with some little nonsense." It not only encour- 

 aged him in kindred speculation, but guided him in his 

 work, for in 1844 he speaks of verifying Sprengel's observa- 

 tions. It may be doubted whether Eobert Brown ever 

 planted a more fruitful seed than in putting such a book 

 into such hands. 



A passage in the Autobiography (p. 44) shows how it 

 was that my father was attracted to the subject of fertilisa- 

 tion : " During the summer of 1839, and I believe during 

 the previous summer, I was led to attend to the cross-fertili- 

 sation of flowers by the aid of insects, from having come to 

 the conclusion in my speculations on the origin of species, 

 that crossing played an important part in keeping specific 

 forms constant." 



The original connection between the study of flowers and 

 the problem of evolution is curious, and could hardly have 

 been predicted. Moreover, it was not a permanent bond. 

 My father proved by a long series of laborious experiments, 

 that when a plant is fertilised and sets seeds under the in- 

 fluence of pollen from a distinct individual, the offspring so 

 produced are superior in vigour to the offspring of self-fer- 

 tilisation, i.e. of the union of the male and female elements 

 of a single plant. When this fact was established, it was 

 possible to understand the raison d'etre of the machinery 

 which insures cross-fertilisation in so many flowers ; and to 

 understand how natural selection can act on, and mould, the 

 floral structure. 



Asa Gray has well remarked with regard to this central 

 idea (Nature, June 4, 1874) : " The aphorism, ' Nature 

 abhors a vacuum,' is a characteristic specimen of the science 

 of the middle ages. The aphorism, ' Nature abhors close 

 fertilisation,' and the demonstration of the principle, belong 

 to our age and to Mr. Darwin. To have originated this, 

 and also the principle of Natural Selection . . . and to 

 have applied these principles to the system of nature, in 

 such a manner as to make, within a dozen years, a deeper 

 impression upon natural history than has been made since 

 Linnaeus, is ample title for one man's fame." 



The flowers of the Papilionacea^ * attracted his attention 

 early, and were the subject of his first paper on fertilisa- 

 tion, f The following extract from an undated letter to Asa 



* The order to which the pea and bean belong. 



t Gardeners 1 Chronicle, 1857, p. 725. It appears that this paper was a piece 



