THE MUTATIONS OF LYCOPERSICUM. 161 



The number of specific mutations which were observed in (Enothera 

 by Professor de Vries was greater than the number that has yet been 

 observed in Lycopersicum; but the scope of mutative action in (Eno- 

 thera embraced only a very small percentage of the abundant progeny 

 of the mother plants ; while in the two cases of mutation in Lycopersi- 

 cum which I observed, that action embraced all the progeny of a small 

 crop of mother plants. The mutative period in (Enothera occurred as 

 a correlative of the extreme activity of natural reproductiveness and 

 geographical distribution, but that period occurred in Lycopersicum as 

 a correlative intensive cultivation. The unusual conditions, although 

 so different in each case, apparently made the mutative opportunity 

 available for the respective species. Other conditions will doubtless 

 be found to give other species that opportunity, with diverse results. 

 When other plants shall have been discovered in their mutative period 

 the scope and diversity of mutative action will probably be found to 

 differ in each case. If so, no one case can be made the absolute stand- 

 ard for such action. 



The observations of Professor de Vries, as well as my own, show 

 conclusively, not only that species may originate by sudden mutation, 

 but that one and the same species may thus originate independently 

 at different times and places and from different plants of a mother 

 species. This fact is not without obvious significance in connection 

 with geographical distribution of living species and the origination and 

 distribution of organic forms during geological time. 



vol. i/xvii — U 



