Darwin's impetus for the experiments of which the results are recorded in this book was 'a mere accidental observation; and indeed it required the accident to be repeated before my attention was thoroughly aroused to the remarkable fact that seedlings of self-fertilised parentage are inferior, even in the first generation, in height and vigour to seedlings of cross-fertilised parentage'. After eleven years of meticulous experimentation and observation, described in this volume, he was ready to publish in 1876 the detailed study which he regarded as a companion volume to his 1862 On the Various Contrivances by which British and Foreign Orchids are Fertilised by Insects. His 'first and most important of the conclusions which may be drawn ... is that cross-fertilisation is generally beneficial, and self-fertilisation injurious': this understanding is of course the basis of all modern plant breeding programmes.