4 INTRODUCTORY REMARKS. CHAP. I. 



same stock two kinds of flowers. The flowers of the one 

 kind are minute and completely closed, so that they 

 cannot possibly be crossed ; but they are abundantly 

 fertile, although producing an extremely small 

 quantity of pollen. The flowers of the other kind 

 produce much pollen and are open ; and these can be, 

 and often are, cross-fertilised. Hermann Miiller has 

 also made the remarkable discovery that there are 

 some plants which exist under two forms; that is, 

 produce on distinct stocks two kinds of hermaphrodite 

 flowers. The one form bears small flowers constructed 

 for self-fertilisation ; whilst the other bears larger and 

 much more conspicuous flowers plainly constructed 

 for cross-fertilisation by the aid of insects ; and without 

 their aid these produce no seed. 



The adaptation of flowers for cross-fertilisation is a 

 subject which has interested me for the last thirty- 

 seven years, and I have collected a large mass of ob- 

 servations, but these are now rendered superfluous by 

 the many excellent works which have been lately pub- 

 lished. In the year 1857 I wrote * a short paper on 

 the fertilisation of the kidney bean ; and in 1862 my 

 work ' On the Contrivances by which British and 

 Foreign Orchids are Fertilised by Insects ' appeared. 

 It seemed to me a better plan to work out one group 

 of plants as carefully as I could, rather than to pub- 

 lish many miscellaneous and imperfect observations. 

 My present work is the complement of that on 

 Orchids, in which it was shown how admirably these 

 plants are constructed so as to permit of, or to favour, 

 or to necessitate cross-fertilisation. The adaptations 



* 'Gardeners' Chronicle,' 1857, 'Annals and Mag. of Nat. Hist. 

 p. 725, and 1858, p. 828. Also 3rd series, vol. ii. 18o8, p. 462. 



