292 CONCLUDING EEMAEKS. 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 

 tlie proper insects; — bearing also in mind the large 

 number of species in many parts of the world which 

 from this same cause are seldom impregnated, 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 they 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. Whether 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 apifera 

 is still a highly vigorous plant, and Qymnadmia triden- 

 tata and Platanthera hyperhorea are said by Asa Gray 

 to be common plants in North America. It is indeed 

 possible that these self-fertile species maj' revert in 

 the course of time to what was undoubtedly their 

 pristine condition, and in this case their various adap- 

 tations for cross-fertilisation would be again brought 

 into action. We may believe that such reversion is 

 possible, when we hear from Mr. Moggridge that 

 Ophrys scolopax fertilises itself freely in one district 

 of Southern France without the aid of insects, and 



