436 FERTILISATION OF FLOWERS. [1858. 



information as to the possibility of grov/ing varieties of legu- 

 minous 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 hib attention by their obvious 

 adaptation to the visits of insects, but should also have con- 

 stituted 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 Leguminosae, he had already begun, 

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

 of other flowers in relation to insects. At the beginning of 

 i860 he worked at Leschenaultia,t 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 i860 that he began widely to apply his knowledge 

 to the relation of insects to other flowers. 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 re- 

 lated to visits of insects ; as I begin to think is almost univer- 

 sally the case." 



Even in July 1862 he wrote to Dr. Asa Gray : — 



" There is no end to the adaptations. Ought not these 

 cases to make one very cautious when one doubts about the 



* He was of course alive to variety in the habits of insects. He pub- 

 lished a short note in the Entomologists Weekly Intelligencer, i860, asking 

 whether the Tineina and other small moths suck flowers. 



f He published a short paper on the manner of fertilisation of this 

 flower, in the Gardeners' Chronicle, 1871, p. 1166. 



