86 Darwin, and after Darwin. 



with, it did indeed appear to me that there was the 

 strongest conceivable ground for inferring that cross- 

 infertility between such varieties would be found by 

 experiment to be a phenomenon of highly gene- 

 ral occurrence amply sufficient ground to prove 

 that allied species on common areas for the most part 

 owed their origin to this character of mutual sterility, 

 and not vice versa as previously supposed. At that 

 time I was not aware that any experiments had been 

 made in this direction. Soon after the paper was 

 published, however, my attention was directed to a 

 laborious research which had been directed to this 

 very point, and carried on for more than thirty years, 

 by M. Jordan l . This had not attracted the general 

 notice which it undoubtedly deserved ; and I have 

 since ascertained that even Darwin began to look 

 into it only a few months before his death. 



Having devoted his life to closely observing in 

 divers stations multitudes of different species of plants 

 annuals and perennials, bulbous and aquatic, trees 

 and shrubs M. Jordan has been able to satisfy him- 

 self, and the French school of botanists to which this 

 line of observation has given rise, that in most cases 

 (or "nearly every where "), when a Linnean species 

 is indigenous to a country and is there of common 

 occurrence, this species within that district is repre- 

 sented by more or less numerous and perfectly constant 

 varieties. These varieties are constituted by such 

 minute differences of morphological character that 



1 Remarques snr le fait de T existence en soci^ti a Fttat salvage des 

 esphes vege tales ajfines et sur d'autres faits relatifs a la question de 

 Tesptce, par Alexis Joulan ; lues au congies de 1' Association Fiancaise 

 pour 1'Avancement des Sciences, 2 me session, Lyon, seance de 28 Aout, 

 1873. 



