ch. xvi.] FERTILISATION OF FLOWERS. 321 



gens this in my garden is never visited by insects, and 

 never sets seeds, without pollen be put on the stigma (where- 

 as the small blue Lobelia is visited by bees and does set 

 seed) ; I mention this because there are such beautiful con- 

 trivances to prevent the stigma ever getting its own pollen ; 

 which seems only explicable on the doctrine of the advan- 

 tage of crosses." 



The paper was supplemented by a second in 1858.* 

 The chief object of these publications seems to have been to 

 obtain information as to the possibility of growing varieties 

 of Leguminous plants near each other, and yet keeping 

 them true. It is curious that the Papilionaceae should not 

 only have been the first flowers which attracted his atten- 

 tion by their obvious adaptation to the visits of insects, but 

 should also have constituted one of his sorest puzzles. The 

 common pea and the sweet pea gave him much difficulty, 

 because, although they are as obviously fitted for insect- 

 visits as the rest of the order, yet their varieties keep true. 

 The fact is that neither of these plants being indigenous, 

 they are not perfectly adapted for fertilisation by British 

 insects. He could not, at this stage of his observations, 

 know that the co-ordination between a flower and the 

 particular insect which fertilises it may be as delicate as 

 that between a lock and its key, so that this explanation 

 was not likely to occur to him. 



Besides observing the Leguminosas, he had already be- 

 gun, as shown in the foregoing extracts, to attend to the 

 structure of other flowers in relation to insects. At the 

 beginning of 1860 he worked at Leschenaultia,f which at 

 first puzzled him, but was ultimately made out. A passage 

 in a letter chiefly relating to Leschenaultia seems to show 

 that it was only in the spring of 1860 that he began widely 

 to apply his knowledge to the relation of insects to other 

 fiowers. This is somewhat surprising, when we remember 

 that he had read Sprengel many years before. He wrote 

 (May 14) : 



" I should look at this curious contrivance as specially 

 related to visits of insects; as I begin to think is almost 

 universally the case." 



Even in July 1862 he wrote to Asa Gray : 



* Gardeners' Chronicle, 1858, p. 8'28. 



t He published a short paper on the manner of fertilisation of this flower, 

 in the Gardeners' Chronicle 1871, p. 1106. 



