Chap. IX. CONCLUDING EEMAEKS. 291 



occasionally producing capsules under cultivation, 

 likewise come under this head. 



Of species which regularly fertilise themselves with- 

 out any aid and yield full-sized capsules, hardly any 

 case is more striking than that of Ophrys apifera, which 

 was advanced by me in the first edition of this work. 

 To this case may now be added two otlier European 

 plants, Orchis or Neotinea intaofa and Epipactis viridi- 

 flora. Two North American species, Gymnadenia 

 tridentata and Platanthera hyperhorea appear to be in 

 the same predicamentj but whether when seK-fertilised 

 they yield a full complement of capsules containing 

 good seeds has not been ascertained. A curious 

 Bpidendrum in South Brazil which bears two additional 

 anthers fertilises itself freely by their aid ; and Dendro- 

 hium cretaoeum has been known to produce perfect self- 

 fertilised seeds in a hothouse in England. Lastly, 

 Spiranfhes australis and two species of Thelymitra, 

 inhabitants of Australia, come under this same head. 

 No doubt other cases will hereafter be added to this 

 short list of about ten species which it appears can 

 fertilise themselves fully, and of about the same 

 number of species which fertilise themselves imper- 

 fectly when insects are excluded. 



It deserves especial attention that the flowers of all 

 the above-named self-fertile species still retain various 

 structures which it is impossible to doubt are adapted . 

 for insuring cross-fertilisation, though they are now 

 rarely or never brought into play. We may therefore 

 conclude that all these plants are descended from 

 species or varieties which were formerly fertilised by 

 insect-aid. Moreover, several of the genera to which 

 these self-fertile species belong, include other species, 

 which are incapable of self-fertilisation. Thelymitra 

 offers indeed the only instance known to me of two 



