Ch. XVI.] FERTILISATION OF FLOWERS. 303 



flower and the particular insect which fertilises it may be as 

 delicate as that between a lock and its key, so that this explana- 

 tion was not likely to occur to him. 



Besides observing the Leguminosje, 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 

 1860 he worked at Leschenaultia,* 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 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 

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

 universally the case." 



Even in July 1862 he wrote to Asa Gray : — 



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

 to make one very cautious when one doubts about the use of 

 all parts ? I fully believe that the structure of all irregular 

 flowers is governed in relation to insects. Insects are tho 

 Lords of the floral (to quote the witty Athenaeum) world." 



This idea has been worked out by H. Miiller, who has written 

 on insects in the character of flower-breeders or flower- 

 fanciers, showing how the habits and structure of the visitors 

 are reflected in the forms and colours of the flowers visited. 



He was probably attracted to the study of Orchids by the 

 fact that several kinds are common near Down. The letters 

 of 1860 show that these plants occupied a good deal of his 

 attention ; and in 1861 he gave part of the summer and all 

 the autumn to the subject. He evidently considered himself 

 idle for wasting time on Orchids which ought to have been 

 given to Variation under Domestication, Thus he wrote : — 



" There is to me incomparably more interest in observing 

 than in writing ; but I feel quite guilty in trespassing on these 

 subjects, and hot sticking to varieties of the confounded cocks, 

 hens and ducks. I hear that Lyell is savage at me." 



It was in the summer of 1860 that he made out one of the 

 most striking and familiar facts in the Orchid-book, namely, 

 the manner in which the pollen masses are adapted for removal 

 by insects. He wrote to Sir J. D. Hooker, July 12 : — 



" I have been examining Orchis pyramidalis, and it almost 

 equals, perhaps even beats, your Listera case; the sticky 



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

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



