408 The Biology of Flowers 



the composition of the labellum the general results have received 

 universal assent, namely "that all Orchids owe what they have in 

 common to descent from some monocotyledonous plant, which, like 

 so many other plants of the same division, possessed fifteen organs 

 arranged alternately three within three in five whorls 1 ." The 

 alterations which their original form has undergone have persisted 

 so far as they were found to be of use. 



We see also that the remarkable adaptations of which we have 

 given some examples are directed towards cross-fertilisation. In only 

 a few of the orchids investigated by Darwin other similar cases 

 have since been described was self-fertilisation found to occur 

 regularly or usually. The former is the case in the Bee Ophrys 

 (Ophrys apifera), the mechanism of which greatly surprised Darwin. 

 He once remarked to a friend that one of the things that made 

 him wish to live a few thousand years was his desire to see the 

 extinction of the Bee Ophrys, an end to which he believed its self- 

 fertilising habit was leading 2 . But, he wrote, "the safest conclusion, 

 as it seems to me, is, that under certain unknown circumstances, and 

 perhaps at very long intervals of time, one individual of the Bee Ophrys 

 is crossed by another 3 ." 



If, on the one hand, we remember how much more sure self- 

 fertilisation would be than cross-fertilisation, and, on the other hand, 

 if we call to mind the numerous contrivances for cross-fertilisation, 

 the conclusion is naturally reached that "It is an astonishing fact 

 that self-fertilisation should not have been an habitual occurrence. 

 It apparently demonstrates to us that there must be something 

 injurious in the process. Nature thus tells us, in the most emphatic 

 manner, that she abhors perpetual self-fertilisation.... For may we not 

 further infer as probable, in accordance with the belief of the vast 

 majority of the breeders of our domestic productions, that marriage 

 between near relations is likewise in some way injurious, that some 

 unknown great good is derived from the union of individuals which 

 have been kept distinct for many generations 4 ? " 



This view was supported by observations on plants of other 

 families, e.g. Papilionaceae ; it could, however, in the absence of 

 experimental proof, be regarded only as a "working hypothesis." 



All adaptations to cross-pollination might also be of use simply 

 because they made pollination possible when for any reason self- 

 pollination had become difficult or impossible. Cross-pollination 

 would, therefore, be of use, not as such, but merely as a means of 

 pollination in general ; it would to some extent serve as a remedy 



1 Fertilisation of Orchids (1st edit.), p. 307. 



2 Life and Letters, Vol. in. p. 276 (footnote). 



3 Fertilisation of Orchids, p. 71. * Ibid., p. 359. 



