290 CONCLUDING REMARKS. Chap. I i 



slow movement of the column from the labellum u\ 

 Spiranthes — the dioecious condition of Catasetum — 

 the fact of some species jn'oducing only a single 

 flower, &c. — all render it certain or highly probable 

 that the flowers are habitually fertilised with pollen 

 from a distinct plant. 



That cross-fertilisation, to the complete exclusion of 

 self-fertilisation, is the rule with the Orchidese, cannot 

 be doubted from the facts already given in relation to 

 many species in all the tribes throughout the world. 

 I could almost as soon believe that flowers in general 

 were not adapted for the production of seeds, because 

 there are a few plants which have never been known to 

 yield seed, as that the flowers of the Orchidese are not 

 as a general rule adapted so as to ensure cross-fertilisa- 

 tion. Nevertheless, some species are regularly or often 

 self-fertilised ; and I will now give a list of all the 

 cases hitherto observed by myself and others. In some 

 of these the flowers appear often to be fertilised by 

 insects, but they are capable of fertilising themselves 

 without aid, though in a more or less incomplete 

 manner ; so that they do not remain utterly barren if 

 insects iail to visit them. Under this head may be 

 included three British species, namely, Cej^halanthera 

 grandifora, Neottia nidus-avis, and perhaps Listera 

 ovata. In South Africa Disa macrantha often fertilises 

 itself; but Mr. Weale believes that it is likewise cross- 

 fertilised by moths. Three species belonging to the 

 Epidendrese rarely open their flowers in the West 

 Indies; nevertheless these flowers fertilise themselves, 

 but it is doubtful whether they are fully fertilised, 

 for a large jaroportion of the seeds spontaneously pro- 

 duced by some members of this tribe in a hothouse 

 were destitute of an embryo. Some species of Dendro- 

 biiim, judging from their structure and from their 



