Preface. ix 



odours. Nor even when a bait is wanted will she 

 give it one minute sooner than necessary. The bril- 

 liancy, the scent, and the nectar are only furnished 

 when the flower is ready for its guests, and recLuires 

 their presence ; just as a thrifty housewife lights her 

 candles when the first guest is at the door. The 

 immature bud is furnished with no such attractions. 

 Still more, even when the flower is mature, when its 

 poUen is ready for transference or its stigma for 

 fecundation, when all the allurements are consequently 

 displayed and insects invited to the feast, she still 

 shows her economy. Guests might come who were 

 not of suf&cient importance, and the banquet be 

 wasted on them; for it is only when insects have a 

 certain shape, size, or weight that she requires their 

 visits, and can use them profitably for her purposes. 

 She requires, moreover, that they shall make their 

 entrance by the main portal, which she has specially 

 adapted to suit their and her requirements. All insig- 

 nificant and unremunerative visitors, all such, more- 

 over, as would creep in by a back entrance, must be 

 kept out ; and the purpose of this treatise is to show 

 by what various contrivances this exclusion is effected. 

 The subject is new, though a branch of the tree 

 planted by Mr. Darwin. For if some feeble ink- 

 lings of the existence in 'flowers of such excluding 

 contrivances may have occurred to other persons, — 

 nay, may even have been distinctly enunciated by 



