'Id'l CONCLUDING REMAKKS. Chap. IX. 



species within the same genus which regularly ferti- 

 lise themselves. Considering such cases as those of 

 Ophrys, Disa, and Epidendrum, in which one species 

 alone in the genus is capable of complete self-ferti- 

 lisation, whilst the other species are rarely fertilised 

 in any manner owing to the rarity of the visits of 

 the projjer insects ; — bearing also in mind the large 

 number of species in many parts of the world which 

 from this same cause are seldom imjjregnated, we are 

 led to believe that the above-named self-fertile plants 

 formerly depended on the visits of insects for their 

 fertilisation, and that from such visits failing thev did 

 not yield a sufficiency of seed and were verging towards 

 extinction. Under these circumstances it is probable 

 that they were gradually modified, so as to become 

 more or less completely self-fertile ; for it would 

 manifestly be more advantageous to a plant to pro- 

 duce self-fertilised seeds rather than none at all or 

 extremely few seeds. Whetlier any species which is 

 now never cross-fertilised will be able to resist the 

 evil effects of long-continued self-fertilisation, so as to 

 survive for as long an average period as the other 

 species of the same genera which are habitually cross- 

 fertilised, cannot of course be told. But Ophrys cqnfera 

 is still a highly vigorous jjlant, and Gymnadenia triden- 

 tata and PlatantJiera hyperhorea are said by Asa Grav 

 to be common plants in North America. It is indeed 

 possible that these self-fertile species may revert in 

 the course of time to what was undoubtedlv their 

 pristine condition, and in this case their various adap- 

 tations for cross-fertilisation would be ao-ain brouirht 

 into action. We may believe that such reversion is 

 possible, when we hear from jMr. IMoggridgo that 

 Ophrys scolopax fertilises itself freely in one district 

 of Southern France without the aid of insects, and 



